Relay Numbering ANSI

Relay Protection role a critical function on electrical system. This device used to protect all electrical equipment and give command to circuit breaker to closed or open. ANSI as american standard regulate a numbering of all relay related to each function on protection system. Herewith some of relay and it number based on ANSI:

  1. Relay No. 12    : Overspeed Protection
  2. Relay No. 21G : Ground Distance
  3. Relay No. 21P : Phase Distance
  4. Relay No. 24    : V/Hz Overfluxing
  5. Relay No. 25  : Synchrocheck
  6. Relay No. 27P : Phase Undervoltage
  7. Relay No. 27TN : Third Harmonic Neutral Undervoltage
  8. Relay No. 27X : Auxiliary Undervoltage
  9. Relay No. 32 : Directional Power
  10. Relay No. 32L : Low Forward Power
  11. Relay No. 32R : Reverse Power
  12. Relay No. 37 : Under Current
  13. Relay No. 38 : Bearing RTD
  14. Relay No. 40 : Loss Excitation
  15. Relay No. 46 : Stator Current Unbalance
  16. Relay No. 47 : Phase Reversal
  17. Relay No. 49 : Thermal Overload
  18. Relay No. 49RTD : Thermal Overload
  19. Relay No. 50BF : Breaker Failure
  20. Relay No. 50DD : Current Distrubance Detector
  21. Relay No. 50G : Ground Instantaneous Overcurrent
  22. Relay No. 50N : Neutral Instantaneous Overcurrent
  23. Relay No. 50P : Phase Instantaneous Overcurrent
  24. Relay No. 50_2 : Negative Sequence Instantaneous Overcurrent
  25. Relay No. 51 : Overload
  26. Relay No. 51G : Ground Time Overcurrent
  27. Relay No. 51N : Ground Time Overcurrent
  28. Relay No. 51P : Phase Time Overcurrent
  29. Relay No. 51V : Voltage Restrained Time Overcurrent
  30. Relay No. 51R : Locked/Stalled Rotor
  31. Relay No. 51_2 : Negative Sequence Time Overcurrent
  32. Relay No. 59B : Bank Phase Overvoltage
  33. Relay No. 59N : Neutral Overvoltage
  34. Relay No. 59NU: Neutral Voltage Unbalance
  35. Relay No. 59P: Phase Overvoltage
  36. Relay No. 59X: Auxiliary Overvoltage
  37. Relay No. 59_2: Negative Sequence Overvoltage
  38. Relay No. 60N: Neutral Current Unbalance
  39. Relay No. 60SP: Split Phase
  40. Relay No. 67G: Ground Directional Overcurrent
  41. Relay No. 67N: Neutral Directional Overcurrent
  42. Relay No. 67P: Phase Directional Overcurrent
  43. Relay No. 67_2: Negative Sequence Directional Overcurrent
  44. Relay No. 68: Power Swing Blocking
  45. Relay No. 78: Out-of-Step Tripping
  46. Relay No. 78V: Loss of Mains
  47. Relay No. 79: Auto Close
  48. Relay No. 81O: Over Frequency
  49. Relay No. 81R: Rate-of-Change Frequency
  50. Relay No. 81U: Underfrequency
  51. Relay No. 87B: Bus Differential
  52. Relay No. 87G: Generator Differential
  53. Relay No. 87L: Segregated Line Current Differential
  54. Relay No. 87M: Motor Differential
  55. Relay No. 87O: Overall Differential
  56. Relay No. 87PC: Phase Comparison
  57. Relay No. 87RGF: Restricted Ground Fault
  58. Relay No. 87T: Transformer Differential
  59. Relay No. 87V: Voltage Differential
  60. Relay No. 50/74: CT Supervision
  61. Relay No. 27/50: Accidental Generator Energization
  62. Relay No. 27TN/59N: 100% Stator Earth Fault
  63. VTFF: VT Fuse Fail.

In common practice, the following relay used to protect motor feeder:

  1. Relay No. 50: Instantaneous Over Current
  2. Relay No. 51: Time Over Current
  3. Relay No. 50N: Neutral Instantaneous Over Current
  4. Relay No. 51N: Neutral Time Over Current
  5. Relay No. 86: Lock Out

And for feeder protection, the following relay is minimum shall be installed:

  1. Relay No. 67: Directional Over Current
  2. Relay No. 67N: Neutral Directional Over Current
  3. Relay No. 27: Under Voltage
  4. Relay No. 59: Over Voltage
  5. Relay No. 86: Lock Out

Reference: various

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