|Definition:|| electric relay, the function of which is to control equipment|
Note 1 to entry: A control relay can be a simple relay that translates an external command into a control signal [e.g. a command to close a circuit-breaker], or it can be a more complex device that translates an external command into a number of sequential control signals [e.g. the closing and opening of disconnectors and circuit-breakers to changeover a circuit from one busbar section to another]. A control relay can also supervise a characteristic quantity (e.g. voltage, frequency) and produce a control signal that is dependent upon its specific functional design (e.g. under frequency load shedding relay).