3 PERFORMANCE OF TRANSFORMER DIFFERENTIAL PROTECTION AND
MONIT
ORING FUNCTIONS
3.1 TRANSFORMER DIFFERENTIAL PROTECTION
Accuracy
Pick-up Formula +/-5% or 20 mA, whichever is greater
Drop-off 0.95 x formula +/- 5%
Pick-up and drop-off repeatability < 1%
Low set differential element operate time (High
Br
eak Contact)
< 33 ms (currents applied at 1.2x pickup level or higher)
Low set differential element operate time (Standard
Contact)
< 36 ms (currents applied at 1.2x pickup level or higher)
High set 1 differential element operate time < 15 ms (currents applied at 2x pickup level or higher)
High set 2 differential element operate time < 25 ms (currents applied at 2x pickup level or higher)
DT operate time (High Break contact)
< 33 ms, whichever is greater (currents applied at 1.2x pickup level or
higher
DT operate time (Standard contact)
< 36 ms, whichever is greater (currents applied at 1.2x pickup level or
higher
Operate time repeatability < 2 ms
Disengagement time < 15 ms
2nd harmonic blocking pick-up Setting +/-5% of setting
2nd harmonic blocking drop-off 0.95 x setting +/-5%
5th harmonic blocking pick-up Setting +/-5% of setting
5th harmonic blocking drop-off 0.95 x setting +/-5%
3.2 MATCHING FACTORS
CT Type Max. sensitivity Permitted Matching Factor range
Matching factor for typical setting
Is1 = 0.2 pu
Standard 43 mA 0.05 - 15 4.65
3.3 CIRCUITRY FAULT ALARM
Pick-up Formula +/-5%
Drop-off 0.95 x formula +/- 5%
Pick-up and drop-off repeatability < 4%
DT operate < 26 ms (currents applied at 2.5x pickup level or higher)
Operate time repeatability < 8 ms
Disengagement time < 26 ms
Timer +/- 2% or 50 ms, whichever is greater
P64x Chapter 21 - Technical Specifications
P64x-TM-EN-1.3 459
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