case study of past major grid power failure

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EXPLAINER: Why the power grid failed in Texas and beyond

Snow and ice grips a neighborhood in East Austin on Tuesday, Feb. 16, 2021. Day six of the statewide freeze and still millions of Texans are without power. (Bronte Wittpenn /Austin American-Statesman via AP)

Carlos Mandez waits in line to fill his propane tanks Wednesday, Feb. 17, 2021, in Houston. Customers had to wait over an hour in the freezing rain to fill their tanks. Millions in Texas still had no power after a historic snowfall and single-digit temperatures created a surge of demand for electricity to warm up homes unaccustomed to such extreme lows, buckling the state’s power grid and causing widespread blackouts. (AP Photo/David J. Phillip)

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DALLAS (AP) — The power outages tormenting Texas in uncharacteristically Arctic temperatures are exposing weaknesses in an electricity system designed when the weather’s seasonal shifts were more consistent and predictable — conditions that most experts believe no longer exist.

This isn’t just happening in Texas, of course. Utilities from Minnesota to Mississippi have imposed rolling blackouts to ease the strain on electrical grids buckling under high demand during the past few days. And power outages have become a rite of summer and autumn in California, partly to reduce the chances of deadly wildfires.

But the fact more than 3 million bone-chilled Texans have lost their electricity in a state that takes pride in its energy independence underscores the gravity of a problem that is occurring in the U.S. with increasing frequency.

WHAT HAPPENED IN TEXAS?

Plunging temperatures caused Texans to turn up their heaters, including many inefficient electric ones. Demand spiked to levels normally seen only on the hottest summer days, when millions of air conditioners run at full tilt.

The state has a generating capacity of about 67,000 megawatts in the winter compared with a peak capacity of about 86,000 megawatts in the summer. The gap between the winter and summer supply reflects power plants going offline for maintenance during months when demand typically is less intense and there’s not as much energy coming from wind and solar sources.

But planning for this winter didn’t imagine temperatures cold enough to freeze natural gas supply lines and stop wind turbines from spinning. By Wednesday, 46,000 megawatts of power were offline statewide — 28,000 from natural gas, coal and nuclear plants and 18,000 from wind and solar, according to the Electric Reliability Council of Texas, which operates the state’s power grid.

“Every one of our sources of power supply underperformed,” Daniel Cohan, an associate professor of civil and environmental engineering at Rice University in Houston, tweeted . “Every one of them is vulnerable to extreme weather and climate events in different ways. None of them were adequately weatherized or prepared for a full realm of weather and conditions.”

The staggering imbalance between Texas’ energy supply and demand also caused prices to skyrocket from roughly $20 per megawatt hour to $9,000 per megawatt hour in the state’s freewheeling wholesale power market.

That raised questions whether some power generators who buy in the wholesale market may have had a profit motive to avoid buying more natural gas and simply shut down instead.

“We can’t speculate on people’s motivations in that way,” said Bill Magness, CEO of ERCOT. He added he had been told by generators that they were doing everything possible to provide power.

WHY WASN’T THE STATE PREPARED?

Gas-fired plants and wind turbines can be protected against winter weather — it’s done routinely in colder, northern states. The issue arose in Texas after a 2011 freeze that also led to power-plant shutdowns and blackouts. A national electric-industry group developed winterization guidelines for operators to follow, but they are strictly voluntary and also require expensive investments in equipment and other necessary measures.

An ERCOT official, Dan Woodfin, said plant upgrades after 2011 limited shutdowns during a similar cold snap in 2018, but this week’s weather was “more extreme.”

Ed Hirs, an energy fellow at the University of Houston, rejected ERCOT’s claim that this week’s freeze was unforeseeable.

“That’s nonsense,” he said. “Every eight to 10 years we have really bad winters. This is not a surprise.”

In California, regulators last week ordered the state’s three major utilities to increase their power supply and potentially make plant improvements to avoid another supply shortage like the one that cropped up in California six months ago and resulted in rolling blackouts affecting about 500,000 people for a few hours at a time.

“One big difference is that leadership in California recognizes that climate change is happening, but that doesn’t seem to be the case in Texas,” said Severin Borenstein, a professor of business administration and public policy at the University of California, Berkeley who has been studying power supply issues for more than 20 years.

WHY THE NEED FOR ROLLING BLACKOUTS?

Grid operators say rolling blackouts are a last resort when power demand overwhelms supply and threatens to create a wider collapse of the whole power system.

Usually, utilities black out certain blocks or zones before cutting off power to another area, then another. Often areas with hospitals, fire stations, water-treatment plants and other key facilities are spared.

By rolling the blackouts, no neighborhoods are supposed to go an unfairly long period of time without power, but that was not always the case this week in Texas. Some areas never lost power, while others were blacked out for 12 hours or longer as temperatures dipped into the single digits.

WHEN DO THEY OCCUR?

Rolling blackouts are usually triggered when reserves fall below a certain level. In Texas, as in California last August, grid operators tell utilities to reduce load on the entire system, and it is up to the utilities to decide how to do that.

In Texas this week, grid operators and utilities knew about the dire weather forecast for at least a week. Last weekend they issued appeals for power conservation, and ERCOT tweeted that residents should “unplug the fancy new appliances you bought during the pandemic and only used once.”

The lighthearted attempts at humor were lost on residents, few if any of whom were told in advance when their homes would lose power. Once the outages started, some utilities were unable to provide information about how long they might last.

WHAT CAN BE DONE TO REDUCE ROLLING BLACKOUTS?

Start with the obvious steps: When power companies or grid operators warn about trouble coming, turn down your thermostat and avoid using major appliances. Of course, those steps are sometimes easier said than done, especially during record-breaking temperatures.

Like in other places, Texans might be more willing to adjust their thermostats a few more notches if regulators imposed a system that required households to pay higher prices during periods of peak demand and lower rates at other times.

“People turn up their furnaces now because there isn’t a financial incentive for them not to do it,” Borenstein said.

Experts also say more fundamental — and costly — changes must be made. Generators must insulate pipelines and other equipment. Investments in electricity storage and distribution would help. Tougher building codes would make homes in places like Texas better insulated against the cold.

Texas, which has a grid largely disconnected from others to avoid federal regulation, may have to rethink the go-it-alone strategy. There could be pressure for the state to require power generators to keep more plants in reserve for times of peak demand, a step it has so far resisted.

“The system as we built it is not performing to the standards we would like to see,” said Joshua Rhodes, an energy researcher at the University of Texas in Austin. “We need to do a better job. If that involves paying more for energy to have more reliability, that’s a conversation we’re going to have to have.”

Koenig reported from Dallas, Liedtke reported from San Ramon, California. The AP’s Paul Weber contributed to this story from Austin, Texas.

13 of the Largest Power Outages in History — and What They Tell Us About the 2003 Northeast Blackout

What gets the most attention is not what causes blackouts in North America and Europe. It’s the system, not a shortage of power plants that is the problem. Take a look at the 13 major power outages over many years, and see that the problems we face are not because we aren’t building enough power plants. Part one of a two-part series on the Northeast Blackout of 2003.

Only one of these outages, July 2012 in India, was due to more electricity demand than could be supplied by existing resources. In the industrialized economies of North America and Europe, we more often lose power due to a subtle and difficult challenge. The electrical grid is prone to system failures and needs modernization.

Crews work on line. Credit: Mike Jacobs

For decades the concern over power grid reliability focused on ensuring that an adequate number of power plants were built. Still today, most of the policy attention, the financial needs, and advanced planning are on building enormous new plants. This is a holdover from past decades when growth in electricity use was high, and the time it took to build a power plant was increasing. But when one looks at what has caused major blackouts, insufficient power plants was only a factor in the India example, where people are being added to the Age of Electricity as services gradually reach more communities.

In North America and Europe, we have a different set of concerns. Load growth is barely 1 percent per year and there have been significant investments in new generation and technologies to save energy and use renewable energy. Still, every year the regulators and the utility industry make a number of announcements comparing the expected demand and the expected supply. In many states, this reporting is required by law. The numbers in these comparisons are easy math. When reviewed, everyone feels assured that the power supply is large enough to meet demand, or that the investments are coming and the required bills for this assurance will be paid. Even Texas, with its energy crunch, has 150 new plants in the planning process .

Unfortunately, it is unexpected disturbances, usually on the wires, that cause almost every blackout. Storms, droughts, and fires knock out whole sections of the system ; control errors and flubbed operations trigger shutdowns; coordination failures cause overloads. Transmission reliability is much more complex than the adequacy of the generation fleet.

The August 2003 Northeast Blackout resulted from a combination of key monitoring systems offline, generators not responding as anticipated or requested, and then an overloaded line sagging from excess heat and short-circuiting to a tree. Obvious to the experts, this blackout could have been prevented if the grid reliability rules, including tree trimming, were mandatory, and the system needs for communications and cooperation were enforceable.

While the attention of utilities and politicians has been on the largest power plants, the practices for running the system were neglected. Coordination between utilities, adoption of flexible schedules, and use of accurate forecasts allow the transmission system to work reliably. Responsibility had been divided by old territorial boundaries between utility companies, even as the system was becoming more regional.

The creation and strengthening of the regional Independent System Operators  has brought great progress inside the regions these serve. However, the utility industry continues to struggle to improve power flows across boundaries, information sharing, and cooperation. These reforms are vital to increasing reliability and lowering costs. We will see in the next post in this series that this modernization will help integrate wind and solar energy supplies with the rest of the grid.

In the summary of 13 power outages below, notice how the weather and the operations of the grid caused the blackouts. Coordination and better information, rather than more old-fashioned power plants, are the recurring need for more reliable systems.

1) October 2012 Hurricane Sandy : Flooding damaged vulnerable equipment and downed trees cut power to 8.2 million people in 17 states, the District of Columbia, and Canada, many for 2 weeks. The impacts from sea level rise and flooding are leading to re-evaluation of local design criteria.

2) July 30 and 31, 2012 Northern India: High demand, inadequate supply coordination, and transmission outages led to a repeating power system collapse that affected hundreds of millions across an area home to half of India’s population. Four key transmission lines were taken offline in previous days. Mid-summer demand in the north exceeded local supply, making the imports and transfers from west vital. Excessive demand tripped a transmission line. Within seconds, ten additional transmission lines tripped. Conditions and failure repeated again the following day. A review found poor coordination of outages and regional support agreements.

3) June 2012 Derecho : Wind storm damaged trees and equipment, cutting power to approximately 4.2 million customers across 11 Midwest and Mid-Atlantic states and the District of Columbia. Widespread tree clearing and line restoration efforts in many cases took 7 to 10 days.

4) October 2011 Northeast U.S.: Record early snowstorm brought down trees and wires. Outages could only follow removal of snow and fallen trees. More than three million customers in Mid-Atlantic and New England states were without power, many over 10 days.

5) September 8, 2011 California-Arizona : Transmission failure was set up by Southern California’s heavy dependence on power imports from Arizona, an ongoing problem. Hot weather after the end of the summer season, as determined by the engineering schedule, conflicted with generation and transmission outages planned for maintenance. Then two weaknesses — operations planning and real-time situational awareness — left operators vulnerable to a technician’s mistake switching major equipment. This outage lasted 12 hours, affecting 2.7 million people.

6) August 28, 2003 London :  Two cables failed, and a leaky transformer could not handle the resulting flows. A section of the city and southern suburbs, totaling 250,000 customers, were off from 6:30 to 7 pm when alternate circuits were arranged.

7) August 14, 2003 Northeastern US and Ontario : Transmission system failed for many reasons seen in major outages that came years before. Information was incomplete and misunderstood; inadequate tree trimming caused short circuit; operators lacked coordination. System imbalances and overloads seen early in the day were not corrected due to lack of enforcement of coordination. 50 million people across eight states and Ontario were without power up to four days.

8) June 25, 1998 Ontario and North Central U.S.: A lightning storm in Minnesota initiated a transmission failure. A 345-kV line was struck by lightning. Underlying lower voltage lines overloaded. Soon, lightning struck a second 345-kV line. Cascading transmission line disconnections continued until the entire northern Midwest was separated from the Eastern grid, forming three isolated “islands” with power. 52,000 people in upper Midwest, Ontario, Manitoba, and Saskatchewan saw outages up to 19 hours.

9) July 2-3, 1996 West Coast: The transmission outage began when a 345-kV line in Idaho overheated and sagged into a tree. A protective device on a parallel transmission line incorrectly tripped that line. Other relays tripped two Wyoming coal plants. For 23 seconds the system remained in precarious balance, until a 230-kV line between Montana and Idaho tripped. Remedial action separated the system into five pre-engineered islands to minimize customer outages. Two million people in the U.S., Canada, and Mexico lost power for minutes to hours.

10) August 10, 1996 West Coast : Hot weather and inadequate tree trimming set up transmission collapse. Through the afternoon five power lines in Oregon and nearby Washington short-circuited on trees. This tripped off 13 hydro turbines operated by BPA at McNary Dam on the Columbia River. Blame fell on inadequate tree-trimming practices, operating studies, and instructions to dispatchers. Approximately 7.5 million customers lost power in seven western U.S. states, two Canadian provinces, and Baja California, Mexico for periods ranging from several minutes to six hours.

11) December 22, 1982 West Coast : Over 5 million people in the West lost power after high winds knocked over a major 500-kV transmission tower. The tower fell into a parallel 500-kV line tower, and the failure mechanically cascaded and caused three additional towers to fail on each line. When these fell, they hit two 230-kV lines crossing under the 500-kV lines. From that point, coordination schemes did not operate, communication problems delayed control instructions. Backup plans failed because the coordination devices were not set for such a severe disturbance. Data displayed to operators was unclear, preventing corrective actions.

12) July 13, 1977 New York City: Transmission failures caused by lightning strike shutting lines, and the tripping offline Indian Point No. 3 nuclear generating plant. When a second lightning strike caused the loss of two more 345-kV lines, the last connection for New York City to the northwest was lost. Power surges, overloads, and human error soon followed. Nine million people in New York City suffered outages and looting up to 26 hours. Poor coordination, malfunctioning safety equipment, and limited awareness of conditions contributed to the outage.

13) November 9, 1965 Northeast U.S. and Ontario : Transmission system failed due to a mistaken setting on a protective device near Niagara Falls. Improper coordination caused four more lines to disconnect. Imbalances continued to swing until power was out for 30 million people. The outage lasted up to 13 hours.

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Power failure: what really happened and why the grid's size & complexity are a big problem.

It's becoming increasingly clear that any argument based on a few states overdrawing power from the grid is only a partial explanation at best.

A Grid to Rule Them All Till about the middle of the last decade, India’s electrical transmission grid, essentially a system to move power from suppliers (generating plants) to wholesale customers like state electricity boards, was a patchwork. It started off decades ago as a large collection of state-level networks with few if any links among states. But beginning in the ’60s, states in individual regions began to link their electrical networks with each other. This process continued gradually, but it wasn’t until 2002, that connections between regions began in earnest. Between 2002 and 2006, the northern, eastern, western and northeastern grids were all linked up through a set of transmission lines creating a power ‘superhighway’ across central and eastern India from Agra and Gwalior in the west towards Sasaram in Bihar (see map). A swathe of India, from Maharashtra and Gujarat to the North East states are now one electrical grid whose crucial artery is this superhighway. The commissioning of the Agra-Gwalior line in 2006, was the final link in closing this mega-loop. It was this Agra-Gwalior link which was to play an important part in the grid collapse. This NEW grid (North East-East-West) is linked with the southern grid, but more loosely. By 2014, the southern states are expected to be as tightly linked with the NEW grid as other states, something which residents of those states might look upon with decidedly mixed feelings now.

Why was it important to integrate the grids this way? Customers for power are widely distributed — important urban and industrial centres such as Gujarat, Maharashtra, Mumbai, Delhi for instance, while the fuel for the power they need is highly localised. The coalfields of Jharkhand and Chhattisgarh are the most critical source, followed by the hydropower rich states in the north, and the northeast. Rather than move the coal to where it’s needed, its cheaper to set up generating stations near the coal fields, and move the electricity to customers, which is where the grid comes in handy.

Coordinating the movement of electricity between the five grids, and within them, is a hierarchy of what are called load dispatch centres — at the state level, at the level of each of the five grids, and finally a national one. The five grid-level dispatch centres, and the national centre are run by Power System Operation Co Ltd (POSOCO), a subsidiary of Power Grid corporation, a central government PSU. The state-level centres, on the other hand, are run by the state governments. This is where the politics comes in. It Happened One Night Why doesn’t the ‘overdrawing by UP and others’ theory hold up? Anyone claiming this as the main reason would have to explain why the grid failed on these two days only, given that overdrawing is the norm, by many states throughout the year. Exhibit 1 in the case against overdrawal being the main culprit, is the state of the grid before the first outage in the early hours of July 30. When there’s heavy demand on the grid, in relation to the actual supply available, the grid ‘frequency’ should drop. That didn’t happen. Think of grid frequency as being similar to the water level in a tank with an outlet and an inlet pipe. If more water is being taken out of the tank than is being pumped in, the water level drops. Similarly, if there is more demand in the grid, than there is supply to meet it, the frequency should drop below 50 Hz — that’s the norm and the standard to which all electrical devices in India, from washing machines, to hair dryers to TVs work. The grid frequency at around 2 am on July 30 was about 49.68 Hz — by the standards of India’s electrical networks, that’s actually a fairly minor deviation from the norm and something which is seen quite often. And exhibit No. 2 is the total demand in the NEW grid which was being met at the time — 74,210 MW, far below India’s generating capacity. “Overdrawal by itself would not have triggered this incident,” says Bhanu Bhushan, a former member of the Central Electricity Regulatory Commission, the apex-level regulator in the sector.

So what did happen? It’s early days yet, but the possible chain of events began in the western part of the superhighway. The day before the outage, two critical components of the grid were already weak. One of the two circuits linking Agra and Gwalior, and the line between Zerda in Gujarat and Kankroli in Rajasthan were down either due to repair or upgrade work. Between them, these two routes were the main link between the western and northern grids.

The second outage of July 31 was a consequence of the first. In the hours leading up to it, a large chunk of lines connecting the east and the north from Balia to Patna to Biharshariff were still down. The crucial Ranchi-Sipat link between the eastern and western regions was down. And the Zerda-Kankroli line was still out of action. If the grid was already compromised before the outage on 30th night, it was tottering on the morning and early afternoon of the 31st. Questions will be asked as to how the grid was allowed to function in such a weak state. Again, a small fault anywhere along the system would have triggered a cascade of trippings. Within the space of a minute, between 1:01 pm and 1:02 pm, 38 links between various parts of the northern, western and eastern grids went down. Most of the generating capacity went too. The Western Grid could also have suffered a collapse — as it islanded itself, the frequency there rose sharply, indicating excess supply of power (since customers in the north were not available) — this could have potentially damaged plants in the region. Whether good luck or good management saved the day, is not known. Better But More Complex “In the ’80s and ’90s, these kinds of grid problems were a far more frequent occurrence,” Bhushan points out. The NEW grid has helped build and maintain a far more even and steady flow of power across the country from surplus to deficit regions, something that was not possible earlier. Wild swings in frequency, which indicate the extent to which the system is out of balance, are far less common today than they were a decade ago. Power stations, which earlier had to be very sensitive to shifts in demand within their region over the course of the day, can now export their surpluses to where its needed. Capacity utilisation of plants has improved. However, as Chitkara points out: “The pricing mechanisms and regulatory frameworks need to match up with the physical development. Bigger systems require better regulatory oversight — the costs of failure can be huge in a large system,” he says. That’s the dilemma. An integrated grid, working in sync, brings huge benefits. Problems are actually fewer. But because its more integrated, when problems do hit, the entire grid can go down. The costs of a single fault, or mistake are far higher. The government has repeatedly failed to meet its own Plan targets of power production. The shortfalls are due to order delays, slow environmental clearances, rehab issues, litigation, and the non-availability of key resources — coal and gas. Coal plants account for 54% of total capacity, hydropower for 22%. The private sector participation in power production, at 60% in 1947, witnessed a downward trend in the 60s and the 70s, mainly because of policy paradigm. In 1979, the share of state sector was as high as 82% of the total production. But, with big public sector entities such as NHPC, NTPC, PFC coming to the forefront, the Central sector’s share has moved up to 31%. First Private Power Plant: It was a 2 MW diesel plant set up in 1905 at Lahori Gate area in Old Delhi. Under the provisions of Indian Electricity Act 1903, an Englishman managed a license for his company M/s John Fleming to set up the plant. It was later converted into Delhi Electric Supply and Traction Company.

