Applications range from classic panel built control systems to modern interfaces between control microprocessors and their power circuits or any application where reliable galvanic separation is required between different circuits. Protective relays can be classified based on their operating principle, construction, or function: 1. They are intended to quickly identify a fault and isolate it so the balance of the system continue to run under normal conditions. For example, unselective protection operation during a medium voltage network fault will cause an outage for an unnecessarily large number of consumers. While this is bad, It's not a. IEEE Guide for Protective Relay Applications to Transmission Lines IEEE Guide for Protective Relay Applications to Transmission Lines Sponsored by the Power System Relaying Committee IEEE 3 Park Avenue New York, NY 10016-5997 USA IEEE Power and Energy Society IEEE Std C37. What controls it: Relay selection.
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