12.47kV Macmillan Substation

This project developed in a two-fold way: the University recognized the need to improve the connection point for two of their utility service points, and had already identified this project in their capital improvement plan. However, based on the need to connect a planned combustion turbine (CT) generator to the 12.47-kV distribution system, this project took on greater urgency and the in-service date was moved forward. This design was an outgrowth of the preliminary design done by Wiley|Wilson as a part of the CT/HRSG bridging documents.

Wiley|Wilson’s electrical distribution upgrade design included the use of metal-clad switchgear, with a dual bus arrangement and automatic bus-tie switching. The switchgear was designed to accept the two existing utility services and a feeder from the new CT. Three additional circuit breakers are planned to allow the connection of future electric generators from an expected new power plant to the campus 12.47 kV distribution system. Six feeder circuit breakers are designed for distribution circuits through the campus. Space for two additional breakers is included in the switchgear and the building layout allows for further additions to the switchgear structure, as needed.

Relaying and protective system design was performed to provide instantaneous and time overcurrent protection for the feeder breakers. Additional protection for the generator and utility breakers includes synchronization checking, reverse power flow protection, phase sequence, and over/under voltage protection. In addition, due to the critical nature of this new switchgear, bus differential protection was included.

A new switchgear building with a full basement was designed to allow for ductbank entry into the building. Design also included ductbanks and vaults for the new feeders, site design, and design and permitting for stormwater management and erosion and sediment control.