Page 293 - Practical Power System and Protective Relays Commissioning

Protection Relays Settings Chapter | 19 287

29:3 3 10 3
I F
PSM 5 5 5 36:625
I S 800
Assuming that the relay will operates on 1 second for a fault on end B:
t:operation
TM 5
T R
0:14 0:14
T R 5 5 5 1:884
PSM 0:0221 36 0:0221
1
TM 5 5 0:530
1:884
Relay setting:
I set 5 800 A
5 0.8 A secondary
PSM 5 36 TM 5 0.53
0:14
t:operation 5 0:53 0:0221
36
5 0.998 second

Subchapter 19.3

Feeder Unit Differential Protection

19.3.1 INTRODUCTION
This protection is used to protect overhead transmission lines and is
commonly used as main 2 in utilities. The disadvantage of this protec-
tion is the blind zone, which is not protected by this protection—this
means the zone between the circuit breaker (CB) and the current
transformer in one end—as this zone is protected by backup protections
(Fig. 19.3.1).

FIGURE 19.3.1 Line differential protection.