Ansi Standard Device Numbers (Ansi /ieee Standard C37.2) Nema

Front 1

1

Back 1

Master Elements

is the initiating device, such as a control switch, voltage relay, float switch, etc., which serves either directly or through such permissive devices as protective and time-delay relays to place an equipment in or out of operation.

Front 2

11

Back 2

Reserved for Future application

Front 3

12

Back 3

Over-speed Device

is usually a direct-connected speed switch which functions on machine over-speed.

Front 4

21

Back 4

Distance Relay

is a relay that functions when the circuit admittance, impedance, or reactance increases or decreases beyond predetermined limits.

Front 5

24

Back 5

Reserved for future Application

Front 6

27

Back 6

Undervolatge Relay

is a relay that functions on a given value of under-voltage.

Front 7

30

Back 7

Annunciator Relay

is a non-automatically reset device that gives a number of separate visual indications of the functions of protective devices, and which may also be arranged to perform a lockout function.

Front 8

32

Back 8

Directional Power Relay

is a device that functions on a desired value of power flow in a given direction or upon reverse power resulting from arcback in the anode or cathode circuits of a power rectifier.

Front 9

37

Back 9

Undercurrent or Underpower Relay

is a relay that function when the current or power flow decreases below a predetermined value.

Front 10

40

Back 10

Field Relay

is a relay that functions on a given or abnormally low value or failure of a machine field current, or on excessive value of the reactive component of armature current in an a-c machine indicating abnormally low field excitation.

Front 11

41

Back 11

Field Circuit Breaker

is a device that functions to apply or remove the field excitation of a machine.

Front 12

43

Back 12

Manual Transfer or Selector Device

is a manually operated device that transfers the control circuits in order to modify the plan of operation of the switching equipment or of some of the devices.

Front 13

46

Back 13

Reverse-phase or Phase-balance Relay

is a relay that functions when the polyphase currents are of reverse-phase sequence, or when the polyphase currents are unbalanced or contain negative phase-sequence components above a given amount.

Front 14

47

Back 14

Phase-sequence Voltage Relay

is a relay that function upon a predetermined value of polyphase voltage in the desired phase sequence.

Front 15

49

Back 15

Machine or Transformer thermal Relay

is a relay that functions when the temperature of a machine armatureor other load-carrying winding or element of a machine or the temperature of a power rectifier or powertransformer (including a power rectifier transformer) exceeds a predetermined value.

Front 16

50

Back 16

Instantaneous Overcurrent or Rate of Rise Relay

is a relay that functions instantaneously on an excessive value of current or on an excessive rate of current rise, thus indicating a fault in the apparatus or circuit being protected.

Front 17

51

Back 17

AC Time Overcurrent Relay

is a relay with either a definite or inverse time characteristic that functions when the current in an a-c circuit exceed a predetermined value.

Front 18

52

Back 18

AC Circuit Breaker

is a device that is used to close and interrupt an a-c power circuit under normal conditions or to interrupt this circuit under fault of emergency conditions.

Front 19

2

Back 19

Time Delay Starting or Closing Relay

is a device that functions to give a desired amount of time delay before or after any point of operation in switching sequence or protective relay system, except as specifically provided by service function 48, 62, and 79.

Front 20

3

Back 20

Checking or Interlocking Relay

is a relay that operates in response to the position of a number of other devices (or to a number of predetermined conditions) in an equipment, to allow an operating sequence to proceed, or to stop, or to provide a check of the position of these devices or of these conditions for any purpose.

Front 21

4

Back 21

Master Contactor

is a device generally controlled by device function 1or the equivalent and the required permissive and protective devices, that serves to make and break the necessary control circuits to place an equipment into operation under the desired conditions and to take it out of operation under other or abnormal conditions.

Front 22

5

Back 22

Stopping Device

is a control device used primarily to shut down an equipment and hold it out of operation. (This device may be manually or electrically actuated, but excludes the function of electrical lockout [see device function 86] on abnormal conditions.)

Front 23

6

Back 23

Starting Circuit Breaker

is a device whose principal function is to connect a machine to its source of starting voltage.

Front 24

7

Back 24

Anode Circuit Breaker

is a device used in the anode circuits of a power rectifier for the primary purpose of interrupting the rectifier circuit if an arc-back should occur.

Front 25

8

Back 25

Control Power Disconnecting Device

is a disconnecting device, such as a knife switch, circuit breaker, or pull-out fuse block, used for the purpose of respectively connecting and disconnecting the source of control power to and from the control bus or equipment.

