About 18,000 people lost power Monday morning due to an issue with the power feed.
Power has been restored to all but five KUB customers and LCUB has one outage reported, affecting about 1,187 customers.
LCUB officials said there was an "uncontrollable and unexpected equipment failure" at the Karns substation that affected transmission from the Tennessee Valley Authority and caused the Ebenezer, Westland, Cedar Bluff and Town Center substations to lose power, as well as the Karns substation.
About 16,000 LCUB customers were affected by the outage.
LCUB crews worked to reroute power where possible. Officials said that should allow them to restore power to the majority of the customers. However, that fix did not include the Karns substation.
"Unfortunately, some customers cannot be restored with these switching techniques," Matthew Fagiana, an LCUB official, said. "We have crews working as safely and quickly as possible to restore Karns substation."
KUB had about 2,000 customers affected by an issue with the power feed into the KUB system as well. Power was restored to all KUB customers around 10 a.m. Monday morning.
WBIR will update this story as more information becomes available.