115kV Orchard Substation

115kV – Orchard Substation

Obsolete Relay Replacement – Indian Orchard, Massachusetts

Project Scope:

Provided engineering and design for the retirement of an existing 115kV breaker failure relay and reclosing scheme.  Installed (2) SEL 351-6 relays for the breaker failure and reclosing scheme.  New relays were connected to the existing station frame relay access device.

  • Provided relay calculation basis document
  • Created SEL logic diagrams
  • Created SEL relay settings file (.rdb)
  • Prepared bill of material
  • Prepared construction drawings, including demolition and removal
  • Created nameplate list for new relays, devices, and test switches

orchardDesign Challenges & Solutions:

Due to space consideration in the existing control house, the panels containing the existing breaker failure relays did not provide sufficient space for the new relays. The existing relay panels were designed to be abandoned, and the new relays were designed to fit on one panel. The existing steel plate for the panel was to be removed and replaced with a new panel to mount the new equipment including: SEL351 breaker failure relays, auxiliary lockout relays, and associated test switches for breakers.


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