Substation1
ANSI/IEEE Standard C37.2

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

Devices function numbers

No Name Description
81 frequency relay A device that responds to the frequency of an electrical quantity, operating when the frequency or rate of change of frequency exceeds or is less than a predetermined value.
82 dc load-measuring reclosing relay A device that controls the automatic closing and reclosing of a dc circuit interrupter, generally in response to load circuit conditions.
83 automatic selective control or transfer relay A device that operates to select automatically between certain sources or conditions in equipment or that performs a transfer operation automatically.
84 operating mechanism A device consisting of the complete electrical mechanism or servomechanism, including the operating motor, solenoids, position switches, etc., for a tap changer, induction regulator, or any similar piece of apparatus that otherwise has no device function number.
85 carrier or pilot-wire relay A device that is operated or restrained by a signal transmitted or received via any communications media used for relaying.
86 lockout relay A device that trips and maintains the associated equipment or devices inoperative until it is reset by an operator, either locally or remotely.
87 differential protective relay A device that operates on a percentage, phase angle, or other quantitative difference of two or more currents or other electrical quantities.
88 auxiliary motor or motor generator A device used for operating auxiliary equipment, such as pumps, blowers, exciters, rotating magnetic amplifiers, etc.
89 line switch A device used as a disconnecting, load-interrupter, or isolating switch in an ac or dc power circuit. This device function number is normally not necessary unless the switch is electrically operated or has electrical accessories, such as an auxiliary switch, a magnetic lock, etc.
90 regulating device A device that functions to regulate a quantity or quantities, such as voltage, current, power, speed, frequency, temperature, and load, at a certain value or between certain generally close limits for machines, tie lines, or other apparatus.
91 voltage directional relay A device that operates when the voltage across an open circuit breaker or contactor exceeds a given value in a given direction.
92 voltage and power directional relay A device that permits or causes the connection of two circuits when the voltage difference between them exceeds a given value in a predetermined direction and causes these two circuits to be disconnected from each other when the power flowing between them exceeds a given value in the opposite direction.
93 field-changing contactor A device that functions to increase or decrease, in one step, the value of field excitation on a machine.
94 tripping or trip-free relay A device that functions to trip a circuit breaker, contactor, or equipment; to permit immediate tripping by other devices; or to prevent immediate reclosing of a circuit interrupter if it should open automatically, even though its closing circuit is maintained closed.
95 Device numbers 95 - 99 used only for specific applications

Notes:
These device numbers are used in individual specific installations if none of the functions assigned to the numbers from 1 through 94 are suitable. ;