The distribution system shown in Figure is to be protected by over current system of protection [Figure description: A 33 kV supply on the left feeds, in order along a horizontal line, circuit breakers/relay locations 1 and 2, then a bus junction, then breaker 3 and breaker 4, then a second 33 kV supply on the right. From the middle bus (between breakers 2 and 3) a vertical feeder runs down and goes through breaker 5 to a Load. So the system is a ring/double-end-fed line with two 33 kV sources at its two ends and a load tapped at the middle through breaker 5.] For proper fault discrimination directional over current relays will be required at locations
- A. 1 and 4
- B. 2 and 3
- C. 1, 4 and 5
- D. 2, 3 and 5
Answer: B. 2 and 3
Explanation: Directional relays are required at 2 and 3 (bus-side ends) so that each trips only for faults on its own section with power flowing from the other source.