Page 202 - Practical Power System and Protective Relays Commissioning
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202 Practical Power System and Protective Relays Commissioning
FIGURE 18.5.1 Definite time philosophy.
FIGURE 18.5.2 Inverse definite minimum time.
18.5.2 NONDIRECTIONAL OVERCURRENT AND EARTH
FAULT PROTECTION
Relay characteristics types used in Over Current (OC) and Earth Fault (EF)
relays as follows:
1. Standard inverse (SI) (normal inverse);
2. Very inverse (VI);
3. Extremely inverse (EI);
4. Long time inverse;
5. DT D2 (0.1 2.0 seconds);
6. DT D4 (0.2 4 seconds);
7. DT D8 (0.4 8.0 seconds).
