No initial evidence had been found that the Texas power market had been manipulated when grid operator the Electric Reliability Council of Texas (ERCOT) on Feb. 2 ordered rolling blackouts, but investigations would continue, Texas regulators told legislators on Tuesday. The blackouts were necessary as some 82 power plants—out of 550 on the grid—went down for various reasons while freezing temperatures caused a record-breaking demand spike, ERCOT said.

ERCOT, which operates 85% of the power demand in Texas, released a partial list of plants that went out of service—but only after the organization was pressed by senators overseeing the joint hearing of the state’s Business and Commerce and Natural Resources committees. The grid operator had previously refused to disclose which facilities had gone down to protect market competitiveness.

Power plants that were offline between Feb. 1 and Feb. 4, mainly because of weather conditions, included 22 plants operated by Calpine, nine by Luminant—including its brand new Oak Grove units—and eight by NRG Energy. Luminant CEO David Campbell told state senators that the company had “learned from the event,” and the outages had proven costly: Pre-tax earnings were expected to fall by $30 million.

"Even though it’s designed to withstand the weather, you have vulnerability in these plants and you do learn when you go through the hard weather to do it,” he told lawmakers.

During the hearing, ERCOT CEO Trip Dodgett was asked by Sen. Troy Fraser (R-Horseshoe Bay) what ERCOT planned to do to make sure that such a blackout doesn’t happen again. Dodgett responded that the grid organization had launched a new alert system that would call or send e-mails to regulators, the governor’s office, and the state operations center when there was a danger that demand could exceed supply. The state operations center, in turn, notifies police and fire officials and other first responders.

On Monday, meanwhile, the Federal Energy Regulatory Commission (FERC) initiated a staff inquiry into the blackouts, as well as restrictions on natural gas, which were spread across Arizona and New Mexico. FERC said the inquiry would look to identify the causes of the disruptions and to identify any appropriate actions for preventing their recurrence.

The North American Reliability Corp. (NERC) last week said it was working with regional entities to examine which generation and transmission issues on the bulk power system were affected and what can be done to minimize risk in future events.

NERC said it would also study electric and gas interdependencies. “This study will be a broad look at areas in North America where extreme cold weather or loss of a major gas supply could impact electricity production, review existing procedures designed to mitigate the reliability impacts from such events, and, conversely, identify if rolling electric system outages could adversely impact the operation of electric powered gas compressors needed to maintain adequate gas pressures.”

Sources: POWERnews, PUC, ERCOT, Austin American-Statesman, Houston Chronicle, Texas Tribune, FERC, NERC