Grid Economics The system is supposed to incentivise producers to supply more at a time of heavy load. But as soaring fuel costs have boosted the cost of power, this ‘incentive effect’ has weakened sharply. Besides the physical infrastructure, the economics of the grid has changed sharply in the past decade. Buyers and sellers declare the power they are likely to draw from the grid, or supply to it, 24 hours in advance to enable engineers plan and distribute loads between different entities. Delhi for example might announce on Wednesday, that it will draw 2,300 MW in the morning of Thursday, increase that to 3,000 MW by the afternoon, and then gradually wind down in the evening. But if Delhi actually draws more than it said it would, that’s what’s called ‘overdrawing’. The system attempts to make states pay a price for doing so. When there is heavy demand in the system, and the frequency starts to drop, the cost of each unit of power starts rising automatically, making it more expensive to buy power, or making it more remunerative to supply more to the grid than a supplier earlier committed to. Alternatively, if a buyer chooses to cut demand at such a time of stress, he gets rewarded by being paid this so-called UI rate. And for sellers who over commit, but underdeliver, the UI rate becomes a penalty they have to pay. The aim is to bring demand and supply back in balance. Its a different matter that some states are in heavy default of their UI dues. But what regulators discovered a few years ago was that some states began intentionally scheduling more power than they actually needed. At times when they knew the grid was going to be overworked, they would tell the system they needed to draw say 3,500 MW, when they actually only needed 3,000 MW. Thus they got the credit for being responsible members of the system at a time of stress, while making a tidy sum of money in the process, from the UI benefits they received. Similarly producers had an incentive to announce they would supply far less power than they actually could, then supply more, benefiting in the process. So the regulator effectively capped the benefits that any player could get from the UI system, by replacing a single rate with a set of slabs. As a result, the per unit UI price has fallen from Rs 6.7 per unit in 2009-10 to Rs 4.09 per unit in 2011-12. Court rulings have also put paid to attempts to raise the UI rate. But over time, fuel costs and the cost of generating each extra unit of electricity have soared, leading to a scenario where the cost of generation of each unit is more than the UI rate. Put simply, the costs outweigh the returns, leading to a situation where in times of heavy demand, power producers would rather cut production below what they scheduled, and pay the UI penalty, rather than produce more power as the UI system was supposed to incentivise them to do. Chitkara argues that the shift to a so-called ancillary services market, mooted by POSOCO a few years ago is needed. Ancillary service providers are special producers, who can ramp up power supply very quickly to cope with shortfalls in supply in the grid.

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“Power companies get exactly what they want”: How Texas repeatedly failed to protect its power grid against extreme weather

Texas regulators and lawmakers knew about the grid’s vulnerabilities for years, but time and again they furthered the interests of large electricity providers.

This article is co-published with ProPublica, a nonprofit newsroom that investigates abuses of power. Sign up for ProPublica’s Big Story newsletter to receive stories like this one in your inbox as soon as they are published.

Also, sign up for The Brief , our daily newsletter that keeps readers up to speed on the most essential Texas news.

In January 2014, power plants owned by Texas’ largest electricity producer buckled under frigid temperatures. Its generators failed more than a dozen times in 12 hours, helping to bring the state’s electric grid to the brink of collapse.

The incident was the second in three years for North Texas-based Luminant, whose equipment malfunctions during a more severe storm in 2011 resulted in a $750,000 fine from state energy regulators for failing to deliver promised power to the grid.

In the earlier cold snap, the grid was pushed to the limit and rolling blackouts swept the state, spurring an angry Legislature to order a study of what went wrong.

Experts hired by the Texas Public Utility Commission, which oversees the state’s electric and water utilities, concluded that power-generating companies like Luminant had failed to understand the “critical failure points” that could cause equipment to stop working in cold weather.

In May 2014, the PUC sought changes that would require energy companies to identify and address all potential failure points, including any effects of “weather design limits.”

Luminant argued against the proposal .

In comments to the commission, the company said the requirement was unnecessary and “may or may not identify the ‘weak links’ in protections against extreme temperatures.”

“Each weather event [is] dynamic,” company representatives told regulators. “Any engineering analysis that attempted to identify a specific weather design limit would be rendered meaningless.”

By the end of the process, the PUC agreed to soften the proposed changes. Instead of identifying all possible failure points in their equipment, power companies would need only to address any that were previously known.

The change, which experts say has left Texas power plants more susceptible to the kind of extreme and deadly weather events that bore down on the state last week, is one in a series of cascading failures to shield the state’s electric grid from winter storms, ProPublica and The Texas Tribune found.

Lawmakers and regulators, including the PUC and the industry-friendly Texas Railroad Commission, which regulates the oil and gas industry, have repeatedly ignored, dismissed or watered down efforts to address weaknesses in the state’s sprawling electric grid, which is isolated from the rest of the country.

About 46,000 megawatts of power — enough to provide electricity to 9 million homes on a high-demand day — were taken off the grid last week due to power-generating failures stemming from winter storms that battered the state for nearly seven consecutive days. Dozens of deaths , including that of an 11-year-old boy, have been tied to the weather. At the height of the crisis, more than 4.5 million customers across the state were without power.

As millions of Texans endured days without power and water, experts and news organizations pointed to unheeded warnings in a federal report that examined the 2011 winter storm and offered recommendations for preventing future problems. The report by the Federal Energy Regulatory Commission and the North American Electric Reliability Corporation concluded, among other things, that power companies and natural gas producers hadn’t properly readied their facilities for cold weather, including failing to install extra insulation, wind breaks and heaters.

Another federal report released three years later made similar recommendations with few results. Lawmakers also failed to pass measures over the past two decades that would have required the operator of the state’s main power grid to ensure adequate reserves to shield against blackouts, provided better representation for residential and small commercial consumers on the board that oversees that agency and allowed the state’s top emergency-planning agency to make sure power plants were adequately “hardened” against disaster.

Experts and consumer advocates say the challenge to the 2014 proposal by Luminant and other companies, which hasn’t been previously reported, is an example of the industry’s outsize influence over the regulatory bodies that oversee them.

“Too often, power companies get exactly what they want out of the PUC,” said Tim Morstad, associate director of AARP Texas. “Even well-intentioned PUC staff are outgunned by armies of power company lawyers and their experts. The sad truth is that if power companies object to something, in this case simply providing information about the durability of certain equipment, they are extremely likely to get what they want.”

Luminant representatives declined to answer questions about the company’s opposition to the weatherization proposal. PUC officials also declined to comment.

Michael Webber, an energy expert and mechanical engineering professor at the University of Texas at Austin, said the original proposal could have helped in identifying trouble spots within the state’s power plants.

“Good engineering requires detailed understanding of the performance limits of each individual component that goes into a system,” Webber said. “Even if 99.9% of the equipment is properly rated for the operational temperatures, that one part out of 1,000 can bring the whole thing down."

Luminant defended its performance during last week’s deep freeze, saying it produced about 25% to 30% of the power on the grid Monday and Tuesday, compared with its typical market share of about 18%.

In a public statement, officials said the company executed a “significant winter preparedness strategy to keep the electricity flowing during this unprecedented, extended weather event.” They declined to disclose whether any of the company’s generating units failed during last week’s winter storms.

State officials are again promising reforms. Lawmakers have called on officials with the PUC and the Electric Reliability Council of Texas, which operates the power grid that spans most of the state, to testify at hearings later this week. Gov. Greg Abbott has called on lawmakers to mandate the winterization of generators and power plants, and Texas Attorney General Ken Paxton said he was launching an investigation into ERCOT and almost a dozen power companies, including Luminant. Separately, the PUC announced its own investigation into ERCOT.

Texas is the only state in the contiguous U.S. that operates its own electric grid, making it difficult for other regions to send excess power in times of crisis, especially when they are facing their own shortages, as they were last week. All other states in the Lower 48, as well as peripheral areas of Texas , are connected to one of two grids that span the eastern and western halves of the country.

Because Texas operates its own grid, the state isn’t subject to federal oversight by FERC, which can investigate power outages but can’t mandate reforms. Many energy experts say the very nature of the state’s deregulated electric market is perhaps most to blame for last week’s power crisis.

In Texas, a handful of mega-utilities controlled the distribution and pricing of the power they produced until two decades ago, when the Legislature shifted to a system where companies would compete for customers on the open market. Lawmakers said the change would result in lower power bills and better service, a promise that some experts and advocates say hasn’t been kept.

But under this system, power companies aren’t required to produce enough electricity to get the state through crises like the one last week. In fact, they are incentivized to ramp up generation only when dwindling power supplies have driven up prices.

Other states with deregulated power markets, including California, have made reforms and added additional safeguards after experiencing similar catastrophes.

“The fault on this one is at the feet of the Legislature and the regulators for their failure to protect the people rather than profits, the utility companies, rather than investing millions of dollars in weatherization that had been recommended in review after review of these kinds of incidents,” said Tom “Smitty” Smith, a longtime Texas consumer advocate and environmental activist. “They have chosen not to do that because it would be too expensive for the utilities and ultimately to the consumers.”

“We'll be opportunistic”

Three years after the 2011 storms, the Texas electric grid faced another major cold weather test when a polar vortex swept across the state. Freezing temperatures helped to knock out nearly 50 generating units at Texas power plants in the first week of 2014, bringing ERCOT perilously close to ordering rotating outages.

The event quickly faded from public attention because it was a near-miss that didn’t actually leave people without electricity or heat. But because the state had come so close to blackouts, the North American Electric Reliability Corporation, which has some authority to regulate power companies in the country, launched an investigation. The probe found similar problems to those that dogged the state after the 2011 storms, primarily equipment that failed to stand up to the freezing temperatures.

Despite the equipment failures that brought the electric grid to the brink of disaster, the polar vortex was a financial windfall for power-generation companies. In the months that followed the storm, some of the companies stressed to investors the financial benefits of the two days of cold weather and accompanying high energy prices.

“This business benefited significantly from increased basis and storage spreads during the polar vortex earlier this year,” Joe McGoldrick, an executive with Houston-based CenterPoint Energy, said in a November 2014 earnings call. “To the extent that we get another polar vortex or whatever, absolutely, we’ll be opportunistic and take advantage of those conditions.”

A CenterPoint spokeswoman said McGoldrick was the head of the company's gas marketing division, but has since left the company. She said that division was sold last year and had no role in responding to last week's storms.

"The remarks made in 2014 do not reflect the core values of CenterPoint Energy," Natalie Hedde, communications director, said.

Texas has relied on the principle that higher prices will spur greater power generation when the state needs it most, a structure that helps explain the persistence of blackouts, said Ed Hirs, a University of Houston energy expert.

In extreme weather events like last week’s freeze, prices per megawatt hour jumped from an average of around $35 to ERCOT’s maximum of $9,000.

Hirs said it’s in the power generators’ interest to “push ERCOT into a tight situation where price goes up dramatically.”

“They are giving generators incentive to withdraw service,” he added. “How else do you get the price to go up?”

Texans have already been hit with sky-high bills since last week’s event, with some climbing as high as $16,000 , according to The New York Times. At an emergency meeting Sunday, the three-member PUC ordered electric companies to suspend disconnections for nonpayment and delay sending invoices or bill estimates.

Power companies weren’t the only ones that saw the 2014 event more as a success story than a sign of weakness.

ERCOT concluded that operators “handled a difficult situation well” and took “prompt and decisive actions” that had prevented systemwide blackouts. In the “lessons learned” section of its final report, the agency promoted the continuation of its winterization site visits, which are not mandatory.

Winterization efforts were paying dividends in the form of fewer generating units falling victim to cold weather, the report stated.

Federal regulators agreed. During a meeting of the National Association of Regulatory Utility Commissioners in February 2014, a month after the storm, a top-ranking official from NERC stated that the response showed “industry is learning [and] using the resources and tools available to improve their preparations and operations of the grid during a significant weather event.”

But NERC’s investigation exposed problems that would bring Texas to a crisis point last week.

In the 2014 report, NERC methodically laid out how power-generating equipment failed during the cold snap, detailing 62 examples that included frozen circulating water that caused a supply loss and moisture in the air causing valves to freeze. In all, those cold-related failures were responsible for the vast majority of lost power during the event, the agency found.

The incident also highlighted the need to improve winter performance of natural gas pipelines, which NERC found hampered the ability of gas-fired power plants to generate electricity. The agency declined to comment, saying it doesn’t discuss investigations.

Natural gas and power generation are highly dependent on each other: Natural gas processing requires electricity, which may be produced in turn by burning natural gas.

Citing preliminary figures from ERCOT that show natural-gas-fired power plants performed worse than those fueled by other types of energy during this year’s power crisis, energy experts say producers and distributors of that fossil fuel played a major role in the catastrophe.

Natural gas producers and pipeline companies in Texas are regulated by the Railroad Commission.

R.J. DeSilva, a spokesperson for the agency, declined to say whether it requires natural gas producers and pipeline companies to weatherize wellheads or pipelines. He noted that poor road conditions made it impossible for crews from natural gas companies to inspect wells and said some producers reported “the inability to produce gas because they did not have power.”

Because so many homes are heated with natural gas, fossil fuel plays a much more central role in the winter than it does in the hot summer months.

“When all this began, millions of Texans wrapped their pipes to keep them from freezing, and the Railroad Commission didn’t order — has never ordered — the gas companies, the gas producers and gas pipeline companies … to wrap their pipes to protect them from freezing,” said Smith, the consumer advocate.

Failed legislation

After days of scrambling to address the myriad crises that pummeled his city last week, former longtime state Rep. Sylvester Turner — now mayor of Houston, the state’s largest city — had a message for his former colleagues.

“You need to dust off my bill, and you need to refile it,” the Democrat said during a press conference Friday, referring to legislation he filed in 2011 that would have required the PUC to ensure ERCOT maintained adequate reserve power to prevent blackouts. “Because it’s not about just holding hearings.”

The state’s deregulated market is to blame for the crisis, according to some experts who say the catastrophe shows that the system ultimately prizes profits over people. But some of the architects of the system are doubling down.

In a blog post published last week on the website of U.S. House Minority Leader Kevin McCarthy, former Texas Gov. Rick Perry suggested that the current disaster was worth it if it keeps rates low and federal regulators from requiring changes to the system.

“Texans would be without electricity for longer than three days to keep the federal government out of their business,” said Perry, who was governor from 2000-15 and presided over the early days of energy deregulation in Texas. “Try not to let whatever the crisis of the day is take your eye off of having a resilient grid that keeps America safe personally, economically, and strategically.”

Perry, who returned to his job on the board of Dallas-based pipeline giant Energy Transfer LP after serving as energy secretary in the Trump administration, received at least $141,000 in campaign contributions from Luminant’s former parent company, TXU Corp., between 2002 and 2009, when he was governor.

On Saturday, Turner warned about the soaring residential utility bills that Texans would be getting in the coming weeks. In 2012, when Turner was still a state representative, he wrote a letter to the then-chairman of the House State Affairs Committee, raising concerns about PUC rule changes that increased the price caps companies could charge for power to $9,000 per megawatt hour.

Those price caps remain the same today.

This time, Turner called on lawmakers to pursue substantive reforms that don’t simply “scapegoat” ERCOT, referring to the increasing calls for an investigation into the council, including by Abbott. “You must include the Public Utility Commission in these reforms because they provide direct oversight over ERCOT, and all of those commissioners are appointed by the governor,” Turner said.

In 2013, Turner attempted, unsuccessfully, to pass a measure that would have replaced the governor’s appointees on the PUC with an elected commissioner. The same year, he tried to salvage a measure that would have increased the administrative penalty for electric industry participants that violate state law or PUC rules.

The Texas Sunset Advisory Commission, which audits state agencies every 12 years to determine how they can better function or if they should be abolished, recommended in 2013 that the PUC exercise additional oversight of ERCOT, including a review and approval of annual budgets and annual review of “PUC-approved performance measures tracking ERCOT’s operations.”

One of the recommendations called on the PUC to increase the administrative penalty to $100,000 a day per violation, stating that the $25,000 daily penalty “may not be sufficient for violations that affect grid reliability, which can cause serious grid failures, such as blackouts.”

Lawmakers passed a bill during that year’s legislative session that adopted many of those recommendations, but the change in penalties was left out. An amendment by Turner to restore the higher fee in the bill failed.

Another former Democratic lawmaker who now leads a major Texas city similarly tried and failed to pass legislation that would bring greater accountability to the state.

In 2015, Dallas Mayor Eric Johnson , then a state representative, authored a bill that would have required state agencies, including the PUC, to plan and budget for severe weather using state climatologist data.

“It would have forced state agencies to prepare for an event like what just happened and to account for that in their agency plans,” Johnson said during a Thursday press conference addressing the crisis. “It was quite unfortunate, because we can’t say that it would have prevented this situation but certainly may have.”

Then, two years ago, facilities owned or controlled by utilities regulated by the PUC were exempted from legislation that requires the Texas Division of Emergency Management to “identify methods for hardening utility facilities and critical infrastructure in order to maintain essential services during disasters.”

The bill’s author, Republican state Rep. Dennis Paul , declined to comment. State Sen. Eddie Lucio Jr., who co-sponsored the measure, said he did not know why the PUC was exempted.

“Demanding answers”

For the past two decades, consumer groups have fought without success for a larger role in how the state manages its power grid. Giving residents a stronger presence on the ERCOT board would have forced the agency to take the lessons of extreme winter storms in 2011 and 2014 more seriously, said Randall Chapman, a ratepayer attorney and longtime consumer advocate.

“It would have changed things entirely,” Chapman said. “Residential consumers are the ones who have been through outages before. They are the ones with the broken water pipes, the ones freezing in their homes. They would be demanding answers.”

Chapman said the groups were stymied when the Legislature agreed to reserve only a single seat on the ERCOT board for a representative of residential consumers. In comparison, eight seats, including alternates, are filled by representatives of energy retailers, power generators and investor-owned utility companies.

“Residential consumers need a stronger voice over at ERCOT,” Morstad of AARP Texas said. “Decisions are made every week that affect the health and safety of millions of Texans. You need a strong voice there to call B.S. when companies aren’t following through on winterizing or other things that are critical to reliability of the electric system.”

In 2011, Texas Comptroller Glenn Hegar co-authored a bill while serving in the state Legislature that would have increased the size of the ERCOT board and allowed for more consumer representation. It didn’t pass.

Hegar said the failures displayed in the last week once again bring the significance of representation to the forefront.

“As a result of this extremely unfortunate event where so many people were out of power and now have damage to their homes and their businesses, there needs to be a broader range of representation on the board and to bring those voices as we move forward in trying to decide what we want our electric grid to be,” Hegar said.

Lexi Churchill and Perla Trevizo contributed reporting.

Disclosure: AARP Texas, the University of Houston, the University of Texas at Austin, CenterPoint Energy and the Texas Comptroller of Public Accounts have been financial supporters of The Texas Tribune, a nonprofit, nonpartisan news organization that is funded in part by donations from members, foundations and corporate sponsors. Financial supporters play no role in the Tribune’s journalism. Find a complete list of them here .

Editor's note: This story has been updated to include comment from CenterPoint Energy.

Correction, Feb. 24, 2021 at 3:20 p.m. : This story originally misstated the unit of measurement used in pricing electricity. Prices are in dollars per megawatt hour, not dollars per megawatt.

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How Texas’ Power Generation Failed During the Storm, in Charts

By Veronica Penney Feb. 19, 2021

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A huge winter storm slammed Texas earlier this week, knocking out power plants and leaving millions of residents without electricity and heat for days, amid freezing conditions.

A major part of the problem: The state’s power plants were not prepared for the frigid temperatures that accompanied the storm. Natural gas, coal and nuclear plants — which provide the bulk of Texas’ power in the winter — were knocked offline, and wind turbines froze, too.

Texas’ Power Generation Took a Hit During the Storm. Natural Gas Was Hit Hardest.

Power generation in Texas by fuel source

40,000 megawatt hours

Natural gas power, the state’s top source of electricity, took the biggest hit during the storm.

Natural gas

Major winter

storm starts

Coal, nuclear and wind power were also disrupted.

Natural gas power, the state’s top source of electricity, took the biggest hit during the storm .

megawatt hours

The state’s top source of electricity, took the biggest hit.

Conservative politicians and pundits were quick to blame wind farms and renewable energy more broadly for the power outages. But natural gas — which is a crucial power source when electricity usage peaks — was hit hardest.

