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PV20 Submarine Cable Replacement Project

About

Vermont Electric Power Company proposes to replace four cables from the underwater Vermont-New York border to a new termination station, to be located just northeast of the existing termination station in Grand Isle, Vermont. The project would also include replacing two overhead transmission line structures to connect the new cables from the new termination station to the remainder of VELCO’s Plattsburgh to Vermont line called the PV20 line. The existing seven submarine cables, the existing Grand Isle termination station and its associated equipment and structures will be decommissioned and removed once the new facility and equipment is energized.  

The PV20 line was constructed as an integral part of VELCO’s initial transmission system to deliver low cost hydro power from the St. Lawrence – Franklin D. Roosevelt Power Project in New York to Vermont under a 1957 contract between the State of Vermont and VELCO. This system was placed into service in September 1958. 

Needs & Benefits

The existing submarine cables that comprise the PV20 line are damaged, with one being no longer usable, and are at the end of their expected useful service life. VELCO and the New York Power Authority (NYPA) have determined that the risk of a cable failure is too high based on evaluations of the cables’ condition and that replacing the existing cables is required in order to maintain this vital transmission line. 
 
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, rely on this important transmission line to be in service to meet current federally mandated reliability requirements.
 
Failure of two or more of the existing working cables could result in the total disconnection of the PV20 line, putting reliability at risk from the lengthy outage required to restore and repair the line. An outage could reduce Vermont’s ability to deal with contingencies by as much as 350 MW, exposing the system to voltage collapse problems for several contemporaneous contingencies which could not be remedied with area generation.   

Components

The project consists of a the following upgrades:

  • Install four submarine cables from the Vermont to New York border
  • Construct a new Grand Isle terminal station 
  • Install twooverhead transmission line structures to connect the new cables from the new termination station to the remainder of the PV20 line
  • Remove existing seven cables and the existing Grande Isle termination station and associated equipment and transmission line structures

 

Impacts

VELCO’s aesthetic consultant reviewed the preliminary design plans and performed a visual analysis of the areas proposed Project. It is anticipated that the vast majority of the surrounding area will not have visibility of the Project. Where visible, the Project elements will be partially screened by the intervening mature vegetation. Due to the relocation of the terminal station to a more robustly screened site, the existing screening along Vermont Route 314, the similarity between proposed and existing structures and the removal of the existing terminal station, the Project is not anticipated to cause undue adverse effects to the area.
 
A full analysis of potential aesthetic impacts and proposed landscaping to mitigate those impacts will be included with the Certificate of Public Good Petition to be filed with the Public Service Board in June. 

During operation the PV20 elements do not produce noise. During the Project’s construction and commissioning noise will be produced, but will be temporary. 
 

Project Timeline

  • Spring 2015
    • Public meetings
  • Summer 2015
    • Regulatory and permitting process
  • Summer 2016
    • Potential early partial construction start (subject to approval)
  • Spring 2017
    • Full construction start (cable install/removal in Lake Champlain)
  • Winter 2017
    • Anticipated completion 
  • Spring/Summer 2018
    • Removal of old facilities