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High temperatures and fires over the Labor Day weekend put the grid to the test. While the California Independent System Operator managed to keep supply and demand in balance Sept. 5-7, tens of thousands of customers of the three investor-owned utilities lost power or had it shut off because of wildfires during and after the holiday weekend.

With threatening winds of more than 50 mph forecast for the next few days, “the fires are anything but behind us,” Gov. Gavin Newsom warned at a Sept. 8 noon press conference.

Strong, hot winds led Pacific Gas & Electric to cut off power to 167,000 customers in 22 counties the evening of Sept. 7. “The National Weather Service has placed most of Northern and Southern California, including 1.5 million PG&E customers, under Red Flag Warnings for fire danger,” the utility stated. Those without power include 30,000 customer accounts in Tuolumne County, 23,000 in Nevada County, 21,000 in El Dorado, 18,000 in Sonoma County, and nearly 5,000 in Napa County.

Power was expected to be restored by late Wednesday with dry offshore winds dying down, PG&E reported during a Tuesday evening press briefing.

Southern California Edison warned Sept. 8 that more than 57,500 customers may have their power disconnected because of projected high Santa Ana winds. Sixteen thousand of those are in Los Angeles County and another 15,000 are in San Bernardino County.

Between 25,000 and 15,000 SCE customers lost power last Friday night either due to fire or high heat, not from grid related rolling blackouts. Intense temperatures compromise transformers and down wires, Robert Villegas, utility spokesperson, said.

Of those subject to shutoffs, 2,500 were victims of the explosive Creek Fire. Most of them were dealing with mandatory evacuations so the outage may have been the least of their concerns. But the affected lines will have to be inspected in this area before being energized.

Nearly 17,000 San Diego Gas & Electric customers may have their power cut late Tuesday because of high winds and fire danger. If they are shut off, they will not regain power before Thursday.

Several thousand SDG&E customers also lost power over the weekend due to heat and fire harming distribution equipment. That includes 3,400 customers in the vicinity of the Valley Fire, with 1,600 of those still blacked out, SDG&E Spokesperson Helen Gao said Tuesday afternoon.

Record-breaking heat, but sufficient power

Although CAISO called Stage 2 alerts last Saturday and Sunday, it managed to balance supply and demand, largely because customers cut back on their usage. That came at the cost of worsening air quality, however, with diesel generators firing up to avoid taking power from the grid.

Fires in Southern California caused CAISO to lose 1,600 MW of generation that otherwise would have been available on Saturday. Both a 550 kV transmission line and 230 kV line were unable to ship power, stranding about 900 megawatts of hydropower and a few hundred MW elsewhere, including solar power in Imperial County, according to John Phipps, CAISO director of real time operations. The cause was the Creek Fire.

After the grid operator called Stage 2 alerts Sept. 5 and 6, the Los Angeles Department of Water & Power and Sacramento Municipal Utility District each sent about 300 MW each day.

The Department of Water Resources provided even more supplies over the three-day weekend. Between increased hydropower generation and load shifting, DWR sent 662 MW to the grid on Sept. 5, 786 MW the next day and 749 MW on Monday, according to spokesperson Ryan Endean.

CAISO’s actual peak Sept. 6 was almost 4,000 MW below the projected peak of 49,000 MW, reaching 46,145 MW. On Sunday, demand peaked at 46,864 MW.

Monday’s peak was a good 5,000 MW lower, reaching 41,774 MW. But high, dry winds starting that evening threatened much of the state.

SMUD and the Balancing Authority of Northern California kept power flowing to their customers through the weekend.

SMUD does not expect power flow problems this week, “barring unforeseen circumstances like loss of resources due to wildfire,” Chris Capra, utility spokesperson, said.

Closure deadlines of So Cal coastal plants extended

In related action, the State Water Resources Control Board voted last week to extend again the closing deadlines of four controversial aging fossil plants along the Southern California coast on reliability grounds. A decade ago, the board voted to phase out these and 16 other seawater cooled coastal plants because of the harm to the aquatic environment.

“Once-through cooling power plant operations impose heavy environmental impacts on our oceans and communities, and an extension of these compliance dates aren’t without significant consideration,” E. Joaquin Esquivel, State Water Board chair, said Sept. 1.

The Alamitos, Huntington Beach and Ormand plant closure dates were extended by three years, until the end of 2023, to provide gas-fueled power as needed. Redondo Beach now will remain online until the end of next year.