Reliable power: the winds of West Texas vs. a maintenance worker mistake in Florida

Michael Giberson

It is rare that these little “learning moments” come nicely packaged, but the two near contemporaneous power system emergencies in Florida and Texas on February 26, 2008 present such a package. Still, otherwise intelligent industry observers seem to miss the point. Example, the Smart Grid News of March 26, which presents an overly harsh interpretation of the “challenges” of working with wind, and points to the Texas event as supporting evidence.

ERCOT operators had to react promptly on February 26 to balance load through demand response (DR) because of system reliability problems caused by wind intermittency. But systems reliability was not the only issue caught in the headlights by this event. The Wall Street Journal also spotlighted the economic impact; namely that the unexpected loss of wind generation caused wholesale power prices to soar from $30 per MWH to $105 per MWH in West Texas.

The article continues with a discussion of “system reliability and pricing challenges” and concludes with an ominous, “Federal and state incentives and mandated renewable standards, along with investor interest …, will all drive additional wind generation. Whether the grid can keep up is another matter.”

No mention was made of the Florida event, but here is the short version: a worker’s error while performing maintenance led to a fire at transmission substation which tripped a series of transmission lines out of service and shut down several major power plants. About 2600 MW of capacity was lost from the system. About 2.5 million Floridians lost power during the event.

So in Florida, 2.5 million people suddenly could not buy power at any price, because in the few seconds that the transmission lines went down and power plants went off line, the local integrated utility system operators didn’t have time to react.

In Texas, later that same day, wind power unexpectedly dropped well below day-earlier forecasts over a period of several hours. Some other non-wind generators in Texas were operating below schedule at the same time, and evening electrical load was beginning to shoot up. The combination of factors left the independent power system operators at ERCOT scrambling to keep the system in balance, which they did in part by calling on market-based voluntary load reductions. No one lost power, though prices did spike in reaction to the emergency conditions.

As the Energy Legal Blog notes, ERCOT has recently released its operations report on the event. One problem – ERCOT has relied upon day-ahead forecasts of wind power capacity, but the wind is not (yet?) so reliably forecasted so far in advance. The Texas grid operator is seeking to advance a wind forecasting tool under development, which was scheduled to be added to the system in conjunction with a switch in the ERCOT market system later this year.

While in Florida businesses were shut down and millions of people were made significantly worse off, in Texas mosts residents were likely unaware of the problems until they read about in the newspaper the next day. Of course there is much more to the picture than is captured in these two public events, but my point is that the “unreliability of wind” just needs to be kept in perspective. (Or better, just priced appropriately.)

It is not yet clear whether Florida Power & Light will be integrating an improved worker error forecasting system into its operations.