Important Questions of Protective Relays:

1. What is protective relay ? Explain its function in an electrical system.

2. Discuss the fundamental requirements of protective relaying.

3. Describe briefly some important types of electromagnetic attraction relays.

4. Derive the equation for torque developed in an induction relay.

5. Write a brief note on relay timing.

6. Define and explain the following terms as applied to protective relaying :

(i) Pick-up value (ii) Current setting (iii) Plug-setting multiplier (iv) Time-setting multiplier

7. Sketch a typical time/P.S.M. curve.

8. Describe the various steps for calculating the actual relay operating time.

9. Explain with the help of neat diagram the construction and working of :

(i) Non-directional induction type overcurrent relay

(ii) Induction type directional power relay

10. Describe the construction and principle of operation of an induction type directional over-current relay.

11. Explain the working principle of distance relays.

12. Write a detailed note on differential relays.

13. Describe the Translay scheme of protection.

14. Write short notes on the following

(i) Percentage differential relays (ii) Definite distance relays (iii) Time-distance relays

15. What is the difference between a fuse and a relay ?

16. What is the difference between an overcurrent relay and current differential relay ?

17. Back-up protection is not a good substitute for better maintenance. Discuss.

18. Why are differential relays more sensitive than overcurrent relays ?

19. What is the difference between a balanced voltage relay and a Translay relay ?

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