Download GTU (Gujarat Technological University) BE/BTech (Bachelor of Engineering / Bachelor of Technology) 2019 Winter 6th Sem New 2160908 Electrical Power System ? Ii Previous Question Paper
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ? VI (New) EXAMINATION ? WINTER 2019
Subject Code: 2160908 Date: 06/12/2019
Subject Name: Electrical Power system ? II
Time: 02:30 AM 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) Write voltage and current relationship of transmission line using A, B,
C, D parameters. Write expression of A, B, C, D parameter in terms of
Y and Z for medium transmission line and long transmission line.
03
(b) Define positive, negative and zero sequence component. 04
(c) Derive equation of voltage and current of long transmission line
considering uniformly distributed parameters through the line.
07
Q.2 (a) Draw wave form of short circuit current of an alternator. Explain the
subtransient, transient and steady state period.
03
(b) Explain Reactive power compensation of transmission line in brief. 04
(c) A 3-phase 50 Hz, 120 km transmission line has following parameters.
R= 0.2?/km, L= 1.2 mH/km and c= 0.014?f/ km. Determine sending
end voltage and efficiency. A line delivering power of 45 MW at
132KV and 0.85 power factor lagging. Use Nominal T method for
calculation.
07
OR
(c) The voltage across three phase unbalanced load are Va=200<40?,
Vb=320<90?, Vc =480 <340?.Determine symmetrical component of
voltage. Phase sequence abc.
07
Q.3 (a) Classify transmission line. 03
(b) Draw and Explain zero sequence network of transformer for Y-Y, ?-
?, ?-Y, Y-? connection with and without neutral grounded
04
(c) Obtain expression of three phase power in terms of sequences
component.
07
OR
Q.3 (a) Explain any two causes which are producing Transient on line. 03
(b) Explain zero sequence impedance and network for synchronous
machine.
04
(c) Write criteria for selection of circuit breaker. 07
Q.4 (a) Define surge impedance. Explain surge impedance loading of
transmission line.
03
(b) A 50 MVA, 11KV, 3-phase synchronous generator was subjected to 3-
phase fault and line to line fault. A generator neutral is solidly
grounded. Find out positive sequence and negative sequence reactance
of synchronous generator if 3-phase fault is 1780A and line to line fault
current is 2590A.
04
(c) Derive expression for fault current for single line to ground fault as an
unloaded generator.
07
OR
Q.4 (a) Give model of synchronous machine with load under transient
condition.
03
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1
Seat No.: ________ Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE - SEMESTER ? VI (New) EXAMINATION ? WINTER 2019
Subject Code: 2160908 Date: 06/12/2019
Subject Name: Electrical Power system ? II
Time: 02:30 AM 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) Write voltage and current relationship of transmission line using A, B,
C, D parameters. Write expression of A, B, C, D parameter in terms of
Y and Z for medium transmission line and long transmission line.
03
(b) Define positive, negative and zero sequence component. 04
(c) Derive equation of voltage and current of long transmission line
considering uniformly distributed parameters through the line.
07
Q.2 (a) Draw wave form of short circuit current of an alternator. Explain the
subtransient, transient and steady state period.
03
(b) Explain Reactive power compensation of transmission line in brief. 04
(c) A 3-phase 50 Hz, 120 km transmission line has following parameters.
R= 0.2?/km, L= 1.2 mH/km and c= 0.014?f/ km. Determine sending
end voltage and efficiency. A line delivering power of 45 MW at
132KV and 0.85 power factor lagging. Use Nominal T method for
calculation.
07
OR
(c) The voltage across three phase unbalanced load are Va=200<40?,
Vb=320<90?, Vc =480 <340?.Determine symmetrical component of
voltage. Phase sequence abc.
07
Q.3 (a) Classify transmission line. 03
(b) Draw and Explain zero sequence network of transformer for Y-Y, ?-
?, ?-Y, Y-? connection with and without neutral grounded
04
(c) Obtain expression of three phase power in terms of sequences
component.
07
OR
Q.3 (a) Explain any two causes which are producing Transient on line. 03
(b) Explain zero sequence impedance and network for synchronous
machine.
04
(c) Write criteria for selection of circuit breaker. 07
Q.4 (a) Define surge impedance. Explain surge impedance loading of
transmission line.
03
(b) A 50 MVA, 11KV, 3-phase synchronous generator was subjected to 3-
phase fault and line to line fault. A generator neutral is solidly
grounded. Find out positive sequence and negative sequence reactance
of synchronous generator if 3-phase fault is 1780A and line to line fault
current is 2590A.
04
(c) Derive expression for fault current for single line to ground fault as an
unloaded generator.
07
OR
Q.4 (a) Give model of synchronous machine with load under transient
condition.
03
2
(b) A 132 KV 3-phase transmission line has equilateral spacing D eq=
3m.The conductor radius = 10 mm, Temperature = 22?C and pressure
= 73 cm of Hg. Surface factor mo = 0.84. Obtain relative density and
critical disruptive voltage.
04
(c) Derive equation of restriking voltage across circuit breaker after
removal of short circuit.
07
Q.5 (a) Write methods of reducing corona. 03
(b) Discuss capacitance switching. 04
(c) Consider the three bus system shown in fig.1 the generators are 100
MVA with a transient reactance of 10% each. Both the transformers are
100MVA with a leakage reactance of 5% The reactance of each line to
a base of 100 MVA. 110KV is 10%. Find the value of fault current for
a three phase solid short circuit on bus no: 3. Assume prefault voltages
to be 1.0 p.u. and prefault currents to be zero.
07
OR
Q.5 (a) Discuss the phenomena of wave reflection and wave refraction. 03
(b) Describe formation of corona in H.V. transmission line. write merits
and demerits of Corona
04
(c) Introduce symmetrical components and state their application. Derive
symmetrical components of a given set of three unbalanced line.
07
fig.1
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This post was last modified on 20 February 2020