Switchgear & Protection-Engineering-March2020 - Grad Plus

Switchgear & Protection-Engineering-March2020


B.E. (Electrical)
403147 : SWITCHGEAR & PROTECTION
(2015 Pattern) (Semester – II)


Time : 1 Hour                                                                                                    Max. Marks : 30
Instructions to the candidates:
1) Answer Q.1 or Q.2, Q3 or Q.4, and Q5. or Q.6.
2) Neat diagrams must be drawn wherever necessary.
3) Figures to the right indicate full marks.
4) Use of non-programmable scientific calculator is allowed.
5) Assume suitable data, if necessary.

Q1) a) Write a short note on ‘Zones of Protection’ [4]
b) The time-current characteristics of an overcurrent relay for TMS=1 is as
given below. [6]

PSM 2 3 5 7 10 13 15 18 20
Operating 
time
10 6.8 4.4 3.4 2.8 2.5 2.4 2.3 2.2


If current plug setting is adjusted to 50% and the time multiplier is
adjusted to 0.75, Calculate the time of operation of relay when the fault
current is 3000 A and the relay is connected to a CT ratio 400/5.

OR


Q2) a) Draw and explain the trip circuit breaker. [4]
b) What are the essential qualities of protective relaying? Explain in details.[6]

Q3) a) Explain the concept of current chopping with neat waveform. [4]
b) Explain high and low resistance interruption principle of circuit breaker.[6]

OR

Q4) a) Explain the resistance switching in case of circuit breaker. [4]
b) Derive the equation for restriking voltage and rate of rise of restriking voltage (RRRV) [6]

Q5) a) Explain the following terms with respect to circuit breaker. [4]
i) Breaking capacity
ii) Making capacity
b) Explain construction and working of Air circuit breaker. [6]

OR


Q6) a) Explain what is autoreclosing in circuit breaker. [4]
b) With neat diagram explain the construction and working of puffer type SF6 circuit breaker. [6]

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