Download GTU (Gujarat Technological University Ahmedabad) B.Tech/BE (Bachelor of Technology/ Bachelor of Engineering) 2020 Winter 5th Sem 2150908 Electrical Power System I Previous Question Paper
Enrolment No.___________
GUJARAT TECHNOLOGICAL UNIVERSITY
BE- SEMESTER?V (NEW) EXAMINATION ? WINTER 2020
Subject Code:2150908 Date:20/01/2021
Subject Name:Electrical Power System ? I
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) Discuss the advantage of high transmission voltage
03
(b) State and prove the Kelvin`s law for size of conductor for
04
transmission.
(c) A 50 Km long transmission line supplies load of 5 MVA at 0.8
07
p.f lag at 33 KV. The efficiency of the transmission line is 90
%. Calculate the volume of conductor Aluminum required for
the single phase 2 wire system. Take resistivity of Aluminum
transmission trans
as 2.85 ?10 -8 .mt
Q.2 (a) What is skin effect why it is absent in d.c
03
(b) What is the effect of unsymmetrical spacing of conductor in
04
three phase transmission system?
(c) Drive the expression for the capacitance of single phase
07
transmission line.
Q.3 (a) Define and explain string efficiency. Can its value be equal to
03
100?
(b) Give reasons for the following :
04
(i) A.C.S.R. conductors are preferred for transmission and
distribution lines.
(ii) Conductors are not fully stretched between supports
(c) An insulator string consist of three units, each having a safe
07
working voltage of 15kv. The ratio of self-capacitance to shunt
capacitance of each unit is 8:1. Find the maximum safe
working voltage of the string. Also find string efficiency.
Q.4 (a) List out line supports with its three features
03
(b) What are the factors that affect the sag in the transmission line?
04
(c) Discuss the various conductor material used for overhead line.
07
What are their relative advantages and disadvantages?
Q.5 (a) What is the main difference between AC and DC distribution
03
system
(b) Drive the expression for capacitance of single core cable.
04
(c) Discuss the advantages and disadvantages of (i) pin type
07
insulator (ii) suspension type insulator
Q.6 (a) With neat diagram, show the various part of high voltage
03
single core cable
1
(b) What is the difference between radial, ring and interconnected
04
distribution system?
(c) Explain the following method for cable grading:
07
(i)Capacitance grading(ii) Intersheath grading
Q.7 (a) What are the advantages of per unit system
03
(b) How the current distribution and the voltage at various loading
04
points can be determined in a DC ring type distribution
system?
(c) A DC two wire distributor 250 m long and fed at one end is
07
load uniformly at the rate of 1.6A/meter. Total resistance of
the distributor is 0.0002 ohms/meter. Determine the voltage at
the fed to maintain at 250 V. (i) at far end (ii) at the midpoint
of distributer.
Q.8 (a) Define and explain primary and secondary distribution system
03
with single line diagram
(b) Represent p.u model of transformer with and without tap
04
changer.
(c) Derive expression for inductance per phase for 3-ph overhead
07
transmission line when conductors are asymmetrically place
but transposed
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This post was last modified on 04 March 2021