Protection of Feeders and Transmission Lines Interview Questions:

Following are the below Protection of Feeders and Transmission Lines Interview Questions and Important Questions which is very useful for interviews and exams

1. How earth fault protection is achieved in case of feeders ? Explain with sketches.

2. Explain overcurrent protection of feeders. How is the protection system graded with respect to the time of operation of relays for a radial feeder.

3. Describe in detail the protection of parallel feeder and ring mains.

4. Explain a scheme of protection for a ring main.

5. Describe a suitable protective system for a ring main formed by a power station and four substations, and explain clearly its working when a fault occurs. Explain the special features that a protective relay should possess in this case and also indicate the limitations of the system.

6. Describe the protection of ring mains feeder with an example.

7. Explain the time graded and current graded systems in overcurrent protection.

8. Explain the principle of time grading and current grading in a simple radial system equipped with IDMT overcurrent relays for protection.

9. Discuss the merits and demerits of various pilot-wire relaying schemes for protecting transmission lines.

10. Explain the term ‘pilot’ with reference to power line protection. What are the different types of pilot schemes which are presently employed in transmission line protection.

11. Describe pilot wire protection, its merits and demerits in detail.

12. Explain the operating principles of pilot wire protection.

13. Compare merits and demerits of various pilot wire relaying schemes for protecting transmission lines.

14. What is the Merz-Price voltage protection scheme ? How does it protect feeders ? Explain it with a neat diagram.

15. Discuss the problems of wire pilot differential relaying. Why are wire pilot relaying schemes used for short lines ? Discuss with necessary diagram the principle of operation of Translay feeder protection scheme.

16. Explain with the help of neat sketches the setup of carrier current relaying employed in transmission line protection. Explain the utility of (i) line trap unit and (ii) coupling capacitor unit.

17. Discuss why carrier current protection is suitable for important interconnected lines.

18. Explain carrier current protection scheme with block diagram and neat sketches. Discuss how phase comparison scheme can be used to protect feeder from both ends.

19. Draw the schematic diagram of the carrier current protection scheme of lines. Also explain its working principle.

20. Explain the directional comparison method of carrier current protection.

21. Explain in detail carrier current protection scheme. Describe carrier phase comparison relay with neat sketches.

22. What are the advantages of distance protection over other types of protection of feeders ?

23. Describe any type of impedance relay and show how they provide discriminatory protection.

24. Discuss the directional reactance scheme for distance protection.

25. Explain the zonal protection scheme for feeder. Describe the reactance relay characteristic for 3-zone protection. Also draw the contact circuit for the same.

26. Explain with necessary diagram the principle of operation of a distance protection scheme. How a 3-zone stepped units help to achieve fast discrimination ? How many units are required for a complete protection scheme ? How the CTs and VTs associated with these relays are connected to a 3-phase transmission line ? Indicate the reasons of mode of connections of CTs and VTs in such a way.

27. Describe the trip circuit diagram of 3-zone distance relay used for the protection of a transmission line, Why 3-zones are necessary ? How their reach setting and time setting is done ?

28. Discuss with a neat sketch the general principle of operation of a distance protection scheme. How many units are required for a complete distance protection scheme ?

29. Explain clearly the necessity of using 3-zone stepped distance protection scheme to achieve fast and discriminative protection of transmission line.

30. Explain stepped time-distance characteristics of three distance relaying units used for first, second and third zones of protection.

31. Discuss three zone protection scheme using Mho relay to protect trnasmission lines. Explain how static Mho relay is realized with phase comparator.

32. Give schemes of protection for a parallel feeder fed from (i) one end (ii) both the ends.

33. Using carrier system of protection, what is the basis of choice of frequency in power line carrier system.

34. Write short notes on the following:

• Time graded protection of feeders.
• Protection of parallel feeders.
• Protection of ring mains.
• Pilot wire protection of feeders using Merz-Price system.
• Translay protection to a 3-phase feeder.
• Split-conductor protection.
• Carrier current protection of transmission lines.