Answer / Subodh Rastogi

Definite, overload (O.L.), reverse power protection, and OSR (Over-current, Over-voltage, Under-voltage) relays are various types of protective devices used in electrical systems. To work with them, it's essential to understand their specific operating principles and applications. Definite relays are designed to trip when a predetermined set of conditions is met, while overload relays protect against excessive current flow. Reverse power protection prevents the motor from running in reverse direction, and OSR relays provide comprehensive protection by sensing variations in current, voltage, and frequency.

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