Avista is interconnected with another utility in Adams County, this interconnection is nearing its design ratings. With renewable energy interconnection requests and native load growth, Avista determined that building a substation to intersect the nearby 230-kV line was the best solution for the area’s needs. Commonwealth provided engineering design services for the one of Avista’s 230 kV substations. This design included the civil/structural, physical, protection and integration design, as well as, material procurement, transmittal of final design, construction support, and record drawings. The bus configuration is a traditional double-breaker, double-bus. The substation will be laid out with the 230 kV yard to the northwest end of the yard, with the future auto-transformer and 115 kV yard extending to the southeast.
Commonwealth designed a four position, double-bus, double-breaker 230-kV transmission switching station with two complete positions and two future positions. The initial general plan included disconnect switches on each 230 kV bus to facilitate the easy construction of the auto-transformer position and one future line position. The ultimate general plan laid out all four 230 kV positions, a second auto-transformer position in a potential fifth position and tied into a four-position breaker-and-a-half 115 kV transmission station which could be expanded. Ultimate build was completed to ensure adequate space was available for construction and maintenance.
This substation is being used as the new standard engineering and drafting reference for 230 kV substations going forward, providing a model for design and drafting which can be efficiently replicated on future projects.