CHAPTER 1: INTRODUCTION SPECIFICATIONS
845 TRANSFORMER PROTECTION SYSTEM – INSTRUCTION MANUAL 1–11
TRANSFOMER PERCENT DIFFERENTIAL PROTECTION
Differential/Restraint Characteristic:.........Dual Slope, Dual Breakpoint
Minimum Pickup level:......................................0.05 to 1.00 x CT in steps of 0.01
Slope 1 range:.......................................................1 to 100% in steps of 1%
Slope 2 range:.......................................................1 to 100% in steps of 1%
Breakpoint 1:.........................................................0.50 to 2.00 x CT in steps of 0.01
Breakpoint 2:.........................................................2.00 to 30.00 x CT in steps of 0.01
2
nd
harmonic inhibit level: ..............................0.1 to 40.0% in steps of 0.1%
2
nd
harmonic inhibit mode:............................Per-phase, Average, 2-out-of-3, 1-out-of-3
5
th
harmonic inhibit level:...............................1.0 to 40.0% in steps of 0.1%
Dropout level:........................................................97 to 98% of Pickup
Operate time:........................................................< 16/22 ms at >3 x Pickup @60Hz (harmonic inhibits
disabled/enabled)
< 18/26 ms at >3 x Pickup @50Hz (harmonic inhibits
disabled/enabled)
Level accuracy:....................................................± 0.5% of reading current, or ±1% of rated
TRANSFORMER OVERLOAD
Operating Parameter:.......................................Winding 1, 2, 3 loads
Pickup level:...........................................................50 to 300% in steps of 1%
Dropout level:........................................................97 to 98% of Pickup
Level Accuracy:....................................................Per current input
Operate time:........................................................<25 ms at >3 x Pickup at 60 Hz,
<30 ms at >3 x Pickup at 50 Hz
Timer Accuracy: ..................................................±3% of delay setting or ± ¼ cycle (whichever is greater) from
pickup to operate
INSTANTANEOUS PHASE DIFFERENTIAL FUNCTION
Pickup level:...........................................................3.00 to 30.00 per unit in steps 0.01
Dropout level:........................................................97 to 98% of Pickup
Operate time:........................................................<12 ms at >3 x Pickup@60Hz
<15 ms at >3 x Pickup@50Hz
PHASE/NEUTRAL/GROUND TIME OVERCURRENT (51P/N/G)
Current:....................................................................Phasor or RMS
Pickup Level:..........................................................0.050 to 30.000 x CT in steps of 0.001 x CT
Dropout Level: ......................................................97 to 98% of Pickup
Level Accuracy:....................................................For 0.1 to 2.0 x CT: ±0.5% of reading or ±0.4% of rated,
whichever is greater;
For > 2.0 x CT: ±1.5% of reading
Curve Shape:.........................................................IEEE Extremely/Very/Moderately Inverse;
ANSI Extremely/Very/Normally/Moderately Inverse;
Definite Time, IEC A/B/C and Short Inverse;
IAC Extremely/Very/Inverse/Short Inverse;
FlexCurve A/B/C/D, I
2
t, I
4
t
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
Voltage Restrained Function (51V):.............Modifies Pickup from 0.1 < V < 0.9 VT Nominal in a fixed
linear relationship
FAST PATH:
Add 1.5 cycles to the curve time to obtain the TOC operating time, i.e., from fault inception
until operation.
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