Front 26

9

Back 26

Reversing Device

is a device that is used for the purpose of reversing a machine field or for performing any other reversing functions.

Front 27

10

Back 27

Unit Sequence Switch

is a switch that is used to change the sequence in which units may be placed in and out of service in multiple-unit equipments

Front 28

13

Back 28

Synchronous-Speed Device

is a device such as a centrifugal switch, a slip-frequency relay, a voltage relay, and undercurrent relay , or any type of device that operates at approximately the synchronous speed of a machine.

Front 29

14

Back 29

Under-Speed Device

is a device that functions when the speed of a machine fall below a pre -determined value.

Front 30

15

Back 30

Speed or Frequency Matching Device

is a device that functions to match and hold the speed or frequency of a machine or of a system equal to, or approximately equal to, that of another machine, source, or system.

Front 31

16

Back 31

Reserved for Future Application

Front 32

17

Back 32

Shunting or Discharge Switch

is a switch that serves to open or to close a shunting circuit around any piece of apparatus (except a resistor, such as a machine field, a machine armature, a capacitor, or a reactor).

Note: This excludes devices that perform such shunting operations as may be necessary in the process of starting a machine by devices 6 or 42, or their equivalent, and also excludes device function 73 that serves for the switching of resistors.

Front 33

18

Back 33

Accelerating or Decelerating Device

is a device that is used to close or to cause the closing of circuits which are used to increase or decrease the speed of a machine.

Front 34

19

Back 34

Starting-to-Running Transition Contactor

is a device that operates to initiate or cause the automatic transfer of a machine from the starting to the running power connection.

Front 35

20

Back 35

Electrically operated Valve

is one used in a vacuum, air, gas, oil, or similar line, when it is electrically operated or has electrical accessories such as auxiliary switches.

Front 36

22

Back 36

Equalizer Circuit Breaker

is a breaker that serves to control or to make and break the equalizer or the current-balancing connections for a machine field, or for regulating equipment in a multiple -unit installation.

Front 37

23

Back 37

Temperature Control Device

is a device that function to raise or lower the temperature of a machine or other apparatus, or of any medium, when its temperature falls below, or rises above, a predetermined value.

Note: An example is a thermostat that switches on a space heater in a switchgear assembly when the temperature falls to a desired value as distinguished from a device that is used to provide automatic temperature regulation between close limits and would be designated as device function 90T.

Front 38

25

Back 38

Synchronizing or Synchronism-Check Device

is a device that operates when two a-c circuits are within the desired limits of frequency, phase angle, or voltage, to permit or to cause the paralleling of these two circuits

Front 39

26

Back 39

Apparatus Thermal Device

is a device that functions when the temperature of the shunt field or the amortisseur winding of a machine, or that of a load limiting or load shifting resistor or of a liquid or other medium, exceeds a predetermined value: or if the temperature of the protected apparatus, such as a power rectifier, or of any medium decrease below a predetermined value.

Front 40

28

Back 40

Flame Detector

is a device that monitors the presence of the pilot or main flame of such apparatus as a gas turbine or a steam boiler.

Front 41

29

Back 41

Isolating Contactor

is a device that is used expressly for disconnecting one circuit from another for the purposes of emergency operation, maintenance, or test.

Front 42

31

Back 42

Separate Excitation Device

is a device that connects a circuit, such as the shunt field of a synchronous converter, to a source of separate excitation during the starting sequence; or one that energizes the excitation and ignition circuits of a power rectifier.

Front 43

33

Back 43

Position Switch

is a switch that makes or breaks contact when the main device or piece of apparatus which has no device function number reaches a given position.

Front 44

34

Back 44

Master Sequence Device

is a device such as a motor-operated multi-contact switch, or the equivalent, or programming device, such as a computer, that establishes or determines the operating sequence of the major devices in a equipment during starting and stopping or during other sequential switch operations.

Front 45

35

Back 45

Brush-Operating or Slipping Short-Circuiting Device

is a device for raising, lowering, or shifting the brushes of a machine, or for short-circuiting its slip rings, or for engaging or disengaging the contacts of a mechanical rectifier.

Front 46

36

Back 46

Polarity or Polarizing Voltage Device

is a device that operates, or permits the operation of, another device on a predetermined polarity only, or verifies the presence of a polarizing voltage in an equipment.

