Vermont Electric Power Company proposes to upgrade the Florence Substation. The upgrade is needed because a recent conditions assessment revealed deficiencies within the substation. The transmission system upgrade will improve reliability of electric facilities serving portions of Vermont.
Needs & Benefits
The original VELCO Florence Substation was built in 1978, with various modifications and improvements occurring over the subsequent 43 years of service. VELCO conducted a conditions assessment of the substation and identified the need to replace some of the equipment due to condition. Deficiencies were identified in equipment such as the protection and controls system, 115 kV breakers, 46 kV breakers, switches, capacitor bank and control building.
VELCO proposes to construct a new substation to the north and adjacent to the existing substation. VELCO proposes to design the new substation in a ring bus configuration as opposed to the existing radial bus configuration. In a ring bus configuration, the circuit breakers are connected to form a ring and the circuits feeding the loads are connected between the breakers. In a radial bus configuration, each circuit is fed from a single circuit breaker. A ring bus provides improved reliability and maintainability over a radial bus, as any of the circuit breakers can be opened and isolated for maintenance without interruption of service. In addition, in the event of a fault, the breakers on both sides of the faulted circuit trip, and thereby isolate the fault, while the other circuits remain in service.
After VELCO has successfully commissioned the new substation and placed it into service, VELCO will retire and remove the existing substation.
The project will require VELCO to install a temporary configuration to maintain service to the Green Mountain Power (GMP) sub-transmission system.
The Project consists of the following primary components:
- Construct a new 115/46 kV ring bus substation with all new components adjacent to the existing substation, including installing:
- a new 115/46 kV, 33.6/44.8/56 MVA transformer.
- Four (4) 46 kV vacuum circuit breakers
- One (1) 115 kV, SF6 circuit breaker
- Ten (10) MVar capacitor bank and associated reactor and SF6 Breaker
- A protection and control system that provides diversity, redundancy, and communication aided schemes
- A control building that is able to accommodate the new protection and controls system, redundant AC and DC station services, communication equipment, and security systems.
- One (1) 115 kV, and four (4) 46 kV instrument voltage transformers in support of the new protection and controls system.
- Passive secondary oil containment system for the new 115/46 kV transformer.
- A new fence to accommodate the new substation. The substation fence will enclose a 39,500 square foot area to the north of the existing substation fence. For comparison, the existing substation fence encloses an area of 24,900 square feet. In addition, VELCO will install a fence at the top of the hillside for safety purposes.
- Two (2), three pole structures to connect the existing 115 kV transmission line to the new substation.
- Perform tree clearing to accommodate new substation and pole structures
- Remove existing substation, including all above and below grade components and restore the area to fit in with the surrounding property
- May - July 2021
- Public meetings
- Summer/fall 2021
- Regulatory/permitting process
- May - December 2022
- Anticipated construction start
- December 2022
- Anticipated completion