Early Wednesday, more than 8,000 Seattle City Light customers from Highland Park to Burien lost power. The image above, from SCL’s outage map, shows the outage zone at its peak; half the affected homes/businesses got power back after about three hours, and less than an hour after that, the outage was down to 585 customers. But the problem affected thousands more people because it happened along a highway, closed all lanes, and jammed traffic through much of the morning commute. So what exactly happened? We asked SCL’s Julie Moore, who responded today, explaining the cause resembled what took out ~2,000 customers last Friday/Saturday:
The outage cause was similar to the one last Friday. While doing a planned maintenance project, a piece of equipment failed and the overhead pulling rope dropped down on to our primary voltage electrical system, causing the lines to fault. We again needed a clearance – when we intentionally cut power to a particular area –for the electrical workers to safely remove the pulling rope from the primary lines and then we were able to restore the system to its normal configuration.
It is unusual for this piece of equipment to fail and we are looking into why it failed. The work being done is designed to replace and upgrade older static wire and replace with a new wire that has an optic cable capability. This work is still ongoing and the targeted completion date is the end of August.