Front 47

38

Back 47

Bearing Protective Device

is a device that functions on excessive bearing temperature, or on another abnormal mechanical conditions associated with the bearing, such as undue wear, which may eventually result in excessive bearing temperature.

Front 48

39

Back 48

Mechanical Condition Monitor

is a device that functions upon the occurrence of an abnormal mechanical condition (except that associated with bearing as covered under device function 38), such as excessive vibration, eccentricity, expansion shock, tilting, or seal failure.

Front 49

42

Back 49

Running Circuit Breaker

is a device whose principal function is to connect a machine to its source of running or operation 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 field protecting means, primarily for frequent opening and closing of the breaker.

Front 50

44

Back 50

Unit Sequence Starting Relay

is a relay that function to start the next available unit in a multiple-unitequipment upon the failure or non-availability of the normally preceding unit.

Front 51

45

Back 51

Atmospheric Condition Monitor

is a device, that functions upon the occurrence of an abnormal atmospheric condition, such as damaging fumes, explosive mixtures, smoke or fire.

Front 52

48

Back 52

Incomplete Sequence Relay

is a relay 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. If the device is used for alarm purposes only, it should preferably be designated as 48A (alarm).

Front 53

53

Back 53

Exciter or DC Generator Relay

is a relay that forces the d-c machine field excitation to build up during starting or which functions when the machine voltage has been built up to a given value.

Front 54

54

Back 54

?future use?

High-Speed DC Circuit Breaker

is a circuit breaker which starts to reduce the current in the main circuit in 0.01 second or less, after the occurrence of the d-c overcurrent or the excessive rate of current rise.

Front 55

55

Back 55

Power Factor Relay

is a relay that operates when the power factor in an a-c circuit rises above or falls below a predetermined value.

Front 56

56

Back 56

Field Application Relay

is a relay that automatically controls the application of the field excitation to an a-c motor at some predetermined point in the slip cycle.

Front 57

57

Back 57

Short-Circuiting or Grounding Device

is a primary circuit switching device that functions to short-circuit or to ground a circuit in response to automatic or manual means.

Front 58

58

Back 58

Rectification Failure Relay

is a device that functions if one or mote anodes of a power rectifier fail to fire, or to detect and arc-back or on failure of a diode to conduct or lock properly.

Front 59

59

Back 59

Overvoltage Relay

is a relay that functions on a given value of over-voltage.

Front 60

60

Back 60

Voltage or Current Balance Relay

is a relay that operates on a given difference in voltage, or current input or output, or two circuits.

Front 61

61

Back 61

Reserved for Future Application.

Front 62

62

Back 62

Time-Delay Stopping or Opening Relay

is a time-delay relay that serves in conjunction with the device that initiates the shutdown, stopping, or opening operation in an automatic sequence or protective relay system

Front 63

63

Back 63

(Pressue Switch?)

Liquid or Gas Pressure or Vacuum Relay

is a relay that operates on given values of liquid or gas pressure or on given rates of change of these values.

Front 64

64

Back 64

Ground Protective Relay

is a relay that functions on failure of the insulation of a machine, transformer, or of other apparatus to ground, or on flashover of a d-c machine to ground.

Note: This function is assigned only to a relay that detects the flow of current from the frame of a machine or enclosing case or structure of piece of apparatus to ground, or detects a ground on a normally ungrounded winding or circuit. It is not applied to a device connected in the secondary circuit of current transformer, in the secondary neutral of current transformers, connected in the power circuit of a normally grounded system.

Front 65

65

Back 65

Governor

is the assembly of fluid, electrical, or mechanical control equipment used for regulating the flow of water, steam, or other medium to the prime mover for such purposes a starting, holding speed or load, or stopping.

Front 66

66

Back 66

Notching or Jogging Device

is a device that functions to allow only a specified number of operations of a given device or 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.

Front 67

67

Back 67

AC Directional Overcurrent Relay

is a relay that functions on a desired value of a-c over-current flowing in a predetermined direction.

Front 68

68

Back 68

Blocking Relay

is a relay that initiates a pilot signal for blocking of tripping on external faults in a transmission line or in other apparatus under predetermined condition, or cooperates with other devices to block tripping or to block re-closing on an out-of-step condition or on power savings.

Front 69

69

Back 69

Permissive Control Device

is generally a two-position, manually-operated switch that, in one position, permits the closing of a circuit breaker, or the placing of an equipment into operation, an in the other position prevents the circuit breaker or the equipment from being operated.

