IEEE Standard for Electrical Power System Device Function Numbers, Acronyms, and Contact Designations, IEEE Std C37.2-2008
Suffixes | Description |
_1 | Positive-Sequence |
_2 | Negative-Sequence |
A | Alarm, Auxiliary Power |
AC | Alternating Current |
AN | Anode |
B | Bus, Battery, or Blower |
BF | Breaker Failure |
BK | Brake |
BL | Block (Valve) |
BP | Bypass |
BT | Bus Tie |
BU | Backup |
C | Capacitor, Condenser, Compensator, Carrier Current, Case, or Compressor |
CA | Cathode |
CH | Check (Valve) |
D | Discharge (Valve) |
DC | Direct Current |
DCB | Directional Comparison Blocking |
DCUB | Directional Comparison Unblocking |
DD | Disturbance Detector |
DUTT | Direct Underreaching Transfer Trip |
E | Exciter |
F | Feeder, Field, Filament, Filter, or Fan |
G | Ground or Generator |
GC | Ground Check |
H | Heater or Housing |
L | Line or Logic |
M | Motor or Metering |
MOC | Mechanism Operated Contact |
N | Neutral or Network |
O | Over |
P | Phase or Pump |
PC | Phase Comparison |
POTT | Pott: Permissive Overreaching Transfer Trip |
PUTT | Putt: Permissive Underreaching Transfer Trip |
R | Reactor, Rectifier, or Room |
S | Synchronizing, Secondary, Strainer, Sump, or Suction (Valve) |
SOTF | Switch On To Fault |
T | Transformer or Thyratron |
TD | Time Delay |
TDC | Time-Delay Closing Contact |
TDDO | Time Delayed Relay Coil ｄｒｏｐ-Out |
TDO | Time-Delay Opening Contact |
TDPU | Time Delayed Relay Coil Pickup |
THD | Total Harmonic Distortion |
TH | Transformer (High-Voltage Side) |
TL | Transformer (Low-Voltage Side) |
TM | Telemeter |
TT | Transformer (Tertiary-Voltage Side) |
U | Under or Unit |
X | Auxiliary |
Z | Impedance |
Acronyms | Description |
AFD | Arc Flash Detector |
CLK | Clock or Timing Source |
CLP | Cold Load Pickup |
DDR | Dynamic Disturbance Recorder |
DFR | Digital Fault Recorder |
ENV | Environmental Data |
HIZ | High Impedance Fault Detector |
HMI | Human Machine Interface |
HST | Historian |
MET | Substation Metering |
PDC | Phasor Data Concentrator |
PMU | Phasor Measurement Unit |
PQM | Power Quality Monitor |
RIO | Remote Input/Output Device |
RTD | Resistance Temperature Detector |
RTU | Remote Terminal Unit / Data Concentrator |
SER | Sequence of Events Recorder |
TCM | Trip Circuit Monitor |
VTFF | Vt Fuse Fail |
Device No. | Description |
1 | Master Element |
2 | Time Delay Starting or Closing Relay |
3 | Checking or Interlocking Realy |
4 | Master Contactor |
5 | Stopping Device |
6 | Starting Circuit Breaker |
7 | Rate of Change Relay |
8 | Control Power Disconnecting Device |
9 | Reversing Device |
10 | Unit Sequence Switch |
11 | Multifunction Device |
12 | Overspeed Device/Protection |
13 | Synchronous-Speed Device |
14 | Underspeed Device |
15 | Speed or Frequency Matching Device |
16 | Communication Networking Device |
17 | Shunting or Discharge Switch |
18 | Accelerating or Decelerating Device |
19 | Motor Starter / Starting-to-Running Transition Contactor |
20 | Electrically-Operated Valve |
21 | Distance Relay |
21G | Ground Distance |
21P | Phase Distance |
22 | Equalizer Circuit Breaker |
23 | Temperature Control Device |
24 | Volts-per-Hertz Relay / Overfluxing |
25 | Synchronizing or Synchronism-Check Device |
26 | Apparatus Thermal Device |
27 | Undervoltage Relay |
27P | Phase Undervoltage |
27TN | Third Harmonic Neutral Undervoltage |
27X | Auxiliary Undervoltage |
27 AUX | Undervoltage Auxiliary Input |
27/27X | Bus/Line Undervoltage |
28 | Flame Detector |
29 | Isolating Contactor |
30 | Annunciator Relay |
31 | Separate Excitation Device |
32 | Directional Power Relay |
32L | Low Forward Power |
32N | Wattmetric Zero-Sequence Directional |
32P | Directional Power |
32R | Reverse Power |
33 | Position Switch |
34 | Master Sequence Device |
35 | Brush-Operating or Slip-ring Short Circuiting Device |
36 | Polarity or Polarizing Voltage Device |
37 | Undercurrent or Underpower Relay |
37P | Underpower |
38 | Bearing Protective Device / Bearing Rtd |
39 | Mechanical Condition Monitor |
40 | Field Relay / Loss of Excitation |
