Posted on: Thursday, May 13, 2004

Misrouted signal led to HECO power failure

Advertiser Staff

A March 3 power failure that knocked out electricity to about 40,000 Hawaiian Electric Co. customers was caused by a failure in modules in the microwave communications system that controls the electric transmission system, HECO said.

HECO said this week that this was the first time a protective signal was misrouted, inadvertently de-energizing a transmission line.

The power failure began at 7:42 am. March 3 and affected customers in Waikiki, Manoa, Palolo, St. Louis Heights, McCully, Mo'ili'ili, Kaimuki, Diamond Head and Kapahulu for at least 45 minutes. Some customers were without power for about four hours.

HECO said the problem began when a 138-kilovolt transmission line serving the Pukele substation was de-energized to allow for work on the line. At the same time, however, the digital microwave communication system used to ensure the line stays de-energized malfunctioned, causing the circuit breaker on a second 130-kilovolt line to open, leading to the failure.

A consulting firm from the Mainland was brought in to help with HECO's investigation.