Front 70

70

Back 70

Rheostat

is a variable resistance device used in an electric circuit, which is electrically operated or has other electrical accessories, such a auxiliary , position, or limit switches.

Front 71

71

Back 71

(Liquid or Gas )Level Relay

is a relay that operates on given values of liquid or gas level or on given rates of change of these values.

Front 72

72

Back 72

DC Circuit Breaker

is a circuit breaker that is used to close and interrupt a d-c power circuit under normal conditions or to interrupt this circuit under fault or emergency conditions.

Front 73

73

Back 73

Load-Resistor Contactor

is a contactor that is used to shunt or insert a step of load limiting, shifting, or indicating resistance in a power circuit, or to switch a space heater in circuit, or to switch a light or regenerative load resistor, a power rectifier, or other machine in and out of circuit.

Front 74

74

Back 74

Alarm Relay

is a relay other than an annunciator, as covered under device function 30, that is used to operate, or to operate in connection with, a visual or audible alarm.

Front 75

75

Back 75

Position Changing Mechanism

is a mechanism that is used for moving a main device from one position to another in an equipment: as for example, shifting a removable circuit breaker unit to and from the connected, disconnected, and test positions.

Front 76

76

Back 76

DC Overcurrent Relay

is a relay that function when the current in a d-c circuit exceeds a given value.

Front 77

77

Back 77

Pulse Transmitter

is used to generate and transmit pulses over a telemetering or pilot-wire circuit to the remote indicating or receiving device.

Front 78

78

Back 78

Phase-Angle Measuring or Out-Of-Step Protective Relay

is a relay that functions at a pre-determined phase angle between two voltages or between two currents or between a voltage and current.

Front 79

79

Back 79

AC Reclosing Relay

is a relay that controls the automatic reclosing and locking out of an a-c circuit interrupter.

Front 80

80

Back 80

(Liquid or Gas) Flow Relay

is a relay that operates on given values of liquid or gas flow or on given rates of change of these values.

Front 81

81

Back 81

Frequency Relay

is a relay that functions on a predetermined value of frequency (either under or over or on normal system frequency) or rate of change of frequency.

Front 82

82

Back 82

DC Reclosing Relay

is a relay thast controls the automatic closing and re-closing of a d-c circuit interrupter, generally in response to load circuit conditions.

Front 83

83

Back 83

Automatic Selective Control or Transfer Relay

is a relay that operates to select automatically between certain sources or conditions in a equipment, or performs a transfer operation automatically.

Front 84

84

Back 84

Operating Mechanism

is 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 which otherwise has no device function number.

Front 85

85

Back 85

Carrier or Pilot-Wire Receiver Relay

is a relay that is operated or restrained by a signal used in connection with carrier-current or d-c pilot-wire fault directional relaying.

Front 86

86

Back 86

Locking-Out Relay

is an electrically operated hand, or electrically reset relay or device that functions to shut down or hold an equipment out of service, or both, upon the occurrence of abnormal conditions.

Front 87

87

Back 87

Differential Protective Relay

is a protective relay that functions on a percentage or phase angle or other quantitative difference of two currents or of some other electrical quantities.

Front 88

88

Back 88

Auxiliary Motor or Motor Generator

is one used for operating auxiliary equipment, such as pumps, blowers, exciters, rotating magnetic amplifiers, etc.

Front 89

89

Back 89

Line Switch

is a switch used as a disconnecting, load-interrupter, or isolating switch in an a-c or d-c power circuit, when this device is electrically operated or has electrical accessories, such as an auxiliary switch, magnetic lock, etc.

Front 90

90

Back 90

Regulating Device

is 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.

Front 91

91

Back 91

Voltage Directional Relay

is a device which operates when the voltage across an open circuit breaker or contactor exceeds a given value in a given direction.

Front 92

92

Back 92

Voltage and Power Directional Relay

is a relay that permits or causes the connection of two circuits when the voltage difference between them exceed 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.

Front 93

93

Back 93

Field-Changing Contactor

is a contactor that functions to increase or decrease, in one step, the value of field excitation on a machine.

Front 94

94

Back 94

Tripping or Trip-Free Relay

is a relay that function to trip a circuit breaker, contactor or equipment, or to permit immediate tripping by other devices; or to prevent immediate re -closure of a circuit interrupter if it should open automatically even though its closing circuit is maintained closed.