Exam.
Code: 0934
Sub. Code: 6663
2023
B.E. (Electrical and Electronics Engineering)
urth Semester
\}E-/:OD& Power Systems - I
Time allowed: 3 Hours
Max. Marks: 50
NOTE: Attempt five questions in all, including Quest
ion No. I which is compulsory
and selecting two questions JSrom each Part,
Missing data (if any) can be
appropriately assumed,
X-X-X
14) Advantages of per unit system.
B) Explain the term line loadability. (2)
o} Differentiate the stranded and bundle conductors ()
used in transmission lines,
D) Write all the effects of vibrations occur in overhead 2)
transmission lines.
E) What is the effect of considering the images (2)
of the conductors in. the calculation of-
inductance and capacitance of the transmission (0]
lines?
Part A
24) A 50-MVA, 1 1-kV, three-phase generator
has a sub-transient reactance of 10%.
generator connected to the power system
shown has the following specifications:
The (5)
Q% e @0
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Load
Generator Gy : 50-MVA, 1 1-kV, three-phase
generator, X" = 0.10 pu
Generator G,: 40-MVA, 6.6-kV, three-phase
generator, X" = 0,12 pu
Transformer T,: Three-phase transformer,
100 MVA, 1 1/220 kV,X=0.15pu *
Transformer T,: Thrée single-phase units
each rated 50 MVA, 6.6/132 kV, X = 0.10
Load: 75 MVA at 0.8 pf lagging pu
Transmission line: Z;,.= 30 +]150 Q; Zss = 20
+j40 Q; Zys = 25 +j60Q
Assuming a volt-ampere base of 150 MVA,
compute the pu values for the power
Draw
system.
a single line diagram of the power system and show the pu values of the system
parameters.
i
B) Explain all types of the Conductors used
in the power transmission lines with suita
ble (5)
diagrams.
34) Draw the cross section o% a three-core belted
high voltage cable and describe its variou
parts. s (5)
B) What is meant with the grading of the cable
s? Explain why and how the grading of cable
s
is done.
P.T.O.
<
Sub. Code: 6662
)
4A) Explain in details with
suitable diagram all methods
efficiency of the insulators, l{‘sed for the improvement
in string
St
B) Write a short note on the
reflectioh .and refraction
lines. of travelling waves'in tra
1 nsmission
E G
Part B
5A) A three-phase, 400-kV,
50-Hz, fully transposed
circuit is constituted of
and is arranged as sho bundle cor;ductors
wn If the outside diamet
er of each conductor (5)
the series resistance, series is 2.0 cm, calculate
reactance, and shunt admitt
conductors ance per km when the thr
share equal currents and ee
equal charge magnitudes.
temperature equal to 70°, Take the conductor
Assume the following dat
and temperature coeffi
a: resistance at 20°C = 0,22
cient of con Q per km
ductor = 0.0043 per °C,
reactance, and shunt adm Calculate the series res
ittance if the length of istance,
the line is 200 km.
F OO e s
,1“1501—‘“44———-—_
.15111
B) What is transposition of
a transmission line? Why
is it necessary? Derive an expression
for the inductance of & thr
ee-phase fully transposed
line. ()
6A)
(5)
clearance is 5 m.
Derive expressions for the
Inductance of a conductor
external flux, due to (i) internal flux and
(ii) (5)
‘7A) Derive expressions for the
ABCD constants for a lossless
distributed paraméters for long transmission line. Assume
the line, : (5)
B) Prove that the voltage at
the mid-point of a long line
terminated at the receivin
an inductive shunt'reactor g end by
Xisn, is @ maximum and is give
n by Vr/cos(Bl/2). Take the
(5)
of the line equal to / and length
Vg/ Va= 1.0. Also show that
the current at mid-point is
Assume that the ling is IGss free. zero
X-X-X
