Crew members at Kauai Island Utility Cooperative conducted repair work Thursday on a faulty transformer that caused an islandwide outage a day earlier. 

Spokeswoman Shelley Paik said an insulation breakdown at the Port Allen Generating Station is the probable cause of the transformer failure that caused generators to trip offline, affecting 25,000 members. 

Electricians are replacing the bushings on the transformer. Paik said work might be completed by the end of the day Thursday.  

The power outage occurred at 5:15 p.m, leaving people in the dark at dinnertime. Power was restored to nearly all customers by about 10:30 p.m. Crew members restored power to Halelani Village in Puhi about 2 a.m.