For the second morning in a row, some Pacific residents woke up Wednesday, Jan. 8, with no electrical power.
Last Tuesday, about 2,000 residents were without power when two switches became overheated in the extreme cold and blew out.
Crews had power restored to most residents within five hours and to the remainder in seven hours.
The following morning, at about 6:30 a.m., Ameren’s SCADA system relay sensors showed that one of the two transformers in the North Columbus Street substation in Pacific had failed. Some 3,000 customers were without power.
Crews arrived on the site to test all wires, looking for faults, and tested the gasses and determined that the 30-year-old transformer had completely failed and could not be repaired.
Crews routed electricity to other transformers in the city to restore power by 11 a.m. and began plans to bring in a portable transformer.
Ben Lynch, Ameren substation engineer, and Mark Nealon, Ameren system meter and smart grid manager, arrived to inspect the substation and the failed transformer.
“We looked at our schedule and decided that we could replace the transformer with a new one overnight,” said Lynch, who supervises the highly trained high-voltage substation crews assigned to oversee the transfer.
“It takes a special crew to deal with this high voltage,” said Trina Muniz, Ameren spokesperson, who also was at the Pacific site.
“This is a different crew than your typical line men,” Muniz said.
The two transforms in the Pacific substation each receive 34 kilovolts of current, and transform, or step it down, to 12 kilovolts for distribution to Pacific homes and businesses.
What Pacific residents see from Columbus Street is a thick stand of 30-foot-tall cedar trees with electric lines emerging from the top. But a good line of sight was needed for crews who work inside the tightly packed substation.
Crews removed four cedar trees that blocked the view into the fenced substation.
“We don’t like to cut any trees,” Lynch said. “But we have to see what we’re doing in there.”
Substation crews, very familiar with the Pacific substation, arrived at the scene.
A 550-ton crane was brought to the site by Budrovich Crane Rental to lift out the old transformer and lift in a new one.
Setting up the crane for the lift required transferring 220,000 pounds of counterweights onto the crane to keep it stable for the lift.
“We wouldn’t have needed that much weight in most circumstances,” Lynch said. “But we have to get really high to lift the transformer over the lines.”
At 7 p.m., the 13- by 11- by 12-foot new transformer, which costs $500,000, arrived. By that time, crews had disconnected the old transformer and it was slowly lifted out of the substation.
At 8:20 p.m., Lynch told reporters crews should start to lift the new transformer in no more than 30 minutes. At exactly 8:59 p.m. the new transformer was secured to the crane and ready to move.
With the crane arm extended 165 feet in the air, the 80,000-pound transformer was inched 70 feet straight up, swung over the 50-foot pole and live electric wires, and set down in the substation with inches to spare on two sides. The transfer was completed in seven minutes and 19 seconds. But that was only the beginning.
Crews would work through the night to hook up the new transformer, then relay crews would check every relay connection and every line. Power was surging through the new transformer by noon on Thursday, approximately 30 hours after the transformer failed.
Replacing a transformer is a big deal, officials said. Ameren Missouri replaces about six transformers a year.
The Pacific unit that failed had been in the substation since it was installed there in 1983.
“That’s 30 years,” Lynch said. “That’s a pretty good life for a transformer.”
Lynch also noted that one of the factors that enabled Ameren to switch out the heavy high-voltage transformer so quickly was the support it received from the city of Pacific.
“We had absolute support from Pacific,” Lynch said. “They cleared streets and closed off access to the site. The city was a real pleasure to work with.”