Losing a substation transformer could be a nightmare in the utility business. It would cause a power outage for hundreds of members. And, without proper planning, the outage could last for many days.
On Saturday afternoon, June 20, with temperatures near 90 degrees, we lost that critical piece of equipment in our Sharpsburg substation, which serves several hundred members in southern Mercer County, including a number of agricultural businesses. An insulation bushing on the substation transformer was damaged. We are not sure what caused the damage. Testing is being completed to determine the cause and the extent of damage.
Some background on substation transformers:
A transformer is the primary piece of equipment in a substation. It takes the incoming 69,000 volts from the transmission company, and converts it to 7,200 / 12,470 volts for the local distribution lines. A problem with the transformer means the entire substation is out of power and all the members it serves. A distribution substation transformer costs around $400,000, making it impractical to have one laying around in inventory “just in case” (especially since they typically last upwards of 40 years).
We do regular inspections and ongoing maintenance of all of our substation transformers. One substation transformer can’t be kept on hand as a spare backup for all of our substations: Different substations have different incoming voltages; and the substation transformers can be different sizes (megawatts) based on the nearby load. A substation transformer is specifically designed and built for just that one substation.
What we did when the Sharpsburg transformer failed:
When the Sharpsburg transformer failed on June 20, we routed power from other area substations to serve the Sharpsburg area, as a temporary fix. We used our St. Henry substation to provide power. And we used our Chickasaw delivery point to provide backup to St. Henry.
Damage to a substation transformer could be permanent. They cannot be easily or quickly fixed or replaced. So the next step in our process was to bring in a mobile substation. This was brought in late Saturday night, June 20, and energized by 6 a.m. Sunday morning. A mobile substation is a completely self-contained trailer mounted substation consisting of a transformer, cooling equipment, high voltage switchgear, protection devices, etc.
How our long-term planning paid off:
We belong to a group called Heartland Emergency Equipment. Heartland is comprised of 12 electric cooperatives in Ohio and one in Indiana. Heartland owns six mobile substations of varying sizes. We pay annual fees to be part of Heartland, and with the other co-ops we share in the cost of equipment maintenance and purchases.
Heartland is an example of one of our principles, Cooperation Among Cooperatives. This is our substation transformer inventory. You could think of it as insurance, as well as inventory. We could not afford to have this equipment on our own. And, we cannot afford to be without this emergency equipment.
Without this arrangement, our members in that area would be in dire straits right now.
Here’s what another co-op manager said, who is part of the Heartland group:
“I’m so glad we have this 'insurance policy' company in place. I’ve experienced what it’s like to lose a substation transformer without having access to a mobile substation. It’s not fun!”
This incident also underscores the importance of long-term planning. Planning a system design that allows for feeding from other sources. And planning for emergencies with like-minded cooperatives in the Heartland group.
Accidents are going to happen. Equipment is going to fail. But it’s good to know that we have more than one plan for addressing those situations when they happen.
You might ask: what’s happening long-term with our Sharpsburg substation? We’re having the transformer tested to see if it can be repaired. If not, we’ll buy a new one. We expect the mobile substation to be in service at least through the remainder of 2020.
Thank you for your understanding. Please call our office if you have any questions.