- Ptarmigan Substation
Ptarmigan Substation was initially proposed by Xcel Energy in the late 1990s to meet load demand in the growing Silverthorne area. The substation was to be a 230-kV in-and-out substation with a 230/25-kV transformer and 25-kV metal-clad switchgear with provisions for future transformers and feeders. Originally the site was to be next to the Blue River in Silverthorne, but this plan was rejected over environmental concerns. After more than a decade of permitting, the town accepted a site built into the side of a mountain with the stipulation that the visibility of the substation would be reduced tree plantings and painting of high-profile structures to match the landscape.
Building into the side of a mountain created design considerations. Because of the Rocky Mountain elevation, all equipment had to be rated to meet high-altitude requirements. The site also required a large retaining wall, with some portions reaching 40 feet tall. The town requested the wall be decorative to match the landscape. To limit the amount of cut required for the site, the grade on site was 5 percent.
Silverthorne is conveniently close to many of Colorado’s popular ski resorts and receives nearly 80 inches of snow each year. To create safe working environments inside the substation, operating platforms for breakers and switches were installed.
The Ptarmigan yard consists of a three-position 230-kV ring bus with two line positions and one distribution transformer position. In all, the project involved 11 230-kV switches, three 230-kV dead tank breakers, one 230-kV live tank breaker, one 230/25-kV transformer, one 25-kV nine-cubicle metal-clad switchgear, one 25-kV metal-clad capacitor bank, two overhead 230-kV lines with power line carrier schemes. Control schemes were completed for the 230-kV transmission lines, breaker failures, transformer, 230-kV bus, 25-kV bus, 25-kV feeders, and 25-kV capacitor bank.
The completion of Ptarmigan Substation helped make Xcel Energy successful in serving the town of Silverthorne, completing a project nearly 20 years in the making.
- Project management
- Detailed engineering and architectural design
- Material procurement support
- Permitting support
- Construction support
- Unique retaining wall design to accommodate 40-foot mountain cut-in
- Custom designs to account for extreme snowfall conditions
- Complex grounding modeling and analysis due to soil variance from significant soil cut-in
- Extensive permitting support to establish final site location after nearly 15 years of previous permitting efforts by others