Power System: Part-2 Objective Questions with Answers

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

Ans:C

[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

Ans:D

[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)  a→2,b→3,c→4,d→1
(b)  a→2,b→4,c→3,d→1
(c)  a→4,b→3,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)  a→2,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

Ans: A

[7] For the system shown below, S_D1 and S_D2 are complex power demands at bus 1 and bus 2 respectively. If |V₂|=1pu, the VAR rating of the capacitor (Q_G2) connected at bus 2 is [GATE2012]

(a) 0.2 pu

(b) 0.268

(c) 0.312

(d) 0.4pu

Ans: B

[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

Ans: D

[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
Answer: A

[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
Answer: B

[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
Answer: B

[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
Answer: B

[13] Bundled conductors are employed to improve the [Gate 1997]
(a) Appearance of the transmission line
(b) Mechanical stability of the line
(c) Current carrying capability of the line
(d) Corona performance of the line
Answer: D