PG&E; Wraps Up Probe of Power Outage, Blames Human Error
Human error, not a system flaw, remains the prime reason 2 million San Francisco area residents lost power in last month’s massive blackout, Pacific Gas & Electric Co. said after completing an internal investigation.
The investigation uncovered no significant glitches in operations or in the design of San Francisco’s electric transmission system, the San Francisco Chronicle reported Saturday.
The PG&E; report, which proposes only minor adjustments, is to be filed Monday with the state Public Utilities Commission.
Employees at the utility’s San Mateo substation simply failed to follow procedure, the report said.
A four-member construction crew neglected to remove grounding rods while installing a new transformer before that section of the substation was put back into service Dec. 8, the utility said.
Then, control room operators failed to reactivate protective devices before powering the substation. The electrical short would have been confined to the substation--instead of spreading to the entire San Francisco electric system--if the system’s sensors, relays and circuit breakers had been functioning, PG&E; said.
In addition, PG&E; did not warn the state’s new grid operator, the Independent System Operator, that it was re-energizing its equipment at the substation 10 days ahead of schedule, the report said.
Also, about 16 circuit breakers at PG&E; substations did not work properly after the outage, making it harder to restore power.
The outage remains under investigation by the grid operator and the PUC, which is examining whether the crew was adequately trained. The PUC report is expected in March.
PG&E; has received more than 2,800 claims from customers for losses and has acted on 500 of them, the utility said.