Comerford Substation

Comerford Substation, Monroe, NH

230kV Switchyard Revitalization

This project included (2) separate project scopes:

  • 230kV Switchyard Revitalization
  • 230kV Disconnect Switch Replacement at TransCanada’s Request.

The Comerford Generation Station is a (4) turbine, 160 MW hydroelectric station, located along the Connecticut River. There are (4), two-winding generator step-up transformers which step up the 13.8kV generator output, to supply the 230kV switchyard. Each pair of GSUs are connected to the 230kV bus, via motor operated disconnect switches, to a common breaker position in a breaker and a half arrangement.

Engineering, Design, and Construction Support Services Included:

  • Replacement of all (11) Mineral Oil Dielectric Fluid (MODF) filled and live tank circuit breakers with SF6 breakers.
  • Installation of a new SF6 breaker.
  • Replacement of (28) motor-operated disconnect switches.
  • Installation of line traps for (5) lines.
  • Replacement of dead-end insulators supporting main and cross buses.
  • Installation of CCVTs on (3) lines.
  • Replacement of CCVT’s on (3) lines.
  • Designed a new control house incorporating:
    • Control, relay, and communication equipment required to operate the outdoor switchyard, including provision for Bulk Power Conversion.
    • Station AC and DC auxiliary services, and standby generator.
    • HVAC.
    • Heat detection system.
    • Primary and emergency lighting system.
    • Operator’s desk.
  • Switchyard Grounding: Analyzed and modified the existing ground grid design to meet present Client standards. Extended the existing ground grid design to connect to the new equipment, control house, and the expanded fence.
  • Redesigned the fenced area around the control building and new line positions.
  • Provided material lists and revise cable schedules.
  • Provided structural and electrical calculations and design.


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