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Texas' Power Grid Was 4 Minutes And 37 Seconds Away From Collapsing. Here's How It Happened.

Ice covers trees and power lines in South Austin last week.
Gabriel C. Pérez
Ice covers trees and power lines in South Austin last week.

We’ve heard Texas’ power grid came close to total failure early the morning of Feb. 15, but not exactly how close.

Officials at the Electric Reliability Corporation of Texas (ERCOT), which manages the state’s grid, showed its board a timeline Wednesday of events leading up to the grid's near-collapse. That timeline showed the grid was just 4 minutes and 37 seconds away from a cascading series of events that could have left Texas in the dark for weeks — if not more.

To keep the grid running, officials said, operators need to have enough power to maintain a constant frequency of around 60 hertz (you can learn more about that here). But on the evening of Sunday, Feb. 14, temperatures were falling, snow and ice were blanketing Texas and people were turning up their thermostats.

Meanwhile, power plants across the state were going offline because of the cold weather; natural gas, coal, nuclear and wind energy sources were all failing. Equipment and pipelines were freezing up. At 12:15 a.m. Monday, ERCOT went to its first level of energy emergency alert.

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But that wasn’t enough. At 1:07 a.m., ERCOT went to the second level. This triggered some power reductions for industrial customers that volunteer to have power turned off when supply gets scarce.

Things kept getting worse. By 1:23 a.m., one-third of the state’s power-generation capacity was down. The highest alert was triggered, and ERCOT ordered power providers to start rolling blackouts.

If there’s not enough power on the grid to meet demand, ERCOT officials said, the frequency of the grid drops below that 60 hertz level. That can cause physical damage to equipment that moves power around the state. And it can force more power plants to shut down — possibly leading to a complete failure of the grid.

But those initial rolling blackouts didn’t solve the problem.

Still more power plants went offline because of the weather. And by 1:43 a.m. Monday, the frequency of the grid was falling to dangerous levels. At about 1:51 a.m., the grid dropped below 59.4 hertz. That may not sound much different than 60 hertz, but if the frequency stayed under that threshold for 9 minutes or more, ERCOT officials said, it would trigger that cascading failure of the grid.

Within minutes, the frequency fell to about 59.3 hertz. Grid operators told power providers to expand rolling blackouts again.

Four minutes and 23 seconds after it dipped below 59.4 hertz, the frequency began to rise as more customers were dumped from the grid. If it had stayed below that threshold for another 4 minutes and 37 seconds, the lights might still be out in Texas, ERCOT officials said.

By about 2:03 a.m., the grid was back at or above 60 hertz. But by that time, there was not enough power being produced to undo the blackouts — and as many of us know, some of the lights would stay out for days, until more power plants came back online.
Copyright 2021 KUT 90.5. To see more, visit KUT.

A timeline of Texas' power grid frequency on the morning of Monday, Feb. 15, 2021.
A timeline of Texas' power grid frequency on the morning of Monday, Feb. 15, 2021.

Matt has been a reporter at KUT off and on since 2006. He came to Austin from Boston, then went back for a while--but couldn't stand to be away--so he came back to Austin. Matt grew up in Maine (but hates lobster), and while it might sound hard to believe, he thinks Maine and Texas are remarkably similar.