High-frequency protection converts the phase angle (or power direction) of currents at both ends of a line into high-frequency signals, which are transmitted via a high-frequency channel to the opposite end. A PLC channel can also be used to provide remote tripping functions for transformer protection, shunt reactor protection and remote breaker failure relaying. There are many references available that discuss PLC applications. IEEE 643 IEEE Guide for Power-Line Carrier Applications is a particularly. High frequency and RF (radio frequency) relays are high switch speed, high reliability and RF insulated relays designed for use in computers, testing equipment and radio broadcast systems. Additional features may include an internal diode, magnetic shielding and hermetic seals.
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