EE2402 PROTECTION AND SWITCHGEAR ANNA UNIVERSITY NOV/DEC 2011 PREVIOUS YEAR QUESTION PAPER for EEE -7th Semester ...
Posted by R.Anirudhan
B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2011.
Electrical and Electronics Engineering
EE 2402 — PROTECTION AND SWITCHGEAR
Time : Three hours Maximum : 100 marks
Answer ALL questions.
PART A — (10 × 2 = 20 marks)
1. What is surge absorber? How do they differ from surge diverter?
2. Define the term ‘‘Insulation Coordination”.
3. Compare Static and Electromagnetic relay.
4. A relay is connected to 400/5 ratio current transformer with current setting of 150%.
Calculate the Plug Setting Multiplier when circuit carries a fault current of 4000 A.
5. Explain the secondary of current transformer should not be open.
6. What is meant by time-graded system protection?
7. Distinguish between recovery voltage and restriking voltage.
8. List the factors affecting the transient recovery voltage.
9. Give the advantage of SF6 circuit breaker over Air blast circuit breaker.
10. What are the basic requirements of circuit breaker?
PART B — (5 ×16 = 80 marks)
11. (a) Discuss and compare the various methods of neutral earthing. (16)
(b) (i) Describe the essential qualities of a protective relaying. (8)
(ii) Briefly explain the various methods of overvoltage protection of overhead transmission line. (8)
12. (a) Describe the construction and operation of an inductive type directional overcurrent
relay with a neat diagram. Also explain its operational characteristics. (16)
(b) Explain the principle of distance relays stating clearly the difference between impedance relay, reactance and mho relay. Indicate the difference on R-X diagrams and show where each type is suitable. (16)
13. (a) (i) Explain the factors which cause difficulty in applying Merz-Price circulating current principle to a power transformers. (8)
(ii) A three phase transformer of 220/11000 Line Volts is Connected in star / delta. The protective transformers on 220 V side have a current ratio of 600/5. What should be the current transformer ratio on 11000 V side? (8)
(b) Describe the differential pilot wire method of protection of feeder. (16)
14. (a) (i) Explain how arc is initiated and sustained when the circuit breaker contacts break. (6)
(ii) Explain in detail the various methods of arc extinction in a circuit breaker. (10)
(b) (i) What is current Chopping? Explain how can the effect of current chopping be
(ii) Derive an expression for the Rate of Rise of Restriking Voltage (RRRV) in a
15. (a) Explain with a neat sketch, the construction and working of minimum oil circuit
breaker. Also give its merits and demerits. (16)
(b) (i) Describe the various types of rating of a circuit breaker. (8)
(ii) Describe the various methods of testing of circuit breaker. (8)