(Screengrab from Seattle City Light website at peak of outage)

8:30 AM: Thanks for the texts. Ours is out too. We’re getting reports from a widespread area – as far north as Admiral. More to come.

8:38 AM: City Light map says more than 16,000 homes/businesses are out. Remember that intersections are four-way stops when the signals are out.

8:46 AM: City Light says via Twitter that they “believe the outage was caused by a switching problem and estimate power will be restored about 9:15 a.m.”

8:50 AM: It’s been six days since a similarly widespread outage (WSB coverage here) was blamed on a “relay malfunction,” though that one lasted only a few minutes.

8:53 AM: Our power’s back (Fauntleroy/Gatewood line). Yours? We of course will be following up with SCL. Also note that – as happened after last Tuesday’s even-shorter outage – there may be some lingering effects like flashing traffic signals.

9:26 AM: Just talked with Scott Thomsen at City Light, who is looking into questions such as whether this was human error, a mechanical problem, etc. He says the “routine maintenance” at the Delridge Substation continues so that’s one thing this did have in common with last Tuesday’s outage. We will update again later when we get more followup information.

2:23 PM: SCL’s Thomsen says via e-mail: “Crews were testing switchgear at the Delridge Substation as a part of our maintenance and reliability work. When one of the workers closed the doors for the switchgear they were testing, the vibrations tripped a relay, which then opened, cutting off power for the electrical bus (imagine a giant power strip connected to four feeder lines going out of the substation into the neighborhoods). Our engineering staff is looking at what we can do to dampen vibrations and avoid a repeat of this problem, which does occasionally affect utilities.”