Download AKTU (Dr. A.P.J. Abdul Kalam Technical University (AKTU), formerly Uttar Pradesh Technical University (UPTU) B-Tech 5th Semester (Fifth Semester) 2016-2017 Elements Of Power System Nee 501 Question Paper
(Following Paper ID and Roll No. to be ?lled in your
I?upcr ID: 2012377
Answer Books)
Roll No.
B.TECH.
Regular Theory Examination(0dd Sem-V) 20 16-17
ELEMENTS OF POWER SYSTEM
Time : 3 Hours . Max. Marks ,: 100
Section - A
l Attempt all parts. All parts carry equal marks. Write
answer of each part in short. (l0><2=20)
a) Draw the symbols of various components of a power
system. which are used in Single-Line diagram
representation.
b) Explain the following components of distribution
power system
i) Feeder ii) Service mains
0) Draw and explain 3-Wire dc system.
(1) Why receiving end voltage appears high compared
to sending end voltage in case of lightly loaded-
transmission lines?
e) . What is the need for stranding the conductors?
f) What is proximity effect?
g) Why is leakage condUctance negligible in overhead
lines?
501/11/2016/5600 _(1) . [P.T.O.
, NEE-501
h) What is the mechanism of breakdown of an under
ground cable?
i) Where do we use grounding transformer?
j) What is meant by ?Skin effect??
Section, - B
Note: Attempt any five questions fi?om this section
2.
(5X10=50)
What is the difference between isolator and circuit
breaker? A single phase ac system supplies a load of 200
kW and if this system is converted to 3-phase, 3-wire ac
system by running a third similar conductor, calculate the
3-phase load that can now be supplied if the voltage
between the conductors is the same. Assume p.f. and
transmission ef?ciency to be same in both cases.
Explain the limitations of ?Kelvin law?. A 2-wire feeder
carries a constant current of 250A throngh out the year. .
The portion of capital cost which is proportional to the
area of cross section is Rs. 5 per kg of copper conductor.
The interest and depreciation 0ft0ta1 10% per annum and
the cost of energy is 5 paisa per kWh. F ind the most
economical area of cross section of the conductor. Given
that the density of copper is 8.93 gm/cm2 and its speci?c
resistance is 1.73 x 10?8 9?" .
F ind the inductance per phase per Km of double c'ircuit
3-phase line system shown in ?g (1). The conductors are
transposed and are of radius 0.75 cm each. The phase
sequence is abc.
NEE-501
H ,
4' l n C.
5m
__ L F-Sm .
b . 045m * o-m b?
3m
,4?
c. 4?
99??
Explain Corona loss. How is disruptive critical voltage
estimated? Give advantages'and disadvantages ofCorona ,
loss.
A string of n suspension insulators is to be ?tted with a
guard ring. If the pin to earth capacitance are all equal to
C, derive the general expression for the line to pin
capacitor in terms of n, C and P (number of pins), so as
to give uniform voltage distribution over the string.
Why do the vibrations get generated in conductors? How
are they damped? '
A 132 KV transmission line has the following data :
Wt. ofconductor = 680 kg/km; Length .of span = 260 m
Ultimate strength = 3100 kg; Safety factor = 2
Calculate the height above ground at which the conductor
should be supported. Ground clearance required is 10 m.
501/ 1 1/2016/5600 (2)
501/11/2016/5600 (3) [P.T.O.
NEE-SOI
With the help of the phasor diagram and mathematical
equations, explain the method and advantages of resonant
grounding.
Explain the factors, which are considered during designing
a transmission line? Also explain how ground wire
selection is done.
Section - C
Note: Attempt any two questions from this section
10.
ll.
12.
. g (2X15=30)
What are the commonly used insulating materials for
underground cables? Describe with a neat sketch, the
construction of a 3-core belted-type cable.
Calculate the KVA taken by a 10 km long, 3 -phase 3-core
cable, if the capacitance measured between any two cores
is 0.3 pF/km when it is connected to 10 KV, 50 Hz bus-
bar.
Describe the various conductor con?gurations and choice
of number of circuits for EHV transmission lines.
Compare HVDC with HVAC transmission on at least 5
major grounds.
Explain surge impedance loading. Determine ABCD
constants for a 3-phase 50 Hz transmission line 200 km
long having the following distributed parameters
1:1. 3 x 10?3H/Km, C: 9 x10-9F/Km,r=0.20?2/Km
g= 0.
++++
501/11/2016/5600 (4)
This post was last modified on 29 January 2020