ANSI Device Numbers

The ANSI standard device numbers ( As per ANSI/IEEE standard C37.2) are used in the design of an electrical power system. These devices protect the electrical network in the case of a fault in the system. The list of ANSI device numbers with their acronyms is as given below.

List of ANSI device numbers and acronyms

  • 1 – Master Element
  • 2 – Time-delay Starting or Closing Relay
  • 3 – Checking or Interlocking Relay, complete Sequence
  • 4 – Master Protective
  • 5 – Stopping Device, Emergency Stop Switch
  • 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
  • 13 – Synchronous-Speed Device
  • 14 – Underspeed Device
  • 15 – Speed or Frequency Matching Device
  • 16 – Data Communications Device
  • 17 – Shunting or Discharge Switch
  • 18 – Accelerating or Decelerating Device
  • 19 – Starting-to-Running Transition Contactor
  • 20 – Electrically-Operated Valve ( Solenoid Valve )
  • 21 – Distance Relay
  • 21G – Ground Distance
  • 21P – Phase Distance
  • 22 – Equalizer circuit breaker
  • 23 – Temperature control device, Heater
  • 24 – Volts per hertz relay
  • 25 – Synchronizing or synchronism-check device
  • 26 – Apparatus thermal device, Temperature Switch
  • 27 – Undervoltage relay
  • 27P – Phase Undervoltage
  • 27S – DC undervoltage relay
  • 27TN – Third Harmonic Neutral Undervoltage
  • 27TN/59N – 100% Stator Earth Fault
  • 27X – Auxiliary Undervoltage
  • 27 AUX – Undervoltage Auxiliary Input
  • 27/27X – Bus/Line Undervoltage
  • 27/50 – Accidental Generator Energization
  • 28 – Flame Detector
  • 29 – Isolating Contactor
  • 30 – Annunciator Relay
  • 31 – Separate Excitation Device
  • 32 – Directional Power Relay
  • 32L – Low Forward Power
  • 32H – High Directional 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 ( Vibration )
  • 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 – Fire Detector
  • 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
  • 50EF – End Fault Protection
  • 50G – Ground Instantaneous Overcurrent
  • 50IG – Isolated Ground Instantaneous Overcurrent
  • 50LR – Acceleration Time
  • 50N – Neutral Instantaneous Overcurrent
  • 50NBF – Neutral Instantaneous Breaker Failure
  • 50P – Phase Instantaneous Overcurrent
  • 50SG – Sensitive Ground Instantaneous Overcurrent
  • 50SP – Split Phase Instantaneous Current
  • 50Q – Negative Sequence Instantaneous Overcurrent
  • 50/27 – Accidental Energization
  • 50/51 – Instantaneous / Time-delay Overcurrent relay
  • 50/74 – Ct Trouble
  • 50/87 – Instantaneous Differential
  • 51 – AC Time Overcurrent Relay
  • 51G – Ground Time Overcurrent
  • 51LR – AC inverse time overcurrent (locked rotor) protection relay
  • 51N – Neutral Time Overcurrent
  • 51P – Phase Time Overcurrent
  • 51R – Locked / Stalled Rotor
  • 51V – Voltage Restrained Time Overcurrent
  • 51Q – Negative Sequence Time Overcurrent
  • 52 – AC circuit breaker
  • 52a – AC circuit breaker position (contact open when circuit breaker open)
  • 52b – AC circuit breaker position (contact closed when circuit breaker open)
  • 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
  • 59Q – 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
  • 64R – Rotor earth fault
  • 64REF – Restricted earth fault differential
  • 64S – Stator earth fault
  • 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
  • 67Ns – Earth fault directional
  • 67P – Phase Directional Overcurrent
  • 67SG – Sensitive Ground Directional Overcurrent
  • 67Q – Negative Sequence Directional Overcurrent
  • 68 – Blocking Relay / Power Swing Blocking
  • 69 – Permissive Control Device
  • 70 – Rheostat
  • 71 – Liquid Switch, Level Switch
  • 72 – DC Circuit Breaker
  • 73 – Load-Resistor Contactor
  • 74 – Alarm Relay
  • 75 – Position Changing Mechanism
  • 76 – DC Overcurrent Relay
  • 77 – Telemetering Device, Speed Sensor
  • 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 – Pilot Communications, Carrier or Pilot-Wire Relay
  • 86 – Lock-Out Relay, Master Trip Relay
  • 87 – Differential Protective Relay
  • 87B – Bus Differential
  • 87G – Generator Differential
  • 87GT – Generator/Transformer Differential
  • 87L – Segregated Line Current Differential
  • 87LG – Ground Line Current Differential
  • 87M – Motor Differential
  • 87O – Overall Differential
  • 87PC – Phase Comparison
  • 87RGF – Restricted Ground Fault
  • 87S – Stator Differential
  • 87S – Percent Differential
  • 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
  • 95 – For specific applications where other numbers are not suitable
  • 96 – Transmitter
  • 97 – For specific applications where other numbers are not suitable
  • 98 – For specific applications where other numbers are not suitable
  • 99 – For specific applications where other numbers are not suitable