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