Storms, high winds cause damage to Basin Electric, member transmission equipment

Storms bringing high winds caused severe damage to Basin Electric and many member systems’ equipment in May and June.

Basin Electric had severe damage to 18 transmission structures on one line and 16 on another in South Dakota. Transmission System Maintenance crews repaired two miles of the 230-kilovolt (kV) line, allowing it to go back into service on June 26. The other, a 345-kV line from Leland Olds Station to Groton, South Dakota, is still being repaired.

East River Electric

In May, Basin Electric Class A member East River Electric Power Cooperative’s system was impacted by two separate severe storms over a two-day span. On May 11, 36 distribution substations, four transmission customer substations, and eight delivery point substations, were impacted by severe weather. In total, the weather event affected more than 23,000 member-consumers and damaged 13 transmission structures on a line section serving East River Electric member and Basin Electric Class C member Southeastern Electric Cooperative.

During the May 12 storm, the areas in East River Electric's system experienced a derecho as well as 16 reported tornadoes where 127 distribution substations, 16 transmission customer substations, and 32 delivery point substations (along with its transmission service from Otter Tail Power) were impacted, affecting over 51,000 member-consumers. The storm damaged 264 East River Electric transmission structures on 45 line sections and 14 distribution substations were impacted by an outage of over 24 hours, with four substations over 48 hours.

East River Electric member and Basin Electric Class C member Sioux Valley Energy in Colman, South Dakota, saw damage to a large portion of its service area, including significant damage to its distribution system. Employees even had to evacuate its dispatch center briefly.

Throughout the storm, East River Electric’s system operations personnel worked to reroute power and restore members wherever possible. As the storm passed, crews were dispatched to assess the situation and East River Electric’s Operations division began developing plans for restoring power to the impacted substations. Due to the widespread damages, the power restoration process took several days. On May 15, East River Electric restored power to the last of the wholesale power supply substations that were impacted by the storm. Repairs on the broken transmission structures continued over the next few weeks.

Then on May 30, 63 distribution substations, nine transmission customer substations, and 16 delivery point substations, along with its transmission service from Montana-Dakota Utilities, Otter Tail Power Company, and Xcel Energy were impacted by more severe weather. In total, this weather event affected more than 27,000 member-consumers and damaged 65 transmission structures on eight different line sections. On the following day East River Electric restored power to the last of the wholesale power supply substations that were impacted by the storm. Repairs on the broken transmission structures continued over the next few days.

“The real challenge was the large footprint of the storm and the different construction types throughout East River's service territory,” said Scott Shewey, East River Electric’s chief financial officer. “The key was early and constant communication with our vendors and other co-ops. A lot of the downed lines had pole heights that were lower usage sizes which resulted in the need for us to call on our pole vendors and neighboring transmission co-ops.”

Basin Electric Class A member Northwest Iowa Power Cooperative out of Le Mars, Iowa, supplied poles to East River Electric and had them coming within 24 hours and Class A member Corn Belt Power Cooperative from Humboldt, Iowa, supplied poles and crossarms. Class C member Roughrider Electric Cooperative headquartered in Hazen, North Dakota, supplied poles and insulators. Class A member Mor-Gran-Sou Electric Cooperative headquartered in Flasher, North Dakota, provided poles and crossarms.

Southeastern Electric Cooperative

On May 12, Basin Electric Class C member Southeastern Electric Cooperative headquartered in Marion, South Dakota, experienced a severe thunderstorm minutes after there was a tornado warning. Wind speeds were in excess of 109 miles per hour and hit a substantial section of the system’s service area.

Southeastern Power’s power supplier, East River Electric, learned it had many transmission poles and lines laying on the ground throughout a sizable portion of its territory; however, was able to back feed some of its lines to re-energize some substations. Others took a few days to restore. Southeastern Electric’s crews worked diligently to get as much of the damage repaired as possible before East River Electric could restore power to the substations. Almost every account had some damage to a building, grain bin, or house.

Altogether, Southeastern Electric had a total of 6,441 members affected by the storm, which was determined to be a derecho. A maximum of 4,191 members were out of service at one time. Nearly all members who could safely receive power had their service restored by noon on May 15, however several members had their service their services disconnected and/or turned off while repairs were made.

Damages included approximately 85 poles, eight transformer poles and countless primary and secondary wire breaks. 

Just over two weeks later on May 30, another storm hit, affecting 2,633 members and leaving 10 poles broken and nine substations offline either momentarily or for longer periods of time.

Codington-Clark

On the evening of May 19, a windstorm went through Basin Electric Class C member Codington-Clark Electric Cooperative, headquartered in Watertown, South Dakota. Because most of its distribution system is underground, most of the damage was sustained on farm and home sites with debris blowing into secondary poles, junction boxes, and overhead wiring. The co-op only had five poles break off in the wind. The vast majority of outages were caused by the loss of transmission lines.

Renville Sibley Cooperative Power Association

Basin Electric Class C member Renville Sibley Cooperative Power Association in Danube, Minnesota, experienced a storm on the morning of Memorial Day, where high winds knocked down poles and lightning struck close enough to blow two main fuses at one of the co-op’s substations causing outages. Another storm came through in the afternoon causing more outages.

Outages that day were caused by wind, lightning, fallen tree branches, and a grain bin rolling into a pole. In total, the co-op experienced 11 outages affecting 870 members with a total of 32 poles broken. During the storm lineworkers set existing broken poles to restore power quickly, then worked for two-and-a-half weeks replacing the poles and repairing many other issues that were found during the repair work.

Storms have continued to cause damage in Basin Electric’s service area in July.