Hawaiian Electric Light Co. and Maui Electric Co. officials acted reasonably during the Oct. 15 power outages, but a new report commissioned by the two companies is recommending several technical fixes in the utilities' transmission systems.

More than 120,000 customers on Maui and the Big Island lost power on Oct. 15 when earthquakes with magnitudes of 6.7 and 6.0 struck off the coast of the island of Hawai'i.

Idaho-based Power Engineers Inc. said HELCO's and MECO's systems were in proper operating condition when the earthquakes hit and that operators were able to restore power relatively quickly.

Big Island and Maui customers were able to get their power back hours before O'ahu customers because of the types of generators they use, Power Engineers said. Unlike O'ahu turbines that are largely steam driven, generators on Maui and Hawai'i run on diesel, which are easier to restart when they lose power.

Electricity on Maui was restored within eight hours while the outage on the Big Island, which affected about 62,000 of HELCO's 76,000 customers, lasted less than six hours. About 291,000 HECO customers on O'ahu went without power for most of the day.

In its report, Power recommended that HELCO officials use protective relays and fuses on the transmission lines that are less likely to malfunction in earthquakes. The consultants also suggested that MECO install automated circuit breakers on machinery used to restart generators that shut down.

Reach Rick Daysog at rdaysog@honoluluadvertiser.com.