Page 283 - Practical Power System and Protective Relays Commissioning
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Protection Relays Chapter | 18 277
FIGURE 18.12.7 Zero-sequence network for different transformer connections.
Refer to Fig. 18.12.7 for the equivalent zero-sequence network of differ-
ent transformer connections.
18.12.7.2 Three-Winding Transformers
Refer to Fig. 18.12.8 for the equivalent zero-sequence network of a star/star/
delta transformer.
18.12.7.3 Zigzag Earthing Transformers
Refer to Fig. 18.12.9 for the zero-sequence network of a zigzag earthing
transformer.
18.12.8 SYSTEM EARTHING
There are different methods of earthing the power system as follows:
1. Solid earthing:
Direct connection for the star-connected system has the advantage of
low overvoltages but the disadvantage is a high fault current used in