“All sources underperformed expectations,” said Daniel Cohan, an associate professor of civil and environmental engineering at Rice University in Houston. “But far, far more than everything else combined were the shortfalls from natural gas.”

During the blackouts, the grid lost roughly five times as much power from natural gas as it did from wind. Natural gas production froze, and so did the pipelines that transport the gas. Once power plants went offline, they were not prepared to restart in the below-freezing conditions.

Demand for natural gas to heat homes and businesses also spiked, contributing to shortages. And high gas prices further disrupted generation, as operators who could not turn a profit took their plants offline.

Several coal plants and one of Texas’ four nuclear facilities were also knocked offline by cold temperatures.

The usually-balmy state does not require power plants to be winterized — “as we've painfully come to find out,” said Joshua Rhodes, a research associate at The University of Texas at Austin Energy Institute.

Just as generation was dropping from the grid, demand for electricity in Texas hit a record high for winter, rivaling demand seen during some of the hottest summer days. The Electric Reliability Council of Texas, which oversees the majority of the state’s power grid, reported that demand peaked at 69,000 megawatts on Sunday, surpassing its planned worst-case scenario.

Shortly after, the grid operator instructed utilities to begin controlled power outages to avoid longer-term damage.

How Power Generation Compared to Worst-Case Plans

This was ERCOT’s worst-case plan for peak demand and extreme outages.

Natural gas, coal, nuclear and hydroelectric power

On the evening of Feb. 14, power generation briefly surpassed ERCOT’s worst-case estimate.

But power generation dipped much lower from Feb. 14 through 17.

Solar power

Natural gas, coal, nuclear and hydro

In its seasonal risk assessment, ERCOT anticipated that “extreme” winter demand could spike as high as 67,000 megawatts statewide if conditions matched the 2011 ice storm that led to blackouts in parts of the state. Researchers estimate that had the grid been able to deliver it, power needed for heating would have pushed demand around 5,000 megawatts higher earlier this week.

Governor Greg Abbott blamed the blackouts on solar and wind energy , but those power sources were not major players in the state’s emergency plans.

Dr. Cohan said the state's emergency scenario wasn't so far off in some of its predictions, but it failed to anticipate the scale of outages caused by this winter storm, particularly among natural gas power plants.

“None of their scenarios envisioned that we could possibly have over 30,000 megawatts of outages at the same time,” he said. “That’s more than double their worst-case.”

Experts are still assembling a full picture of what contributed to the power failures and lawmakers have called for an investigation into ERCOT’s preparedness and handling of the situation.

An earlier version of a graphic with this article misstated the source of the chart’s data. It was from the U.S. Energy Information Administration, not the U.S. Energy Information System. 

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• Published: 01 March 2024

Increasing the resilience of the Texas power grid against extreme storms by hardening critical lines

• Julian Stürmer 1 , 2 ,
• Anton Plietzsch   ORCID: orcid.org/0000-0001-7480-2493 1 , 3 ,
• Thomas Vogt   ORCID: orcid.org/0000-0002-2135-4436 1 ,
• Frank Hellmann   ORCID: orcid.org/0000-0001-5635-4949 1 ,
• Jürgen Kurths 1 , 4 , 5 ,
• Christian Otto   ORCID: orcid.org/0000-0001-5500-6774 1 ,
• Katja Frieler   ORCID: orcid.org/0000-0003-4869-3013 1 &
• Mehrnaz Anvari   ORCID: orcid.org/0000-0001-6643-9508 1 , 6  

Nature Energy volume  9 ,  pages 526–535 ( 2024 ) Cite this article

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• Complex networks
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• Energy security

The Texas power grid on the Gulf Coast of the United States is frequently hit by tropical cyclones (TCs) causing widespread power outages, a risk that is expected to substantially increase under global warming. Here we introduce a new approach that combines a probabilistic line failure model with a network model of the Texas grid to simulate the spatio-temporal co-evolution of wind-induced failures of high-voltage transmission lines and the resulting cascading power outages from seven major historical TCs. The approach allows reproducing observed supply failures. In addition, compared to existing static approaches, it provides a notable advantage in identifying critical lines whose failure can trigger large supply shortages. We show that hardening only 1% of total lines can reduce the likelihood of the most destructive type of outage by a factor of between 5 and 20. The proposed modelling approach could represent a so far missing tool for identifying effective options to strengthen power grids against future TC strikes, even under limited knowledge.

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Modern societies depend heavily on reliable access to electricity. Power outages have the potential to disrupt transportation and telecommunication networks, heating and health systems, the cooling chain underpinning food delivery and more 1 , 2 , 3 . Depending on the cause of power outages and the amount of physical damages to infrastructures, the recovery of the electric network and the social infrastructures dependent on it, often takes days or even months 4 . Such outages are often driven by extreme weather events. In Norway 90% of all overhead line failures are caused by extreme weather, which involves strong winds, icing and lightning strikes 5 . In February 2021, a winter storm in Texas led to outages that in turn caused a breakdown of the gas supply and thus the heating sector 6 , 7 , 8 . Further, tropical cyclone (TC) impacts can be particularly devastating. In the summer months, the Gulf Coast and the East Coast of the United States are frequently hit by TCs that entail widespread outages and costs of billions of dollars, as detailed in the State of Reliability reports of the North American Electric Reliability Corporation 9 , 10 . For example, Hurricane Ike hitting southeast Texas on 13 September 2008 destroyed around 100 towers of high-voltage transmission lines and cut off electric power for between 2.8 million and 4.5 million customers for weeks to months 11 , 12 . On 29 August 2021, Hurricane Ida made landfall in Louisiana and destroyed major transmission lines delivering power into New Orleans, causing power outages that affected more than a million customers 13 .

Reliability against line failures in high-voltage power grids is usually discussed in terms of the N-1 (rarely also N-2) security of the system, that is, the ability of the system to stay fully functional upon the failure of one or two elements 14 . When a line fails, the power flow automatically reroutes through the intact grid. To avoid damages from overloads caused by the rerouting, highly loaded lines are removed by automatic protection devices or, in some cases, manually from the network. These secondary failures of lines can trigger a cascade 15 , 16 , 17 , 18 , 19 , 20 , 21 of additional failures. If N-1 security is given, single line failures do not trigger such cascades. However, multiple concurrent failures—as probably occurred in the US–Canadian blackout in 2003 22 and as are typical for TCs, which cause widespread primary damages—can trigger substantial secondary failures. These cascades play an important role in amplifying the resulting blackouts 23 .

The N-1 approach to system resilience cannot be scaled to such events. Even an exhaustive N-5 security assessment is infeasible, and major TCs often damage tens or even hundreds of lines. These damages cannot be fully mitigated by an electric network. N-1 security is typically studied by simulating the reaction of the system to every possible failure scenario. As the number of these scenarios scales exponentially with the number of failures, it is computationally infeasible to consider all possible scenarios for larger events.

Several earlier studies have analysed the spatial and temporal patterns of lines destroyed by TCs using statistical methods such as negative binomial regression models 24 , 25 and non-stationary Poisson processes 26 . However, these studies did not consider the impact of these damages on the power grid. In an effort to address this gap, machine learning techniques were applied to predict power outages caused by various types of storm on a 2-km grid 27 , but this approach does not provide information on how these outages occur or how they can be prevented.

TC-induced failures affecting large numbers of lines have been recently studied from a detailed mechanistic perspective 28 , 29 , 30 , 31 . Aiming to capture the primary damages well, these works focus on the development of sophisticated line failure models. The TC impacts on the power grid are then described by removing all damaged elements at once or in large batches and using optimal dispatch models to estimate how much load such a damaged system can still provide. This requires the (rather strong) assumption of a perfect, omniscient system operator 31 , 32 , 33 . A further crucial limitation of this approach is that the optimization in these models ensures that operational bounds are never violated. Thus, these models do not capture failure cascades.

Here we go beyond the existing literature by introducing a co-evolution modelling approach. It combines a spatio-temporal stochastic line failure model with a stepwise modelling of the resulting power outages, accounting for automatic or manual line protection mechanisms and unavoidable overproduction. This approach allows us to (1) consider a large number of potential realizations of line failures along the TC’s tracks and (2) assess cascading secondary failures. Further, critical power lines in the high-voltage transmission system whose protection could most effectively prevent cascades and the associated widespread power outages can be identified. This is especially interesting from a climate change perspective because the proportion of very intense TCs in the North Atlantic is projected to increase under global warming 34 , 35 , 36 .

Modelling cascading losses in the Texas grid

Our co-evolution modelling approach explicitly captures the dynamical interplay of an extreme wind event with the power grid by temporally resolving both the primary wind damage and the resulting cascades of secondary failures. We will use this approach to study a selection of seven historical TCs that impacted the Texas power grid between 2003 and 2020. These cover different types of trajectory and intensity (Supplementary Note 1 and Supplementary Figs. 1 and 2 ). The selected storms include major hurricane-strength TCs, such as hurricanes Ike and Harvey that made landfall in Texas in September 2008 and August 2017, respectively, and destroyed numerous high-voltage (115–500 kV) transmission lines (about 106 (ref. 37 ) and 97 lines 38 were reportedly destroyed by Harvey and Ike, respectively) (Fig. 1a ). Further, we consider five TCs, that is, Hurricanes Claudette (2003), Hanna (2020) and Laura (2020) and Tropical Storms Erin (2007) and Hermine (2010) that caused less damage to the Texas grid 39 , 40 , 41 , 42 , 43 , either because they were substantially weaker (for example, Erin and Hermine) or because they primarily affected neighbouring states (for example, Hanna, which made landfall in Louisiana). The TCs considered here affected different parts of the Texas grid; Claudette, Erin and Hanna continued to move westward after landfall and affected the southern and western parts of the grid. The rest of the considered TCs were steered northward by the Coriolis effect after landfall and mainly affected the western parts of the grid 34 .

a , Probability distribution ρ of the total number of wind-induced line failures N p as generated by the probabilistic line failure model for each of the seven recent TCs hitting Texas. The storms are categorized according to the Saffir–Simpson scale (number in brackets behind the storms’ names), and tropical storms that did not reach hurricane strength at landfall are denoted by TS. TCs are sorted according to the means of the distributions μ p , which are indicated as solid vertical lines. The mean numbers of damaged lines for Hurricane Harvey (105) and Hurricane Ike (90) are very close to the reported numbers in the high-voltage (115 kv to 500 kV) transmission grid (106 for Harvey and about 97 for Ike). b , Probability distribution of the associated total power outage P out after TC passage. The dashed vertical lines p r out indicate the reported power outages listed in Supplementary Table 1 , and the solid vertical lines P out represent the means. The inset highlights large cascading failures that can also occur for the less impactful TCs. Methods provides the model parameters used in the simulations. Each storm is presented with the same colour in a and b .

When a TC hits a power grid, lines do not collapse simultaneously but sequentially over the hours or days of the TC’s passage. Making use of the chronological order of the line destructions, we divide each considered TC landfall scenario into a sequence of 5-minute time steps. In most of these individual steps, only one additional line fails, that is, these situations can be addressed by power distribution models also used for N-1 or N-2 security assessments. At this resolution, it is also reasonable to assume that cascades of secondary failures have run their course before further lines are destroyed by the TC 44 , 45 (further discussion regarding the temporal resolution is in Methods and Supplementary Note 9 ).

We solve individual scenarios by representing the Texas power grid in a direct current (d.c.) power flow approximation with conservative load balancing assumptions ( Methods and Supplementary Notes 3 and 4 ). Our co-evolution approach allows us to account for the ‘path dependency’ of the solution: every time a line collapses, overload protection can cause more lines to fail. At the same time, control mechanisms are immediately activated to restore energy balance and limit the effect of the failures (Supplementary Note 4 ). If an islanded part of the grid cannot be rebalanced, this part and all lines in it are considered failed. Primary damages that occur later along the TC track then meet a partially destroyed, rebalanced grid. Thus, the effect of later failures can be more, or even less, intense. It is the resilience of these intermediate, partially destroyed states that ultimately decides whether the impact of the TC is amplified by secondary failures.

Unfortunately, neither detailed information about the topology of the exposed power grid, nor about the exact number and the location of power lines destroyed by the TCs, nor the type of consumers who lost power is publicly accessible. Here we use a synthetic model of the Texas power grid introduced by Birchfield et al., which includes four different high-voltage levels, 115, 161, 230 and 500 kV (ref. 46 ) ( Methods and Supplementary Fig. 2 ).

The employed probabilistic line failure model is forced by the modelled historical wind fields of the studied TCs ( Methods and Supplementary Note 2 ). The probability of line failure is described in terms of wind speeds and allows generating a large sample of temporally resolved realizations of line failure sequences, here 10,000 sequences per storm. These scenarios differ greatly with regard to the individual failed lines and thus cover a wide range of plausible scenarios (Fig. 1 ). In the default setting considered here, we assume a homogeneous base failure rate for all transmission lines. This is our main calibration parameter and is tuned to reproduce observed numbers of damaged lines and match power outages (Fig. 1a,b and Supplementary Note 5 ). By looking at five additional weaker storms, we found that our modelling results are aligned with the inclusive reports of power outages and rare damages in the transmission grid (Supplementary Note 5 and Supplementary Fig. 10 ).

The structure of outages

Caused by strong winds, primary damages are concentrated in areas close to the centre of the storm, and the number of primary line failures follows a Poisson binomial distribution. However, for all seven TCs, cascading secondary failures due to overload protection and unavoidable islanding substantially increase the total number of affected lines and can lead to large 20-GW to 30-GW power outages (Fig. 1b ). As the most populous city in Texas and a major load centre, the disconnection of Houston from the electrical network causes the disconnection of a huge number of consumers. Many generators providing energy to the major load centres are clustered in the west of Texas. The largest events feature both of these regions going offline (Figs. 2d and 3 , Supplementary Note 5 and Supplementary Fig. 9 ). Smaller events (Figs. 2c and 3a,d,g ) tend to show damage patterns more localized to the storm tracks. The resulting distributions of total outages are heavily multimodal for all TCs (Fig. 1b ).

a , Schematic variation of power outage P out and total energy not supplied E out (red area) before (Pre-contingency), during (Hurricane phase) and after (Restoration phase) the TC passage (loosely based on ref. 38 ). b , Summary of all realizations of power outage trajectories simulated for Hurricane Claudette. Trajectories fall into two categories: those that aggregate damages gradually over time (Type I) and those that include a large cascade (Type II). c , d , States of the power grid at the beginning and the end of the TC passage for two exemplary Type I and Type II trajectories highlighted in panel b . Lines shown in black are destroyed (primary damages) or deactivated (secondary failures) during TC passage (Supplementary Video 1 shows the structure of failures during the simulation). The colour code of the remaining lines indicates relative line loading, with darker colours indicating higher relative loads. Blue dashed lines indicate the track of the storm centre and blue arrows denote the direction of the storm’s movement. Blue shaded circles indicate snapshots of the storm’s wind field, with darker colours indicating higher wind speeds. Methods and Supplementary Note 5 provide the specification of the model parameters and an animation of the cascading failures and load dynamics during the passage of Claudette.

a – i , Probability \({p}_\mathrm{e}\!^{\mathrm{out}}\) that the failure of a given power line is involved in three different modes of the power outage distribution for Harvey ( a – c ), Claudette ( d – f ) and Hanna ( g – i ). S represents the southern community and W the western region in Texas. Modes are indicated by the insets, and the exact ranges of considered power outages are shown below these insets. Probability \({p}_\mathrm{e}\!^{\mathrm{out}}\) is calculated as the number of realizations having a total outage within the specified ranges in which the considered line fails, divided by the total number of realizations in the specified range. The different elements of the Texas power grid are coloured according to their respective outage probability. The probability distributions shown in the insets are identical to those shown in Fig. 1b .

Large outages do not accumulate gradually over time. Instead the disconnections of the load centre of Houston and the production centre in the Northwest occur suddenly during one large cascade (Fig. 2b ). Spatially, it is noteworthy that these cascading failures can lead to outages in areas not directly affected by the storm (Fig. 4 provides a comparison of the spatial distribution of primary damages and cascading, secondary failures caused by Hurricane Harvey). For instance, during Harvey, Hanna and Claudette, the northwestern section is not reached by strong winds (Fig. 3 ).

Transmission lines are coloured according to their most probable line status. Blue lines are most likely directly damaged by strong winds (primary damages), whereas red lines are most likely deactivated due to cascading secondary failures. Grey lines have a higher probability of remaining operational than failing due to primary damages or secondary failures (Supplementary Note 5 provides details on the model calibration).

To test the robustness of our results with regard to the details of the model calibration, we repeated the simulations for a wide range of failure rates and randomized the failure rates for each line (Supplementary Notes 5 and 6 ). Further, we used a large ensemble of 10,000 realizations for each storm to ensure that it represents a wide range of plausible grid states. We found the main characteristics of the cascading failure dynamics, such as the occurrence of sudden large cascades and multimodal outage distributions, to be robust (Supplementary Table 3 ). For instance, across all parameter settings, we find Harris County to be the most vulnerable part of the Texas grid to TC impacts, in line with a recent analysis of the National Centers for Environmental Information 47 . These findings suggest that our main results are independent of the details of the line failure model and its calibration.

Increasing resilience

We find that large cascades are triggered by the failure of individual lines. This suggests that hardening those lines that are likely to trigger cascades (for example, by replacing them with underground cables) could be an effective resilience-building strategy. To identify the critical lines that should be hardened, we define a priority index as the probability that the wind-induced damage of this specific line triggers a large cascade, that is, a cascade that increases the outage by more than 15 GW, averaged over all seven TCs (equations ( 2 ) and ( 4 ) in Methods ). For most transmission lines, the priority index is zero, but 8% of them have a value above 10 −4 , and 20 lines (about 1% of the grid) have a priority index above 10 −3 .

For comparison, we also calculate the priority index based on a conventional, static model in which all damages are applied at once. The static index of a line is then defined, analogously to the priority index, as the conditional probability of a large outage given that the line is in the set of lines damaged by a TC ( Methods and Supplementary Note 7 ). According to both the co-evolution model and the static model, the critical lines are mostly located in and around Houston (Fig. 5a,b ). However, the co-evolution model also identifies several critical lines not in the area that are not among those identified by the static model.

a , The 20 lines of the Texas power grid with the highest priority index (equation ( 4 )) obtained from the static model (orange lines), the co-evolution model (blue lines) and both models (green lines). b , Detail enlargement (black rectangle in a ) of Houston and Harris County, which contain most of the critical lines. c , Power outage distributions of Hurricane Harvey as a function of the number of protected critical lines, as obtained by the co-evolution model (blue) and the static (orange) model. d , Relative reduction of the probability of large power outages as a function of protected lines as obtained from the static model (lines) and the co-evolution model (dots) for the three hurricanes Harvey (blue), Ike (orange) and Claudette (green).

To estimate how well the models identify critical lines, we consider the relative reduction in the probability of large power outages that can be achieved by hardening the lines identified. We order the lines according to their priority index and evaluate the impact of the TC on the system after hardening the most critical one to 20 lines. The probability of large power outages is reduced smoothly when the number of hardened lines is increased. After hardening the 20 most critical lines identified by the co-evolution model, the probability of large-scale outages is reduced by a factor 5 to 20. Smaller storms rarely trigger large power outages and cascading failures anymore, and the probability is dramatically reduced for the most damaging storms Harvey and Ike (Fig. 5 and Supplementary Fig. 12 ). The power outage distributions resulting from Harvey and Ike are shifted from the second peak (around P out  ~25 GW) to the first peak with P out  ≤ 10 GW (Fig. 5c ).

The level of outage reduction reached by hardening the lines according to the priority index derived from the co-evolution model is generally higher than the protection of the same number of lines selected according to the priority index derived by the static model (Fig. 5d ). The static model allows identifying some of the most critical lines (Supplementary Note 7 ), but the marginal reduction in large outage probability saturates already after 6–10 lines. For the co-evolution model, additional hardening continues to be effective until at least 20 lines (Fig. 5c,d ). This demonstrates that the latter, with its detailed picture of the partially destroyed states, reveals genuine and critical information for increasing the resilience of the system. These results are robust when assuming randomized failure rates (Supplementary Note 5 ).

A co-evolution model of the Texas power grid was introduced as an efficient approach to temporally resolve the line failures and secondary grid outages induced by TCs. The model can describe in considerable detail how cascading secondary failures amplify the impact of these storms by triggering large-scale power outages. It thus can be used to identify critical lines that should be protected to effectively increase the system’s resilience and prevent the most severe outages.

