CHAPTER 1: INTRODUCTION SPECIFICATIONS
850 FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL 1–23
SENSITIVE GROUND TIME OVERCURRENT (51SG)
Operating Parameter:.......................................Isg (RMS or Fundamental)
Pickup Level:..........................................................0.005 to 3.000 xCT in steps of 0.001 xCT
Dropout Level: ......................................................97 to 98% of Pickup
Level Accuracy:....................................................For 0.1 to 2.0 xCT: ±0.5% of reading or ±0.4%of rated
(whichever is greater)
For > 2.0 xCT: ±1.5% of reading > 2.0 xCT rating
Dropout Level: ......................................................97 to 98% of Pickup
Curve Shape:.........................................................IEEE Extremely/Very/Moderately Inverse
ANSI Extremely/Very/Normally/Moderately Inverse
IEC A/B/C and Short Inverse
IAC Extreme/Very/Inverse/Short Inverse
I2t, I4t, FlexCurves A/B/C/D, Definite Time
Curve Multiplier:...................................................0.05 to 600.00 in steps of 0.01
Reset Time: ............................................................Instantaneous, Timed
Curve Timing Accuracy: ..................................Currents > 1.03 to 20 x pickup: ± 3% of operate time or
± ½ cycle (whichever is greater) from pickup to operate
SENSITIVE GROUND INSTANTANEOUS OVERCURRENT (50SG)
Operating Parameter:.......................................Isg (Fundamental Phasor Magnitude)
Pickup Level:..........................................................0.005 to 3.000 xCT in steps of 0.001 xCT
Dropout Level: ......................................................97 to 98% of Pickup
Level Accuracy:....................................................For 0.1 to 2.0 xCT: ±0.5% of reading or ±0.4% of rated
(whichever is greater)
For > 2.0 xCT: ±1.5% of reading > 2.0 xCT rating
Operate Time:.......................................................< 12 ms at 3 × Pickup at 60 Hz
Timer Accuracy:..................................................±3% of operate time or ± ¼ cycle (whichever is greater)
SENSITIVE GROUND INSTANTANEOUS OVERCURRENT (50SG)
Operating Parameter:.......................................Isg (Fundamental Phasor Magnitude)
Pickup Level:..........................................................0.005 to 3.000 xCT in steps of 0.001 xCT
Pickup Level:..........................................................0.005 to 3.000 xCT in steps of 0.001 xCT
Dropout Level: ......................................................97 to 98% of Pickup
Level Accuracy:....................................................For 0.1 to 2.0 xCT: ±0.5% of reading or ±0.4% of rated
(whichever is greater)
For > 2.0 xCT: ±1.5% of reading > 2.0 xCT rating
Level Accuracy:....................................................For 0.1 to 2.0 xCT: ±0.5% of reading or ±0.4% of rated
(whichever is greater)
For > 2.0 xCT: ±1.5% of reading > 2.0 xCT rating
Operate Time:.......................................................< 12 ms at 3 × Pickup at 60 Hz
Timer Accuracy:..................................................±3% of operate time or ± ¼ cycle (whichever is greater)
SENSITIVE GROUND DIRECTIONAL OVERCURRENT (67SG)
Directionality: .......................................................Co-existing forward and reverse
Polarizing: ...............................................................Voltage, Current, Dual
Polarizing Voltage:..............................................V_0 or VX
Polarizing Current:..............................................Ig
Operating Current: .............................................Isg
Level Sensing:.......................................................Ig, Isg
Characteristic Angle:.........................................-90º to 90º in steps of 1°
Limit Angle: ............................................................40º to 90º in steps of 1°, independent for forward and
reverse
Angle Accuracy: ..................................................± 2º
Pickup Level:..........................................................0.005 to 3.000 x CT in steps of 0.001 x CT
Dropout Level: ......................................................97 to 98%
Operate Time (no direction transition):.....< 12 ms typical at 3 × Pickup at 60 Hz
< 15 ms typical at 3 × Pickup at 50 Hz
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