The original VELCO St. Johnsbury Substation was built in 1972, with various modifications and improvements occurring over the subsequent nearly fifty years of service. VELCO conducted a condition assessment of the substation and identified the need to replace some of the equipment due to condition. Deficiencies were identified in the equipment such as the control building, 220 circuit switcher, 34.5 kV circuit breakers, protection and control relays, and the substation fence.
The project will require VELCO to install a temporary configuration and temporary 34.5 kV lines to maintain service to the GMP subtransmission system.
The following upgrades to the VELCO St. Johnsbury Substation will improve reliability of electric facilities serving portions of Vermont.
- Replace the existing 25’ x 31’ VELCO control building with a new, approximately 32’ x 70’ control building that will accommodate the protection and control system, redundant AC & DC station services, communication equipment, and security systems. The new control building will be located on the southern side of the substation.
- Replace the existing 220 circuit switcher with a new K220 SF6 gas circuit breaker that meets VELCO’s design standards.
- Expand the fence to accommodate the new control building, and to improve access to equipment for maintenance. The substation fence expansion will be approximately 15 feet to the north, 15 feet to the west, and 55 feet to the south.
- Reconstruct and widen driveway to 20 feet with turn-around. Improve site drainage.
- Perform tree clearing to accommodate the temporary infrastructure, temporary substation/construction area support area, expanded substation yard and driveway improvements.