41 | Field Circuit Breaker |
42 | Running Circuit Breaker |
43 | Manual Transfer or Selector Device |
44 | Unit Sequence Starting Relay |
45 | Atmospheric Condition Monitor |
46 | Reverse-Phase or Phase Balance Current Relay or Stator Current Unbalance |
47 | Phase-Sequence or Phase Balance Voltage Relay |
48 | Incomplete Sequence Relay / Blocked Rotor |
49 | Machine or Transformer Thermal Relay / Thermal Overload |
49RTD | RTD Biased Thermal Overload |
50 | Instantaneous Overcurrent Relay |
50BF | Breaker Failure |
50DD | Current Disturbance Detector |
50G | Ground Instantaneous Overcurrent |
50N | Neutral Instantaneous Overcurrent |
50P | Phase Instantaneous Overcurrent |
50_2 | Negative Sequence Instantaneous Overcurrent |
50/27 | Accidental Energization |
50/74 | Ct Trouble |
50/87 | Instantaneous Differential |
50EF | End Fault Protection |
50IG | Isolated Ground Instantaneous Overcurrent |
50LR | Acceleration Time |
50NBF | Neutral Instantaneous Breaker Failure |
50SG | Sensitive Ground Instantaneous Overcurrent |
50SP | Split Phase Instantaneous Current |
51 | Ac Time Overcurrent Relay |
51 | Overload |
51G | Ground Time Overcurrent |
51N | Neutral Time Overcurrent |
51P | Phase Time Overcurrent |
51V | Voltage Restrained Time Overcurrent |
51R | Locked / Stalled Rotor |
51_2 | Negative Sequence Time Overcurrent |
52 | Ac Circuit Breaker |
53 | Exciter or Dc Generator Relay |
54 | Turning Gear Engaging Device |
55 | Power Factor Relay |
56 | Field Application Relay |
57 | Short-Circuiting or Grounding Device |
58 | Rectification Failure Relay |
59 | Overvoltage Relay |
59B | Bank Phase Overvoltage |
59P | Phase Overvoltage |
59N | Neutral Overvoltage |
59NU | Neutral Voltage Unbalance |
59P | Phase Overvoltage |
59X | Auxiliary Overvoltage |
59_2 | Negative Sequence Overvoltage |
60 | Voltage or Current Balance Relay |
60N | Neutral Current Unbalance |
60P | Phase Current Unbalance |
61 | Density Switch or Sensor |
62 | Time-Delay Stopping or Opening Relay |
63 | Pressure Switch Detector |
64 | Ground Protective Relay |
64F | Field Ground Protection |
64S | Sub-harmonic Stator Ground Protection |
64TN | 100% Stator Ground |
65 | Governor |
66 | Notching or Jogging Device/Maximum Starting Rate/Starts Per Hour /Time Between Starts |
67 | Ac Directional Overcurrent Relay |
67G | Ground Directional Overcurrent |
67N | Neutral Directional Overcurrent |
67P | Phase Directional Overcurrent |
67SG | Sensitive Ground Directional Overcurrent |
67_2 | Negative Sequence Directional Overcurrent |
68 | Blocking Relay / Power Swing Blocking |
69 | Permissive Control Device |
70 | Rheostat |
71 | Liquid Switch |
72 | Dc Circuit Breaker |
73 | Load-Resistor Contactor |
74 | Alarm Relay |
75 | Position Changing Mechanism |
76 | Dc Overcurrent Relay |
77 | Telemetering Device |
78 | Phase Angle Measuring or Out-of-Step Protective Relay |
78V | Loss of Mains |
79 | Ac Reclosing Relay / Auto Reclose |
80 | Liquid or Gas Flow Relay |
81 | Frequency Relay |
81O | Over Frequency |
81R | Rate-of-Change Frequency |
81U | Under Frequency |
82 | Dc Reclosing Relay |
83 | Automatic Selective Control or Transfer Relay |
84 | Operating Mechanism |
85 | Carrier or Pilot-Wire Receiver Relay |
86 | Locking-Out Relay |
87 | Differential Protective Relay |
87B | Bus Differential |
87G | Generator Differential |
87GT | Generator/Transformer Differential |
87LG | Ground Line Current Differential |
87S | Stator Differential |
87S | Percent Differential |
87L | Segregated Line Current Differential |
87M | Motor Differential |
87O | Overall Differential |
87PC | Phase Comparison |
87RGF | Restricted Ground Fault |
87T | Transformer Differential |
87V | Voltage Differential |
88 | Auxiliary Motor or Motor Generator |
89 | Line Switch |
90 | Regulating Device |
91 | Voltage Directional Relay |
92 | Voltage And Power Directional Relay |
93 | Field-Changing Contactor |
94 | Tripping or Trip-Free Relay |
50/74 | Ct Supervision |
27/50 | Accidental Generator Energization |
27TN/59N | 100% Stator Earth Fault |