ERCOT News Release
ERCOT Summary of Monday''s Electric Grid Events
Voluntary Conservations Efforts Requested for Tuesday
Austin, April 17, 2006 â€“ The Electric Reliability Council of Texas (ERCOT) Monday instructed transmission operators across the region to curtail approximately 1,000 megawatts of load to meet a generation shortfall related to the April heat wave. The appeal resulted in short-term load curtailments, or â€œrolling blackouts,â€? for various customers across the ERCOT region, but kept the lights on region-wide.
The load curtailment instructions began at 4:15 p.m. and were discontinued shortly after 6 p.m.
Earlier, curtailment of interruptible loads (known as Loads Acting as a Resource, or LaaRs) appeared to have stabilized the situation until a loss of four generating units in central and north Texas about 4 p.m. This loss of generation necessitated the shedding of â€œfirm loadâ€? to restore frequency to acceptable limits.
In addition, a media appeal was issued asking Texas electric consumers to voluntarily curtail electric usage. Customers were encouraged to turn up their thermostats by a few degrees and avoid using any non-essential appliances or lighting during the critical peak hours of 3 p.m. to 7 p.m.
ERCOT is appealing to customers across the region to observe these conservation efforts during those hours again on Tuesday, when the heat wave is expected to continue.
- Turn thermostats up
- Reduce lighting
- Avoid running non-essential electric equipment and appliances
â€œWe were caught in a generation shortfall due to the fact that this heat wave occurred during a time of year when temperatures are generally mild and demand for electricity is normally low,â€? said ERCOT Chief Operations Officer Sam Jones. Consequently, many generation plants were down for maintenance, which is typical during April, a traditional â€œshoulderâ€? month when temperatures are typically mild.
â€œThe good news is that we kept the lights on region-wide, as our plan is designed to do. The bad news is that some customers were inconvenienced. We appreciate their sacrifice.â€?
Actual locations of the load curtailments are determined by the regionâ€™s transmission operators. Typically, loads are curtailed for short periods of time, and critical-need customers such as hospitals and nursing homes are not curtailed.
The ERCOT grid broke its all-time April peak demand record on Monday, with a preliminary estimate of 51,714 megawatts. The all-time system peak is 60,290 megawatts, set last Aug. 23, during the traditional summer peak season when more resources are available.
Timeline (times are approximate):
- 3 p.m.: ERCOT began step 1 of its Emergency Electric Curtailment Plan. Step 1 involves ordering all available generating capacity to go online.
- 4 p.m.: ERCOT went to step 2 and shed 1150 MW of interruptible industrial load by calling on all loads acting as resources (LAARs) to shut down.
- 4:05 p.m.: ERCOT experienced an unexpected loss of four generation units, and at 4:13 p.m. instituted step 4 and instructed transmission owners to shed 1,000 MW of firm load.
- 4:25 p.m.: ERCOT issued step 3, a media appeal for voluntary curtailment. Due to time constraints step 4 was issued before step 3.
- 6:00 p.m.: ERCOT withdrew its â€œfirm load shedâ€? instructions.
- 6:15 p.m.: ERCOT lifted its voluntary load curtailment request via the news media.
ERCOTâ€™s last use of the EECP was during the February 2003 ice storm. The last time interruptible loads were curtailed was August, 1999. The last time involuntary firm load shed occurred in the ERCOT region was December 22, 1989.
ERCOT is a membership-based 501(c)(4) nonprofit corporation, governed by a board of directors and subject to oversight by the Public Utility Commission of Texas and the Texas Legislature. Its members include consumers, cooperatives, generators, power marketers, retail electric providers, investor-owned electric utilities, transmission and distribution providers and municipally owned electric utilities.