Our model goes well beyond the state of the art, as represented by statistical and economic models that can capture only a static picture of the event and the network 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 , 33 . We have shown that such static approaches do not allow the identification of all critical lines during extended events. Instead, we see that criticality is revealed by observing the system in a large ensemble of partially destroyed states, that is, by ‘tracking’ the destruction of the system and associated power outages and failed lines. We expect that this co-evolution approach will also be a promising tool to understand and protect other grids exposed to spatio-temporally extended extreme events. However, this study is subject to several limitations. First, TC damages do not occur due to wind alone and they do not exclusively damage transmission grid lines. Flooding plays a major part in storm damages, and damages at the distribution level to substations and to transformers are not directly accounted for. Further, power grid operators do anticipate and prepare the system for incoming storms and can react to conditions on the ground beyond the simple rebalancing we use here. To fully understand the societal impact of an outage, it is also crucial to understand how quickly the system can be restored afterward.

Second, we did not have access to the real topology and parameters of the Texas grid. In accordance with established research practice, we used a high-quality surrogate model that is expected to reflect the electrical and spatial characteristics of the Texas grid well 46 , 48 . Still, it is clear that when comparing TC impacts on the surrogate and on the real grid, we should expect differences. Further, given that only very few intense TCs have made landfall in Texas in the last decades and given the intrinsic stochasticity of the damages, a precise match with historic conditions is not an appropriate goal and would very probably lead to overfitting.

Third, to take these data limitations into account, the line failure model we introduce here is intentionally kept rather abstract. Mathematically, the only assumption is that the failure rate of a transmission line segment is proportional to the square of the average wind speed and its length. The proportionality factor is determined by calibration of the overall model and thus will reflect other kinds of failure that occur as well to some degree. The overall model should not be interpreted as a fully realistic mechanistic model of the storm event but a trade-off that successfully reveals structural aspects of the vulnerability of power grids in the presence of considerable modelling and data uncertainties.

Whereas the model based on wind speeds and historical TC tracks already identified crucial structures in the grid, the co-evolution approach could naturally be extended to more sophisticated models and broader settings. A crucial first step would be to apply this method on the real grid topology of Texas. Another important avenue of broadening the model is to account for TC-induced flooding (coastal flooding, pluvial or fluvial flooding) and associated destructions. These may follow a different temporal pattern, where the adequacy of the approach proposed here has to be newly tested. This would also provide a first step towards an assessment of genuine compound events in which several stresses for the grid coincide.

Further, combining the developed priority index to identify critical lines with additional information about the cost of a reinforcement of the considered lines could also enable the identification of the most cost-efficient way to reduce the probability of power outages above a critical limit to an intended value (Supplementary Note 6 ).

Finally, as the proportion of very intense hurricanes in the North Atlantic is projected to increase under global warming 49 , an important aim for future research is to (1) map out the associated changes in TC risk to the Texas power grid (and other vulnerable grids) and (2) assess the benefits and limitations of adaptation measures. This can be achieved by driving the co-evolution model with ensembles of synthetic tracks of future TCs at different levels of global warming 35 .

Power grid data of Texas

For the study we used the publicly available power grid test case ACTIVSg2000 (ref. 48 ) that covers the area of the so-called ERCOT Interconnection, which supplies 90% of the electricity demand in Texas 48 . The test case is synthetic but resembles fundamental properties of the real grid, such as the spatial distribution of power generation and demand 50 . It encompasses 2,000 buses with geographic locations, 3,116 branches (both transmission lines and transformers) and covers four different voltage levels. The test case comes with all required electrical parameters ranging from the power injections of buses to the power flow capacities of transmission lines and transformers. The flow capacities C ij play a particularly important role for the simulation of cascading failures as they determine the amount of power that can be transported by individual lines and transformers without potentially damaging the equipment.

Historical tropical cyclone data

TC storm tracks are extracted from the International Best Track Archive for Climate Stewardship (IBTrACS) 47 , 51 as time series of cyclone centre coordinates along with meteorological variables such as maximum sustained wind speeds and minimum pressure on a 3–6 h snapshot basis. From the track records, we compute time series of wind fields within a radius of 300 km from the storm centre using the Holland model for surface winds, as implemented in the Python-package CLIMADA 36 , 52 , at a spatial resolution of 0.1° (approximately 11 km) and a temporal resolution of 5 minutes. The intensities of the considered storms are also shown along the respective tracks in Supplementary Fig. 1 whereas other properties of the storms are listed in Supplementary Table 1 .

Transmission line failure model

To model wind-induced failures of transmission lines, we first differentiate between overhead transmission lines and underground cables in the power grid of Texas. Following Birchfield et al., we analyse lines that are shorter than 12.875 km (8 miles) and connect a total load of at least 200 MW as underground cables 46 . All other lines are assumed to be overhead transmission lines. The latter are then divided into segments of length l  ≈ 161 m, which corresponds to the average distance between transmission towers in Texas 53 . We model failure of segments as a Poisson process with a time varying rate r ( v t ) depending on the average wind speed experienced by a segment. A similar mathematical setup is considered in ref. 27 ; however, instead of trying to model the spatial characteristics of the failure rates, they aggregate over space, arriving at a purely temporal model. To illustrate the implications of this mathematical form of the failure model, we quickly review some properties of the Poisson process for a constant rate r . For this process the time to failure is distributed as \(r{\rm{e}}^{-{r\tau}}\) and the mean time to failure is 1/ r . The probability for the line to have failed by time τ is just \(1-{\rm{e}}^{r.\tau }\) . If rτ is small the probability is well approximated by r.τ . To simulate this process, we discretize it in time steps τ . As the wind field is changing slowly relative to our time steps, we simply fix the rate during the time step to its initial value. Then the probability of failure of a line segment k experiencing winds of v t during a step of duration τ is given by:

According to equation ( 1 ), the probability of simultaneous failures of different line segments increases with time step size τ . A further discussion of the role of the time resolution can be found in Supplementary Note 9 . To obtain a failure model we fix the functional dependence of r on v and then calibrate the overall rate on the real data. The line failure model established by Winkler et al. assumes that the failure probability is proportional to the ratio of the wind force and the breaking force 54 . According to the guidelines published by the American Society of Civil Engineers 55 , the wind force \({F}_{k}\!^{\mathrm{wind}}\left(v\right)\) is quadratic in v , and we adopt this dependence for our failure rate, arriving at the failure model \({p}_{k}\left({v}_\mathrm{t}\right)={c}_{\mathrm{cal}}{v}_\mathrm{t}\!^{2}\tau\) . The c cal is calibrated to reproduce the number of transmission line outages for Harvey and Ike (Supplementary Note 5 ).

To make sure that our calibration arrives at plausible values, we insert the physical constants from Winkler et al. to arrive at the form of the failure model:

The parameter F brk represents the breaking force 56 . Then the calibration is done in terms of r brk , the failure rate when the wind field equals the breaking force. The full wind force equation and the meaning and the values of all parameters can be found in Supplementary Note 2 and Supplementary Table 2 . In all figures shown in the main text, r brk  = 0.002 h −1 , which we consider plausible, because even during strong storms lasting hours, most transmission lines do not fail. Finally we observe that the calibrated model reproduces power outages in our simulations for all storms considered (Supplementary Note 5 ).

To rule out a strong dependence on details of this model, we also consider a model with a random local variation in failure probability of line segments \({p}_{k}\left({v}_\mathrm{t}\right)={c}_{\mathrm{cal},\mathrm{random}}{v}_\mathrm{t}\!^{2}\tau\) , where c cal,random is drawn uniformly in a plausible range (Supplementary Note 5 ).

Cascading failure model

Wind-induced line failures can trigger cascades of overload failures in the branches of the power grid. As cascading failures typically evolve on smaller timescales than the temporal resolution τ of the wind field, we can assume a timescale separation. When the network topology is changed by a primary damage event, the power flows P ij on the branches are rerouted using the d.c. power flow model

Here P i is the net active power injection at the buses, θ i is the bus voltage angle and B ij is the element of the nodal susceptance matrix that comprises the network topology. More details on the assumptions of the d.c. power flow model and the software used can be found in Supplementary Note 3 . If the new state of the network exhibits any overloaded branch (| P ij | >  C ij ), they are deactivated and the process is repeated. When the network reaches a state without overloads, the algorithm advances to the next primary damage event. When a load or generator gets disconnected or the grid is split into several parts, the global active power balance has to be restored in each network component. Motivated by a primary frequency control in real power grids, we adjust the outputs of generators uniformly, while respecting their output limits defined in the dataset. Whenever the generator limits do not allow us to fully restore the global active power balance, we either conduct a uniform minimal load shedding or consider the blackout of the whole network component in the case of an unavoidable overproduction. The details of the algorithm are explained in Supplementary Note 4 , and the code is available from https://doi.org/10.5281/zenodo.10077864 .

Quantification of power outages

We use the following three different quantities to track the power outages arising in our simulations: (1) \({P}_{L}\left(t\right)\) denotes the total supplied load ( L ) at the end of each time step ( t ), that is, after the cascading algorithm finished, respectively; P L is the power outage trajectory. It is calculated by adding up the demands of all connected loads across all islands that exist at the given time. Because our co-evolution model assumes that cascading failures happen instantaneously, \({P}_{L}\left(t\right)\) represents a step function for each individual TC scenario as shown in Fig. 2b . We have simulated 10 4 scenarios for each TC. (2) Any cascading failure that actually causes a loss of supplied load results in a vertical transition of size \({\Delta P}^{\mathrm{out}}\) in \({P}_{L}\left(t\right)\) (Fig. 2a,b ). One such transition is annotated with \({\Delta P}^{\mathrm{out}}\) for the highlighted scenario in Fig. 2b . (3) All cascading failures that are triggered in a given TC scenario lead to a final power outage \({P}^{\,\mathrm{out}}={P}_{L}\!^{\mathrm{init}}-{P}_{L}\!^{\mathrm{final}}\in \left(0\,\mathrm{GW},\,67.1\,\mathrm{GW}\right)\) . The interesting statistics of P out are shown and discussed in Fig. 1b .

Identification of critical lines

We identify critical overhead transmission lines by means of a priority index defined for each line ( i , j ) as

where H denotes the set of considered TCs (seven TCs in this study) and \({p}_{{ij}}\!^{\left({II}\,\right)}\) is the probability of a large cascade being triggered by the wind-induced failure of line ( i , j ). More specifically, we call cascades large if their associated power outage \({\Delta P}^{\mathrm{out}}\) lies above an empirical threshold of 15 GW (indicated as Type II in Fig. 2b and Fig. 5d ). Equation ( 4 ) includes an averaging over all considered TCs to discern lines that are critical for multiple TCs. This allows us to propose line reinforcements that increase the resilience not only for a particular TC. Some properties of the 20 most critical lines found in this study are listed in Supplementary Table 3 . Figure 5a,b shows the location of these lines and demonstrates that reinforcing them indeed increases the resilience of the power grid substantially. More details of the critical lines and a possibility to incorporate economic considerations into our analysis are discussed in Supplementary Note 6 .

Baseline method

Here we apply the static model as a baseline method. By static model (Supplementary Note 7 ), we mean that all primary damages occur simultaneously and then the d.c. power model along with global active power balance are activated once to bring back the energy balance in the system and to evaluate the total final power outages P out . As discussed in Supplementary Note 9 , the final power outage distributions are independent of the time resolution of the wind field, however the primary damages leading to large outages, that is, 20 GW to 30 GW, can be completely different ones. To indicate the critical lines obtained from the static model, first, we separate all scenarios in which \({P}^{\,\mathrm{out}} > 15\,\mathrm{GW}\) . Then we use equation ( 4 ) to calculate the priority index of the primary damages leading to large cascades. The top 20 lines with the highest priority index have been listed in Supplementary Table 4 . As seen in this table, except for the six lines highlighted in red, the other lines are completely different from lines obtained from the co-evolution model.

Data availability

The observed TCs from IBTrACS 47 , 51 are distributed under the permissive World Meteorological Organization open data license through the IBTrACS website ( https://www.ncei.noaa.gov/products/international-best-track-archive ) and can be directly retrieved through the CLIMADA 36 , 52 platform. The electrical network data are openly available from Texas A&M University’s power grid test case repository ( https://electricgrids.engr.tamu.edu/electric-grid-test-cases/activsg2000/ ).

Code availability

All code necessary to reproduce the findings in this work is openly available. The time-dependent wind fields are computed using the open-source platform CLIMADA 35 , 48 . The implementations of the transmission line failure and the d.c. power model are available from https://doi.org/10.5281/zenodo.10077864 and https://gitlab.pik-potsdam.de/stuermer/itcpg.jl .

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Acknowledgements

This project has received funding from the Deutsche Forschungsgemeinschft (DFG) through the projects ExSyCoGrid (DFG HE 6698/4-1, A.P., F.H.) and CoCoHype (DFG KU 837/39-2, J.S, M.A., F.H., J.K.), the German Academic Scholarship Foundation and the German Federal Ministry of Education and Research (BMBF) under the research projects QUIDIC (01LP1907A, C.O., T.V., K.F.) and CoNDyNet 2 (BMBF grant number 03EF3055F, M.A., A.P., F.H., J.K.).

Open access funding provided by Fraunhofer-Gesellschaft zur Förderung der angewandten Forschung e.V.

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Potsdam Institute for Climate Impact Research, Potsdam, Germany

Julian Stürmer, Anton Plietzsch, Thomas Vogt, Frank Hellmann, Jürgen Kurths, Christian Otto, Katja Frieler & Mehrnaz Anvari

Institute for Theoretical Physics, TU Berlin, Berlin, Germany

Julian Stürmer

Fraunhofer Research Institution for Energy Infrastructures and Geothermal Systems, Cottbus, Germany

Anton Plietzsch

Institute of Physics and Astronomy, University of Potsdam, Potsdam, Germany

Jürgen Kurths

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Stürmer, J., Plietzsch, A., Vogt, T. et al. Increasing the resilience of the Texas power grid against extreme storms by hardening critical lines. Nat Energy 9 , 526–535 (2024). https://doi.org/10.1038/s41560-023-01434-1

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Connecting Past and Future: A History of Texas’ Isolated Power Grid

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Julie A. Cohn

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Juli A. Cohn, "Connecting Past and Future: A History of Texas’ Isolated Power Grid" (Houston: Rice University’s Baker Institute for Public Policy, December 1, 2022),  https://doi.org/10.25613/dpmy-r389 .

As Winter Storm Uri wreaked havoc across Texas in February 2021, pundits, politicians and the public reflected on the unique status of the state’s isolated electric power grid. “Texans would be without electricity for longer than three days to keep the federal government out of their business,” former Texas Gov. Rick Perry reportedly told Rep. Kevin McCarthy of California. [1] “It’s all politics,” a former executive of the North American Electric Reliability Corporation quipped to me. [2] And even today, a Wikipedia page on the Texas power grid states, “The Texas Interconnection is maintained as a separate grid for political, rather than technical reasons.” [3] These explanations reflect some of the mythology around electric power in Texas, and some truth. Dwelling on Texas exceptionalism as the primary reason for maintaining an isolated system, however, obscures the legitimate reasons power companies chose to stay in intrastate commerce in the past, and limits consideration of the real opportunities for and challenges of building new interstate links today.

This brief examination of the history of Texas power companies and their decisions regarding these links — called interconnections — offers several important points:

• Texas companies were not the only ones that chose to avoid federal regulation in the wake of the 1935 Public Utility Holding Company Act (PUHCA).
• Several Texas companies retained their interstate links despite the introduction of federal oversight in 1935.
• Individual power companies made decisions about when and with whom to interconnect throughout the 20th century; state governments, in general, did not.
• Over the decades, power companies, government agencies and other entities have considered the efficacy of building new links between the Texas grid and one of the other two major grids (the Western and Eastern Interconnections) in the continental United States.
• A recent project to build a link between the Texas grid and the Eastern Interconnection has obtained approval from the state of Texas and the federal government, but still faces challenges from other state, regional and local entities.
• The isolated Texas grid has offered benefits for Texans by way of expanded renewable power, new transmission infrastructure and operating reliability.
• Through a surreptitious operation in the 1970s called the “Midnight Connection,” a Texas utility attempted to connect the state’s grid synchronously to the Eastern Interconnection; this was probably the origin of the mythology around the Texas grid.

These points suggest that the building of new interstate ties between the Texas grid and the Eastern and Western Interconnections should be explored with strict regard to economics and reliability, instead of politics. While Texas braggadocio may continue to play a role in the public discourse, Texas power companies, like those elsewhere, are opportunists. Moreover, Texas power customers, like those elsewhere, want reliable, cost-effective and — for many — preferably green power. Practical issues including technical feasibility, the cost of new infrastructure, public acceptance of large-scale transmission lines, and the need to resolve who will pay for what will likely present the biggest challenges to a future of new links between Texas and the rest of the continental United States.

What Is the Texas Interconnected System?

The Texas Interconnected System is one of three large networks that together provide electric power to more than 150 million customers in the continental United States. The Electric Reliability Council of Texas (ERCOT) operates the 52,700-plus miles that make up this system, while individual generators and transmission companies own the physical infrastructure. [4] The ERCOT network serves 90% of the power customers in Texas; power companies linked into either the Eastern or Western Interconnections serve the remaining 10%. The map in Figure 1 illustrates the region served by ERCOT (most of the state, excluding the light gray areas).

Figure 1 — ERCOT Weather Zone Map

The network controlled by ERCOT is often called the Texas grid. The term “grid” is a colloquialism that typically refers to the collection of generating facilities and transmission lines that produce electric power and ship it across long distances. The technical term is “bulk-power system.” [5] The term “grid” is also sometimes used to refer to the distribution networks that deliver power to individual customers. In this paper, I will use the terms “Texas grid” or “Texas Interconnected Power System” to mean the bulk-power system controlled by ERCOT, and “ERCOT” to mean the agency itself.

During World War II, Texas power companies organized two large power pools to meet the electricity needs of the defense industries. The two networks, called at various times the South and North Texas Interconnected Systems, the South and North Interconnections, and the South and North Texas Power Pools, linked public and private power companies across the state and operated at top capacity during the war years. After their intensive use during the war, the interconnections served primarily to facilitate assistance between companies during planned and emergency outages. [6] In 1967, the companies linked the two networks together and began consistently referring to them as the Texas Interconnected System. This name is still used to refer to the isolated Texas grid under today’s national regulatory schemes; the Texas grid is also sometimes called the ERCOT Interconnection, as illustrated by the map in Figure 2.

Figure 2 — ERCOT-branded Version of the NERC Interconnection Map

The Texas grid operates as a synchronized network of alternating current (AC) facilities. [7] Part of ERCOT’s job is to ensure that the network is stable, e.g., always cycling at or very close to 60 hertz (cycles per second). The network currently has four direct current (DC) ties — two links with the Eastern Interconnection and two links to Mexico [8] — which are used for scheduled and emergency power trades and are not treated as interconnections supporting interstate or international trade. In addition, 19 generators located at four different power plants are switchable, meaning they can deliver power into either the Texas grid or the Eastern Interconnection, but not both at the same time. [9] These switchable generators represent less than 4% of ERCOT’s total generating capacity of 92,000-plus megawatts.

From a regulatory standpoint, the Texas picture is somewhat complicated. [10] The Public Utility Commission of Texas (PUCT) oversees the wholesale and retail markets within the ERCOT region and regulates the location and rates for transmission and distribution lines. [11] The agency also regulates retail rates charged by utilities outside the ERCOT region. The latter utilities, however, participate in markets overseen by the Federal Energy Regulatory Commission (FERC), and their wholesale rates are subject to federal regulation. Additionally, the PUCT participates in transmission planning with states outside the ERCOT region. FERC regulates reliability on all elements of the nation’s bulk-power system, including all parts operated in Texas. [12] To add two more acronyms, the North American Electric Reliability Corporation (NERC) serves as the FERC-designated Electric Reliability Organization (ERO) that develops and monitors reliability standards throughout the bulk-power system. [13] When Texas companies participate in interstate wholesale power markets across AC transmission lines, their wholesale transactions fall under FERC oversight. The federal commission reviews and authorizes cost-based rates in noncompetitive interstate markets and makes rules for competitive interstate markets. [14]

Early Electrification in Texas

The current regulatory and operating structure in Texas developed over many decades, but in the beginning, the state’s power companies functioned with a great deal of autonomy.

