JNTU papers B – Tech II Semester Supplimentary Examinations, Switchgear and protection – Aug/Sep 2008

JNTU III B.Tech II Semester Supplimentary Examinations, Aug/Sep 2008

Switchgear and protection

(Electrical & Electronic Engineering)


1. (a) Explain briefly about various Switch gear components.

(b) Give the importance of ratings and specifications of Circuit Breaker.


2. (a) Compare the arc rupture in oil and air blast circuit breakers and summarize the relative advantages and disadvantages of these types of switch gear.

(b) Explain the operating duty of a circuit breaker.


3. Distinguish between Over current relays, Directional relays and Differential relays?


4. Discuss the unbalanced loading and overload protection in alternators. ‘Overload protection is not necessary for alternators’ ? Justify yourself?


5. What is Buchholtz relay? Which equipment is protected by it? For what types of faults is it employed? Discuss its working principle.


6. (a) Explain over-current protection of feeders.

(b) How is the protection system graded with respect to the time of operation of relays.


7. (a) Discuss about effectively grounded system and ungrounded system.

(b) A 132 kV, 3-Phase, 50Hz, 100km long transmission line has a capacitance of

0.012?F per km per phase. Determine the inductive reactance and kVA rating of the arc suppression coil suitable for this line.


8. (a) What are volt time curves.

(b) What is their significance in power system studies.

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