Hawaiian Electric Co. is warning that there's no guarantee against another islandwide blackout as company officials sort out what went wrong Friday night and why.

The power outage threw Oahu into darkness Friday evening when four of HECO's largest power lines, each carrying 138,000 volts from the Kahe and Waiau power plants to Central Oahu, tripped off.

That led to the generators shutting down islandwide to prevent more severe damage that could have led to an outage of days rather than hours, according to HECO spokesman Darren Pai.

The outage snarled traffic as motorists had to cope with driving without traffic, highway or street lights.

It shut down business on one of the busiest shopping days of the year, cut short Friday night festivities and sent residents scurrying to find flashlights and generators to deal with a night without television, computers and other electronic equipment.

As of 8:30 p.m., HECO restored power to all but 125 customers in scattered neighborhoods, spokeswoman Barbara Heckathorn said last night. Crews were being dispatched throughout the night to restore service.

No major problems or injuries were reported, but many residents wondered why they had to endure another islandwide outage after they lost electricity in 2006 following the Big Island earthquake and aftershock.

Pai said HECO'S top priority yesterday was to restore power and said he did not know when HECO will be able to determine the cause of the lines tripping off.

He said HECO will first determine whether it was actually lightning that tripped off the lines, although, he said, lightning was “;the first line of inquiry.”;

Pai said an inspection from helicopters yesterday showed no major damage to the four transmission lines, HECO'S largest, which resumed transmitting power yesterday.

“;We're always looking for ways to improve, but unfortunately, it doesn't matter how much you spend, how much you invest in the system. There's no way to completely guarantee that we will never have this type of situation again,”; Pai said.

Once the islandwide system shut down, it required a delicate balance of resuming power without overloading or damaging the lines, a process that takes hours, according to Pai.

The power must be restored carefully by balancing the electricity generated with the electricity in use. If there's an “;imbalance,”; it could cause the entire system to have to restart the process, he said.

HECO Working To Restore Power

 

HECO employees have been working around the clock to restore power around the island.

 

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As HECO investigated the causes of the blackout - as well as why it took so long to restore power - many Oahu residents were wondering why lightning or any other damage to one part of the electrical system could shut down the power for the rest of the island.

“;We were an island of perplexed people, wondering, 'Not again,'”; remarked Doug Carlson, a media consultant and HECO spokesman during the 1980s. “;I just conclude that there must have been something wrong somewhere in the system that did not operate properly, whether it was human or mechanical, to allow an entire island to go down when a problem surfaced in one area of the island.”;

Oahu residents went though an islandwide outage on Oct. 15, 2006, when a Big Island earthquake led to a shutdown of the Kahe generators and subsequently the entire system. HECO needed about 18 hours to restore electricity to most of the company's customers.

A factor in that shutdown of the Kahe generators was faulty switches, which have since been replaced, Pai said.

This time, it was the four transmission lines from the power plants to subtransmission lines of 46,000 volts in Central Oahu that triggered the outage. Three of Kahe's six 138,000-volt lines shut down, while at least one of Waiau's 138,000-volt lines went out.

Pai said HECO also will be looking at whether the peak use of electricity early Friday evening might also have been a factor in the shutdown.

Another generating unit that is scheduled to start operations in Campbell Industrial Park next year might help in restoring power quicker by providing power with combustion rather than steam engines, he said.

But he said it still would take hours to restore power to all customers in an islandwide outage.

“;That's why we really appreciate our customers' patience and understanding,”; he said. “;We know it's very difficult to go without power for that period of time.”;