Error by PG&E preceded blackouts

Effort to ramp up output actually scaled it back

A mistake by Pacific Gas and Electric Co. may have played a role in people losing power on one of the two days that California experienced rolling blackouts during an extreme heat wave last month. On Aug. 15, one day after an energy supply shortage caused California’s first rolling blackouts in 19 years, PG&E erroneously directed a 400megawatt power plant in Fresno County to scale back.

The company says it intended to tell a smaller plant to wind up to full capacity but the message to reset output instead went to the larger, natural gaspowered Panoche Energy Center, located near Interstate 5 about 50 miles west of Fresno.

PG&E’s misstep at a little before 6:15 p.m. meant that as much as 255 megawatts of power was unavailable to the state’s grid just as demand was reaching its highest point. The California Independent System Operator, which manages most of the state’s electric grid, ordered utilities to shed 470 megawatts

of demand at about 6:25 p.m., leading to rolling blackouts.

PG&E told The Chronicle that the “temporary ramping down of Panoche’s energy output” lasted for less than half an hour and would have accommodated only “roughly 0.5%” of the total 44,913 megawatts demanded from the grid at the time.

The energy supply emergency that resulted in rolling blackouts that day lasted only about 20 minutes.

PG&E’s revelation does not discredit the other explanations about why Californians endured rolling blackouts on Aug. 14 and 15 and almost experienced more on other days as recently as Labor Day weekend.

Also straining the grid were the intense and widespread nature of the heat, which in August sharply limited the state’s ability to rely on outofstate power imports. California energy leaders have said the state may be leaning too heavily on its ability to bring in electricity from beyond its borders. While regulators insist solar and wind energy itself is not the problem, they have said the state may need to rethink its rules about energy supplies and reserves.

In an email, PG&E spokesperson James Noonan said company officials “remained in close coordination” with the system operator throughout the heatinduced energy crisis.

“When the error was identified, we corrected it immediately and ordered the plant to return to full generating capacity, where it stayed for the remainder of the day,” Noonan said.

PG&E has been “open and transparent” with the system operator about what happened with the Panoche plant and provided grid managers with full details about the matter on Aug. 18, Noonan said.

“We continue to work closely with all stakeholders to ensure the delivery of safe, reliable and clean energy in the months and years ahead,” he said in the email.

Though the system operator mentioned the problems as part of its explanation for the rolling blackouts before, it initially did not disclose the names of the facilities. That changed when the organization recently posted a fact sheet explaining that the Panoche plant and the Blythe Energy Center in Riverside County both had separate issues last month.

At 2:57 p.m. on Aug. 14, the Blythe facility went offline “due to plant trouble,” the system operator said. It had been generating 475 megawatts at the time.

Then on Aug. 15, the Panoche plant “unexpectedly ramped down its generation,” the system operator said, noting that grid managers were told by the facility’s scheduling coordinator that “the unit ramped down quickly because of an erroneous dispatch from the scheduling coordinator to the plant.”

PG&E is not named in the fact sheet, but the company confirmed to The Chronicle that it is the scheduling coordinator in question. Though grid managers at the system operator are the ones who decide if rolling blackouts are needed, scheduling coordinators — utilities and other entities authorized to deal directly with the grid operator — are the ones who actually tell certain power plants whether to increase or decrease their generation of electricity.

If nothing else, the issue highlighted by

PG&E further underscores how vulnerable California’s electric grid has become to supply shortages during a heat wave — which scientists say the state can expect plenty more of because of climate change.

“There’s essentially no margin for error,” said Michael Wara, a climate and energy policy expert at Stanford University's Woods Institute for the Environment. “The answer is still better planning, better coordination between the different decision makers and a larger margin for error. Because we can’t expect everything to go right to keep the lights on. We need to plan for a situation where a few things don’t.”

Regulators at the California Public Utilities Commission are working on a broader report about how the rolling blackouts happened and plan to release it this month. A commission spokeswoman said regulators are aware of PG&E’s erroneous power plant order and will consider it in their analysis.