Across North America, public and private power companies began lighting, and then further electrifying, homes, businesses and cities in the late 19th century. [15] These activities were regulated through franchise agreements between power companies and city governments until 1907. That year, the states of Wisconsin and New York established regulatory commissions to oversee the service areas and fees charged by power companies. Many investor-owned power companies advocated for state-level regulation because it would end costly competition between companies, and also foreclose the local political shenanigans that had been involved in securing franchise agreements in many cities. [16] By 1920, 44 states had established electric utility regulatory commissions.

Electrification took place somewhat differently in Texas. Early street-lighting companies appeared in Texas cities in the 1880s, [17] but neither the state’s utilities nor the Texas Legislature embraced state-level regulation. Rather, the Legislature made small concessions to communities that sought to control the state’s burgeoning power companies. In 1905, the Legislature granted district courts the authority to settle disputes between utilities and general-law cities. [18] Two years later, general-law cities with populations greater than 2,000 were able to set rates by ordinance. The cities had to ensure that a power company’s costs were covered, with a minimum rate of return of 10%. In 1913, the Legislature granted home-rule cities the authority to regulate utilities, and in 1925, it passed a law requiring utilities to make certain disclosures to assist in rate-setting. In 1931, the Legislature lowered the population minimum to 500 and inverted the 10% rate of return, making it a maximum rather than a minimum. It prohibited rate discrimination in 1935 and eliminated the minimum population size in 1937, allowing cities of any size to regulate utilities. [19] But not until 1975 did the Texas Legislature finally institute state-level electric utility regulation.

In the early years, some Texas power companies had great difficulty financing new power plants and power lines to meet growing customer demand, as was the case for electric companies across the country. For example, Houston Lighting & Power Company (HL&P), which originated in 1882, had a rocky first few decades in Houston involving bankruptcies, mergers and take-overs, frustrations with city government, maintenance challenges and poor investor returns. [20] American Cities Railway and Light Company, a holding company with properties across the South, acquired HL&P in 1906. In 1914, the company entered a profit-sharing agreement with the city of Houston, presumably to bring an end to contentious annual negotiations over rates charged to customers. This agreement, in one form or another, remained in place through the 1940s. [21] By 1920, HL&P was on the brink of receivership, unable to expand its physical facilities quickly enough to meet demand and unable to finance the acquisition of other companies. Electric Bond and Share Company, originally part of General Electric Company and one of the largest utility holding companies in the world, acquired HL&P in 1922.

Across the country, power companies expanded their territories by buying up competitors, failing companies and smaller neighboring companies. [22] Holding companies provided a lucrative mechanism by which a small number of investors could obtain ownership of numerous, faraway power companies without putting much of their own cash at risk. In the mid-1920s, Congress initiated an investigation of holding companies, focusing in particular on Electric Bond and Share, and determined that 20 companies controlled 61% of the industry across North America. Further, the investigation construed the holding companies as pyramids in which a $1 million investment could result in control over more than $370 million worth of power companies. [23] Several of the largest holding companies, including Electric Bond and Share, Middle West Utilities Company, and Stone and Webster (through a subsidiary called Engineers Public Service Company) owned multiple properties in Texas. As such, to understand the current isolation of the Texas grid, it is important to remember that before 1935 — and, indeed, well into the 1940s — many Texas power companies were part of large, multistate holdings that in some cases were interconnected.

Autonomous power companies across the continent also built links to their neighbors’ power plants to increase system reliability, access broader power markets, achieve economies of scale and conserve energy resources — which at that time meant using falling water to the maximum extent possible while minimizing the amount of coal needed to produce the next kilowatt of electricity. [24] These links, or interconnections, allowed the companies to share electric power during planned or emergency outages and to economize by relying first on the power that was least costly to generate and transmit. Until World War II, most of these interconnections operated intermittently; in only a few places did companies exchange power continuously. [25]

Utilities in Texas followed this pattern of expansion in very much the same way. Dallas-area Texas Power & Light Company built the first true interconnection in the state in 1924. [26] In 1926, HL&P started building interconnections to sell excess power, and linked its network of transmission lines to the Gulf States Utilities system just east of Huffman, Texas, in 1927. [27] Gulf States, a subsidiary of Engineers Public Service, operated a power system that stretched from Southeast Texas across Louisiana. [28] The map in Figure 3 illustrates the HL&P interconnections in place by the early 1930s. [29] Note that the line leading from Huffman to Beaumont continues through Orange, Texas, and all the way across the Texas-Louisiana border. A connection between HL&P and Texas Power & Light is also visible near the town of Peters, Texas.

Figure 3 — Houston Lighting & Power Company

In similar fashion, many Texas companies built interconnections — some staying in-state and others linking across state lines — to achieve their individual economic and reliability goals.

Thus, by the 1930s, electrification in Texas resembled electrification in many other parts of the country, apart from the regulatory relationships within the state. Across the state, a mix of publicly and privately owned entities provided electrical services. Holding companies dominated the systems with subsidiaries in nearly every major city. Companies such as HL&P built interconnections with neighboring utilities to achieve the benefits of reliability, economies of scale and energy resource management. And many of these interconnected systems operated across state lines.

The Public Utility Holding Company Act, the Federal Power Act and Industry Restructuring

The Public Utility Holding Company Act (PUHCA), passed by Congress in 1935, upended the economic order of electrification in the United States. Through it, Congress targeted companies like Electric Bond and Share specifically because they represented outsized monopoly control of a major economic sector of the country and their broad base of customer-investors had been hit hard by the economic crashes endured during the Great Depression. [30] Though the utilities fought tooth and nail, enlisting the support of newspaper publishers and editors to scare small investors, Congress retained provisions collectively called the “Death Clause” in the final version of the bill. [31] The cartoon in Figure 4 illustrates the type of media pressure the utilities were able to exert.

Figure 4 — Wheeler-Rayburn Bill Death Sentence Comic, July 3, 1935

The Death Clause required holding companies to simplify their pyramid structures, sell off their multistate holdings or interconnect their subsidiaries into a single system, and undergo the financial scrutiny of the U.S. Securities and Exchange Commission (SEC). The accompanying Federal Power Act authorized the Federal Power Commission (FPC), which was later replaced by FERC, to regulate wholesale interstate power transactions and order interconnections between utilities when it was in the national interest.

Several of the largest holding companies, including Electric Bond and Share, responded by suing to overturn PUHCA. [32] The lawsuits went all the way to the Supreme Court, which upheld the act in 1938. [33] The SEC began hearing reorganization plans from major holding companies with subsidiaries in Texas in 1940. By this date, Electric Bond and Share still owned 36 subsidiaries in 27 states, including Houston Lighting & Power and five others in Texas. Engineers Public Service Company, formerly part of Stone and Webster, owned 10 subsidiaries with properties in 15 states, including Gulf States Utilities and two others in Texas. Middle West Utilities owned 50 subsidiaries in 16 states, including West Texas Utilities and several others in the state. Of the reorganization plans received from the holding companies, the SEC ruefully reported in 1941, “most of the plans submitted ... although helpful in some respects, amounted to little more than arguments attempting to justify the retention of the existing scattered holdings.” [34]

Throughout the 1940s, the SEC ordered each of the holding companies listed above to reorganize or dissolve. The affected subsidiaries made distinct decisions about interstate versus intrastate interconnections: Electric Bond and Share dissolved, and Houston Lighting & Power became a wholly independent intrastate company in 1943. Engineers Public Service sold off Gulf States Utilities, which continued to operate in both Texas and Louisiana. Middle West Utilities dissolved, but one of its subsidiaries, Central and South West Corporation, registered as a holding company with properties in Texas, Oklahoma and other states. Importantly, as the SEC variously approved registration of holding companies across the country with regionally integrated systems or ordered dissolution, individual utilities elected to either continue or cease their own interstate interconnections. [35]

Two major lawsuits at that time illustrate the reluctance of utilities across the country to subject themselves unnecessarily to federal regulation. In Jersey Central Power & Light Co. v. FPC, the New Jersey utility sought to prove that its link to another utility that periodically transmitted power to Staten Island in New York should not subject it to federal regulation. [36] In another instance, two days before PUHCA went into effect, a Connecticut utility cut all its connections with out-of-state utilities except for one small wholesaler that sent power to Fisher’s Island, technically a part of New York state. [37] In the former case, the court found that the New Jersey utility operated in interstate commerce and was subject to federal regulation. In the latter case, because the Connecticut utility required the wholesaler to cease providing power to Fisher’s Island, the court found it was not subject to federal regulation.

Federal regulation posed legitimate costs and delays to power companies that continued for decades. In 1965, for example, the president of a Utah utility explained the issue at a Senate Commerce Committee hearing:

In 1962, Utah Power & Light, an FPC regulated utility, requested a general rate increase in Utah. After extensive hearings and thorough consideration, the Public Service Commission of Utah granted the request. Utah Power & Light was then required, however, to file the state-approved rates with the FPC. The FPC review cost the company two years and one month in delay, $100,000 in lost revenue, and $64,000 in company expenses, and imposed an onerous burden on its staff before reaching the same result that the state commission had ordered. [38]

While federal regulation imposed additional procedures and costs, companies that chose to remain in interstate commerce found commensurate benefits through their interconnections. In the absence of those benefits, however, it made more sense to end links across state lines.

Houston Lighting & Power’s annual reports offer some evidence of the decision-making that may have taken place. The company sought to avoid any implication of interstate commerce once it was no longer a part of Electric Bond and Share. HL&P had a favorable franchise agreement and cost-sharing contract with the city of Houston and no state-level oversight. In addition, with an expanded customer base and an enlarged system overall, there was no pressing need to continue exchanging power with interstate Gulf States. As the 1931 map in Figure 3 illustrates, before the enactment of PUHCA, the company forthrightly displayed its interconnection point with Gulf States; a service area map included in the 1940 annual report, however, illustrates none of the company’s interconnections.

Interestingly, in its 1945 annual report, the company once again prominently displayed points of interconnection, including one to Gulf States. The war years had changed the calculation.

World War II and Interstate Interconnections

While PUHCA rendered certain decisions about interstate interconnection appropriate in a regional business context, the country’s entry into World War II introduced new considerations. The federal government went to great lengths to ensure sufficient electric power for the war industries. In 1939, the FPC worked with regional power pools to map out power supplies for defense work. In 1941, the commission ordered interconnections between utilities in regions anticipating increased war production activity. Most significantly for Texas power companies, in 1942, the FPC issued an order that relieved utilities of federal regulation if they joined interstate interconnections for the purpose of providing electricity to the war industries. [39] There followed a number of FPC emergency orders directing companies to interconnect, including HL&P and other Texas utilities that were able to supply power to networks in Louisiana, Arkansas and Oklahoma. [40] The effects of both PUHCA, which caused disconnections, and the FPC emergency orders, which caused reconnections, are evident in Howard Ricks Fussell's history of Gulf States, which notes: “The Houston company [HL&P] cut its physical connection [to Baytown, Texas] ... and Gulf States picked up the load by closing the connecting switch to the Houston Lighting and Power transmission line west of Dayton [in Texas].” [41] On the very same page, the company then touts its emergency reconnection with HL&P in 1943.

As previously noted, in the early 1940s, Texas utilities formed power pools in both the northern and southern regions of the state to increase war industry production. While little material from that time is available regarding these groupings, in later publications the utilities variously explained the reasoning behind the pools by citing their own desire to participate in defense work, pressure from defense industries in need of more power, and the role of the federal government in pushing them to form the interconnected systems. [42] In addition, 16 Texas-based companies participated in the Southwest Power Pool, a giant network that stretched from Nebraska to South Texas and from New Mexico to Tennessee. [43] In general, these links were praised for their role in ensuring a sufficient power supply for war production without stinting the needs of domestic customers. [44] More importantly, these wartime interconnections served as a test of the efficacy of interstate links for the Texas utilities.

After the war, the Texas companies abandoned their interstate interconnections, although many kept the infrastructure in place for use in possible emergencies. From 1945 to 1949, for example, the HL&P annual reports continued to display the link with Gulf States. [45] In its 1948 annual report, however, HL&P pointedly told its shareholders that “it operate[d] only within the State of Texas, [wa]s not engaged in interstate commerce in the transmission and sale of electric energy, d[id] not operate any project licensed or subject to license under the Federal Power Act; and ... [wa]s not subject to that Act or the jurisdiction of the Federal Power Administration.” [46] In addition, the companies retained their intrastate links, continuing to share power through the North and South Texas Interconnected Systems.

The FPC’s wartime interconnection orders led to some anomalous configurations not anticipated by PUHCA. During 1944, the SEC held protracted hearings on the question of whether Central and South West Corporation (CSW), formerly part of Middle West Utilities, could be considered a holding company with a single network of integrated subsidiaries. [47] At this point, CSW owned several subsidiaries in Texas, Oklahoma and Louisiana — all of which were interconnected with each other and the Southwest Power Pool. [48] At first, the SEC tentatively concluded that two distinct integrated systems existed — one within Texas and the other crossing into each of the states — because “normal operations did not require substantial coordination of both systems.” [49] After examining operating records, the SEC determined that under PUHCA, CSW was a utility holding company with an integrated network of subsidiaries stretching from Texas to Oklahoma to Louisiana. During the post-war years, two subsidiaries — Central Power & Light and West Texas Utilities — chose to operate within the intrastate Texas Interconnected Systems and ceased sharing power across state lines. The others remained engaged in interstate commerce as part of the Southwest Power Pool. Thus, CSW was a single holding company but with two integrated networks of subsidiaries. The hybrid nature of this holding company later led to a major test of the Texas grid and its autonomy from federal regulation — an episode called “the Midnight Connection.”

The Midnight Connection

On May 4, 1976, system operators at West Texas Utilities “performed a midnight wiring of electrical circuits” with Public Service Company of Oklahoma, entering all the members of the Texas Interconnected System into interstate commerce. [50] As soon as executives at both HL&P and Texas Electric Service Company (TESCo) learned of the clandestine power trade, they ordered their facilities to disconnect from the Texas grid. The executives took this action explicitly to avoid falling under federal regulation against their will. Richard Cudahy, who represented CSW at the time and later documented the case in a 1995 essay, averred that “so eager were the Texas utilities to maintain traditional Texas independence that they memorialized the policy of isolation into a written agreement, binding themselves to intrastate operation.” [51] A cascade of lawsuits and pleadings before regulators followed — and lasted into the 1980s. [52] Early in that decade, both the PUCT and FERC approved plans to link the Texas and Oklahoma CSW subsidiaries with a DC line that, by nature of the technology (controlled and intermittent exchanges of power), did not place the other Texas companies under federal regulation. [53] The attempt to tie the Texas Interconnected System synchronously into the Eastern Interconnection ultimately failed, and reinforced both the perceived reliability of the intrastate grid and Texas companies’ business-driven decisions to remain in intrastate power commerce.

Consider the context in which this surreptitious Midnight Connection took place. By the 1970s, the country had experienced its first major cascading power failure (the 1965 Northeast Blackout); developed a national focus on power networks (with complete National Power Surveys issued in 1964 and 1970); witnessed an attempt at a coast-to-coast grid (1967-1975); and undergone congressional attempts to regulate grid reliability. [54] Within Texas, the Legislature had enacted the Public Utility Regulatory Act, placing the state’s power systems — public and private — under state-level regulation. The Texas power companies had formalized their power pools into a single Texas Interconnected System and had established a new entity, ERCOT, to strengthen cooperation and system reliability. In addition, across the country as well as in Texas, customers were paying more for electricity and were rebelling against increasing rates. [55] CSW, up to that time, had maintained its two separate systems: one within Texas and one within the Southwest Power Pool, with links in place between the two for occasional power exchanges but not for continuous coordination. The SEC still recognized CSW as a single utility holding company.

The events leading up to the midnight connection had been triggered by Oklahoma rural cooperatives and municipal companies that bought power from Public Service Company of Oklahoma. Frustrated by high rates, the cooperatives argued that their cost for electricity could be lower if the Oklahoma company would simply import some power from Texas. [56] Unless CSW reconnected its two networks for continuous power sharing, they claimed, it should not be treated as a single holding company under the PUHCA. To counter this challenge, CSW took numerous steps, including a technical study of continuous synchronous interconnection, before implementing the Midnight Connection. CSW’s plan, evidently, was to not only create a single integrated network of its own subsidiaries, but to also link the entire Texas network into the giant Eastern Interconnection. In doing so, it could legitimately maintain its status as a single holding company and avoid selling off any of its properties.

Of the many lawsuits, countersuits and regulatory hearings that ensued, the judge’s order in the 1979 case of West Texas Utilities v. Texas Electric Service Company provides an especially detailed review of the history of the interconnections among all these companies, their varying stances with regard to interstate operations, the technical and economic considerations at stake, and the nature of the Texas Interconnected System. [57] In this case, the plaintiffs (that is, the two subsidiaries of CSW) alleged that HL&P and TESCo had engaged in a conspiracy through either oral or written contracts to restrict their power trades to intrastate commerce. The plaintiffs sought to restrain this conspiracy. In his ruling, presiding district Judge Robert W. Porter found that no conspiracy existed. An appeal was later dismissed by the 5th Circuit Court of Appeals. Both the plaintiffs’ allegations and Porter’s findings offer insight into the status of the Texas Interconnected System and how it was viewed by participating companies at that time:

• In the time between the passage of PUHCA and the Midnight Connection, individual companies in Texas made decisions to interconnect with each other and/or with companies in other states on their own, and there was no evidence in the record that any of the companies within the lawsuit had made agreements with each other to permanently avoid interstate commerce.
• Companies did promise to notify each other in advance should they decide to enter interstate commerce.
• Historically, all members of the Texas Interconnected System had activated interstate interconnections only in times of emergency.
• When the North Texas and South Texas Interconnected Systems formed the single intrastate network in 1967, “all of its members operated and wished to continue operating on an intrastate basis.” [58]
• HL&P, TESCo and other utilities had tested the efficacy of interstate power trades in 1957 and 1968 and found serious reliability issues. They also undertook studies of links between Texas and the Southwest Power Pool. The studies demonstrated reduced reliability with those new links, and in one case the technical expert recommended remaining in intrastate operation.

The thrust of Porter’s opinion indicates that companies like HL&P were not only willing to consider linking the Texas grid to one of the other grids, but that they had investigated and tested the idea in the years between World War II and the Midnight Connection. Without indications that the links would provide a significant economic advantage or greatly increase reliability, however — in fact, finding evidence of decreased reliability — the companies remained committed to their intrastate operations.

For the remainder of the year after the Midnight Connection, the Texas Interconnected System operated as two units. [59] One, which included HL&P and TESCo, remained isolated. The other, which included CSW’s subsidiaries, pursued attempts to operate in synchrony with the Southwest Power Pool, and hence the entire Eastern Interconnection. The links resulted in unreliable operations, and the participants terminated the experiment in January 1977. [60] In related hearings before the PUCT, the companies argued that it would cost approximately $1 billion to build permanent ties between the two power pools. As this evidence suggests, HL&P and TESCo remained committed to the intrastate Texas grid not only because they had resisted the Midnight Connection carried out by CSW, but also because there was no discernible benefit to their power customers or their own corporate bottom lines by doing otherwise.

CSW continued to pursue an advantageous connection between its Texas subsidiaries and its Oklahoma companies. Both FERC and the PUCT approved construction of a DC intertie close to the Texas-Oklahoma boundary. In the wake of the Midnight Connection episode, FERC determined that the nature of DC technology allowed for the participants in the Texas grid to remain outside federal regulation.

Studies and Reports

While power companies built increasingly larger interconnections across the United States during the postwar years, and various entities promoted a national grid, test cases and research reports suggested that not all links served the public good. The most compelling example of the dream of a nationwide grid appeared in the 1964 National Power Survey, which included the map shown in Figure 5.

Figure 5 — Projected Power Changes in 1980

The map illustrates some of the same goals at work today — moving power from locations of abundant renewable resources, on a seasonal basis, to load centers. The concept included Texas as both a power recipient and a power provider. While the federal government never moved to realize this vision, agencies and utilities did experiment with large-scale interconnections. The biggest test occurred in 1967, when a task force headed by the U.S. Bureau of Reclamation activated four AC ties between the Eastern and Western Interconnections to create a single coast-to-coast grid. [61] The relatively small links between two giant systems proved problematic, and after eight years of instability, the participants abandoned the ties. The east-west interconnection, however, did not include Texas.

