Pacific Gas & Electric said its patrols found five instances of wind-related issues during a de-energization event that it conducted June 8 and 9, including damage to PG&E service drops and a branch in contact with a power line that it had de-energized.
Earlier this month, the utility preemptively shut off power to about 22,000 customers in the North Bay and Sierra Nevada foothills, due to predicted high fire-risk conditions. Employees later found multiple instances of “wind-related issues” while patrolling the powerlines in the Sierra Nevada foothills, according to a June 21 report submitted to the California Public Utilities Commission by Meredith Allen, PG&E’s senior director of regulatory relations.
These included two instances where falling branches and trees damaged the utility’s service drops, power lines that connect directly to homes and businesses. Additionally, in three separate cases, PG&E’s employees found vegetation-related hazards, according to the report, including branches that had fallen on to conductors. The utility addressed the issues and cleared the vegetation before re-energizing the lines. Electricity was fully restored to all customers in fewer than 24 hours, according to the report.
PG&E’s decision to de-energize the lines was based on a multitude of factors, the utility said, including red flag warnings issued by the National Weather Service, forecasts of strong winds in the Sacramento Valley foothills and Mendocino area, its own internal weather modeling and reports from observers in the field. According to the utility, any alternate strategies to de-energization—such as patrolling or quick vegetation management work—would have been inadequate.
Utility employees patrolled more than 1,000 circuit miles of power lines following the de-energization event and repaired damaged equipment before restoring power.
The decision to de-energize was made by a designated officer-in-charge at PG&E’s emergency operations center, which is staffed by PG&E’s electric operations, meteorology, customer, public information and government liaison and staff for other functions.
“Once weather conditions improved, PG&E crews visually inspected each mile of impacted power lines to check that they were free from damage and safe to return customers to service,” PG&E said.