Electrical Interview Questions on Protection ( Busbar, Buscoupler, Bussection, Feeder, Trafo)

1. Explain Busbar protection?
2. Explain Bus Coupler protection?
3. Explain Bus Section protection?
4. Explain Feeder protection?
5. Explain Line protection?
6. Explain Transformer protection?
7. Explain Motor Protection?
8. Explain Shunt reactor protection?
9. What is trip circuit supervision relay?
10. What is post and pre condition for trip circuit supervision relay?
11. What are lock out relays?
12. What is isolator replica. How it is used?
13. What is dead zone?
14. How faults are detected in dead zone?
    - Case 1: Consider one CT
15. - Case 2: Consider two CT
16. - Case 3: Consider CTs not covering Breaker and CT zone.
17. How many bay units can be configured to Central unit in Busbar protection?
18. What is the need of duplicating lock out relays?
19. How groups are formed for each protection to lock out relays?
20. Why DC is duplicated?
21. Why relays are duplicated to achieve similar protection?
22. How is signal list prepared?
23. How synchronization takes place?
24. What is check zone?
25. What is discrimination zone?
26. Which type of cable used for connecting IEDs?
27. Which type of cable used for PC to IED?
28. Which type of connector used for FO cable to connect to IED?
29. What information Bay unit have?
30. What is self monitoring of relays?
31. what are high impedance schemes?
32. What are low impedance schemes?
33. Where are 31. and 32. used?
34. For differential protection, what tripping conditions must be fulfilled?
35. Explain the Breaker failure logic?
36. Explain intertrip?
37. Explain, how or logic for intertrip during Busbar operation?
38. What type of relay senses closing onto fault?
39. How are disconnector monitored?
40. How is breaker fail monitored from maloperating?
41. How are settings of busbar protection achieved?
42. What do you do to distance protection, when Voltage transformer's MCB (miniature circuit breaker trips)?
43. What are the annunciation in Feeder protection?
44. What is the switching order to close earth switch?
45. What is the switching order to close circuit breaker?
46. What is automatic switching?
47. What is on load transfer?
48. What is to be taken care of while closing disconnector?
49. What is pole discrepancy relay?
50. What is anti pumping?
51. What can be problems with Circuit breaker?
52. What are SF6 Stages for alarm and trip for circuit breaker?
53. When does Circuit breaker lock out?