In a sequence that likely will be repeated often this summer, California’s independent transmission grid operator, Cal-ISO, Thursday erred on the side of getting out advance warning of possible rolling blackouts only to pull back the emergency measure within minutes of the targeted time for blackouts to begin. As of 4 p.m. (PDT), the blackouts had not become necessary in the second consecutive day of Stage One and Two alerts.

Pacific Gas and Electric Co., whose service area was the focus of the power shortage for the grid, reported that just prior to 2:30 p.m. Cal-ISO said the blackouts weren’t needed for the time being and that they would be monitoring the situation literally minute-by-minute throughout the afternoon.

The supply strain was caused by a combination of warmer than normal temperatures — particularly in the northern half of the state — lower than expected imports of power, more than 1,200 MW of generation off-line in the San Francisco Bay Area where the PG&E utility is headquartered and 10,000 MW of generation statewide out of service for planned and unplanned maintenance.

Because of the loss of generation in the Bay Area, Cal-ISO was having to import more power into that part of the state, “which is straining the local transfer capability,” according to a Cal-ISO spokesperson. Cal-ISO was expecting a peak load of 37,882 MW around 4 p.m., which is the highest peak the state has encountered this year. Rolling blackouts and power alerts earlier in the year were called when peak demand was under the 35,000 MW.

In keeping with Gov. Gray Davis’ push for early warnings of possible blackouts voiced in several forums last week, Cal-ISO notified the public of possible rolling outages beginning at 2:30 p.m. Thursday, adding that “conservation efforts will help lessen the severity and duration of possible outages.” The grid operator at that time said specific information about the location and timing of outages–information the governor is very keen on getting to the public–“must be obtained from local utilities.”

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