Extremely cold weather, exacerbated by the unplanned outages of two large generating resources in north central Texas, forced grid operator ERCOT to declare an energy emergency alert 1 (EEA-1) at 6:52 a.m., Central time Jan. 6, and elevate that to an EEA-2 less than 10 minutes later.
“We lost about 3,700 MW of generation due to forced outages and deratings,” Dan Woodfin, ERCOT’s director of system operations, said during a conference call shortly before noon Central time. He noted that about half the generation lost was due to weather-related issues but said that, despite the lost generation, the grid operator did not have to call for rotating outages.
“No firm load was dropped; any load reductions that we had were from resources that were specifically contracted ahead of time and paid to reduce in exactly these types of circumstances,” Woodfin said.
ERCOT deployed more than 1,000 MW of demand-response resources and more than 600 MW of emergency response service (ERS) resources.
“The deployment of additional resources in the first two stages [of the EEAs] brought sufficient resources online,” he said. “It’s only in the third step of EEA where we’d move to rotating outages.”
An EEA-1, which is considered a “power watch,” is issued within ERCOT when reserves are below 2,300 MW. It requires the grid operator to commit all available generating units and take other preparatory steps. An EEA-2, or “power warning,” is issued when reserves are below 1,750 MW. In response to an EEA-2, the grid operator will deploy demand response resources and/or ERS resources. An EEA-3, or “power emergency,” requires the initiation of rotating outages.
“We were close – probably if we had lost another unit, it would have pushed us into an EEA-3,” Woodfin said.
However, both of the generating units that tripped offline Monday morning had returned to service by noon Central time, he said, and as long as additional generation did not trip offline.
ERCOT had to initiate the EEAs despite precautions taken the night of Jan. 5 due to the forecast of a hard freeze that was expected to move into the area before sunrise the next morning. The grid operator told generation and transmission operators to review their supplies to ensure adequate fuel was available, delay any planned generation or transmission outages, endeavor to return to service any facilities that were out of service, and implement any appropriate winterization procedures.
Those measures, however, were apparently insufficient to keep two large generating facilities in north central Texas in service.
“Based on the preliminary information we’ve received, it appears both [outages] were related to freezing of some of their instrumentation that’s used to provide control for the plant,” Woodfin said.
He did not name the affected generation facilities or their operating companies, as names of the plants and their operators are considered “protected information” by ERCOT’s market protocols for 60 days following an event or incident.
Peak demand on Jan. 6 reached 55,486 MW in the hour ending at 8 a.m., an ERCOT spokesperson told TransmissionHub Jan. 6. That demand, however, was still lower than ERCOT’s winter peak to date – a peak demand of 57,265 MW achieved on Feb. 10, 2011.
More of same to come
“We’re expecting that demand to be similar to what we saw [Jan. 6], so we’ll need all the generation to stay available during … peak [Jan. 7] as well,” Woodfin said, noting that ERCOT advised operators to implement any steps they may need to take to be prepared for the cold weather and be able to respond appropriately.
As it did in preparation for the cold snap on Jan. 6, the grid operator asked generation and transmission operators to defer any discretionary outages, as well as to bring back any units that are currently offline if possible.
ERCOT has also issued a conservation alert and is encouraging consumers to conserve energy through measures including reducing their thermostats to as low a level as comfortable, turning off and unplugging non-essential lights and appliances, and avoiding the use of large appliances such as washers, dryers and electric ovens during peak energy demand hours of 6 a.m. to 9 a.m. and 4 p.m. to 8 p.m.