Southern California Edison released internal and independent investigative reports on the causes of two power outages that affected the downtown Long Beach power grid last July. The incidents disrupted service to customers in the area for several days.
The two reports, while differing in scope and methodology, agree that the cause of the first power outage on July 15 was the failure of several critical components in the underground network to perform their network protection functions due to improper operation and insufficient management oversight of the system.
“We are deeply disappointed that the findings point to shortcomings in SCE’s operation of the network,” said Pete Dietrich, SCE senior vice president for transmission and distribution. “However, we are encouraged that the investigations have identified issues that are correctable, that we will learn from and that can help us improve the way we manage the network to provide the kind of service to our customers that they should expect from us.”
The reports identified the failure of an underground cable splice as the event that triggered the July 15 outage. The Long Beach underground network was designed to withstand the failure of a single component, however, the cable splice failure led to a cascading series of failures due to non-functioning network protection devices, resulting in the entire downtown network being taken offline for inspection and repairs.
Both reports also found that damage sustained during the first outage led to the second outage on July 30.
SCE’s internal report outlined numerous steps the company is taking to correct these issues and prevent future incidents. The company has already taken some corrective actions on the system, including complete and thorough inspections of every underground vault on the downtown network system and additional and ongoing inspections on other parts of the grid in Long Beach.