Monroe HVDC Converter Station

Monroe HVDC Converter Station, Monroe, NH

Phase/Converter Terminal Retirement

The Monroe Converter Station project consisted of the decommissioning, removal, and/or relocation (on-site) of most HVDC Phase 1 facilities; including the converter building, valve hall and associated equipment, and an underground storage tank for an oil-water separator system. Installation and commissioning of new equipment was also included. The project comprised of the removal of HVDC Phase 1 equipment at (5) additional substations: Moore Station (TransCanada), and other Client Substations (Comerford, Tewksbury 22, Tewksbury 22A, and North Litchfield). At project completion, the station provided 230kV VAR support.

Engineering, Design, and Construction Support Services Included:

  • New, pre-engineered control house, including P&C cabinets, overhead cable trays, O&M storage and work area, battery rack, restroom, communications room, technicians’ cubicle offices HVAC, protection, metering, control, SCADA, fiber optic, site security, station service equipment, and separation of protection systems.
  • Trenwa cable trench system to access new and relocated equipment.
  • 230kV circuit breakers to connect relocated VAR support equipment to Pole 1 and 2 buses.
  • 230/13.8kV 75 MVA power transformer.
  • Substation bus conductors, CCVT’s, circuit switchers, disconnect switches, 34.5kV cable terminations, insulators and components, grounding, control and power cables, yard lighting, and lightning protection.
  • New concrete foundations as required.
  • Control house foundation to accommodate pre-engineered metal building sized.
  • Equipment foundations for new CCVT’s, breakers, arrestors, disconnect switches, circuit switchers, reconfigured high bus support structures, relocated capacitor banks, and upgraded foundation for new (replaced) transformer.
  • New containment pits for (3) transformers.
  • Aluminum and steel support structures for electrical equipment.
  • Assisted the demolition subcontractor with demolition of existing foundations and the existing converter and control house, including design of safely infilling and capping the deep abandoned basements of these (2) attached buildings.
  • DC power, including 125 VDC batteries and charger systems, safety switches, and DC cabinets for the control house.
  • Design/review the grounding grid.
  • 208 GRD.Y/120 VAC, (3)-Phase, (4)-wire AC panel boards.
  • (2) Station service transformers with fused safety switches, auto-transfer switch, and meter cabinet.
  • 230kV and 13.8kV control, protection, instrumentation, remote terminal unit, digital fault recorder and alarm annunciation for all circuit breakers, lines, buses, capacitor banks, and transformers.

Performed Various Studies and Analysis, Including:

  • Battery sizing calculations.
  • Switching/lightning protection study.
  • Grounding study and ground grid tests.
  • Civil/structural analysis of foundations and support structures.
  • Structural and HVAC calculations for new control house.
  • Station service AC & DC loads.
  • Lighting, voltage drop, conduit fill, and burden calculations.


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