August 21, 2017

Grid operator Southwest Power Pool keeps the lights on during August 21 eclipse

Electrically, Aug. 21 was just another day for Southwest Power Pool (SPP), whose accurate forecasts and skilled real-time operations staff ensured that lights (and air conditioners) stayed on without interruption even while darkness fell at midday across its 14-state footprint during the totality of a solar eclipse.

The eclipse’s most significant impact on the SPP region was to load, or the amount of electricity being consumed by homeowners, businesses and industrial facilities. Absent the day’s eclipse, SPP anticipated a peak load of approximately 45,000 megawatts across its system Aug. 21. Due to several factors including lower temperatures and irregular human-behavior patterns — e.g., decreased air conditioning on a hot summer day and business and manufacturing closures while employees observed the eclipse — SPP saw demand fall approximately 2,500 MW below the forecast.

In preparation for the relatively sudden and not entirely predictable drop in load, SPP utilized its day-ahead market processes beginning Aug. 20 to commit adequate reserves to accommodate load swings and the resulting impacts to frequency and interchange. For the hours of 10 a.m.–2 p.m. central time Aug. 21 — the hours during which the eclipse’s totality directly affected SPP’s footprint — the regional transmission organization increased its regulation requirement, the amount of reserve energy generators must have online and ready to dispatch should they be required to do so to balance fluctuations on the bulk electricity system.

“By increasing our regulation requirements, we essentially ‘widened the lanes’ of our system and operated more conservatively than we might have on a normal day to accommodate any unpredictable occurrences during this rare event,” Director of System Operations CJ Brown said.

Thanks to these steps taken proactively in advance of the eclipse, and SPP’s market processes that respond in real-time to actual load, the grid operator saw no reliability issues on its system. Moreover, SPP could act in concert with its neighbors in the Eastern Interconnection to ensure they did not burden other balancing authorities by generating either too much or too little generation to serve their own load.

Nature’s response to the eclipse also impacted generation in SPP’s system. SPP operators noted — and mitigated the effects of — a swing in wind generation of about 1,200 MW over the course of approximately an hour or less as the eclipse exited the SPP region. SPP has seen a rapid increase in the amount of wind generation in its region over the past 10 years, and given the rarity of such impactful eclipses, Aug. 21 was the first opportunity to study the impact of such a confluence of circumstances.

“This was a great learning opportunity for SPP,” said Vice President of Operations Bruce Rew. “And I’m proud that our staff and systems were able to ensure that, despite so many variables and the rarity of the solar eclipse, it was essentially a non-event electrically speaking.”

Derek Wingfield, 501-614-3394,