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03/11/2014

ERCOT details outages during Jan. 6 cold snap

It's good that the operator of the state's largest power grid is able to show exactly where the problems are when power gets in short supply during unusual circumstances, but it doesn't always inspire total confidence in the system. The Electric Reliability Council of Texas on Friday released a report on the Jan. 6 cold snap that pushed ERCOT into what it calls a Level 2 Energy Emergency Alert. By the end of the day, 97 power generation units around ERCOT's system had experienced some sort of issue - tripped offline, failed to start or were derated (saw their output decline). Problems according to ERCOT's report included:

  • Generator outages specifically tied to the weather hit units representing 3,541 megawatts of capacity. The bulk of that, units with close to 3,000 megawatts of capacity, reported "frozen instrumentation." (A unit is an individual machine generating electricity; there can be several units at large power plants.)
  • Another 1,643 megawatts, all at natural gas-fired units, were unavailable because of restrictions in their supply of fuel.
  • More than 30 wind farms said were out because their turbines reached their "low temperature limit." Lindsay North, a spokeswoman at the American Wind Energy Association, said that's related to the performance of lubricants and concerns about brittleness of components in Texas wind turbines, which don't have the same cold-hardened designs used in colder climates. North noted that “wind was only 5.7 percent of the capacity taken offline by the cold, even though wind is about 15 percent of the state’s capacity, so wind energy fared far better than the average for other fuel types."

 All told, 9,355 megawatts of capacity was unavailable when the emergency alert was first issued.

In comparison, ERCOT enters a Level 1 Energy Emergency Alert when it has less than 2,300 megawatts of capacity in reserve, meaning that generation supply is available if needed. ERCOT goes to Level 2 when that reserve drops to 1,750 megawatts, and the response includes calling on users that have agreed to have their power curtailed at such times. Level 3 is rotating blackouts, where local utilities drop customer load piecemeal.

ERCOT said it underestimated demand going into Jan. 6 by about 2,400 megawatts, although by 4 a.m. that morning it's expected load "was closer to the actual load for most of the day," owing to updated temperature forecasts.

-- Jim Fuquay

 

 

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