Ascutney Substation Project
In 2011, Vermont Electric Power Company proposed to construct a substation east of the existing substation in Weathersfield, Vermont, to provide a redundant path and additional capacity to deliver power to this area.
The Ascutney Substation is located in Southern Windsor County in the town of Weathersfield, Vermont.
Needs & Benefits
The Ascutney substation interconnects VELCO's electric transmission network in central Vermont. Failures of key transmission components could 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 Ascutney substation does not meet current federally mandated reliability requirements. Specifically, the system cannot meet required reliability criteria because a bus fault (a fault in which a circuit-breaker fails to open), will result in system voltage violations and possible voltage collapse (outage).
As outlined in VELCO’s 2009 Long-Range Transmission Plan, the vulnerability of the current substation design results in system reliability problems, which under certain circumstances may lead to loss of service, system outages and low voltage. These concerns can be addressed by constructing the proposed substation using a robust design such as a ring bug or a breaker-and-a-half substation. Building a new VELCO Ascutney substation with a new six-breaker ring substation to connect the four transmission lines serving southeast Vermont will resolve current reliability criteria violations that result from a single element’s failure at the substation.
- 115kV aluminum bus structure
- Six circuit breakers
- Control building
- Connection to VELCO's existing 115kV transmission lines
- Connection to existing Ascutney substation
- New transformer
Now completed, VELCO and GMP modified existing configuration of lines and constructed a new sub-transmission line within the existing corridor, to connect the new station to the existing transmission and sub-transmission lines and substation. Some of the VELCO owned components of the existing Ascutney substation (including the transformer) were decommissioned and the existing equipment retired as part of this project. The equipment remaining at the previously existing substation serves the Green Mountain Power sub-transmission system.
VELCO's aesthetic consultant reviewed the preliminary design plans and performed a visual analysis of the areas of the proposed Project. The findings indicated that the project had the most potential visibility to the general public from Route 5, Interstate 91 and from the adjacent residential neighborhood along Tenney Hill Road. The analysis also found potential for visibility of line upgrades east of Interstate 91 from these locations.
Landscape mitigation plantings help screen views that are created to the substation and also help screen visibility of the line upgrades. Due to the increased potential for visibility of line improvements, attention was given to the style and locations of transmission line structures, and in particular the angle structures for the lines to access the new substation. A detailed report with proposed landscaping mitigation measures was included with the project petition.
VELCO’s noise consultant assessed the potential noise impacts associated with the substation relocation. A complete engineering noise analysis was provided as part of the Project’s filing with the Public Service Board.
- Spring 2011
- Public Meetings
- Summer 2011
- Regulatory and permitting process
- Spring 2012
- Construction start
- Fall 2013
- Construction complete