Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Summer 7th Sem New 2170908 Switch Gear And Protection Previous Question Paper
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?VII(NEW) EXAMINATION ? SUMMER 2019
Subject Code:2170908 Date:14/05/2019
Subject Name:Switch Gear and Protection
Time:02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
MARKS
Q.1 (a) Define following terms in context to protective relay (i) Reliability (ii)
Selectivity (iii) Discrimination
03
(b) Discuss necessity of Back up protection and types of backup protection in brief. 04
(c) Explain the principle of Directional relay with the help of appropriate phasor
diagram. Also explain the significance of maximum torque angle of the
directional relay.
07
Q.2 (a) Prove that the slope of the internal fault characteristics for a single-end fed
system is 200%.
03
(b) What are the drawbacks of a simple differential scheme? Explain how the
percentage differential relay overcomes the drawbacks of simple differential
relay.
04
(c) What are incipient faults? Discuss in detail the type of protection provided in
transformer to cater to such type of faults.
07
OR
(c) Explain the 3 zone protection of transmission line using MHO relays. How
under-reach and over-reach are set to avoid in this type of protection?
07
Q.3 (a) List and Explain various options for implementing the carrier communication
channel.
03
(b) How do different distance relays perform with respect to their behavior on load,
effect of arc resistance on the reach and response to power swing?
04
(c) Explain the operation of the unit type of carrier based directional protection. 07
OR
Q.3 (a) Differentiate between longitudinal and transverse differential protection in
context to generator protection.
03
(b) What causes loss of prime mover? Can a generator be allowed to run with its
prime mover lost? If not, why?
04
(c) Explain various abnormal conditions to which a modern turbo alternator is likely
to be subjected.
07
Q.4 (a) Why is protection of an induction motor against reversal of phase sequence
required?
03
(b) Explain ratio error and phase angle error in CTs. 04
(c) List and explain various abnormal conditions an induction motor is likely to be
subjected.
07
OR
Q.4 (a) List and explain advantages of numerical relays over other conventional relays. 03
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1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ?VII(NEW) EXAMINATION ? SUMMER 2019
Subject Code:2170908 Date:14/05/2019
Subject Name:Switch Gear and Protection
Time:02:30 PM TO 05:00 PM Total Marks: 70
Instructions:
1. Attempt all questions.
2. Make suitable assumptions wherever necessary.
3. Figures to the right indicate full marks.
MARKS
Q.1 (a) Define following terms in context to protective relay (i) Reliability (ii)
Selectivity (iii) Discrimination
03
(b) Discuss necessity of Back up protection and types of backup protection in brief. 04
(c) Explain the principle of Directional relay with the help of appropriate phasor
diagram. Also explain the significance of maximum torque angle of the
directional relay.
07
Q.2 (a) Prove that the slope of the internal fault characteristics for a single-end fed
system is 200%.
03
(b) What are the drawbacks of a simple differential scheme? Explain how the
percentage differential relay overcomes the drawbacks of simple differential
relay.
04
(c) What are incipient faults? Discuss in detail the type of protection provided in
transformer to cater to such type of faults.
07
OR
(c) Explain the 3 zone protection of transmission line using MHO relays. How
under-reach and over-reach are set to avoid in this type of protection?
07
Q.3 (a) List and Explain various options for implementing the carrier communication
channel.
03
(b) How do different distance relays perform with respect to their behavior on load,
effect of arc resistance on the reach and response to power swing?
04
(c) Explain the operation of the unit type of carrier based directional protection. 07
OR
Q.3 (a) Differentiate between longitudinal and transverse differential protection in
context to generator protection.
03
(b) What causes loss of prime mover? Can a generator be allowed to run with its
prime mover lost? If not, why?
04
(c) Explain various abnormal conditions to which a modern turbo alternator is likely
to be subjected.
07
Q.4 (a) Why is protection of an induction motor against reversal of phase sequence
required?
03
(b) Explain ratio error and phase angle error in CTs. 04
(c) List and explain various abnormal conditions an induction motor is likely to be
subjected.
07
OR
Q.4 (a) List and explain advantages of numerical relays over other conventional relays. 03
2
(b) Define following terms (i) Recovery voltage (ii) Re-striking voltage (iii) RRRV.
Derive an expression for the restiking voltage in terms of system inductance and
capacitance.
04
(c) Draw and explain block diagram of Numerical relay. 07
Q.5 (a) What causes the initiation of electric arc at the instant of contact separation ?
Which of these is chiefly responsible for the creation of arc in circuit breaker
and why?
03
(b) Explain current chopping in brief. 04
(c) Explain auto reclosing. 07
OR
Q.5 (a) List the properties of SF6 gas and its advantages over other arc quenching
medium.
03
(b) Explain following terms: symmetrical breaking current, asymmetrical breaking
current & making current as applied to circuit breaker and show how these
currents can be determined from oscillograms taken during short circuit tests on
a three phase circuit breaker.
04
(c) Write short note on vacuum circuit breaker. 07
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This post was last modified on 20 February 2020