In the late 1960s and throughout the 1970s, various entities examined the value of linking the Texas grid to one of the other interconnections in the United States. A 1968 transmission study by the U.S. Department of the Interior proposed a DC link between the Northwest Power Pool and ERCOT, although long-distance DC transmission was still a relatively young technology at that point. [62] A 1972 FPC study indicated that a traditional AC tie between ERCOT and the Southwest Power Pool could produce a net economic benefit to the public, but the study did not include a cost estimate for building the needed interconnection, nor a detailed technical analysis of the existing and proposed transmission lines. An ERCOT technical review of the report, however, indicated that it would be detrimental from both an economic and reliability standpoint, and a FERC staff review in 1978 offered that an ERCOT link to the Southwest Power Pool would not, in fact, measurably increase reliability. [63] In 1976, the Congressional Research Service forecast measurable benefits from an ERCOT-Southwest Power Pool link and recommended “a definitive study of interconnections between ERCOT and SPP.” [64]

In 1977, the U.S. General Accounting Office (GAO) critiqued reports like these, noting that utility executives generally dismissed FPC recommendations for interconnection unless the links provided measurable economic benefits to the utilities themselves. [65] Further, utilities and regional pool representatives complained to the GAO that they had not been included in the research process, and federal researchers lacked the expertise and familiarity with regional systems to assess the true costs and benefits. In the 1972 ERCOT-Southwest Power Pool example, ERCOT noted that the FPC had failed to assess the technical work and physical investment needed within the Texas grid for it to operate synchronously with the much larger Eastern grid. The GAO called for interconnection studies to address the greater public good afforded by new projects, including resource conservation, environmental protection, and consideration of national emergencies and national defense. The U.S. Department of Energy echoed these findings in 1980. [66]

Apart from the Midnight Connection episode, participants in the Texas grid maintained reliable operations throughout the 1970s. A FERC report described the organization of the power pool, which included a technical committee that defined operating practices to maximize reliability. [67] Member companies retained autonomous control of their physical infrastructure and exchanged power with each other through bilateral agreements. The interconnections among the companies provided for emergency and backup power, but not continuous exchanges.

For the most part, with a generating fleet largely dependent upon natural gas until the late 1970s, operating costs across the state were uniform, and there was little basis for economy exchanges. As late as 1980, individual companies managed their own dispatch, coordinated through seven control areas, with the Texas Interconnected System itself operating two system security centers. The FERC report forecast tighter coordination and increased economy exchanges as utilities statewide shifted from natural gas to coal-fired and nuclear-powered plants. [68] The report also noted that “If ERCOT and [Southwest Power Pool] are interconnected with high-capacity transmission ties, bulk power economy in both regions could be improved through increased coordination.” [69] Thus, federal agencies recommended interconnection as a means of improving business results, but not to increase reliability.

In its 1990 corporate history, HL&P offered that “the reason [for resisting the Midnight Connection] was simple. HL&P and most other utilities in Texas argued that if they interconnected with utilities in neighboring states, they would then be engaged in interstate commerce and subject to regulation by the Federal Power Commission.” [70] This was, according to the corporate history, “a very typical Texas independence.” Cudahy’s lively 1995 essay “The Second Battle of the Alamo” certainly argues that the yearning for independence alone accounted for the vehemence with which HL&P and TESCo fought against links to the Eastern Interconnection. But the isolation of the grid also made sense from business and technical perspectives.

ERCOT: From Reliability Advice to System Operation

Texas utilities organized ERCOT in 1970 as part of a nationwide effort by power companies to address reliability concerns while protecting their relative autonomy from federal oversight. Historically, power companies had exercised responsibility for system reliability by adhering to voluntary standards set by regional groups and eventually national associations. [71] Following the 1965 Northeast Blackout, Congress held hearings to address the incident and discuss ways to prevent future widespread power failures, including legislation that would require federal oversight of the reliability of the nation’s power systems. The power companies, however, resisted this new type of regulation. Working with the FPC and others, they formed the National Electric Reliability Council (NERC, a predecessor to today’s North American Electric Reliability Corporation) in 1968 to institute uniform, yet voluntary, reliability measures across the country. The Texas Interconnected System was one of the 12 original signatories. The owners of bulk-power generation and transmission facilities that composed the Texas Interconnected System, along with municipal companies, rural cooperatives and state agencies, formed ERCOT to improve reliability through “the planning, operation and restoration of member electric power systems.” [72] Moreover, ERCOT participants “committed to providing service solely in the Texas intrastate market,” as it was understood at that time that an interconnection of manageable size ensured “maximum reliability [and] effective communications and required coordination.” [73]

As the Texas Legislature introduced new rules regarding the state’s power systems, the role of ERCOT evolved. While the 1975 approval of the Public Utility Regulation Act (PURA) established the PUCT and its oversight of rates and market entry, ERCOT continued as a private coordinating entity. The utilities turned over operation of their interconnected system to ERCOT in 1981. [74] In 1990, ERCOT incorporated as a not-for-profit corporation with the limited purpose of promoting reliability, including through coordinated operations. [75] Following the passage of amendments to PURA in 1995 that established a competitive wholesale power market, the PUCT made ERCOT the independent system operator of Texas in 1996, an entity that would assure non-discriminatory access to the grid. The 1999 amendments to PURA resulted in additional statutory responsibilities for ERCOT, including management of the wholesale power market, customer switching in a competitive retail power market, and establishment of a stakeholder process.

According to one study, the restructured wholesale and retail markets, over the long term, afforded ERCOT retail customers reduced power costs. [76] ERCOT expanded in size and duties in the years thereafter, although not without scandal, operating challenges and criticism from multiple quarters. [77] Nonetheless, under the agency’s increasingly tight control of grid operations, customers in Texas have avoided a cascading power failure for the past 52 years.

Texas enjoys two distinct advantages with an isolated grid — one technical and the other organizational. The technical advantage stems from system operation standards that are uniform across the nation but implemented in a distinct way in Texas. The organizational advantages relate to the ability of the Texas Legislature to effect change on the grid, especially to its infrastructure.

All power systems in the United States today rely on operating standards established by NERC to ensure system stability. One of these standards requires that subsystems within each interconnection — called balancing authorities — assure stable frequency within their geographic areas and zero difference between planned and actual power exchanges with the neighboring area. Deviations in planned versus actual power exchanges or frequency result in system instability, which, if the deviations are severe enough, will cause a power failure. In the 2016 map in Figure 6, the three main U.S. interconnections are depicted, and within each are circles indicating the balancing authorities. Note that the Texas Interconnected System has only one balancing authority — ERCOT.

Figure 6 — U.S. Electric Power Regions

Within each interconnection, each balancing authority must coordinate with its adjacent balancing authority to achieve stability, as described above. This is accomplished by maintaining an area control error (ACE) of zero using the following equation, both within the control computers and on the part of the human system operators:

The first part of the right side of the ACE equation ( P actual – P sched ) reflects the difference between actual power trades across a link between two systems and scheduled power trades. 10β is a variable that allows one area to provide support to another area for the purpose of restoring stability should there be frequency deviation. The third segment, ( f act – f sched ), reflects the actual frequency measured on the network versus the planned frequency (typically 60 hertz). When the linked systems maintain an ACE of zero, the overall interconnection is stable.

ERCOT, however, has a lesser task than other balancing authorities — and thus a technical advantage — since the Texas Interconnected System does not synchronously exchange power with any neighboring system and consequently has no adjacent balancing authorities with which to coordinate. As a result, ERCOT system operators monitor for frequency deviations, but are not at all concerned about deviations in power exchanges. [78]

The organizational advantage of the isolated Texas grid is exemplified by the Competitive Renewable Energy Zone (CREZ) initiative. [79] In 2005, the Texas Legislature increased goals for the addition of renewables, especially wind power, to the generating fleet for the Texas grid. [80] In addition, to alleviate bottlenecks on the state’s existing transmission infrastructure and further incentivize investment in wind generation, the Legislature called for the creation of CREZs and the construction of new power lines. The law required the PUCT to delineate priority areas for wind development and, with the new power lines, create corridors to link those areas to the heart of the grid. Within nine years, developers doubled the state’s installed wind generation capacity, and transmission line owners added 3,600 miles of high-voltage lines. With only one legislature voting on the plan, and only one regulator overseeing implementation, the initiative moved relatively swiftly, despite challenges from multiple stakeholders. By comparison, similar efforts across the country involving multiple states, and in one case a Canadian province, have been stalled for years.

The DC Alternative for Texas

Recent studies have offered a plethora of scenarios for achieving a greener power system with greater reliance on renewables and less pollution. [81] Proposals to link areas with great wind and solar potential to centers of use, however, often bypass Texas, ostensibly due to the seemingly impenetrable wall around the isolated Texas grid. [82] Other proposals have indicated the potential for connecting windy and sunny regions of Texas to markets in other states without addressing the technical, political and regulatory steps that would be required. [83] Similarly, although technological advances suggest that AC links between the major grids may be more viable than they were in the 1960s and 1970s, a recent technical assessment focused solely on reconnecting the Eastern and Western Interconnections. [84]

In a detailed high-level study by the National Academies of Sciences, Engineering, and Medicine, engineers considered how the use of DC technologies might trigger reconfiguration of the North American grids. [85] They suggested that two different approaches might emerge. One would expand use of high-voltage DC ties between the East, West and Texas grids to allow increased power sharing across much wider regions. Through the other approach, the three big grids would break into smaller units, each with tighter control to minimize cascading disruptions, but with DC links to facilitate continued power exchanges. Recall that for the isolated Texas grid, FERC allows DC interstate ties, which do not trigger federal regulation.

One project has already proposed to take advantage of the opportunity presented by DC technology. Initiated more than a decade ago, the Southern Cross Transmission project envisions a high-voltage DC transmission line extending from eastern Texas to eastern Mississippi. In 2014, FERC issued a final order to connect the ERCOT transmission system providers with the proposed Southern Cross DC terminal at the Texas border. [86] In the order, FERC expressly stated that ERCOT and its member entities would retain their independence from FERC jurisdiction. [87] In addition, the PUCT approved the construction of a power line to link the Texas grid to the Southern Cross terminal, and ordered ERCOT to undertake a number of measures to ensure the stability and reliability of the Texas grid after the line’s activation. [88] Notwithstanding these approvals, the project also requires review from other regulators in Louisiana and Mississippi and acquiescence from landowners and other interest groups located along the route of the power line. [89]

Facing the Realities of the Isolated Texas Grid

As this brief history illustrates, the power companies operating on the Texas grid may be fiercely independent — but this does not sufficiently explain why they have preferred to remain on the isolated Texas Interconnected System for so many decades, while other companies in the state have chosen to participate in interstate grids. In the first place, Texas utilities were not the only ones that sought to evade federal regulation after the passage of the 1935 Public Utility Holding Company Act by ending interstate ties. In addition, not all Texas utilities ended interstate ties, and to this day several of them are federally regulated, including Entergy Texas, which serves areas north and east of Houston; Southwestern Electric Power Company, which primarily serves East Texas; El Paso Electric, which serves areas including and surrounding El Paso; and Southwestern Public Service, which serves the Panhandle region. In general, these are the successors to companies located near the state border that had strong interconnections to operations in surrounding states.

Decisions about interstate interconnections were not made by state legislatures, governors or voters; rather, they were business decisions made by individual utilities, driven by economics, geography and concerns about reliability. Utilities linked to the Texas grid, state and federal agencies, and transmission system operators have periodically investigated building AC interconnections — but have repeatedly encountered technical issues related to reliability and stability. Meanwhile, a recent project designed to link the Texas grid to the Eastern Interconnection through a DC transmission line has already received approval from the PUCT and FERC but is encountering the same opposition that other large-scale energy infrastructure projects have met across the country from state, regional and local entities. On the other hand, the isolated Texas grid has delivered progress toward certain goals: the addition of renewables, development of the wind industry, construction of transmission lines and, for a period of time, reduced costs for ratepayers in the competitive retail market.

The mythology around the isolated grid probably dates back to the Midnight Connection, in the wake of which many theories about Texas utilities’ choices were offered and challenged in courts, law reviews and the press. There is a kernel of truth to the assertion that some Texas utilities have been driven by a desire to be independent of federal regulation. But their decision to remain on the Texas grid is more closely linked to longer-term trends to protect business interests, preserve internal system reliability and avoid extra costs associated with additional levels of government oversight.

More importantly, advances in the use of DC technologies between grids offer opportunities to reevaluate the commitment to isolation. To date, the implementation of DC ties has not precipitated federal regulation of participants in the Texas grid, and further, DC ties may offer sufficient economic opportunities to those companies to make new layers of regulation palatable. The challenges of building large-scale energy infrastructure cannot be ignored, however. Even if new links promise access to new markets for Texas generators and access to backup power during emergencies, in addition to requiring utilities to provide emergency backup power on the other side of the state line, the physical infrastructure itself will sit on properties and in communities that may not welcome it.

To rationally tackle the question of whether and how to end the isolation of the Texas grid, engineers and policymakers should look beyond Texas braggadocio. The exceptionalism of the Texas grid has served its stakeholders well in many ways for many years, but broader considerations related to the public good and public acceptance, environmental need, and economic sense are what will determine whether they will embrace a new scenario for their electric power future.

[1] Kevin McCarthy, “What’s Up in Texas,” The Starting Line (blog), February 17, 2021, https://www.republicanleader.gov/whats-up-in-texas/ .

[2] Former North American Electric Reliability Corporation executive in private conversation with author, February 23, 2021.

[3] Wikipedia, s.v. “Texas Interconnection,” accessed January 28, 2022, https://en.wikipedia.org/wiki/Texas_Interconnection#cite_note-1 .

[4] ERCOT manages the flow of electric power to more than 26 million customers. Electric Reliability Council of Texas, “About ERCOT,” https://www.ercot.com/about .

[5] The North American Electric Reliability Corporation (NERC) defines “bulk-power system” as “(A) facilities and control systems necessary for operating an interconnected electric energy transmission network (or any portion thereof); and (B) electric energy from generation facilities needed to maintain transmission system reliability.” NERC, Glossary of Terms Used in NERC Reliability Standards , updated March 29, 2022, (Atlanta: North American Electric Reliability Corporation, 2016), https://bit.ly/3eDMvXf .

[6] R. J. Costello, Letter to Michael S. Greene, Vice President, TU Electric, and attached “History and Description of ERCOT Region,” August 31, 1990, Electric Reliability Council of Texas. Attachment undated, but produced no later than 1983.

[7] Electric current is either direct or alternating . Direct current (DC) electrons move in only one direction. Alternating current (AC) electrons move back and forth at a very high speed. In the United States, the vast majority of the elements on our power system use AC, at a standard rate of 60 hertz (cycles per second). This means that everything from your generator to the outlet in your kitchen must operate at 60 hertz. With transformers, we convert DC to AC, and vice versa. Technical innovations dating back to 1954 allow for connections between large power pools using DC transmission lines, with transformers at each end of the line. For a discussion of these technologies, see Julie Cohn, The Grid: Biography of an American Technology (Cambridge, MA: MIT Press, 2017), 16–20, 210–12, 35–37 notes 11–23, 99 notes 119–22.

[8] ERCOT, ERCOT DC-Tie Operations, Version 3.0 Rev 13 , ERCOT (Texas, July 31, 2020).

[9] ERCOT, Report on the Capacity, Demand and Reserves in the ERCOT Region, Summer Summary: 2002-2031 , Electric Reliability Council of Texas (Austin, TX, 2021), https://www.ercot.com/files/docs/2021/12/29/CapacityDemandandReservesReport_December2021.xlsx .

[10] For a detailed discussion of the federal and state regulatory histories and the roles of PUCT and ERCOT through the early 2000s, see Houston Advanced Research Center Institute for Energy, Law & Enterprise, Guide to Electric Power in Texas, Third Edition , Houston Advanced Research Center, Institute for Energy, Law & Enterprise, University of Houston Law Center (Houston, TX, January 2003).

[11] Public Utility Regulatory Act, Title II: Texas Utilities Code (As amended), September 21, 2021; Public Utility Commission of Texas, “About the PUCT: Mission & History,” accessed January 31, 2022, https://www.puc.texas.gov/agency/about/mission.aspx .

[12] For a brief explanation of the Federal Energy Regulatory Commission’s authority regarding electric power, please see Adam Vann, “The Legal Framework of the Federal Power Act,” (Washington, D.C.: Congressional Research Service, 2020), https://crsreports.congress.gov/product/pdf/IF/IF11411 .

[13] North American Electric Reliability Corporation, “About NERC,” accessed February 14, 2022, https://www.nerc.com/AboutNERC/Pages/default.aspx .

[14] Federal Energy Regulatory Commission, “What FERC Does,” accessed May 25, 2022, https://www.ferc.gov/what-ferc-does .

[15] For good overviews of early electrification in North America, see Thomas Parke Hughes, Networks of power: electrification in Western society, 1880-1930 (Baltimore: Johns Hopkins University Press, 1983); Jill Jonnes, Empires of Light: Edison, Tesla, Westinghouse, and the Race to Electrify the World , 1st ed. (New York: Random House, 2003); David E. Nye, Electrifying America: Social Meanings of a New Technology, 1880-1940 (Cambridge, MA: MIT Press, 1990).

[16] Harold L. Platt, The Electric City: Energy and the Growth of the Chicago Area, 1880-1930 (Chicago: University of Chicago Press, 1991).

[17] Origin and History of Houston Lighting & Power Company , Houston, TX: Houston Lighting & Power, 1940); Vance Gillmore, And Work was Made Less … A Brief History of Texas Electric Service Company (Fort Worth, TX: Texas Electric Service Company, 1976); Robert H. Gregory, Municipal Electric Utilities in Texas , ed. University of Texas The Bureau of Municipal Research, Municipal Studies, (Austin, TX: The University of Texas Press, 1942).

[18] Gilbert B. Reschenthaler, "Some Aspects of the Economic Performances of Private Electric Utility Companies in Texas" (Ph.D. University of Texas, 1969). General-law cities in Texas have limited powers granted by the state. Home-rule cities are those that have adopted a charter to define the powers and duties of the local government. Texas voters amended the state constitution in 1912 to allow for the establishment of home-rule cities. TML Legal Department, Alphabet Soup: Types of Texas Cities , Texas Municipal League (Austin, TX, December 2017), https://www.tml.org/DocumentCenter/View/244/Types-of-Texas-Cities-PDF .

[19] Gregory, Municipal Electric Utilities in Texas ; Reschenthaler, "Some Aspects of the Economic Performances of Private Electric Utility Companies in Texas."

[20] Bill Beck, At Your Service: An Illustrated History of Houston Lighting and Power (Houston: Houston Lighting and Power Company, 1990); Origin and History of Houston Lighting & Power Company .

[21] Houston Lighting & Power Company: Annual Report, 1940 , Houston Lighting & Power Company (Houston, TX, June 16, 1941). See also Annual Reports for 1942-1950.

[22] Platt, The Electric City: Energy and the Growth of the Chicago Area, 1880-1930 . Platt describes in detail how Samuel Insull drove this process throughout the Chicago region in the early 1900s.

[23] Hughes, Networks of Power: Electrification in Western Society, 1880-1930 , 391-92. Control of Power Companies , (Washington, D.C.: Government Printing Office, 1927).

[24] Julie Cohn, "Utilities as Conservationists? The Paradox of Electrification During the Progressive Era in North America," in Green Capitalism? Exploring the Crossroads of Environmental and Business History , ed. Hartmut Berghoff and Adam Rome (Philadelphia, PA: University of Pennsylvania Press, 2017).

[25] Cohn, The Grid: Biography of an American Technology .

[26] Robert L. Johnson, Texas Power & Light Company: 1912 - 1972 (Texas Power & Light Company, 1973), 60.

[27] Howard Ricks Fussell, A History of Gulf States Utilities Company, 1912 - 1947 , vol. 11 (Houston: Texas Gulf Coast Historical Association, 1967), 35.

[28] Fussell, A History of Gulf States Utilities Company, 1912 - 1947 , 11. Gulf States was part of a conglomerate formed by Stone and Webster Inc. comprising two holding companies and four operating companies. Gulf States held a charter in Texas that allowed for operations in Louisiana.

[29] Beck, At Your Service: An Illustrated History of Houston Lighting and Power , 155.

[30] Philip J. Funigiello, Toward a National Power Policy; the New Deal and the Electric Utility Industry, 1933-1941 (Pittsburgh: University of Pittsburgh Press, 1973); William Lasser, Benjamin V. Cohen: Architect of the New Deal (New Haven, CT: Yale University Press, 2002).

[31] Funigiello, Toward a National Power Policy ; Thomas K. McCraw, TVA and the Power Fight, 1933-1939 (Philadelphia: Lippincott, 1971).

