Substation1
ANSI/IEEE Standard C37.2

Standard for Electrical Power System Device Function Numbers, Acronyms, and Contact Designations

Devices function numbers

No Name Description
41 field circuit breaker A device that functions to apply or remove the field excitation of a machine.
42 running circuit breaker A device whose function is to connect a machine to its source of running or operating voltage. This function may also be used for a device, such as a contactor, that is used in series with a circuit breaker or other fault-protecting means, primarily for frequent opening and closing of the circuit.
43 manual transfer or selector device A manually operated device that transfers control or potential circuits in order to modify the plan of operation of the associated equipment or of some of the associated devices.
44 unit sequence starting relay A device that functions to start the next available unit in multiple-unit equipment upon the failure or non-availability of the normally preceding unit.
45 atmospheric condition monitor A device that functions upon the occurrence of an abnormal atmospheric condition, such as damaging fumes, explosive mixtures, smoke, or fire.
46 reverse-phase or phase-balance current relay A device in a polyphase circuit that operates when the polyphase currents are of reverse-phase sequence or when the polyphase currents are unbalanced or when the negative phase-sequence current exceeds a preset value.
47 phase-sequence or phase-balance voltage relay A device in a polyphase circuit that functions upon a predetermined value of polyphase voltage in the desired phase sequence, when the polyphase voltages are unbalanced, or when the negative phase-sequence voltage exceeds a preset value.
48 incomplete sequence relay A device that generally returns the equipment to the normal or off position and locks it out if the normal starting, operating, or stopping sequence is not properly completed within a predetermined time.
49 machine or transformer thermal relay A device that functions when the temperature of a machine armature winding or other load-carrying winding or element of a machine or power transformer exceeds a predetermined value.
50 instantaneous overcurrent relay A device that operates with no intentional time delay when the current exceeds a preset value.
51 ac time overcurrent relay A device that functions when the ac input current exceeds a predetermined value, and in which the input current and operating time are inversely related through a substantial portion of the performance range.
52 ac circuit breaker A device that is used to close and interrupt an ac power circuit under normal conditions or to interrupt this circuit under fault or emergency conditions.
53 exciter or dc generator relay A device that forces the dc machine field excitation to build up during starting or that functions when the machine voltage has built up to a given value.
54 turning gear engaging device A device either electrically operated, controlled, or monitored that functions to cause the turning gear to engage or disengage the machine shaft.
55 power factor relay A device that operates when the power factor in an ac circuit rises above or falls below a predetermined value.
56 field application relay A device that automatically controls the application of the field excitation to an ac motor at some predetermined point in the slip cycle.
57 short-circuiting or grounding device A device that functions to short-circuit or ground a circuit in response to automatic or manual means.
58 rectification failure relay A device that functions if a power rectifier fails to conduct or block properly.
59 overvoltage relay A device that operates when its input voltage exceeds a predetermined value.
60 voltage or current balance relay A device that operates on a given difference in voltage, or current input or output, of two circuits.