Connecticut River Valley Project
In 2011, Vermont Electric Power Company in coordination with the Independent System Operator of New England (ISO-NE) conducted a Vermont-New Hampshire needs assessment in response to a system deficiency in the Connecticut River Valley area. The study showed the Coolidge to Ascutney line was exposed to overloads under several system conditions and the line exceeds its current carrying capacity and subarea voltages are outside the acceptable limits.
An extensive solutions assessment study was conducted to evaluate various solutions with the participation of several stakeholders within the Planning Advisory Committee.
VELCO proposes to upgrade the existing transmission line between the Coolidge and Ascutney substations to resolve the overloading and voltage violations. In addition, because of voltage violations, upgrades need to be made at the substations in the Connecticut River Valley area, specifically at Ascutney, Chelsea and Hartford, Vermont.
Needs & Benefits
The electric transmission line that connects VELCO’s Coolidge substation to the Ascutney substation exceeds its current carrying capacity, and voltages are outside acceptable limits in the area including the Chelsea, Bellows Falls, and North Road 115kV substations.
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 provider, reveal that the Connecticut River Valley area does not meet current federally mandated reliability requirements.
As outlined in VELCO’s 2009 and re-outlined in the 2012 Vermont Long-Range Transmission Plan, the vulnerability of the current line connecting the Coolidge and Ascutney substations results in system reliability problems, which under certain circumstances may lead to thermal overloads and or voltage instability and collapse.
The project consists of a combination of transmission line and substation upgrades:
- Rebuild 15 miles of existing 115 kV transmission line from Coolidge to Ascutney
- Reconductor 18 miles of 46 kV sub transmission lines (Middlebury, Bethel, Windsor areas) by Green Mountain Power
- Addition of a ring bus at Chelsea substation
- Addition of a new bay and a reactive device at Ascutney substation
- Addition of a 12.5 MVAr capacitor bank at Hartford substation and reduction of the existing capacitor bank to 12.5 MVAr
- Spring 2015
- Public meeting (click here to view public outreach schedule)
- Summer 2015
- Regulatory and permitting process
- Spring 2017
- Construction start (subject to approval)
- Winter 2017/2018
- Anticipated completion