WHEN THE ISLAND OF OAHU was hit by a magnitude 6.6 earthquake at 7:07 a.m. on Oct. 15, 291,000 customers woke up to no power.
But fortunately for them, the Hawaiian Electric Co. Inc. (HECO) has an emergency power restoration system in place for such emergencies. Power was restored to 99 percent of the utility’s customers within 19 hours.
“Since we are an isolated island utility, we have ‘black start capability’ at two of our three generating systems which allows us to start generation after a complete shutdown without electrical input from the power system itself,” said Jose Dizon, HECO’s director of communications. “Once one unit started, we realigned the 138 kV transmission system to feed the other. It usually takes anywhere from four to eight hours to black start an oil-fired steam unit. We did it in 4.5 hours.”
HECO had two critical priorities to contend with: getting power to the most-needed public institutions and organizations first, such as hospitals, police and fire departments, and military bases, and secondly, moving on a strict and methodical schedule so as not to overload the recovering system too quickly.
According to Hawaiian Electric Co. (HECO) spokeswoman Lynne Unemori, its customers lost power when the earthquake knocked out generators at HECO’s downtown and Kahe power plants. The resulting imbalance caused HECO’s computer system to shut the company’s power system down in order to avoid permanent damage, which would cause an even longer power failure.
“We had to operate with a mind to the long term,” Dizon explained. “If we picked up customers too fast, we could trip the generating units and have to start from scratch, or worse, we could cause serious turbine or generator damage, which could take months to repair. On an island system, that could mean long periods of conservation or rolling blackouts.”
Despite these obstacles, by 6:30 p.m. of the day the earthquake struck, 86,000 customers had power restored; by 9:30 p.m., 136,000 had electrical service; and by 2:15 a.m. the next morning virtually all power was restored on the island. EC