HOUSTON — The state’s power grid experienced rotating outages for the first time since 2011 late Wednesday afternoon after a pair of power plants went offline.
The outages affected the Rio Grande Valley for about two hours, said Robbie Searcy, a spokeswoman for Electric Reliability Council of Texas, which operates most of the state’s grid.
Searcy said the Rio Grande Valley has been a particularly challenging area for ERCOT to manage because it has a limited number of transmission lines serving the region. As a result, it’s difficult for the region to pull power from other areas when something unexpected happens, like Wednesday’s power plant shutdowns.
ERCOT ordered the rotating outages, and each of the transmission and distribution systems serving the area had their own plans to implement them, Searcy said. Typically, each outage lasts between 15 and 45 minutes, and they’re rotated among different neighborhoods to limit their impact.
She characterized Wednesday’s event as a different type of outage than the rolling blackouts that affected Texas in February 2011, when cold weather caused failures at dozens of power plants across the state at the same time Texans were trying to use more power to heat their homes and businesses.
While 2011’s blackouts were statewide, Wednesday’s outages were confined exclusively to the Rio Grande Valley.
Searcy said the Valley outages were a controlled event, managed by ERCOT, and intended to prevent the region’s power demands from overwhelming the grid as the power plant operators worked to bring their infrastructure back online.
“This is a controlled situation so we can restore power as quickly as possible after the problem goes away, as opposed to an uncontrolled situation,” Searcy said.
ERCOT describes rotating outages as a temporary “safety valve” that prevent generators from becoming overloaded. Hypothetically, if generators became overloaded, their operators would shut them down and create a domino effect resulting in region-wide outages.
Searcy declined to identify the two power plants that went offline but said they are currently operational. She didn’t know what caused them to fail.
At 5:05 p.m. Wednesday, ERCOT, announced that it had instructed Valley-area transmission and distribution providers to reduce the demand for electricity immediately. It also asked Valley residents to reduce power consumption by turning up their thermostats and delaying their use of large appliances.
“We realized this is a disruption,” Searcy said. “We’re certainly working with transmission providers in the area to improve the import capability into the area.”
Meanwhile, according to ERCOT, two new transmission projects are slated for completion in 2016 to address the bottleneck, though the grid operator has said more are needed.
Interestingly, the situation facing the Rio Grande Valley could be a harbinger of things to come in the Houston area if plans to build a new transmission project into the region don’t move forward, Searcy said.
The Public Utility Commission is deciding whether to advance an ERCOT-endorsed project known as the Houston Import Project, a 130-mile transmission line from east of Waco in Limestone County to northwest Harris County.
ERCOT has said the transmission line is necessary because population and industrial growth in the Houston area is increasing the demand for power here. At the same time, older power plants are closing and new ones aren’t being built to fill the void. The result is that Houston could become increasingly dependent on power generated in other parts of the state, but inadequate transmission lines threaten to prevent all of that power from getting here.
That project has won the endorsement of CenterPoint Energy, the transmission company serving the Houston area. But Houston-based power generators Calpine and NRG Energy have questioned the project and argue that it’s expensive and probably not necessary. They argue they’ll eventually build new generation in the area, even though they can’t offer definitive guarantees that those new plants will come to fruition.
The Public Utility Commission is scheduled to hold a hearing on the merits of the power generators’ case Oct. 17.