Substation testing could cause a Benson outage

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While the testing should go off without anyone noticing, the City of Benson wants every business owner and resident to be aware that there is a remote possibility they could suddenly lose electric power.

Thursday, Dec. 6, the North American Electric Reliability Corporation (NERC) is going to be testing the substation through which power flows from Benson Power, LLC, into the region’s electric grid. The City of Benson’s electricity also comes through the substation and it is tied into some Agralite Electric Cooperative customers.

The city is meeting with GRE, NERC, Agralite and Otter Tail Power at 11 a.m., Tuesday, Nov. 28, to go over the testing plan.

They are testing the relay switches at the substation through which Benson Power’s 55 megawatts of power flow. The switches are designed to detect any fault currents and open the switch to protect the grid. Fault signals are sent to the substation to see if switches react.

“It is part of the national effort to protect the grid,” Benson City Manager Rob Wolfington explained.

The last time the transmission system was tested things didn’t go so well. It was a two-day test where a simple human error, the flipping of a wrong switch, created a cascading problem for the city. That flipping off of the wrong switch the first day shut Benson’s power off.

What no one realized was that the city’s power plant computer logic board had recorded the trip signal. NERC erased the problem at its end of the testing at the substation, but not on the city’s computer. At the time, the city’s computer was off and not even active, Wolfington said.

When the tests were all done, the city turned on its generators, they read the GRE trip signal, and the city’s power was shut down.

GRE and NERC say they now understand the computer language problems that caused the outage and have it fixed....


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