On a sunny, calm day, the first thought when the power goes out often is, “Did an eagle fly into a power line again?”
But, no, that wasn’t the case Tuesday morning. Instead, a routine switching operation at the Swan Lake hydroelectric dam sparked the outage, which affected everyone on the Ketchikan Public Utilities grid.
KPU Electric Division Manager Tim McConnell said it’s not clear why that happened.
“Nothing should have changed, nothing should have happened,” he said. “A relay sensed a fault, opened the breakers, and we immediately lost about 10 megawatts.”
When the power level drops like that, the reaction is complicated for pretty much anyone who isn’t an electrical engineer, so let’s just say it’s not good.
“In this case, the loss in power was so extreme, that is just cascaded, avalanched, opened up all the breakers, and we basically were black,” McConnell said.
KPU staff started trying to restore power, and revved up “old faithful,” one of the diesel generators. She wasn’t feeling very faithful, though, especially considering the high demand at that time of day. The generator tripped offline twice, which is why some people experienced on-again, off-again power.
KPU decided to try the other, smaller generators. But the power demand was just too high for them. So: Off again.
KPU then sent out an announcement asking customers to turn off or unplug electric items, in hopes of reducing demand, at least until things were up and running again.
“So, in the course of that operation, we eventually got all the feeders back online, were able to get full output of our hydroelectric machines by then, and we stabilized the system and the last customer was restored at 12:18 this afternoon,” McConnell said.
He added that KPU engineers will investigate what happened, and look into how to better react to such a situation in the future.