BRATTLEBORO — Starting in April 2017, Green Mountain Power will be updating its substation on Cotton Mill Hill.
"Some of the transformers are quite old," said GMP Spokeswoman Dottie Schnure. "Putting in new transformers will increase reliability and will also allow for future growth in the area. It will give us more operating flexibility."
The $3.6 million project will be paid for out of GMP's capital infrastructure budget, which is funded by ratepayers. The project is expected to be completed in December 2017. While the work is being done, a temporary substation will be installed so there are no interruptions in service.
"It will be in the same footprint as the current substation," said Schnure.
She also said there shouldn't be any major disruptions to traffic due to the construction. "Maybe some minor inconveniences during construction as we move the larger materials in and out but it would only be in the form of lane closures in front of the substation for short periods."
Schnure said most of the construction work will be done in house, but some of the civil work will be put out to bid for Vermont contractors.
The Vermont Public Service Board issued a certificate of public good for the project on Sept. 12.
Work at the South Brattleboro substation will include demolishing and removing switchgear, outdoor electrical equipment, perimeter fence, all equipment foundations, and steel structures and replacing the existing 4.687 MVA and 14 MVA transformers with a single 28 MVA 69 kV to 12.47 kV transformer, which will increase the substation capacity, according to the CPG approval. "Reconstruction will include installing new equipment foundations, ground grid, below-grade trenches and conduit systems, oil containment, circuit breakers, voltage regulators, relays, equipment cabinets, and communication and security systems. A new retaining wall and riprap will be installed on the adjacent slope, and the existing fence will be replaced."
One of the transformers is 54 years old and the other is 28 years old. GMP will test the area for the presence of polychlorinated biphenyls, or PCBs and create a plan to ensure no PCBs enter the environment during demolition.
According to the CPG approval, the Brattleboro region has four substations with circuit ties that provide feeder backup opportunities. "Loss of any one transformer due to a planned or emergency situation decreases the total area transformer capacity to a level that is close to the regional loads. Additional backup limits could quickly consume the difference, resulting in limited future load capacity for the entire area feeder backup. The replacement transformer will increase distributed generation interconnection capacity in the area served by the substation."
Bob Audette can be contacted at 802-254-2311, ext. 160.