Tahlequah Daily Press

August 3, 2011

Heat blamed for transformer explosion

Staff Writer

TAHLEQUAH — The oppressive summer heat is being blamed for the explosion of a high-voltage breaker Monday night at Lake Region Electric Cooperative’s Tahlequah substation on Mud Valley Road.

Temperatures have been well over 100 degrees for several days, with “lows” dipping into the 80s. The extreme heat has also taken a toll on plants, animals and humans.

LREC CEO Hamid Vahdatipour said people may not realize the heat is also hard on electric transmissions and distribution grids. He said when temperatures only cool into the 80s at night, it doesn’t offer ample opportunity for home equipment to recuperate from the extra stress.

“This would also put a higher demand on transformers, breakers and other distribution and transmission systems with no cool-down periods for this equipment,” Vahdatipour said. “The heat continues to build inside the equipment and eventually causes failure.”

The National Weather Service website shows Tahlequah’s temperature at 86 degrees when the transformer explosion and fire were reported to Tahlequah firefighters around 9:30 p.m. Monday.

Power was lost at the substation, and 1,600 LREC members were without electricity. KAMO Electric Cooperative, LREC’s power supplier who owns and operates the substation, dispatched crews to assess damage and fix the problem.

Vahdatipour said LREC crews rerouted power from other substations and backfed the affected customers. Power to most of them was restored within two hours as KAMO crews continued to repair the substation.

“We were confident that back-feeding would be sufficient to supply the overnight demand,” Vahdatipour said. “However, the system would not be able to handle the demand once the sun came up Tuesday.”

The breaker explosion caused insulating mineral oil to be sprayed on the bus work in the substation. All the bus work and insulators had to be wiped clean, Vahdatipour said, so the oil wouldn’t ignite once power was restored to the substation. Six KAMO crewmen and 10 LREC linemen climbed the bus work and wiped it clean.

It was after 1 a.m. Tuesday before power was restored at the substation. LREC crews then rerouted all of the back feeds to their normal position, and the restoration process was complete by 2:30 a.m.

In the first 30 minutes of the outage, LREC dispatch and automated outage system operators answered 373 calls. In the next hour, 409 calls were answered and 118 more calls were patched in by midnight. Vahdatipour said 60 percent of the calls were answered by the automated system, while the remainder were fielded by operators. He said LREC’s ability to handle higher call volumes has increased with the automated system.

Vahdatipour said all members should provide LREC with correct phone numbers.

 He said that during an outage call, the automated outage system can recognize a caller’s ID information and report the outage, without the need for the caller to provide an account number.


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