Download GTU (Gujarat Technological University Ahmedabad) B.Tech/BE (Bachelor of Technology/ Bachelor of Engineering) 2020 Winter 7th Sem 2170908 Switch Gear And Protection Previous Question Paper
Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE- SEMESTER?VII (NEW) EXAMINATION ? WINTER 2020
Subject Code:2170908 Date:21/01/2021
Subject Name:Switch Gear and Protection
Time:10:30 AM TO 12:30 PM Total Marks: 56
Instructions:
1. Attempt any FOUR questions out of EIGHT questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
MARKS
Q.1
(a) Define Following:
03
-Under reach and over reach of relay
-Plug setting multiplier
-Burden
(b) Explain Following with reference to Circuit Breaker:
04
(a) Breaking Current (b) Making Current
(c)
Discuss various zones of protection for a modern power system. Explain
07
primary and back-up protection.
Q.2
(a) Explain in brief, how the percentage differential relay overcomes the
03
drawbacks of simple differential relay.
(b) What is power swing in power system? Evaluate performance of distance
04
relay in case of a power swing.
(c)
A 10 MVA, 13.2 kv generator is protected by restricted earth fault
07
protection. The relay is set to operate on 20% out of balance current. If 85%
of the generator winding is supposed to be protected by the relay, find out
value of resistance to be added in the neutral circuit.
Q.3
(a) Why does a generator needed to be tripped in the case of loss of excitation?
03
(b) Explain following with respect to induction motor protection:
04
(a) Single phasing (b) ground fault
(c)
Explain with neat diagram: construction and working of the numerical
07
relay.
Q.4
(a) Explain why the first ground fault on the rotor does not cause any damage
03
while a second fault can be catastrophic.
(b) Explain following with respect to a circuit breaker:
04
Resistance switching
Arc chopping
(c)
Draw and explain protection of generator against unbalanced loading.
07
Q.5
(a) Why can the secondary of a protection CT not to be open circuited?
03
(b) Discuss the effects of arc resistance on impedance based protection scheme.
04
(c)
Drew and explain carrier current based transmission line protection
07
scheme.
1
Q.6
(a) What is the need of sample and hold circuit in a digital numeric relay?
03
(b) What is single phasing in Induction motor? How protection against single
04
phasing is provided?
(c)
Compare Impedance relay, reactance relay and mho/ offset mho relay for
07
transmission line protection.
Q.7
(a) Compose a suitable choice of circuit breakers for the following voltage
03
ranges with appropriate reason.
(a) 3.3kV to 33kV, (b) 400kV to 760kV.
(b) List important protections provided in a 100MW generator and explain harmonic
04
restrain relay.
(c)
In what manner the CTs are connected for biased differential protection of
07
transformer having (i) delta-star connection. (ii) star-star connection.
Give reason for the CT Connections employed.
Q.8
(a) Give difference between measurement CT and protection CT.
03
(b) Explain Restricted Earth Fault Protection for generator in detail.
04
(c)
Compare SF6 circuit breaker with Air blast circuit breaker.
07
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This post was last modified on 04 March 2021