POWER SYSTEMS MCQS SET 07
PER UNIT QUANTITIES
1.
A single phase distributor of 1 km long has resistance and reactance
per conductor of 0.1Ω and 0.15 Ωrespectively. If the far end voltage
Vb=200V and current is at 100A at 0.8 lag. At the midpoint a current of
100A is tapped at a pf of 0.6 pf with ref to voltage Vm at mid point.
The voltage magnitude at M is ________
a) 218V b) 200V c) 232V d) 220V
Answer: a
2. A single phase motor is connected to 400V, 50Hz supply. The motor draws a current of 31.7A at a power factor 0.7 lag. The capacitance required in parallel with motor to raise the power factor of 0.9 lag (in micro farads) is __________
a) 94.62 b) 282.81 c) 108.24 d) 46.87
Answer: a
3. A single phase motor is connected to 400V, 50Hz supply. The motor draws a current of 31.7A at a power factor 0.7 lag. The additional reactive power (in VAR) to be supplied by the capacitor bank will be ___________
a) 4756 b) 4873 c) 4299 d) 9055.3
Answer: a
4. A 275 kV TL has following line constants A=0.85ʟ5o, B=200ʟ75o. The active power received if the voltage to be maintained is 275kV will be __________
a) 117.63 b) 220 c) 120 d) 115.25
Answer: a
5. A 275 kV TL has following line constants A=0.85ʟ5o, B=200ʟ75o. The active power angle such that the voltage to be maintained at the other end will be 275 kV ____________
a) 22 b) 16 c) 18 d) 24
Answer: a
6. A power system has a maximum load of 15 MW. Annual load factor is 50%. The reserve capacity of plant is _____ if the plant capacity factor is 40%.
a) 3.75 MW b) 4.75 MW c) 18.75 MW d) 5.75 MW
Answer: a
a) 218V b) 200V c) 232V d) 220V
Answer: a
2. A single phase motor is connected to 400V, 50Hz supply. The motor draws a current of 31.7A at a power factor 0.7 lag. The capacitance required in parallel with motor to raise the power factor of 0.9 lag (in micro farads) is __________
a) 94.62 b) 282.81 c) 108.24 d) 46.87
Answer: a
3. A single phase motor is connected to 400V, 50Hz supply. The motor draws a current of 31.7A at a power factor 0.7 lag. The additional reactive power (in VAR) to be supplied by the capacitor bank will be ___________
a) 4756 b) 4873 c) 4299 d) 9055.3
Answer: a
4. A 275 kV TL has following line constants A=0.85ʟ5o, B=200ʟ75o. The active power received if the voltage to be maintained is 275kV will be __________
a) 117.63 b) 220 c) 120 d) 115.25
Answer: a
5. A 275 kV TL has following line constants A=0.85ʟ5o, B=200ʟ75o. The active power angle such that the voltage to be maintained at the other end will be 275 kV ____________
a) 22 b) 16 c) 18 d) 24
Answer: a
6. A power system has a maximum load of 15 MW. Annual load factor is 50%. The reserve capacity of plant is _____ if the plant capacity factor is 40%.
a) 3.75 MW b) 4.75 MW c) 18.75 MW d) 5.75 MW
Answer: a
7.
A 100 MVA synchronous generator operates on full load at a frequency of
50 Hz. The load is suddenly reduced to 50 MW. Due to time lag in
governor system, the steam valve begins to close after 0.4s. The change
in the frequency is ________(H=5 kW-s/KVA).
a) 1 b) 0.5 c) -1.5 d) 0.8
Answer: a
8. A 50 Hz four pole turbo-generator rated 100 MVA, 11 kV has an inertia constant of 8 MJ/MVA. If the mechanical input is suddenly raised to 80 MW for an electrical load of 50MW, then the rotor acceleration is ____________
a) 337.5 b) 3.375 c) 457.5 d) 4.57
Answer: a
9.
A single phase TL has copper conductor of 0.775 cm2 cross section
through which 200 kW at UPF at 330 V is to be maintained. If the
efficiency of transmission line is 90%, then the minimum length of TL is
___________(in km and take specific resistance to be 1.785 μΩ/cm).a) 1 b) 0.5 c) -1.5 d) 0.8
Answer: a
8. A 50 Hz four pole turbo-generator rated 100 MVA, 11 kV has an inertia constant of 8 MJ/MVA. If the mechanical input is suddenly raised to 80 MW for an electrical load of 50MW, then the rotor acceleration is ____________
a) 337.5 b) 3.375 c) 457.5 d) 4.57
Answer: a
a) 13.6 km b) 14 km c) 136 km d) 16.4 km
Answer: a
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