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| Transmission Relay Coordination
Study |
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NSTAR, a major electric utility in Massachusetts, contracted
PLM to do a thorough relay coordination study for an entire
345 kV, 230 kV, and 115 kV looped transmission system.
The study involved a review of directional-distance phase
relays, directional-distance ground relays, and phase
and ground overcurrent relays. The existing relay settings
were modeled in ASPEN, a short-circuit computer program,
and the settings were analyzed both on a circuit basis
and also for relay-to-relay coordination between primary
and backup systems. |
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| 115kV Relay Upgrade |
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The Braintree Electric Light Department hired PLM to upgrade
their 115kV protection system. This included replacement
of electro-mechanical relays with microprocessor-based
relays, providing for redundant battery systems, replacing
115 kV oil circuit breakers with SF6 circuit breakers,
adding breaker failure protection and adding high-speed
Permissive Overreaching Transfer Trip and current differential
line protection via a multiplexed fiber optic communication
system. |
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SCADA System |
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The Norwood Municipal Light Department retained PLM to
assist in the procurement of a new SCADA system to augment
an existing load management system. The SCADA system provides
monitoring and control of two substations and two switching
stations back to redundant master computers. |
