Protective Relays Are Imperative In Monitoring The Safety Of Personnel & Property
TESTING & MAINTENANCE
If the protective relays are not monitoring or measuring properly, they can cause false tripping or non-tripping. Since these devices operate during abnormal conditions on the power system, the only way to ensure correct operation is by a comprehensive inspection, maintenance, tests and calibration programs. The different types of protective relays can monitor current, voltage, frequency, phase/ground faults, bus/line faults or any other type of electrical power disturbance.
When the relay senses an abnormal condition, it will send a signal to a trip coil on a particular device, such as a circuit breaker, switch or other device, that is designed to interrupt the circuit, thus limiting the damage to the equipment and personnel. Protective relays monitor large amounts of current by means of current transformers, which encircle the current carrying conductors. Current transformers step down the monitored current to a usable “secondary“ current of 0-5 amps. This secondary current is used to mechanically or electrically operate the relay.