Tafts Corners Substation Upgrade
The VELCO Tafts Corners substation in Williston, Vermont was constructed in 2004 to support the subtransmission system and designed to be expanded to serve growing distribution loads near the Williston load center. Due to projected load growth in the Williston area, as well as aged distribution equipment, Green Mountain Power (GMP) and Vermont Electric Cooperative (VEC) proposed to increase the capacity of their distribution systems and replace aged equipment.
To meet these needs, VELCO, GMP and VEC proposed to add an additional transformer and related equipment within the existing fenced-in area of the VELCO Tafts Corners substation, as well as related improvements to the distribution system.
Needs & Benefits
The Tafts Corners substation interconnects VELCO's electric transmission network in northwest Vermont and feeds the electric distribution system serving GMP and VEC customers. Failures of key transmission components cause low-voltage conditions that violate system standards, voltage instability/collapse, or thermal overloads, which could result in extended outages for the areas served by the transmission system.
Transmission utilities, such as VELCO, are required to design, operate and maintain a transmission network according to national and regional reliability standards. Planning studies by VELCO and ISO New England, New England's bulk electric system provider, reveal that the existing Tafts Corners substation does not meet current federally mandated reliability requirements.
The Project consists of the following additions within the existing fenced-in yard of the VELCO Tafts Corners substation:
- Three 115 kV circuit breakers and associated equipment
- 115 kV structural steel bus and disconnect switches
- One power transformer with foundation oil containment
- Indoor switchgear; protection, control, metering switchboards, and battery systems
- One take-off structure
- One transitional structure
The project includes two aesthetic mitigation measures that have a significant positive effect outside of the substation yard. The first measure is the removal of the first two 34.5 kV poles immediately south of the substation that transition to the 34.5 kV H-frame at the end of I-89. These poles were replaced with a new take-off structure and a transitional structure built at a lower elevation within the substation.
The second aesthetic mitigation measure is the removal of the VEC's Williston substation.
- Summer 2008
- Permitting and regulatory process