Substation1
ANSI/IEEE Standard C37.2

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

Devices function numbers

No Name Description
61 density switch or sensor A device that operates at a given density value or at a given rate of change of density.
62 time-delay stopping or opening relay A device that imposes a time delay in conjunction with the device that initiates the shutdown, stopping, or opening operation in an automatic sequence or protective relay system.
63 pressure switch A device that operates at a given pressure value or at a given rate of change of pressure.
64 ground detector relay A device that operates upon failure of machine or other apparatus insulation to ground.

Notes:
This function is not applied to a device connected in the secondary circuit of current transformers in a normally grounded power system where other overcurrent device numbers with the suffix G or N should be used; for example, 51N for an ac time overcurrent relay connected in the secondary neutral of the current transformers.

65 governor A device consisting of an assembly of fluid, electrical, or mechanical control equipment used for regulating the flow of water, steam, or other media to the prime mover for such purposes as starting, holding speed or load, or stopping.
66 notching or jogging device A device that functions to allow only a specified number of operations of a given device or piece of equipment, or a specified number of successive operations within a given time of each other. It is also a device that functions to energize a circuit periodically or for fractions of specified time intervals, or that is used to permit intermittent acceleration or jogging of a machine at low speeds for mechanical positioning.
67 ac directional overcurrent relay A device that functions at a desired value of ac overcurrent flowing in a predetermined direction.
68 blocking or "out-of-step" relay A device that initiates a pilot signal for blocking of tripping on external faults in a transmission line or in other apparatus under predetermined conditions, or cooperates with other devices to block tripping or reclosing on an out-of-step condition or on power swings.
69 permissive control device A device with two-positions that in one position permits the closing of a circuit breaker, or the placing of a piece of equipment into operation, and in the other position, prevents the circuit breaker or the equipment from being operated.
70 rheostat A device used to vary the resistance in an electric circuit when the device is electrically operated or has other electrical accessories, such as auxiliary, position, or limit switches.
71 level switch A device that operates at a given level value, or on a given rate of change of level.
72 dc circuit breaker A device that is used to close and interrupt a dc power circuit under normal conditions or to interrupt this circuit under fault or emergency conditions.
73 load-resistor contactor A device that is used to shunt or insert a step of load limiting, shifting, or indicating resistance in a power circuit; to switch a space heater in circuit; or to switch a light or regenerative load resistor of a power rectifier or other machine in and out of circuit.
74 alarm relay A device other than an annunciator, as covered under device function 30, that is used to operate, or that operates in connection with, a visual or audible alarm.
75 position changing mechanism A device that is used for moving a main device from one position to another in equipment; for example, shifting a removable circuit breaker unit to and from the connected, disconnected, and test positions.
76 dc overcurrent relay A device that functions when the current in a dc circuit exceeds a given value.
77 telemetering device A transmitting device used to generate and transmit to a remote location an electrical signal representing a measured quantity; or a receiver used to receive the electrical signal from a remote transmitter and convert the signal to represent the original measured quantity.
78 phase-angle measuring relay A device that functions at a predetermined phase angle between two voltages, between two currents, or between voltage and current.
79 reclosing relay A device that controls the automatic reclosing and locking out of an ac circuit interrupter.
80 flow switch A device that operates at a given flow value, or at a given rate of change of flow.