Montana-Dakota Utilities recently filed with the North Dakota Public Service Commission a consolidated corridor certificate and route permit for the Mandan Transmission Reroute Project for a 230-kV Transmission Line.
As noted in the filing, the project involves rerouting an existing 230-kV transmission line for a new substation and terminating at a new line terminal in the Mandan transmission substation north of Mandan, N.D.; the project was identified in the company’s 10-year plan submitted in July 2020.
The 230-kV transmission line currently terminates in the Heskett transmission substation and connects the Heskett and Mandan transmission system with the company’s transmission system near Napoleon, N.D.
The company added that the Mandan transmission substation was built in 2010, and included plans to ultimately relocate all 230-kV facilities from Heskett to the new substation. With the closures of the Heskett coal-fired generating units 1 and 2, a new 115/69/41.6-kV substation on the Heskett transmission substation site was required and moved forward those plans, the company said.
The existing Heskett transmission substation was built in 1966 with a straight bus arrangement, the company said, noting that moving the Napoleon 230-kV terminal to the Mandan substation would eliminate the straight bus arrangement, which would increase reliability as the straight bus arrangement causes all lines on the bus to trip in the event of a fault or circuit breaker failure.
The company said that terminating all of the 230-kV transmission lines into one substation reduces outage contingencies and improves reliability on Montana-Dakota’s bulk electric integrated system that serves portions of Montana, North Dakota, and South Dakota.
The project is expected to begin this spring, as well as be completed, tested, and placed in service in spring 2022. The company added that the majority of the project is on private land owned by the company and all remaining rights of way (ROWs) have been acquired.
The estimated total cost of the project is about $1.2m, which includes engineering, materials, and construction costs, the company said.