ANSI Standard Device Numbers & Common …

1 Standard Device Numbers & Common AcronymsSuffixes Description_1 Positive-Sequence_2 Negative-SequenceAAlarm, auxiliary PowerACAlternating CurrentANAnodeBBus, Battery, or BlowerBFBreaker FailureBKBrakeBLBlock (Valve)BPBypassBTBus TieBUBackupCCapacitor, Condenser, Compensator, Carrier Current, Case, or CompressorCACathodeCHCheck (Valve)DDischarge (Valve)DCDirect CurrentDCBD irectional Comparison BlockingDCUBD irectional Comparison UnblockingDDDisturbance DetectorDUTTD irect Underreaching Transfer TripEExciterFFeeder, Field, Filament, Filter, or FanGGround or GeneratorGCGround CheckHHeater or HousingLLine or LogicMMotor or MeteringMOCM echanism Operated ContactNNeutral or NetworkOOverPPhase or PumpPCPhase ComparisonPOTTPott: Permissive Overreaching Transfer TripPUTTPutt.

2 Permissive Underreaching Transfer TripRReactor, Rectifier, or RoomSSynchronizing, Secondary, Strainer, Sump, or Suction (Valve)SOTFS witch On To FaultTTransformer or ThyratronTDTime DelayTDCTime-Delay Closing ContactTDDOTime Delayed Relay Coil Drop-OutSuffixes DescriptionTDOTime-Delay Opening ContactTDPUTime Delayed Relay Coil PickupTHDT otal Harmonic DistortionTHTransformer (High-Voltage Side)TLTransformer (Low-Voltage Side)TMTelemeterTTTransformer (Tertiary-Voltage Side)UUnder or UnitXAuxiliaryZImpedanceAcronyms DescriptionAFDArc Flash DetectorCLKC lock or Timing SourceCLPCold Load PickupDDRD ynamic Disturbance RecorderDFRD igital Fault RecorderENVE nvironmental DataHIZHigh Impedance Fault DetectorHMIH uman Machine InterfaceHSTH istorianMETS ubstation MeteringPDCP hasor Data ConcentratorPMUP hasor Measurement UnitPQMP ower Quality MonitorRIOR emote Input/Output DeviceRTDR esistance Temperature DetectorRTUR emote Terminal Unit / Data ConcentratorSERS equence of Events RecorderTCMTrip Circuit MonitorVTFFVt Fuse No.

3 Description1 Master Element2 Time Delay Starting or Closing Relay3 Checking or Interlocking Realy4 Master Contactor5 Stopping Device6 Starting Circuit Breaker7 Rate of Change Relay8 Control Power Disconnecting Device9 Reversing Device10 Unit Sequence Switch11 Multifunction Device12 Overspeed Device /Protection13 Synchronous-Speed Device14 Underspeed Device15 Speed or Frequency Matching Device16 Communication Networking Device17 Shunting or Discharge Switch18 Accelerating or Decelerating Device19 Motor Starter / Starting-to-Running Transition Contactor20 Electrically-Operated Valve21 Distance Relay21 GGround Distance21 PPhase Distance22 Equalizer Circuit Breaker23 Temperature Control Device24 Volts-per-Hertz Relay / Overfluxing25 Synchronizing or Synchronism-Check Device26 Apparatus Thermal Device27 Undervoltage Relay27 PPhase Undervoltage27 TNThird Harmonic Neutral Undervoltage27 XAuxiliary Undervoltage27 AUXU ndervoltage auxiliary Input27/27 XBus/Line Undervoltage28 Flame Detector29 Isolating Contactor30 Annunciator Relay31 Separate Excitation Device32 Directional Power Relay32 LLow Forward Power32 NWattmetric Zero-Sequence Directional32 PDirectional Power32

4 RReverse PowerDevice No. Description33 Position Switch34 Master Sequence Device35 Brush-Operating or Slip-ring Short Circuiting Device36 Polarity or Polarizing Voltage Device37 Undercurrent or Underpower Relay37 PUnderpower38 Bearing Protective Device / Bearing Rtd39 Mechanical Condition Monitor40 Field Relay / Loss of Excitation41 Field Circuit Breaker42 Running Circuit Breaker43 Manual Transfer or Selector Device44 Unit Sequence Starting Relay45 Atmospheric Condition Monitor46 Reverse-Phase or Phase Balance Current Relay or Stator Current Unbalance47 Phase-Sequence or Phase Balance Voltage Relay48

