To Serve and Protect

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Protective relays are electromechanical devices that trip circuit breakers when they detect system faults. Using a variety of elaborate mechanisms, protective relays respond to overcurrent, overvoltage, reverse flow and frequency variances.  When these conditions are present, the protective relays activate circuit breakers to isolate the protected equipment from the fault.

In more modern installations, microprocessor-based relays take the place of the bulkier, less precise, mechanical devices.  These “numerical relays” also provide convenience, by allowing multiple functions in a single package.

Technicians use Protective Relay Test Sets, such as the Megger MPRT or the Doble F6150 Relay test, to perfom routine testing of relays in power plants, industrial sites and similar installations.