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An IDMT over current relay has a current setting of 15% and has a time multiplier setting of 0.5. The relay is connected in the circuit through a CT having 500: 5. The time of operation of the relay if the circuit carries a fault current of 6000 A is ________ sec
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- 157.5 sec.
- 15.75 sec.
- 1.575 sec.
- 1575 sec.
Correct Option: C
| Secondary fault current = 6000 × | = 60 A | |
| 500 |
| P.S.M. = | ||
| setting current |
| = 60 × | = 8 | |
| 5 × 1.5 |
Operating time = 3.15 × 0.5 = 1.575 sec.
