An electric device designed to respond to input conditions in a prescribed manner and after specified conditions are met to cause contact operation or similar abrupt change in associated electric control circuits.

This standard applies only to relays and relay systems used to control power switchgear. It does not cover relays of types designed primarily for industrial control, for switching of communication or other low-level signals, or any other equipment not intended for the control of power equipment.

The purpose of this standard is to specify standard service conditions, standard ratings, and requirements for testing of relays and relay systems associated with power apparatus.