The failure of a fuse on a utility pole behind the Riverside Fire Authority station on Pearl Street led to the pole catching on fire, tripping the breaker at the substation and causing the extended power outage much of Centralia experienced on Saturday.
The outage began at 6:45 a.m. on Saturday. Power was restored to the majority of customers by 2 a.m on Sunday except for the customers directly connected to the pole that was on fire, Centralia Light General Manager M.L. Norton said. Those customers had power restored by 6 a.m. on Sunday.
Norton said the failure of the cut-out fuse was caused by a combination of the heavy rain and the dust gathered on it from the long dry summer. It caused the voltage of the line to instantly ground, which is what tripped the fuse in the cut-out to close. Cut-out failures like this are common, he said. Two others have failed the same way this fall without causing a system-wide shut down. The failed cut-out fuses have been replaced with newer versions that are less likely to fail due to dust accumulation.
The cut-out fuse failed in a way that caused the pole to catch fire, which then caused the line to fail, Norton said. When crews attempted to restore power to the line, it caused the breaker at the substation to trip, which shut down the whole system. It was the result of a cold load pickup, Norton said, describing the situation as when it is cold outside and too many heaters, water heaters and other electrical equipment is suddenly switched on.
When enough are switched on at once, it is a heavy load on the system. The additional load on top of the normal load is what tripped the breaker, Norton added.
Crews gradually reduced the load on the line until the breaker would stay on, Norton said. The process was one of trial and error. Crews would bring the system online and the breaker would shut off, then they would reduce the load and try it again. Once the load was reduced to where the breaker would stay on, the load was gradually increased to the full demand.
Norton said his crews responded in a safe and timely manner to the outage.
