ANSI
Function #
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Description |
Generator
Protection |
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Intertie/
Generator Protection |
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Intertie
Protection |
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Transformer
Protection |
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| 21 |
Phase Distance (Mho
characteristic) |
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| 24 |
Volts/Hz |
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| 25 |
Sync-Check |
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| 27 |
RMS
Undervoltage, 3-Phase |
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| 27G |
RMS Undervoltage,
Neutral |
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| 27TN |
Third-Harmonic
Undervoltage, Neutral Circuit |
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| 32 |
Directional Power,
3-Phase |
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| 40 |
Loss
of Field |
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| 46 |
Negative Sequence
Overcurrent |
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| 47 |
Phase
Rotation |
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| 49 |
Winding thermal protection |
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| 50 |
Instantaneous
Overcurrent, 3-Phase |
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| 50/27 |
Inadvertent Energizing |
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| 50BF |
Breaker
Failure |
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| 50DT |
Definite
time overcurrent for split-phase differential |
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50G
or
50N |
Instantaneous
Overcurrent, Neutral |
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50W1
W2/W3 |
Instantaneous
Phase Overcurrent
(Dual elements per winding) |
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51W1
W2/W3 |
Three winding inverse
time phase overcurrent |
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| 51N |
Inverse
Time Overcurrent, Neutral |
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| 51V |
Inverse
Time Overcurrent, 3-Phase with Voltage Control or Voltage Restraint |
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51NW1
W2/W3 |
Inverse Time Residual
Overcurrent |
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| 59 |
RMS
Overvoltage, 3-Phase |
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| 59D |
Third Harmonic Voltage
Differential |
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| 59G
or 59N |
RMS
Overvoltage, Neutral Circuit or Zero Sequence |
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| 59I |
Peak Overvoltage |
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| 59X |
Multipurpose
overvoltage |
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| 60FL |
VT Fuse-Loss Detection |
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| 64F |
Field
Ground |
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| 64S |
100%
Stator Ground Fault by 20Hz Injection |
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| 67 |
Phase
Directional Overcurrent |
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| 67N |
Residual
Directional Overcurrent |
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| 78 |
Out-of-step (Mho Characteristic)
protection |
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| 79 |
Reconnect
Time Delay |
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| 81 O/U |
Frequency |
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| 81A |
Underfrequency
Accumulation |
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| 81R |
Rate of Change of
Frequency |
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| 87 |
Phase
Differential Current |
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| 87GD |
Ground (zero sequence)
Differential |
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| 87H |
Phase Differential
High Set Overcurrent |
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| 87T |
Phase
Differential (Harmonic Restrained) |
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| EXT |
External |
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