Page 294 - Practical Power System and Protective Relays Commissioning

288 Practical Power System and Protective Relays Commissioning

19.3.2 WORKED EXAMPLE
Worked example:
Line A B 500 kV B 5 1.877 CT 5 1200/1 at both sides choose the relay
characteristic shown in Fig. 19.3.2

FIGURE 19.3.2 Line differential protection characteristic.

j
j I diff j 5 I A 1 I B j
j ½
j I bias j 5 0:5 I A1 1 I B1 jŠ
B 3 1000
Line charging current 5
V 3 O3
1:877 3 1000
I ch 5
500 3 O3
5 2.167 A
I set min 5 2:5 3 2:167 5 5:4175 A
I set 5 0.2 I N
I set 5 0:2 3 1200 5 240 A

I set . 2.5 I ch
I S1 5 240 A primary
240
I S1 5 5 0:2A
1200
I S2 5 2I N
5 2 3 1200 5 2400 A
I S2 5 2400 A primary
2400
I S2 5 5 2 A secondary
1200
K 1 2 slop1 5 30 %
K 2 2 slop2 5 150 %