[32] U.S. Securities and Exchange Commission, Second Annual Report of the Securities and Exchange Commission: Fiscal Year Ended June 30, 1936, 139 (Washington, DC: Government Printing Office, 1937). More than 100 companies had participated in 45 lawsuits against PUHCA by the end of 1935. In turn, the SEC filed suit against Electric Bond and Share and 14 other holding companies during the same year. And the list goes on. For a short summary of these cases, see Wikipedia, s.v. "The Public Utility Holding Company Act," Wikipedia, updated January 30, 2022, accessed February 7, 2022, https://en.wikipedia.org/wiki/Public_Utility_Holding_Company_Act_of_1935 .

[33] SEC, Fourth Annual Report of the Securities and Exchange Commission: Fiscal Year Ended June 30, 1938,  (Washington, D.C.: Government Printing Office, 1939).

[34] SEC, Seventh Annual Report of the Securities and Exchange Commission: Fiscal Year Ended June 30, 1941, 73 (Washington, D.C.: Government Printing Office, 1942).

[35] A. Robert Thorup, "Electric Range War in Texas: A Case Study in Federal-State Energy Regulation," George Washington Law Review 48, no. 3 (March 1980): 397–401. Thorup notes that several large utilities sought to avoid federal regulation by selling off interstate operations (p. 398). A corporate history of Community Public Service Company, a utility serving communities in Texas, New Mexico and other states, forthrightly describes efforts in 1935 to sell off holdings that would subject the company to federal oversight; SEC inquiries into jurisdiction over the company in 1938; FPC assertion of jurisdiction in 1943; and company reorganization in 1944 to comply with federal rules. Bennett L. Smith, Community Public Service Company: Its History, People, and Places (Fort Worth, TX: Bennett L. Smith, 1975), 104–25.

[36] Jersey Central Power & Light Co. v. FPC, 319 U.S. 61 (1943).

[37] Connecticut Light & Power Co. v. FPC, 324 U.S. (1945).

[38] Exemption of Certain Public Utilities from Federal Power Commission Jurisdiction Hearings on S.218 Before the Senate Commerce Comm. , 89th Cong., 1st Sess. 279-280 (1965) (statement of E. Allen Hunter, president of Utah Power & Light Company). Quoted in Thorup, "Electric Range War in Texas: A Case Study in Federal-State Energy Regulation," 409, fn 129.

[39] "F.P.C. Waives Policy on Power Connections," New York Times , October 17, 1942.

[40] Opinions and Decisions of the Federal Power Commission, With Appendix of Selected Orders in the Nature of Opinions , ed. Federal Power Commission, vol. 2 (Washington, D.C.: Government Printing Office, 1943); Opinions and Decisions of the Federal Power Commission, With Appendix of Selected Orders in the Nature of Opinions , vol. 3 (Washington, D.C.: Government Printing Office, 1944).

[41] Fussell, A History of Gulf States Utilities Company, 1912 - 1947 , 11, 82n27.

[42] Houston Lighting & Power Company: Annual Report, 1943 , Houston Lighting & Power Company (Houston, TX, March 15, 1944); Houston Lighting & Power Company: Annual Report, 1944 , Houston Lighting & Power Company (Houston, TX, March 1, 1945); Houston Lighting & Power Company: Annual Report, 1945 , Houston Lighting & Power Company (Houston, TX, March 15, 1946); Beck, At Your Service: An Illustrated History of Houston Lighting and Power ; Fussell, A History of Gulf States Utilities Company, 1912 - 1947 , 11; Johnson, Texas Power & Light Company: 1912 - 1972 ; Smith, Community Public Service Company: Its History, People, and Places .

[43] S. B. Morehouse, "Inter-system power coordination in Southwest region," Electric Light and Power 23, no. 12 (1945): 63-64. The participating Texas companies listed in this article include Texas Power & Light Company, Texas Electric Service Company (East), Brazos River Conservation and Reclamation District, Southwestern Power Administration (a federal agency), Dallas Power & Light Company, West Texas Utilities, Texas Electric Service Company (West), Lower Colorado River Authority, Austin Municipal Water, Light, and Power Department, San Antonio City P. S. Board, Central Power & Light Company, Houston Lighting & Power Company, Sinclair Refining, Dow Magnesium and Dow Chemical.

[44] Julie Cohn, Matthew Evenden, and Marc Landry, "Waterpowers: The Second World War and the Mobilization of Hydro-Electricity in Canada, the United States, and Germany," Journal of Global History 15, no. 1 (2020).

[45] Houston Lighting & Power Company: Annual Report, 1945 ; Houston Lighting & Power Company: Annual Report, 1946 , Houston Lighting & Power Company (Houston, TX, March 15, 1947); Houston Lighting & Power Company: Annual Report, 1947 , Houston Lighting & Power Company (Houston, TX, March 26, 1948); Houston Lighting & Power Company: Annual Report, 1948 , Houston Lighting & Power Company (Houston, TX, February 10, 1949).

[46] Houston Lighting & Power Company: Annual Report, 1948 , 34.

[47] Securities and Exchange Commission: Decisions and Reports, Volume 18, January 1, 1945 to April 26, 1945, 296 and following. (Washington, D.C.: Government Printing Office, 1950).

[48] Southwestern Light & Power Company, Public Service Company of Oklahoma, Oklahoma Power and Water Company, West Texas Utilities Company, Pecos Valley Power & Light Company and Central Power and Light Company.

[49] Securities and Exchange Commission: Decisions and Reports, Volume 18, January 1, 1945 to April 26, 1945, Short, 298.

[50] West Texas Utilities Company and Central Power and Light Company v. Texas Electric Service Company and Houston Lighting and Power Company, No. CA3-76-633-F, 470 F. Spp. 798, Northern District of Texas (1979).

[51] Richard D. Cudahy, "The Second Battle of the Alamo: The Midnight Connection," Natural Resources & Environment 10, no. 1 (Summer 1995): 57. There are no details in the text and no footnote to indicate when this document was created and signed, who signed it or where it might be found. The statement may refer to actions taken after the passage of PUHCA in 1935, agreements related to the establishment of a single Texas grid in 1967 or the establishment of ERCOT after that. I have not succeeded in locating a document like this.

[52] Cudahy, "The Second Battle of the Alamo: The Midnight Connection"; Thorup, "Electric Range War in Texas: A Case Study in Federal-State Energy Regulation." The following agencies and courts addressed aspects of this incident at various points during the years following the connection: the U.S. Supreme Court, the U.S. Fifth Circuit Court, the U.S. Texas Northern District Court, the Nuclear Regulatory Commission, the U.S. Department of Energy, the Securities and Exchange Commission, the Federal Power Commission (later the Federal Energy Regulatory Commission) and the Public Utility Commission of Texas.

[53] Docket 4414, Examiner’s Report: Procedural History , Public Utility Commission of Texas  (1982).

[54] Cohn, The Grid: Biography of an American Technology . A cascading power failure is one in which there is an “uncontrolled successive loss of System Elements triggered by an incident at any location. Cascading results in widespread electric service interruption that cannot be restrained from sequentially spreading beyond an area predetermined by studies.” Glossary of Terms Used in NERC Reliability Standards , Updated  June 28, 2021,  (Atlanta, GA: North American Electric Reliability Corporation, 2016), https://bit.ly/3eDMvXf .

[55] U.S. Department of Energy, Energy Information Administration, "State Energy Data System (SEDS): 1960-2019 Complete, Prices and Expenditures, 1970-2019," ed. U.S. Department of Energy Energy Information Administration (2021). https://www.eia.gov/state/seds/seds-data-complete.php?sid=US#CompleteDataFile .

[56] Some of the cost discrepancies were related to two fuel issues — natural gas prices were rising, but some utilities, such as HL&P, had long-term contracts in place that protected their operating costs while others, like CSW, did not. In addition, other companies, like TESCo, had been developing lignite resources within Texas, or establishing access to coal from Wyoming and Utah. CSW’s subsidiaries within the Texas grid enjoyed lower costs as a result, while those participating in the Southwest Power Pool experienced rising costs. Thorup, "Electric Range War in Texas: A Case Study in Federal-State Energy Regulation."

[57] West Texas Utilities Company and Central Power and Light Company v. Texas Electric Service Company and Houston Lighting and Power Company, No. CA3-76-633-F, 470 F. Spp. 798, Northern District of Texas. The Fort Worth National Archives holds the records for this case, containing thousands of pages of documents. Future research on this topic will include review of these records.

[58] West Texas Utilities Company and Central Power and Light Company v. Texas Electric Service Company and Houston Lighting and Power Company, No. CA3-76-633-F, 470 F. Spp. 798, Northern District of Texas, 808.

[59] Thorup, "Electric Range War in Texas: A Case Study in Federal-State Energy Regulation," 424–26; Docket 14, Amended Final Order: The Application of Houston Lighting and Power Company, et al., for Reconnection of the Texas Interconnect System , signed July 11, 1977, Public Utility Commission of Texas, https://interchange.puc.texas.gov/Documents/14_1_784770.pdf .

[60] Amended Final Order: The Application of Houston Lighting and Power Company, et al., for Reconnection of the Texas Interconnect System , signed July 11, 1977, 4. In this Amended Final Order, the PUCT found that synchronous operation between the portion of the Texas grid that remained interconnected with the Southwest Power Pool was “unsatisfactory for [West Texas Utilities] and all companies interconnected with them because of the wide power swings and delayed stabilization time after an outage.”

[61] Julie Cohn, "When the Grid was the Grid: The History of North America’s Brief Coast-to-coast Interconnected Machine [Scanning our Past]," Proceedings of the IEEE 107, no. 1 (2019).

[62] National Power Grid System Study - an Overview of Economics, Regulatory, and Engineering Aspects: A study prepared by the Congressional Research Service at the Request of Lee Metcalf, Chairman, Subcommittee on Minerals, Materials and Fuels of the Committee on Interior and Insular Affairs, United States Senate, 296, letter from Robert Partridge, National Rural Electric Cooperative Association, to Senator Metcalf (Washington, D.C.: US Government Printing Office, 1976).

[63] National Power Grid System Study - an Overview of Economics, Regulatory, and Engineering Aspects: A study prepared by the Congressional Research Service at the Request of Lee Metcalf, Chairman, Subcommittee on Minerals, Materials and Fuels of the Committee on Interior and Insular Affairs, United States Senate, Short, 18, 121-22; Staff Report on Electric Reliability Council of Texas Interconnection and Reliability Evaluation,  (Fort Worth, TX: Federal Energy Regulatory Commission, Office of Electric Power Regulation, Fort Worth Regional Office, 1978). The FERC staff report noted that ERCOT already had such a substantial operating reserve, attributable in part to the shift to coal and nuclear generation then underway, that interconnection offered negligible additional benefit.

[64] National Power Grid System Study - an Overview of Economics, Regulatory, and Engineering Aspects: A study prepared by the Congressional Research Service at the Request of Lee Metcalf, Chairman, Subcommittee on Minerals, Materials and Fuels of the Committee on Interior and Insular Affairs, United States Senate, Short, 23.

[65] Problems in Planning and Constructing Transmission Lines Which Interconnect Utilites,  (Washington, D.C.: U.S. General Accounting Office, 1977).

[66] The National Power Grid Study,  (Washington, D.C.: United States Department of Energy, 1980).

[67] Power Pooling in the United States: External Review: Staff Report, XIV-9-XIV-19 (Washington, D.C.: Federal Energy Regulatory Commission, 1980).

[68] Energy Supply and Environmental Coordination Act of 1974, Energy Policy and Conservation Act of 1975. 

[69] Power Pooling in the United States: External Review: Staff Report, Short, XIV-19.

[70] Beck, At Your Service: An Illustrated History of Houston Lighting and Power , 338.

[71] Cohn, The Grid: Biography of an American Technology ; David R. Nevius, The History of the North American Electric Reliability Corporation: Helping Owners, Operators, and Users of the Bulk Power System Assure Reliability and Security for More Than 50 Years (Atlanta, GA: North American Electric Reliability Corporation, 2020).

[72] Costello, Letter to Michael S. Greene, Vice President, TU Electric, and attached “History and Description of ERCOT Region”, 4, page 1 of attached "History and Description of the ERCOT Region."

[74] R.A. “Jake” Dyer, The Story of ERCOT: The Grid Operator, Power Market & Prices Under Texas Electric Deregulation , The Steering Committee of Cities Served by Oncor & the Texas Coalition for Affordable Power (Texas, February 2011), http://tcaptx.com/downloads/THE-STORY-OF-ERCOT.pdf .

[75] “Articles of Incorporation of Electric Reliability Council of Texas (A Non-Profit Corporation),"(Austin, TX: Office of the Secretary of State, 1990).

[76] Peter Hartley, Kenneth B. Medlock, and Olivera Jankovska, Electricity Reform and Retail Pricing in Texas , Center for Energy Studies, Rice University’s Baker Institute for Public Policy  (June 2017), https://www.bakerinstitute.org/research/electricity-reform-and-retail-pricing-texas/ . Others offer a different analysis; for example, see Edward A. Hirs III, "Deliberate Inaction: Root Causes of Texas Power Failure Yet to Be Addressed," Houston Chronicle , February 14, 2022.

[77] For example, see Dyer, The Story of ERCOT: The Grid Operator, Power Market & Prices Under Texas Electric Deregulation ; Edward A. Hirs III and Paul W. MacAvoy, "Texas suffers from Soviet-style electricity distribution system," Houston Chronicle , February 22, 2013.

[78] When I asked a system operator at ERCOT what she focuses on when she comes to work each day, she wrote out the complete ACE equation, then struck through the first segment. Personal visit to ERCOT, February 2013.

[79] Julie Cohn and Olivera Jankovska, 2020, Texas CREZ Lines: How Stakeholders Shape Major Energy Infrastructure Projects , https://doi.org/https://doi.org/10.25613/261m-4215 .

[80] The Texas Legislature first set goals in 1999. With a favorable geography for wind power, and both state and federal tax incentives, the wind industry quickly exceeded the goals, and the Legislature took up the topic again in 2005.

[81] Aaron Bloom, Interconnections SEAM Study, National Renewable Energy Laboratory (Ames, Iowa, 2018); Rob Gramlich and Jay Caspary, Planning for the Future: FERC’s Opportunity to Spur More Cost-Effective Transmission Infrastructure, Americans for a Clean Energy Grid (Arlington, VA: Americans for a Clean Energy Grid, January 2021), https://cleanenergygrid.org/wp-content/uploads/2021/01/ACEG_Planning-for-the-Future1.pdf ; Eric Larson et al., Net-Zero America: Potential Pathways, Infrastructure, and Impacts , interim report, Princeton University (Princeton: Princeton University, December 15, 2020), https://netzeroamerica.princeton.edu/img/Princeton_NZA_Interim_Report_15_Dec_2020_FINAL.pdf ; NASEM, The Future of Electric Power in the United States, National Academies of Sciences, Engineering, and Medicine (Washington, D.C.: The National Academies Press, 2021); Avi Zevin et al., Building a New Grid Without New Legislation: A Path to Revitalizing Federal Transmission Authorities , Center for Global Energy Policy (New York: Columbia University, December 2020), https://www.energypolicy.columbia.edu/research/report/building-new-grid-without-new-legislation-path-revitalizing-federal-transmission-authorities .

[82] For a recent example, see Bloom, Interconnections SEAM Study.

[83] For a recent example, see Larson et al., Net-Zero America: Potential Pathways, Infrastructure, and Impacts, interim report.

[84] Thomas J. Overbye et al., "Stability Considerations for a Synchronous Interconnection of the North American Eastern and Western Electric Grids" (55th Hawaii International Conference on Science Sciences (HICSS), Lahaina, HI, January 2022).

[85] NASEM, The Future of Electric Power in the United States , 66–72.

[86] 147 FERC ¶ 61,113, Final Order Directing Interconnection and Transmission Service, Issued May 15, 2014

[87] Ibid., 8.

[88] Docket 45624, Order on Rehearing, Public Utility Commission of Texas (2017); Docket 45624, Revised Order Creating and Scoping Project , Public Utility Commission of Texas (2017).

[89] Edward Klump, "What a $2B Texas project says about U.S. quest for a CO2-free grid," E&E News , October 28, 2021.

This material may be quoted or reproduced without prior permission, provided appropriate credit is given to the author and Rice University’s Baker Institute for Public Policy. The views expressed herein are those of the individual author(s), and do not necessarily represent the views of Rice University’s Baker Institute for Public Policy.

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Understanding Texas’ energy grid failure

HKS faculty member and energy markets expert Bill Hogan explains Texas’ electricity crisis.

Record cold temperatures plunged Texas into a power crisis last week, with millions in the state losing power. The failure demonstrates the vulnerability of power grids to shifting weather patterns that come with climate change. However, the situation in Texas was made more complex by the fact that it is the only state in the country with its own power grid, the Electric Reliability Council of Texas (two other grids, the Eastern Interconnection and Western Interconnection, cover the rest of the United States). To understand what was behind the power failure, we spoke with Bill Hogan , Raymond Plank Research Professor of Global Energy Policy. In 2013, Hogan helped Texas system operators with their current market design. He is also the research director of the Harvard Electricity Policy Group and an expert on energy markets and electricity market design.

Q: You’ve been called the architect of the Texas system. Can you describe the role you played in creating it?

Efficient electricity market design requires a particular blend of engineering and economics. After an initial false start, the Texas market design embraced the fundamentals that I and others had written about for years, going back to the work of Fred Schweppe and his colleagues at MIT in the 1980s. In 2013 I worked directly with the Texas system operators on a major innovation in their market design to provide better pricing under increasing scarcity conditions. This scarcity pricing framework has been important in the intervening years and was a major reason for the high prices during the recent crisis. This crisis situation was unprecedented, but the market design coupled with the swift action of the system operator helped prevent an even worse catastrophe.

Q:  How did you determine your design choices for this system?

The market design adapts the economic fundamentals of textbook supply and demand with the arcane details of the flow of power on a transmission network. There are a few critical features. First, there must be central coordination by the system operator to accept power bids and offers and find the so-called “economic dispatch.” In effect, this is a very large auction being updated every few minutes. Second, in the presence of ubiquitous transmission constraints the market-clearing power prices can differ at every location in the system due to the differential effects on the constraints. Third, in times of scarcity it becomes especially important to price operating reserves to reflect the current conditions on the grid in order to provide incentives to increase supply or lower demand. Finally, these foundations make it possible for market participants who wish to hedge their prices to enter into bilateral hedging contracts, which can be quite valuable for those who take advantage of the opportunity.

Q: And what alternatives might one consider when designing a system like this, especially in light of unusual climate patterns?

The fundamentals of the market design, as summarized here, are both robust and will be of increasing importance with expanded reliance on intermittent energy sources such as renewables. There is no easy way to avoid the fundamentals. And there will always be tradeoffs about how much to spend in advance to protect against extreme conditions. After this decision is made, if conditions are more extreme than anticipated, then the best line of defense is to invoke rotating blackouts and apply pricing that reflects the severity of the situation. This is what happened in Texas, and the actions by the system operator prevented the catastrophe of a complete collapse of the grid, for everyone, and for a much longer period to restore service.

“The rules are complex, but Texas has weak transmission ties to the rest of the North American grid and is subject to the jurisdiction of the Texas regulators, but (largely) not to the Federal Energy Regulatory Commission.”

Q: Broadly speaking, why is the Texas energy grid struggling?

The widespread winter storm produced low temperatures across the region. This is an unusual event, much worse than the worst case that was considered in recent prior planning. The result was loss of power plants, loss of natural gas supply, felled power transmission lines, damaged gas pipelines, damage to water systems, and so on, across the board. There was a loss of more than 50 percent of generation capacity at the same moment as electric power demand surged above the predicted peak forecast.

Power systems are designed to share across the transmission grid in order to provide nearly instantaneous support to one part when another location is in trouble. When the problem is large enough or everywhere is in trouble, the same instantaneous response can propagate the damage and produce a total system failure. The standard policy is to institute controlled “rolling blackouts” that disconnect some load to prevent complete system collapse. This was the response in Texas, and it accomplished this important objective of preventing an even worse catastrophe. In addition, the rules produced much higher prices and provided a powerful incentive to reduce remaining demand and get the generating plants back online. All this was necessary under the circumstances.

Q: How would you answer critics of the exorbitant energy bills that some customers are now receiving?

