It wasn't the heat, LES General Manager Richard Turner said. The LES substation on Franklin Avenue North has much greater capacity than the demand that afternoon when temperatures were in the mid- to high 90s. Less than half the city power customers were without electricity during the outage.
It might have been shorter, but when an LES crew arrived at the station the men found that an automatic lock for the door to the switch house would not open to allow them in, according to Turner and Randy Fagan, the department's meter superintendent who has additional duties.
"It didn't take but five minutes to get through" the door, Fagan said. "That's the first time that happened."
Turner said the electromagnetic lock was installed in response to a requirement from the U.S. Department of Homeland Security. It's possible that the power outage caused the lock to malfunction, the general manager said.
"The lock has a back up battery," Turner continued. "We don't know whether the charger died. It worked once we got in there... Randy's going to fix it so we could run it off a truck battery from the outside."
As for theories on what caused the outage, Fagan said, "I think there's something on the line to cause the fault and send the power to the ground. But we haven't found it yet."
A power system in a nearby county suffered outages from birds and squirrels causing short circuits and, when asked that, Fagan replied that he thought it was "Probably more like a lightning arrester...
Lightning arresters prevent surges of electricity on the line that might otherwise damage the substation, Fagan explained.
The outage "showed some high ground currents coming in," he said. "Everything that happens on the line comes back to the substation. There are some things that don't dissipate."
Turner said, "Substations are sensitive. They're built that way because you have $2 million worth of equipment in there."
The lead-time needed to get a replacement transformer is 13 months, he said.
A dozen LES employees were "riding the circuit" Monday afternoon looking for a cause and the search was to continue Tuesday, the general manager said.
As for the local grid's self-protection system, electronic relays "are looking for something all the time," Turner said. "Some times it takes days to find out what caused it. Sometimes we may never find the cause.
"It's just the nature of the beast."