345kV and 115kV Line Terminal Relay Replacements

Tangibl developed a set of drawing and design packages for replacement of discontinued distance relays with Schweitzer Models 421 and 311L at 345kV and 115kV respectively for a transmission owner in ISO New England.

In addition to revising panel drawings including schematics and wiring diagrams, Tangibl was required to update as-built markups for each station where the work was performed.  The client further required that panel modification details including cutouts and filler plates be provided.  In addition to distance relays on the 345kV line terminals, carrier equipment was also included in the design scope for replacement.  Drawings were created in Microstation for record purposes.

The project was complicated by the fact that the client was moving to new enterprise-wide information systems, including new financial, project- and document-management tools.  In addition, outages were required for relay replacement, so care was taken to simplify the replacement and minimize impact on critical current input circuits and trip output circuits.