21. A lightning stroke discharges impulse current of 10 kA (peak) on a 400 kV transmission line having surge impedance of 250 ohm. The magnitude of transient over voltage travelling waves in either direction assuming equal distribution from the point of lightning strike will be
a) 1250 kV
b) 1650 kV
c) 2500 kV
d) 2900 kV
ans. a
22. The insulation strength of an EHV transmission line is mainly governed by
a) load power factor
b) switching overvoltages
c) harmonics
d) corona
ans. b
23. Steady-state stability of a power system is the ability of the power system to
a) maintain voltage at the rated voltage level
b) maintain frequency exactly at 50Hz
c) maintain a spinning reserve margin at all times.
d) maintain synchronism between machines and on external tie lines.
ans. d
24. The load carrying capability of a long ac transmission line is
a) always limited by the conductor size
b) limited by stability considerations.
c) reduced at low ambient temperatures.
d) decreased by the use of bundled conductors of single conductors.
ans. b
25. An 800 kV transmission line is having per phase line inductance of 1.1 mH/km and per phase line capacitance of 11.68 nF/km. Ignoring the length of the line , its ideal power transfer capability in MW is
a) 1204 MW
b) 1504 MW
c) 2085 MW
d) 2606 MW
ans. c
26. An 800 kV transmission line has a maximum power transfer capacity of P. If it is operated at 400 kV with the series reactance unchanged, then maximum power transfer capacity is approximately
a) P
b) 2P
c) P/2
d) P/4
ans. d
27. A round rotor generator with internal voltage E1=2.0 pu and X=1.1 pu is connected to a round rotor sysnchronous motor with internal voltage E2= 1.3 pu and X= 1.2 pu. The reactance of the line connecting the generator supplies 0.5 pu power, the rotor angle difference between the machines will be
a) 57.42 degrees
b) 1 degree
c) 32.58 degrees
d) 122.58 degrees
ans. c
28. The pu parameters for a 500 MVA machine on its own base are: inertia , M= 20 pu ; reactance ,X= pu.
The pu values of inertia and reactance on 100 MVA common base, respectively, are
a) 4, 0.4
b) 100, 10
c) 4, 10
d) 100,0.4
ans. d
29. A power station consists of two synchronous A and B of ratings 250 MVA and 500 MVA with inertia 1.6 and 1.0 pu respectively on their own base MVA ratings. The equivalent pu inertia constant for the system on 100 MVA common base is
a) 2.6
b) 6.15
c) 1.625
d) 9
ans. d
30. A shunt reactor of 100 MVAr is operated at 98% of its rated voltage and at 96% of its rated frequency. The reactive power absorbed by the reactor is
a) 98. MVAr
b) 10.402 MVAr
c) 96.04 MVAr
d) 100 MVAr
ans. d
a) 1250 kV
b) 1650 kV
c) 2500 kV
d) 2900 kV
ans. a
22. The insulation strength of an EHV transmission line is mainly governed by
a) load power factor
b) switching overvoltages
c) harmonics
d) corona
ans. b
23. Steady-state stability of a power system is the ability of the power system to
a) maintain voltage at the rated voltage level
b) maintain frequency exactly at 50Hz
c) maintain a spinning reserve margin at all times.
d) maintain synchronism between machines and on external tie lines.
ans. d
24. The load carrying capability of a long ac transmission line is
a) always limited by the conductor size
b) limited by stability considerations.
c) reduced at low ambient temperatures.
d) decreased by the use of bundled conductors of single conductors.
ans. b
25. An 800 kV transmission line is having per phase line inductance of 1.1 mH/km and per phase line capacitance of 11.68 nF/km. Ignoring the length of the line , its ideal power transfer capability in MW is
a) 1204 MW
b) 1504 MW
c) 2085 MW
d) 2606 MW
ans. c
26. An 800 kV transmission line has a maximum power transfer capacity of P. If it is operated at 400 kV with the series reactance unchanged, then maximum power transfer capacity is approximately
a) P
b) 2P
c) P/2
d) P/4
ans. d
27. A round rotor generator with internal voltage E1=2.0 pu and X=1.1 pu is connected to a round rotor sysnchronous motor with internal voltage E2= 1.3 pu and X= 1.2 pu. The reactance of the line connecting the generator supplies 0.5 pu power, the rotor angle difference between the machines will be
a) 57.42 degrees
b) 1 degree
c) 32.58 degrees
d) 122.58 degrees
ans. c
28. The pu parameters for a 500 MVA machine on its own base are: inertia , M= 20 pu ; reactance ,X= pu.
The pu values of inertia and reactance on 100 MVA common base, respectively, are
a) 4, 0.4
b) 100, 10
c) 4, 10
d) 100,0.4
ans. d
29. A power station consists of two synchronous A and B of ratings 250 MVA and 500 MVA with inertia 1.6 and 1.0 pu respectively on their own base MVA ratings. The equivalent pu inertia constant for the system on 100 MVA common base is
a) 2.6
b) 6.15
c) 1.625
d) 9
ans. d
30. A shunt reactor of 100 MVAr is operated at 98% of its rated voltage and at 96% of its rated frequency. The reactive power absorbed by the reactor is
a) 98. MVAr
b) 10.402 MVAr
c) 96.04 MVAr
d) 100 MVAr
ans. d
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