B.TECH - Semester 5 switchgear and protection Question Paper 2020 (feb)
Practice authentic previous year university questions for better exam preparation.
Sample Questions
- (c) Compare the characteristics of
- Why protection system is provided in a power system?
- Clearly distinguish the making capacity and breaking capacity of a circuit breaker.
- Name the major problems encountered in HVDC circuit breakers.
- What is protective relay? Point out its function in a power system.
- What are the main features of directional relays?
- Briefly explain the operation of a phase comparator.
- Briefly explain the basic principle of a static differential relay.
- What are the various protective schemes available for power transformer?
- What is insulation co-ordination? Why is it required in a large power system?
- What is earthing of neutral? Why is it done? Answer any one questions from each Module, each carries 20 marks.
- (a) A 50 Hz 3 phase alternator with grounded neutral has an inductance of 1.6 mH per phase and is connected to the bus bars through a circuit breaker. The capacitance to the earth of the circuit between the alternator and the circuit breaker is $0.00...
- (i) Frequency of oscillation, (ii) Active recovery voltage, (iii) Time for maximum RRRV and (iv) Maximum RRRV.
- (b) Explain the principle of resistance switching. Why is it necessary in air blast circuit breakers?
- (c) With help of neat sketch explain the construction, operating principle and advantages of $\mathrm{SF}_{6}$ circuit breaker.
- (a) Briefly discuss the different methods of arc interruption in case of circuit breakers.
- (b) Distinguish clearly between the recovery voltage and restriking voltage and explain the significance of RRRV in the operation of a circuit breaker by deriving necessary expression.
- (a) With help of a neat sketch, explain the operation of induction disc relay.
- (b) Clearly distinguish between over current relays and directional relays. $\quad 6$
- (i) impedance relay (ii) mho relay and (iii) reactance relay. Also give their applications. 8
- (a) Explain the construction and operation of an over current relay.
- (b) Define the terms
- (i) Plug setting multiplier and (ii) Time multiplier setting as used in the context of an IDMTL relay. How many plug setting and time multiplier settings are available with a standard IDMTL relay?
- (c) Write a short note on negative sequence relay.
- (a) What are the merits and demerits of static relay over electromagnetic relay?
- (b) Write short note on amplitude comparators. 6
- (c) Illustrate with neat block diagram of numerical over current protection.
- (a) With help of a neat diagram, explain the basic principle of static overcurrent relays.
- (b) What are the different microprocessor based protective relays? Draw the block schematic and flow chart of a directional relay.
- (a) Enumerate the relaying schemes which are employed for the protection of a modern alternator.
- (b) Describe the construction and working of Buchholz relay.
- (c) What is a travelling wave? Explain the development of such a wave along an overhead transmission line. OR
- (a) With help of neat sketches explain the operation of Merz-Price differential protection scheme of transmissions lines. Mention its advantages and disadvantages.
- (b) Explain the differences between grounded and ungrounded neutral systems.
- (c) With a neat diagram explain the operation of any one type of lightning arrester.