Cynergy performed a circuit breaker, forced fan and fan controller replacement project with a contract value of $3.077 million at the Fort McHenry Tunnel for the Maryland Transportation Authority. The twelve existing double-ended substations are over 30 years old and fed the lighting, power circuits and ventilation fans in the East and West bound tunnels. Keeping the emergency circuits energized during the breaker and transformer upgrades was a critical part of the project. Only half of each substation was allowed to be completed at a time. Temporary circuits had to be installed from another substation to allow the critical circuits to remain in operation. The work had to be closely coordinated and monitored by the Authority during the entire replacement process.
Principle features of the project were as follows;
- Replace 192 forced air fans on medium voltage dry type transformers
- Replace existing mechanical fan controllers with 24 new electronic fan controllers
- Replace 36 1600 amp draw-out breakers
- Replace 48 800 amp draw-out breakers
- Replace 103 400 amp and less molded case breakers
- Retrofit 88 existing spaces to accept future breakers
- Install Kirk key interlocks on all new main and tie breakers
- Provide new fiber optic communications and twisted pair cabling
- Installed a complete data communications network using Modbus protocol
- Removal of existing breakers and DC operating circuits
Under the contract every 480 volt draw-out and molded case circuit breaker had to be replaced with a new breaker. The existing breakers were Federal Pacific and the new breakers were Square D. Each draw-out breaker was a manually operated type, multi-function electronic trip with LSIG settings. A custom made cradle was designed and installed to retrofit the existing cubicles to accept the new breakers. New doors and nameplates were also provided. A Kirk key interlock system was provided for all main and tie breakers.
Miscellaneous installation items included; spare bussed spaces for future breakers, fiber optic communications for all draw-out breakers, new replacement forced fans and fan controllers for each dry type transformer. Installation of fiber optic multi-mode cable, cable terminating, modems, RS-485 cable and cable testing for new communications to all draw-out breakers. Field breaker and substation testing, coordination study, commissioning and owner training for all new equipment and systems were provided.
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