WorksheetsT&D Quiz Unit 2
Total questions: 30
Worksheet time: 34mins
The length of a transmission line is 100km and the line voltage is 66kv. The line is considered to be
Short
Medium
Long
Very long
The sending end voltage of a transmission line is 150KV and the receiving end voltage is 100KV. The voltage regulation is
20%
40%
50%
100%
The transmission efficiency for a short transmission line delivering 50MW whose sending end voltage is 110KV, sending end pf is 0.9 and receiving end current is 280A is
90%
94%
96%
98%
Considering ABCD parameters for a transmission line, for a symmetrical network
A=B
A=C
B=C
A=D
Considering ABCD parameters for a transmission line, for a reciprocal network,
AB-CD=0
AD-BC=1
AB-CD=1
AC-BD=1
The characteristic impedance of a transmission line is given by
Sqrt(z/y)
Sqrt(z.y)
Sqrt(y/z)
Sqrt(1/yz)
The propagation constant of a transmission line is given by
Sqrt(z/y)
Sqrt(z.y)
Sqrt(y/z)
Sqrt(1/yz)
The surge impedance loading of a line is the power delivered by a line to a load impedance
L=Sqrt(R/C)
R=Sqrt(L/C)
L=Sqrt(RC)
R=Sqrt(LC)
The supply voltage in diagram shown is
210V
70V
50V
230V
Ferranti effect on long overhead lines is experienced when it is
Lightly loaded
On full load at unity pf
On full load at 0.8pf lag
In all these cases
Corona loss is less when the shape of the conductor is
Circular
Flat
Oval
Independent of shape
Corona loss increases with
Increase in supply frequency and conductor size
Increase in supply frequency but reduction in conductor size
Decrease in supply frequency and conductor size
Decrease in supply frequency but increase in conductor size
The corona loss on a particular system at 50Hz is 1KW per phase per KM.The corona loss on the same system with supply frequency 25Hz will be
1KW / Phase / KM
0.5KW / phase / KM
0.667KW / phase / KM
None of the above
A transmission line of 80KM length is operating at 400Hz, it can be classified as
Short line
Medium line
Long line
All of the above
The voltage and current in a circuit are given by
v=10sin(wt-pi/6)
i=10sin(wt+pi/6)
The power consumed is given as
100 watts
50 watts
86.6 watts
25 watts
Which of the following statements regarding corona are true?
1) It causes radio interference
2) It attenuates lightning surges
3) It amplifies switching surges
4) It causes power loss
5) It is more prevalent in the middle conductor of a transmission line employing a flat configuration
1, 3 and 5
2, 3 and 4
1,2,4 and 5
2,3,4 and 5
Corona loss can be reduced by the use of hollow conductor because
the current density is reduced
the eddy current in the conductor is eliminated
for a given cross section, the radius of the conductor is increased
of better ventilation in the conductor
For a transmission line with resistance R, reactance X and negligible capacitance, the transmission constant A is
0
1
R+jX
R+X
The charging current in a transmission line increases due to corona effect because corona increases
Line current
Effective line voltage
Power loss in lines
Effective conductor diameter
If in a short transmission line, resistance and inductive reactance are found to be equal and regulation appears to be zero, then the load will have
Unity power factor
Zero power factor
0.707 leading power factor
0.707 lagging power factor
For a transmission line with negligible losses, the laggign reactive power delivered at the receiving end for a given receiving end voltage is directly proportional to the
square of the line voltage drop
line voltage drop
line inductive reactance
line capacitive reactance
A 50Hz, 3 phase transmission line of length 100KM has a capacitance of 0.03/(pi) microfarad/KM. It is represented as a Pi model. The shunt admittance at each end of the transmission line will be
150x10e-6 mho
100x10e-6 mho
50x10e-6 mho
10e6 / 50 mho
A 3 phase line having negligible resistance and 22 ohm inductive reactance per phase operates with 110KV sending end voltage and 100KV receiving end voltage. The maximum power that the line can transmit is
500*(sqrt 3) MW
500 MW
1500 MW
500 / sqrt(3) MW
In which one of the following models of transmission lines, is the full charging current assumed to flow over half the length of the line only?
Equivalent Pi
Short line
Nominal Pi
Nominal T
If Vs = Vr = 66KV for a three phase transmission line and reactance is 11 ohms/phase, then the maximum power transmission per phase would be
132 MW
396 MW
66 MW
None of the above
The values of A, B, C and D constants for a short transmission line are respectively
Z, 0, 1 and 1
0, 1, 1 and 1
1, Z, 0 and 1
1, 1, Z and 0
The ABCD constants of a 3 phase transmission line are
A = D = 0.8 at angle 1 degree
B = 170 at angle 85 degrees
C = 0.002 at angle 90.4 degrees.
The sending end voltage is 400KV. The receiving end voltage under no load condition is
400 KV
500 KV
320 KV
417 KV
In a short transmission line, voltage regulation is zero when the power factor angle of the load at the receiving end is
tan-1(X/R)
tan-1(R/X)
tan-1(X/Z)
tan-1(R/Z)
Surge impedance loading of a transmission line can be increased by
1) Increasing its voltage level
2) Addition of lumped inductance in parallel
3) Addition of lumped capacitance in series
4) Reducing the length of the line
Of these statements,
1 and 3 are correct
1 and 4 are correct
2 and 4 are correct
3 and 4 are correct
The good effect of corona on overhead lines is to
Increase the line current carrying capacity
Increase the power factor due to corona loss
reduce radio interference from the conductor
reduce the steepness of surge fronts
