Avista needed to fulfill a large generator interconnection, in this case, a wind farm with firm deadlines for the design completion to meet the contractual in-service date. Commonwealth supported Avista by managing the scoping process which developed the preferred layout. Commonwealth provided engineering design services for the needed substation for interconnection. 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 initial design functions as a three-position ring bus which can be expanded into a six-position, breaker-and-a-half arrangement.
The substation intersected a radial 115 kV transmission line and provides the Point of Interconnection for the wind generation facility. The physical layout followed the bus configuration of two bays from the standard breaker-and-a-half configuration with only three circuit breakers and their associated switches. The ultimate general plan was laid out for six-line positions in a three-bay, breaker-and-a-half bus arrangement. There were no plans for adding distribution feeders since this location is in an area not served by Avista Utilities. The panel house was sized to accommodate current and future transmission lines. Material procurement is complete and construction will be completed the summer of 2019.