An explanation of North Beach outages

Last evening we wrote about the power outages that some North Beach residents have been experiencing the last couple of days.

We wrote:

According to John Gustafson with Seattle City Light, the cause is the warm weather. He tells us that with the underground electrical system in that area, the warmer weather that we’ve had the last couple of days can cause the wires to crack.

Several people commented on that post that the reasoning didn’t make sense. Today, Scott Thomsen with Seattle City Light sent us a better explanation.

When our crews responded to the first outage, they found that a section of underground cable had failed. They removed that section of cable and installed a new one. They re-energized it and it was holding. After they left, a different section of cable serving that same area failed.

This is a problem with older underground cable like those that serve this area. The insulation degrades over time, especially cable that is buried directly into the ground without conduit, which was common in the 1970s and early 80s. That’s why we are working on a silicone injection project in this area to extend the life of the cable that is in good enough condition. Sections that are not good enough for injection will be scheduled for replacement.