It had been about three years since Texas experienced major rolling blackouts, but they happened this week in the Rio Grande Valley. The Electric Reliability Council of Texas (ERCOT), the group that manages nearly all of the Texas grid, says the blackouts are related to longstanding problems with the transmission system in the region.
Trouble started on Wednesday afternoon when two power plants suffered breakdowns. Fearing that high demand and low supply of electricity could damage the regional grid and cause an uncontrolled blackout, ERCOT called for “rotating outages” (industry speak for rolling blackouts) to keep some power on the lines.
Grid managers have known for some time the valley runs a higher risk of rolling blackouts. The reason is that the transmission system in the Valley is more isolated than other parts of Texas. It cannot easily bring in electricity from the rest of the ERCOT grid when needed. That can cause blackouts in the Valley even when the rest of the grid is stable, according to ERCOT.
“The valley area has some significant limitations as far as how much power it can import into that region,” says Robbie Searcy, an ERCOT spokesperson. “Right now when there is a hot early fall afternoon and we have these sort of generation outages there is a risk to the transmission system in that area.”
Searcy says there are two large projects underway to improve transmission. One will upgrade lines from the Corpus Christi area into the Valley and add a link to the Laredo area. The second project will bring in a new transmission line between Hidalgo County to the Brownsville Ship Channel.“The challenge right now is those are large projects and they wont be complete until 2016,” says Searcy. “So it’s possible that in the coming years we could continue to see some challenges in the Rio Grande area.”
Electric providers also imported power from Mexico during the emergency.
“Although ERCOT essentially operates as an island, We do have some limited direct current ties with other grids and one of those connects to Mexico,” says Searcy. “Right now the capacity on that particular tie is about 170 megawatts total. It’s in the process of being upgraded and by next summer the capacity of that particular tie will be 300 megawatts.”