Frozen valves, control equipment and transducers at Texas' largest power plants caused Wednesday's emergency rolling outages, and it remains unclear whether plant operators properly prepared and maintained their facilities for winter, state power regulators said Thursday.
The Electric Reliability Council of Texas canceled on Thursday emergency procedures that began early Wednesday morning after recovering more than half of the 8,000 megawatts of electricity lost a day earlier.
The equipment that froze should have been insulated as part of the power plants' preparation for winter, ERCOT's CEO Trip Doggett said. ERCOT and the Public Utility Commission are looking into whether insulation at the 50 plants that failed was done properly or whether it was inadequate for the unusually frigid temperatures.
"We have to let the owners of the generators speak to their issue," Doggett told reporters. "Usually these plants go through a winterization process in preparation for cold weather to ensure heat and insulation is wrapped around pipes, valves and other equipment. So it's only speculating why that wasn't adequate in this case."
Clara Tuma, a spokeswoman for the Lower Colorado River Authority that operates five power-generating plants, said it prepared for the cold, bringing in heaters for the units and installing tarps to protect them from wind. Valves were opened to keep water flowing and avoid freezing pipes, she said. She declined to say whether any units had failed, but said it had "the same issues as every other utility provider."
This week, we knew the weather was chilly and was getting colder, so we were in an "all hands on deck" situation," Tuma said.
Things were so dire Wednesday, Mexico exported power across the border, Doggett said. By Thursday, however, Mexico was struggling with its own cold weather and could no longer help.
By Thursday afternoon, Luminant, which had four units fail Wednesday, had three generating power again, the company said in a statement.
But while the emergency is over for now, Doggett warned the rare freezing temperatures plaguing Southeast Texas meant residents need to conserve energy until temperatures moderate over the weekend.
"Our optimism is tempered by concern, especially in South Texas," Doggett said. "It's very cold in the valley today, much colder than normal, and we continue to have plant outages in the valley that concern us."
Still, questions about what caused three-quarters of the state to suffer several controlled outages remained unanswered, and Doggett refused to take questions from reporters who dialed into a news conference held in Austin on Thursday. It was the first time the council answered media queries, more than 30 hours after the first outage at 5:09 a.m. Wednesday.
Doggett declined to list the failing plants, saying it could harm competition in a state that has deregulated electricity distribution and many consumers can choose a provider.
Already, he said, ERCOT is preparing for the summer when oppressive heat creates transmission line problems, Doggett said.
Terry Hadley, spokesman for the Public Utility Commission, said it remains unclear whether the insulation was improper or if there was a problem with the integrity of the pipes. At the moment, there are "expectations" that the plant operators will prepare for extreme weather, but after this incident there could be more regulation put in place. Similar issues are rare in colder areas of the country, partly because they deal with such temperatures all the time and are better prepared, he said.
"But that doesn't excuse not being able to operate when an unusual cold event happens in Texas," Hadley said.
Officials have found no pattern and no area of the state or operator that was more or less prone to issues, Doggett said.
"It included units that were online that tripped offline and it also included units that were attempting to come online that were unsuccessful," he said, explaining how the grid fell below the 2,300 megawatts of reserves, triggering the emergency.
The outages, Doggett said, are the last step taken to ensure the grid's security is not compromised -- a situation that could cause statewide blackouts. The grid was never close to going down.
"We were very secure," he added.
ERCOT: Reports of Thursday rolling outages are erroneous
Despite published reports from other local media outlets indicating that rolling outages were taking place between 6 and 8 a.m., ERCOT told NBC DFW on Thursday morning that it did not schedule any rolling outages Thursday.
Just after 6:30 a.m., ERCOT said Thursday morning's peak demand was more than 56,800 MW, but that there were no plans to implement rolling outages as it had on Wednesday.
“We are very appreciative of the sacrifices of those who were without power during the rotating outages, and we also appreciate the conservation efforts by consumers during this emergency situation, as well as the load resources in our demand response programs,” ERCOT CEO Trip Doggett said in the press release. “We also want to thank the media for their assistance in getting information out to the public about the need to conserve.”
How to conserve electricity in times of crisis
Why the emergency is over, ERCOT is still urging Texans to conserve energy.
Residents and businesses are urged to reduce their electricity use to the lowest level possible, including these steps:
See more conservation tips at “Powerful Advice,” Public Utility Commission of Texas.
NBC DFW's Frank Heinz contributed to this report.