5 Incomplete Sequence Relay / Blocked Rotor49 Machine or Transformer Thermal Relay / Thermal Overload49 RTDRTD Biased Thermal Overload50 Instantaneous Overcurrent Relay50 BFBreaker Failure50 DDCurrent Disturbance Detector50 GGround Instantaneous Overcurrent50 NNeutral Instantaneous Overcurrent50 PPhase Instantaneous Overcurrent50_2 Negative Sequence Instantaneous Overcurrent50/27 Accidental Energization50/74Ct Trouble50/87 Instantaneous Differential50EF End Fault Protection50 IGIsolated Ground Instantaneous Overcurrent50 LRAcceleration Time50 NBFN eutral Instantaneous Breaker Failure50 SGSensitive Ground Instantaneous Overcurrent50 SPSplit Phase Instantaneous Current51Ac Time Overcurrent Relay51 Overload51 GGround Time Overcurrent51 NNeutral Time Overcurrent51 PPhase Time Overcurrent51 VVoltage Restrained Time Overcurrent51 RLocked / Stalled RotorANSI Standard Device Numbers & Common No.

6 Description51_2 Negative Sequence Time Overcurrent52Ac Circuit Breaker53 Exciter or Dc Generator Relay54 Turning Gear Engaging Device55 Power Factor Relay56 Field Application Relay57 Short-Circuiting or Grounding Device58 Rectification Failure Relay59 Overvoltage Relay59 BBank Phase Overvoltage59 PPhase Overvoltage59 NNeutral Overvoltage59 NUNeutral Voltage Unbalance59 PPhase Overvoltage59 XAuxiliary Overvoltage59_2 Negative Sequence Overvoltage60 Voltage or Current Balance Relay60 NNeutral Current Unbalance60 PPhase Current Unbalance61 Density Switch or Sensor62 Time-Delay Stopping or Opening Relay63 Pressure Switch Detector64 Ground Protective Relay64 FField Ground Protection64S Sub-harmonic Stator Ground Protection64TN100% Stator Ground65 Governor66 Notching or Jogging Device /Maximum Starting Rate/Starts Per Hour/Time Between Starts67Ac Directional Overcurrent Relay67 GGround Directional Overcurrent67 NNeutral Directional Overcurrent67 PPhase Directional Overcurrent67 SGSensitive Ground Directional Overcurrent67_2 Negative Sequence Directional Overcurrent68 Blocking Relay / Power Swing Blocking69 Permissive Control Device70 Rheostat71 Liquid

7 Switch72Dc Circuit Breaker73 Load-Resistor Contactor74 Alarm Relay75 Position Changing MechanismDevice No. Description76Dc Overcurrent Relay77 Telemetering Device78 Phase Angle Measuring or Out-of-Step Protective Relay78 VLoss of Mains79Ac Reclosing Relay / Auto Reclose80 Liquid or Gas Flow Relay81 Frequency Relay81 OOver Frequency81 RRate-of-Change Frequency81 UUnder Frequency82Dc Reclosing Relay83 Automatic Selective Control or Transfer Relay84 Operating Mechanism85 Carrier or Pilot-Wire Receiver Relay86 Locking-Out Relay87 Differential Protective Relay87 BBus Differential87 GGenerator Differential87 GTGenerator/Transformer Differential87 LGGround Line Current Differential87 SStator

8 Differential87 SPercent Differential87 LSegregated Line Current Differential87 MMotor Differential87 OOverall Differential87 PCPhase Comparison87 RGFR estricted Ground Fault87 TTransformer Differential87 VVoltage Differential88 auxiliary Motor or Motor Generator89 Line Switch90 Regulating Device91 Voltage Directional Relay92 Voltage And Power Directional Relay93 Field-Changing Contactor94 Tripping or Trip-Free Relay50/74Ct Supervision27/50 Accidental Generator Energization27TN/59N100% Stator Earth Fault