The pain is severe, for both those facing the higher bills and even more for those who lost their power. The high bills go to two different groups. First, those energy intermediaries that sold hedging contracts received an agreed upon price that has probably been higher than market conditions until the crisis, and they are like any insurance provider who is responsible for making good on the promise of the contract price. Second, the minority of customers who chose not to hedge and enjoyed lower prices until the crisis, and who also chose to continue consuming electricity even when others were being curtailed, now face the higher bills. The curtailed customers who were selected for the rolling blackouts were by definition not consuming power and would not see higher bills for the curtailed period, although some probably would have preferred to pay and not be curtailed.

Q: Why is Texas the only state with its own power grid?

There is a long history here of the state wanting full control over its own destiny. The rules are complex, but Texas has weak transmission ties to the rest of the North American grid and is subject to the jurisdiction of the Texas regulators but (largely) not to the Federal Energy Regulatory Commission. Even the limited ties were not much help in the current crisis because other areas were also in rolling blackout conditions on a smaller scale and they did not have excess power to willingly share with Texas.

Q: What measure might have made Texas’ energy grid less vulnerable, and how can Texas avoid another crisis like this in the future?

As in the past, there will be a full post-mortem analysis. However, it is hard to conceive of a planning mechanism that would have provided full protection against an event that was much worse than the worst case envisioned. And as some important figures in the region have already said, the costs of such protection paid every year might be seen as too high a cost to pay to avoid such a rare outcome. 

Q: What role, if any, does the use of renewable energy play in this crisis? And what role can it play in solving it?

Renewable energy was part of the Texas energy supply. Some of it still worked, and some wind turbines were frozen or solar panels were covered in snow and unable to help. But the discussion about renewable energy is a distraction given the scale and scope of the current problem. The discussion for the future with increased renewable energy should await the post-mortem. The design of the system with increasing renewables was an active focus of policy discussion before this event, and this discussion will be continuing.

Q: What lessons can we learn from this event?

There will be many further analyses to provide guidance for the future. It will be important to avoid jumping to conclusions and learning the wrong lessons.

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Case Study: Causes of the Texas Power Grid Failure

In mid-February of 2021, a record-breaking winter storm swept through the U.S., and in Texas, the electricity grid failed, resulting in more than 100 deaths and nearly $200 billion worth of damage, according to reports. The devastation left many wondering, “Why did the freezing temperatures impact the state to this extent?”

Approximately 90 percent of Texas relies on its own, separate power grid controlled by ERCOT, the Electric Reliability Council of Texas. In the days during and following the massive outage, the finger-pointing and blaming began. By using the Cause Mapping ® method of root cause analysis, we can begin to understand the many causes that led to the failure and how a similar tragedy can be prevented in the future. This catastrophic incident impacted multiple goals: safety, production, customer and arguably more goals. It can be overwhelming to begin an incident investigation on an issue of this magnitude.

Here, we begin by asking Why questions, starting with, “Why was there an extended loss of electrical power?” From there, we continue to ask Why questions. By starting this way, a 3-Why Cause Map™ diagram may look like this:

This is a much more complex issue than a few Why questions, but to uncover more evidence-based details about the failure we must ask why and how it happened until we understand the causes. When the Arctic blast hit the U.S., for the Texas grid, demand exceeded supply despite the state’s deregulated electricity marketplace , leaving millions without power and water for days in subfreezing temperatures. Upon further research, we learn that the available power supply went as low as 46 gigawatts, but the demand surged to 68 GWh, bringing the grid to the brink of failure .

By continuing to gather evidence and ask why the grid failure occurred, our Cause Map diagram expands. Click on the thumbnail below to download a PDF of the 22-Why.

Of course, an incident of this magnitude should be analyzed to the level of detail required to find the best solutions to control the causes of the grid failure. A Cause Map diagram can expand to include more detailed information of what happened in February and why to the level of detail needed. For more information on the Cause Mapping method and how it can be used to analyze your organization’s incidents, attend one of our upcoming free webinars or other trainings .

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Math Could Have Saved the Texas Power Grid

Here's why the power went out in the Lone Star State last winter—and how we can prevent future failures.

Functions often fail at the edge of their range of validity, leading to so-called edge cases: a situation that occurs only at an extreme operating parameter. An edge case can be expected or unexpected. A stereo speaker might distort audio when played at maximum volume, or a website designed to handle 10,000 users might crash when 50,000 people try to log on. Quantitatively different behavior happens at a system’s boundaries, and a failure to plan for these anomalies can have devastating consequences.

“Our all-time peak demand record is about 75,000 megawatts,” says Joshua D. Rhodes, Ph.D., who works in the Webber Energy Group at the University of Texas at Austin. “In order to keep the lights on in Texas, we would have had to push the system up to 76,000 megawatts, further than we’ve ever pushed it before.” Professor Rhodes’s research focuses on the bulk electricity system, and the grid optimization models he builds frequently result in edge cases. “I push the grid to extremes—or what I thought were extremes.”

.css-1i6271r{margin:0rem;font-size:1.625rem;line-height:1.2;font-family:UnitedSans,UnitedSans-roboto,UnitedSans-local,Helvetica,Arial,Sans-serif;padding:0.9rem 1rem 1rem;}@media(max-width: 48rem){.css-1i6271r{font-size:1.75rem;line-height:1;}}@media(min-width: 48rem){.css-1i6271r{font-size:1.875rem;line-height:1;}}@media(min-width: 64rem){.css-1i6271r{font-size:2.25rem;line-height:1;}}.css-1i6271r em,.css-1i6271r i{font-style:italic;font-family:inherit;}.css-1i6271r b,.css-1i6271r strong{font-family:inherit;font-weight:bold;} “Zero is always a good case test, because something might go wrong at zero.”

In the past, that might have meant testing solar or wind extremes on the grid and making sure supply kept up with demand. “We went into winter 2021 having run scenarios where we had high demand and low supply, but all of these showed as fine,” Rhodes says. “That’s because we were using historical weather norms to look into the future.”

Planning for edge cases is formidable, expensive, and sometimes overlooked. At best, unconsidered edge cases fail to address users at the margins; at worst, they cause drastic system failures. A confluence of edge cases brought down the Challenger space shuttle in 1986 (see sidebar).

When two or more edge cases meet, they form a corner case. Corner cases are valuable when debugging a complex system, but they are often harder and more expensive to test because they require maximal configurations in multiple dimensions. What happens when a self-driving car misinterprets a traffic signal because of a lightning flash, and plows through an intersection? These corner cases are improbable, but not outside the realm of possibility, and experts plan for them through equations that test a system’s validity.

Functions are most useful. “Zero is always a good case test, because something might go wrong at zero,” says Tony Mann, director of the Maths Centre at the University of Greenwich in London. Given that a function can’t be divided by zero and zero has no logarithm, this value might cause software to malfunction if it wasn’t specifically planned for. “Or we take the square root of a negative number and see if software would fail, because most systems can’t handle complex or imaginary numbers.”

Zero is used to signify any kind of null input (whether that’s undefined, an empty array, or the number zero), revealing whether a system behaves as expected. Testing 1 and 2 in a function, by contrast, shows how the system operates with “normal” input. Testing “max” (that is, the upper limit of an application) is a way to stress-test an application—even if the max seems implausible. An error can provide valuable information that might change the design of a product or service ahead of any real-life disaster. “Typically, an edge case arises when you build something and, over time, conditions arise that weren’t foreseen; the assumptions you made originally are no longer valid,” Mann explains.

In the case of the Texas power failure, frozen cooling-water systems and fuel-supply issues pushed the grid toward an extreme corner case that saw the power plant fleet unable to supply enough power to meet demand, according to Rhodes. This failure underscored “the need to plan a reliable grid with the constraint (or boundary) on that supply,” he explains. Boundary testing for such scenarios can be expensive, but the costs of forgoing testing might be greater. “I don’t know that the multisystem failure pushed us to the edge,” Rhodes says, “but it certainly brought the edge closer to us.”

Challenger: A Case Study

A mere 73 seconds after liftoff, on January 28, 1986, NASA’s Challenger space shuttle blew apart , killing all seven astronauts aboard. A review commission found a few edge cases that contributed to the spacecraft’s demise, but most notably, exceptionally cold temperatures were to blame.

Challenger ’s solid rockets were rated for temperatures of 39 degrees Fahrenheit or higher, but ground temperature at launch was just 24 degrees. That, in turn, caused a seal located on the shuttle’s right solid rocket booster—known as an O-ring —to malfunction at launch, letting out hot, pressurized gas. The gas ruptured a strut connecting the booster to the external fuel tank, destroying both.

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Grid Failures — Case Studies and ‘Defence’ Plan against Failures

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Northeast Power Failure - Nov. 9 and 10, 1965, The Federal Power Commission Report ,Dec. 1965.

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Prevention of Power Failures - The Federal Power Commission Report ,Volume I, July 1967.

The Con-Edison Power Failure, July 13 and 14, 1977, Staff Report, Federal Energy Regulatory Commission, U.S. Department of Energy, Washington, DC 20461.

Andre Cheimanoff and Claude Corroyer, The Power Failure of December 19, 1978, Revue Générale de 1’Electricité ,April 1980.

Workshop on power system disturbances ,Paris, CIGRE SC 39, August 1994.

M. Trotignon et al., Defence plan against major disturbances on the French EHV power system: Present realisation and prospects of evolution ,CIGRE 1992, Paper 39–306.

O. Faucon et al., Co-ordinated Defence Plan - An integrated protection system , CIGRE Symposium, Helsinki 1995.

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Mariani, E., Murthy, S.S. (1997). Grid Failures — Case Studies and ‘Defence’ Plan against Failures. In: Control of Modern Integrated Power Systems. Advances in Industrial Control. Springer, London. https://doi.org/10.1007/978-1-4471-0993-8_6

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Charles Q. Choi is a science reporter who contributes regularly to IEEE Spectrum.

Just a few vulnerable patches in North American power grids are responsible for most of the continent’s largest blackouts, a new study finds. These insights could lead to ways to make power grids more robust, researchers say.

Power failures sometimes only have mild and fairly local effects, but other times similar initial failures cascade to cause major failures across power grids. Understanding the causes of these cascades is challenging because the conditions of power grids can vary greatly by peak usage times, level of power demand, seasons and other factors.

To shed light on how failure cascades are triggered, scientists from Northwestern University in Evanston, Illinois. analyzed U.S. Federal Energy Regulatory Commission data regarding the U.S.-South Canada power grid , which has more than 100,000 transmission lines. Using information spanning the years 2008 to 2013, they developed a model of the behavior of these lines within electrical networks across North America.

The research team's simulations revealed that over the entire network, only 10.8 percent of all transmission lines were vulnerable to the kind of "primary failure" that could trigger a cascade. They also found that 85 percent of all primary failures occurred roughly 20 percent of these links, which altogether made up about 2.16 percent of all links. These more-vulnerable components were typically geographically clustered near each other and were often located near densely populated areas.

"In the North American power grid, the set of power lines that are susceptible to failures were found to represent a surprisingly small fraction of the whole network," says study co-author Takashi Nishikawa, an applied mathematician at Northwestern.

Their findings also suggest that power failures cannot spread essentially without bound. Their simulations found that while the physics underlying the spread of power failures do not put constraints on how far a failure can hop in a single step, they generally tend to stay close to where they originated. "The power grid is quite robust against the propagation of failures — perhaps surprisingly robust, when we consider all the complexities involved," Nishikawa says.

These findings "suggest that the vulnerability of individual network components should be considered in prioritizing power line upgrades," Nishikawa says. "Selecting which power lines to upgrade based on the pattern of past or simulated failures would likely be a cost-effective way to mitigate future cascades. How well such a strategy actually works in real power grids needs to be seen, but our findings suggest that this type of failure-based resource allocation is a promising approach."

Understanding how failures might cascade in power grids might also shed light on similar phenomena in other networks, "such as traffic networks, supply chains and food webs," Nishikawa says.

The scientists detailed their findings in the Nov. 17 issue of the journal Science .

• How to Turn the Lights Back on After a Blackout - IEEE Spectrum ›

Charles Q. Choi is a science reporter who contributes regularly to IEEE Spectrum . He has written for Scientific American , The New York Times , Wired , and Science , among others.

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The Dangers of Power Grid Failure: Causes, Case Studies, and Implications

This article explores the causes of power grid failure, examining natural disasters, equipment failure, cyber attacks, and human error. It presents case studies of the Northeast Blackout of 2003 and the India Blackout of 2012, along with expert insights on the lessons learned. The article also delves into the implications of power grid failure, including economic consequences, public safety concerns, and national security risks. Preemptive measures and solutions, such as grid modernization initiatives, increased investment in infrastructure, and strengthened cybersecurity measures, are discussed. The conclusion emphasizes the importance of addressing power grid vulnerabilities and encourages further research and collaboration.

Introduction

The power grid is the backbone of modern society, providing electrical energy to support critical infrastructure, businesses, and households. However, power grid failure can have serious consequences, leading to widespread blackouts, economic losses, and public safety concerns. This article examines the causes of power grid failure, presents case studies of notable incidents, discusses the implications of such failures, and explores preemptive measures and solutions to strengthen the resilience of our power grid.

Causes of Power Grid Failure

Power grid failure can occur due to a variety of factors, including natural disasters, equipment failure, cyber attacks, and human error.

Natural Disasters

Natural disasters such as hurricanes, earthquakes, and wildfires pose a significant risk to power grid infrastructure. These events can damage transmission lines, substations, and other critical components, resulting in widespread power outages. For example, Hurricane Sandy in 2012 caused extensive damage to the power grid in the northeastern United States, leaving millions without electricity for days.

According to John McDonald, a power industry expert, "Natural disasters are an unavoidable reality, and the power grid must be built to withstand these events. This requires implementing robust design standards and conducting regular maintenance and inspections to identify vulnerabilities. Additionally, having redundant systems and backup power sources can help mitigate the impact of a natural disaster on the power grid."

Equipment Failure

Equipment failure is another common cause of power grid failure. Over time, aging infrastructure, faulty equipment, and lack of maintenance can contribute to the degradation and failure of critical components such as transformers and circuit breakers. A single equipment failure can have cascading effects, leading to widespread blackouts.

David Owens, the former executive vice president of the Edison Electric Institute, highlights the importance of proactive maintenance and investment in grid infrastructure: "Regular inspections, timely repairs, and strategic upgrades are crucial to prevent equipment failure and minimize the risk of power grid failure. By investing in modern technologies and replacing aging infrastructure, we can enhance the reliability and resilience of the power grid."

Cyber Attacks

In today's interconnected world, cyber attacks pose a growing threat to the power grid. Hackers with malicious intent can target control systems and critical infrastructure, disrupting power generation, transmission, and distribution. A successful cyber attack can result in widespread blackouts and compromise the security of the entire electrical grid.

Jonathan Pollet, a cybersecurity expert, warns, "As the power grid becomes increasingly digitized, it becomes more vulnerable to cyber attacks. Protecting the grid from cyber threats requires a multi-layered approach, including stringent access controls, regular security assessments, and continuous monitoring of network traffic. Collaboration between the power industry and cybersecurity experts is essential to stay ahead of evolving threats."

Human Error

Human error can also contribute to power grid failures. Mistakes made by operators, engineers, or maintenance personnel can have far-reaching consequences, leading to system overloads, equipment damage, or incorrect configuration of protective relays. Training and procedures play a critical role in reducing the risk of human error and ensuring the reliable operation of the power grid.

Kevin Kane, a power grid operations specialist, emphasizes the need for continuous training and rigorous processes: "Human error can never be completely eliminated, but through proper training, clear procedures, and real-time situational awareness, we can minimize the likelihood of errors and quickly respond to any issues that arise."

Case Studies

To better understand the impact of power grid failure, let's examine two notable case studies: the Northeast Blackout of 2003 and the India Blackout of 2012.

Northeast Blackout of 2003

The Northeast Blackout of 2003 was one of the most significant power outages in North American history, affecting over 50 million people in the United States and Canada. The blackout, which lasted for several days, was caused by a combination of equipment failure, software bugs, and human error.

Analysis of Causes and Impact

The blackout was triggered by the tripping of a power line in Ohio, which caused a chain reaction of failures across the interconnected power grid. An insufficient alarm system and inadequate situational awareness further contributed to the spread of the outage. The economic impact of the blackout was estimated to be between $4 billion and $10 billion.

Expert Insights on Lessons Learned

Robert Santchi, an electrical engineer, stresses the importance of enhanced situational awareness: "The Northeast Blackout of 2003 highlighted the need for real-time information and better communication between grid operators. Implementing technologies such as synchrophasors and advanced monitoring systems can provide operators with the necessary data to detect and mitigate potential issues before they escalate into widespread blackouts."

India Blackout of 2012

The India Blackout of 2012 affected over 600 million people and was one of the largest power outages in history. The blackout was caused by a combination of factors, including a failure in the northern grid, inadequate transmission capacity, and operational issues.

Examination of the Factors Involved

The blackout was triggered when the northern grid, which supplies power to several states, collapsed due to excessive load. Insufficient transmission capacity and poor coordination between regional grids exacerbated the situation, leading to a cascading failure. It took several hours to restore power to all affected areas.

Expert Commentary on Preventive Measures

Suresh Kumar, an energy policy expert, emphasizes the importance of investing in transmission infrastructure: "The India Blackout of 2012 highlighted the need for robust transmission networks and coordinated operation between regional grids. By enhancing transmission capacity and adopting modern grid management techniques, India can reduce the risk of similar incidents in the future."

Implications of Power Grid Failure

Power grid failure can have significant implications for various aspects of society, including economic consequences, public safety concerns, and national security risks.

Economic Consequences

Power grid failures can lead to substantial economic losses, both in terms of lost productivity and the cost of repairs. Industries heavily reliant on electricity, such as manufacturing and data centers, can suffer severe financial setbacks during a blackout. Additionally, power outages can disrupt supply chains and cause ripple effects throughout the economy.

According to a study by the Federal Energy Regulatory Commission (FERC), power outages in the United States cost the economy an average of $80 billion to $188 billion annually. Investing in grid resilience and implementing measures to prevent power grid failures can help mitigate these economic impacts.

Public Safety Concerns

Power grid failures pose significant public safety concerns. Blackouts can disrupt essential services such as hospitals, emergency response systems, and traffic management. People who rely on life-support equipment or medical devices may be at risk during prolonged power outages. Additionally, the lack of street lighting and the disruption of public transportation can compromise personal safety, leading to an increase in accidents and crime rates.

National Security Risks

The power grid is a critical infrastructure asset and a potential target for malicious actors seeking to disrupt a nation's functioning. Power grid failures can have severe national security implications, especially if they are caused by a cyber attack or an intentional act of sabotage. A prolonged blackout can cripple a country's ability to respond to emergencies, maintain law and order, and defend against external threats.

Preemptive Measures and Solutions

To address power grid vulnerabilities and enhance resilience, several preemptive measures and solutions can be implemented.

Grid Modernization Initiatives

Grid modernization initiatives aim to transform the power grid into a more flexible, reliable, and responsive system. This involves incorporating advanced technologies such as smart grids, energy storage, and renewable energy integration. By utilizing real-time data and analytics, grid operators can optimize power flow, detect abnormalities, and proactively manage grid stability.

Increased Investment in Infrastructure

Increased investment in grid infrastructure is essential to maintain and upgrade aging components. By replacing outdated equipment, enhancing transmission and distribution systems, and strengthening grid interconnections, the resilience of the power grid can be significantly improved. Public-private partnerships and government funding programs can play a crucial role in funding these infrastructure investments.

Strengthened Cybersecurity Measures

Given the growing threat of cyber attacks, strengthening cybersecurity measures is paramount to protect the power grid. This includes implementing robust access controls, regular security assessments, and continuous monitoring of network traffic. Active collaboration between the power industry, government agencies, and cybersecurity experts is essential to develop and enforce effective security protocols.

Power grid failure poses significant risks to our society, economy, and national security. By understanding the causes of power grid failure, studying past case studies, and recognizing the implications, we can take proactive measures to enhance the resilience of our power grid. Grid modernization initiatives, increased investment in infrastructure, and strengthened cybersecurity measures are key steps towards mitigating the risk of power grid failure. It is crucial for policymakers, industry experts, and researchers to collaborate and address the vulnerabilities of our power grid to ensure a reliable and secure energy future.

Call to Action

To learn more about power grid vulnerabilities and contribute to the dialogue on enhancing grid resilience, I encourage you to participate in conferences, workshops, and research initiatives focused on this topic. By sharing insights, lessons learned, and innovative solutions, we can collectively work towards a more resilient power grid that can withstand the challenges of the future.

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