Page 208 - Practical Power System and Protective Relays Commissioning
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208 Practical Power System and Protective Relays Commissioning
FIGURE 18.5.9 Directional relays connections.
FIGURE 18.5.10 Residual voltage-broken delta-connection.
18.5.5.1 Ring Main Circuit Overcurrent and Directional
Relays Grading
Refer to Fig. 18.5.11 for the grading method for a ring main circuit.
1. Open Ring at A
Grade A -E -D -C -B
2. Open Ring at A
Grade A-B-C-D-E
Grading times are given as an example in Fig. 18.5.11, relays B,C,D ,E
can also be nondirectional relays.
