Redundancy saved the day

Shawn Hayward
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Replacing burned Sunnyside transformer will take more than a year

Darren Moore was on duty at 9:30 a.m. on Saturday, Jan. 4, when he got a call telling him the lights had gone out on the Avalon and Burin peninsulas.

This transformer at a station in Sunnyside caught fire on Jan. 4, starting a sequence of events that knocked out power to 190,000 Newfoundland Power customers.

Moore is general manager of transmission and rural operations with Newfoundland and Labrador Hydro. He later found out that a fire at one of the two transformers in Sunnyside had knocked out power to both peninsulas. There had been a severe blizzard that day with high winds throughout eastern Newfoundland.

The fire itself knocked out power to the Burin. When a breaker that protected the transformer failed to operate, a second breaker had to open to clear the fault, cutting the Avalon Peninsula grid off from the rest of the island. The load became too high on the Avalon grid, and an auto-protection feature tripped the generating unit at Holyrood, extending the outage to the Avalon and putting a total of 190,000 Newfoundland Power customers in the dark.

Both transformers at Sunnyside were capable of compensating for the other in the event of a failure. An NL Hydro crew was on hand at Sunnyside and other critical sites because of the bad weather, according to Moore. When fire knocked out one transformer they worked to contain the emergency and restore power using the remaining transformer.

“We had crews out at critical stations,” says Moore. “The crews worked towards isolating the transformer that was burning from the power grid, then restored power from the second transformer which was capable of carrying the full system.”

Meanwhile, local fire departments were dispatched to cordon off the area, which was spewing toxic smoke from the transformer’s oil tank. Oil is used in transformers as coolant and an insulator.

NL Hydro was able to use a 138-kilovolt alternate power route that runs between Sunnyside and Glenwood to feed the system using the one remaining transformer, according to Moore.

“Typically with our power grid, we’re set up to have redundant secure supply for all our customers, so in this case that station was designed to have two transformers supplying that portion of the grid,” he says. “If either one of them failed for any reason the other transformer could take care of the customers.”

Moore says he’s thankful for the local fire departments’ work keeping people away from the blaze and monitoring the situation, but in the end NL Hydro brought in firefighters and equipment from the hydroelectric plant in Churchill Falls to extinguish the flames. The Nalcor firefighters had foam that could be used on high-voltage fires and training on how to fight them. Firefighters started battling the blaze at midnight, Jan. 7, and had it doused by the next morning.

A team of engineers, people in operations, and outside consultants are now investigating the cause of the fire using what remained after it was extinguished. 

“The transformer case is still there,” he says. “A lot of auxiliary equipment damaged. The top of the transformer which is typically bolted down to main tank, opened up, once the fire started it almost looked like opening a can with a can opener type thing.”

Moore says his office is working with the NL Hydro engineering department to prepare specifications for a new transformer at Sunnyside. The power grid isn’t currently affected by the loss of the burned transformer. Moore says NL Hydro’s Plan B in the event of the second transformer failing would be to disconnect one from a station in Stony Brook near Grand Falls-Windsor, and install it at Sunnyside, a process that he says would take at least a week. It took less than a day to make the switch between the two Sunnyside transformers.

“Right now we don’t have any redundancy, because it’s only one transformer in service,” he says. “So customers are in service and have secure supply, but certainly don’t have the backup supply that they once had until we get the transformer replaced.”

The tendering process for a new transformer typically takes more than a year.

“We’ll do whatever we can do to expedite it and get that redundant supply back to the customers,” says Moore.

The environmental clean up of the oil and residue from the smoke is still ongoing at Sunnyside, with international consulting company Stantec contracted to oversee the work. Moore says the work may go into the spring when the snow melts.

“That has to be cleaned up and treated as an oil spill, although our feeling is the majority of the oil went up in smoke basically,” says Moore.  “Any soot or oil stains on the ground we’re cleaning up as per regulations and Stantec is basically engaged to make sure that happens for us in consultation with our environmental department.”

This article was updated from a previous version.

shawn.hayward@thepacket.ca

@Shawn_M_Hayward

Organizations: NL Hydro, Newfoundland and Labrador Hydro, Newfoundland Power Stantec

Geographic location: Sunnyside, Eastern Newfoundland, Holyrood Glenwood Churchill Falls Buchans

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