Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Winter 7th Sem New 2170908 Switch Gear And Protection Previous Question Paper
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ? VII (New) EXAMINATION ? WINTER 2019
Subject Code: 2170908 Date: 26/11/2019
Subject Name: Switch Gear and Protection
Time: 10:30 AM TO 01:00 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) With neat diagram explain the working of shaded pole type
electromagnetic induction disc relay.
03
(b) Classify the types of relays with respect to different category. 04
(c) Explain the following protection scheme as applied to synchronous
generator:
(a) Loss of excitation protection
(b) Stator inter-turn fault protection
07
Q.2 (a) Discuss the difficulties in implementing HVDC circuit breaker. 03
(b) Explain the behavior of Merz?Price protection during normal load,
external fault and internal fault condition.
04
(c) Compare the performance of distance relay in respect of its sensitivity to
following:
(a) Effect of arc resistance,
(b) Effect of power swing
(c) Directional property
07
OR
(c) Select CT ratios and determine the TMS, and Plug setting of the IDMT
relays at location O and A, for the over-current protection of radial feeder
shown in Fig.1. The characteristic of IDMT relay is given in the Table-2.
Minimum fault currents at each point are given Table-1. Maximum load
current from each bus are indicated in the Fig. ___.
Location O Location A Location B
If,Min 3000 A 2000 A 1000 A
Table-1
PSM 2 3 3.6 5.5 6 8 10 18
Top for TMS=1 10 6.2 5 4.25 4 3.5 3 2.1
Table-2
07
Q.3 (a) Draw logic diagram for implementing 3-step distance protection scheme
using impedance relay.
03
(b) Explain the loss of excitation protection as applied to synchronous motor. 04
(c) Which are the types of SF6 circuit breaker? With neat diagram, explain
the working of Puffer type SF6 circuit breaker.
07
OR
Q.3 (a) Explain the line trap units for carrier-aided protection of transmission line. 03
(b) What are the advantages of carrier current protection scheme? 04
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Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ? VII (New) EXAMINATION ? WINTER 2019
Subject Code: 2170908 Date: 26/11/2019
Subject Name: Switch Gear and Protection
Time: 10:30 AM TO 01:00 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) With neat diagram explain the working of shaded pole type
electromagnetic induction disc relay.
03
(b) Classify the types of relays with respect to different category. 04
(c) Explain the following protection scheme as applied to synchronous
generator:
(a) Loss of excitation protection
(b) Stator inter-turn fault protection
07
Q.2 (a) Discuss the difficulties in implementing HVDC circuit breaker. 03
(b) Explain the behavior of Merz?Price protection during normal load,
external fault and internal fault condition.
04
(c) Compare the performance of distance relay in respect of its sensitivity to
following:
(a) Effect of arc resistance,
(b) Effect of power swing
(c) Directional property
07
OR
(c) Select CT ratios and determine the TMS, and Plug setting of the IDMT
relays at location O and A, for the over-current protection of radial feeder
shown in Fig.1. The characteristic of IDMT relay is given in the Table-2.
Minimum fault currents at each point are given Table-1. Maximum load
current from each bus are indicated in the Fig. ___.
Location O Location A Location B
If,Min 3000 A 2000 A 1000 A
Table-1
PSM 2 3 3.6 5.5 6 8 10 18
Top for TMS=1 10 6.2 5 4.25 4 3.5 3 2.1
Table-2
07
Q.3 (a) Draw logic diagram for implementing 3-step distance protection scheme
using impedance relay.
03
(b) Explain the loss of excitation protection as applied to synchronous motor. 04
(c) Which are the types of SF6 circuit breaker? With neat diagram, explain
the working of Puffer type SF6 circuit breaker.
07
OR
Q.3 (a) Explain the line trap units for carrier-aided protection of transmission line. 03
(b) What are the advantages of carrier current protection scheme? 04
2
(c) With the help of schematic block diagram, explain the realization of
transformer protection using numerical protection.
07
Q.4 (a) Draw the flow chart for implementing over current protection scheme
using numerical relay.
03
(b) Differentiate between transfer trip and permissive inter trip. 04
(c) Determine the plug setting and % bias setting to permit 25% overload for
50 MVA, 132 kV/66 kV, delta-star transformer. The CT ratios on delta
and star side is 300/5 and 1200/5 respectively.
07
OR
Q.4 (a) Explain Slepian?s theory of arc interruption. 03
(b) Explain the phenomena of field emission and thermionic emission at the
time of contact separation in circuit breaker.
04
(c) To obtain complete damping of transient oscillations analyze the critical
value of shunt resistance. Also draw transient oscillations for different
values of R.
07
Q.5 (a) Classify the various types of faults and abnormal condition in motors. 03
(b) Explain the application of reverse phasing protection to induction motor. 04
(c) Analyze the performance of the CT by drawing its equivalent circuit and
vector diagram. Also differentiate between protective CT and measuring
CT.
07
OR
Q.5 (a)
Define reach, under reach, and over reach of the relay.
03
(b) Classify the faults and abnormal operating conditions in synchronous
machine.
04
(c) A 50 Hz, 13.6 kV, 3-phase alternator with grounded neutral has inductance
of 12 mH per phase and is connected to busbar through a circuit breaker.
The capacitance to earth between the alternator and the location of circuit
breaker is 0.03?F per phase. Neglect the resistance of the alternator.
calculate the following:
i) Maximum value of restriking voltage across the contacts of
circuit breaker.
ii) Frequency of transient oscillations
iii) Maximum value of RRRV
07
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This post was last modified on 20 February 2020