Page 318 - Practical Power System and Protective Relays Commissioning

312 Practical Power System and Protective Relays Commissioning

Action:
1. HV CB tripping of T 1 ;
2. Incoming of transformer T 2 6.4 kV trip;
3. Turbine tripping;
4. Generator excitation tripping.
10. Generator differential protection
A biased differential relay is used in the following circumstances
(Fig. 19.6.4)

FIGURE 19.6.4 Biased differential protection for generators.

(I N 5 generator nominal current):
P 5 O3 V L . I N . cos [
P 333 3 10 3
I N 5 p ffiffiffi 5 p ffiffiffi
3V L :cos φ 3V L :cos φ
333 3 10 3
5 p ffiffiffi 5 10; 924 A
3 3 22 3 0:8
10; 924
I N secondary 5 5 0:84 A
13; 000

I set 5 0:1 I N
5 0:1 3 0:84
5 0:084 A
Set bias stop 5 20%
11. Reverse power protection
P Reverse set 5 0.01 3 333 5 3.33 MW