## Power System Objective Questions from Competitive Exams:

Questions [ 1 & 2] Carries Two Marks Each:
[1] Three generators are feeding a load of 100MW. The details of the generators are
Rating(MW)  Efficiency()  Regulation(p.u.)
on 100MVA base

Generator-1               100                  20                      0.02
Generator-2               100                  30                      0.04
Generator-3               100                  40                      0.03
In the event of increased load power demand, which of the following will happen? [GATE 2009]
(a) All the generators will share equal power
(b) Generator – 3 will share more power compared to Generator – 1
(c) Generator – 1 will share more power compared to Generator – 2
(d) Generator – 2 will share more power compared to Generator – 3
[2] A 500MW, 21kV, 50Hz, 3-phase, 2-pole synchronous generator having a rated p.f. =0.9, has a moment of inertia of 27.5 x 103 kg-m2. The inertia constant (H) will be  [GATE 2009]
(a) 2.44 s
(b) 2.71s
(c) 4.88s
(d) 5.42s
[3] For a fixed value of complex power flow in a transmission line having a sending end voltage V, the real power loss will be proportional to [GATE 2009]
(a) V
(b) V2
(c) 1/V2
(d) 1/V
[4] How many 200W/220V incandescent lamps connected in series would consume the same total power as a single 100W/220V incandescent lamps? [GATE 2009]
(a) Not possible
(b) 4
(c) 3
(d) 2
[5] Match the items in list I with the items in list II and select the correct answer using the codes given below the lists [GATE 2009]
LIST 1                                                   LIST2
TO                                                         USE
a.Improve power factor                           1.shunt reactor
b.Reduce the current ripples                    2.shunt capacitor
c.Increase the power flow in line              3.series capacitor
d.Reduce the ferranti effect                      4.series reactor

(a)  a2,b3,c4,d1

(b)  a2,b→4,c→3,d1
(c)  a→4,b3,c→1,d→2
(d)  a→4,b→1,c→3,d→2
[6] Match the items in list I with the items in list II and select the correct answer using the codes given below the lists [GATE 2009]
LIST 1                                   LIST2
Type of Transmission Line         Type of Distance Relay
Preferred
a.short line                                      1.Ohm Relay
b.Medium line                                 2.Reactance Relay
c.Long line                                      3.Mho Relay

(a)  a2,b→1,c→3
(b)  a→3,b→2,c→1
(c)  a→1,b→2,c→3
(d)  a→1,b→3,c→2
[7] For the system shown below, SD1 and SD2 are complex power demands at bus 1 and bus 2 respectively. If |V2|=1pu, the VAR rating of the capacitor (QG2) connected at bus 2 is [GATE2012]
(a) 0.2 pu
(b) 0.268
(c) 0.312
(d) 0.4pu

[8] A cylindrical rotor generator delivers 0.5 pu power in the steady-state to an infinite bus through a transmission line of reactance 0.5 pu. The generator no-load voltage is 1.5 pu and the infinite voltage is 1.5 pu. The inertia constant of the generator is 5MW-s/MV and the generator reactance is 1 pu.The critical clearing angle, in degrees, for a three-phase dead short circuit fault at the generator terminal is  [GATE2012]
(a) 53.5
(b) 60.2
(c) 70.8
(d) 79.6

[9] For a fault at terminals of the synchronous generator the fault current is max for a [Gate 1997]
(a) 3 phase fault
(b) 3 phase to ground fault
(c) Line to ground fault
(d) Line to line fault

[10] Reactance relay is normally preferred for protection against [Gate 1997]
(a) Earth faults
(b) Phase faults
(c) Open circuit faults
(d) None of the above

[11] A 100 MVA, 11kV, 3 phase, 50Hz, 8 pole synchronous generator has a inertia constant H = 4 seconds. The stored in the rotor of the generator at synchronous speed will be [Gate 1997]
(a) 100MJ
(b) 400MJ
(c) 800MJ
(d) 12.5MJ

[12] The use of high speed circuit breakers [Gate 1997]
(a) Reduces the short circuit current
(b) Improves system stability
(c) Decreases system stability
(d) Increases the short circuit current