# Power Systems (Test 5)

## Gate Exam : Ee Electrical Engineering

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Q.1
Shunt reactors are sometimes used in high voltage transmission system to
A. limit the short circuit current through the line.
B. compensate for the series reactance of the line under heavily loaded condition.
D. compensate for the voltage drop in the line under heavily loaded condition.
Explaination / Solution:
No Explaination.

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Q.2
For the Y-bus matrix of a 4-bus system given in per unit, the buses having shunt elements are. A. 3 and 4
B. 2 and 3
C. 1 and 2
D. 1, 2 and 4
Explaination / Solution:
No Explaination.

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Q.3
The horizontally placed conductors of a single phase line operating at 50 Hz are having outside diameter of 1.6 cm, and the spacing between centers of the conductors is 6 m. The permittivity of free space is 8.854 × 10-12 F/m. The capacitance to ground per kilometer of each line is
A. 4.2 × 10-9 F
B. 8.4 × 10-9 F
C. 4.2 × 10-12 F
D. 8.4 × 10-12 F
Explaination / Solution: Workspace
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Q.4
Match the items in List-I with the items in List-II and select the correct answer using the codes given below the lists. List-I List-II 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 Codes:
A. 2 3 4 1
B. 2 4 3 1
C. 4 3 1 2
D. 4 1 3 2
Explaination / Solution:
No Explaination.

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Q.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. List I List II 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
Explaination / Solution:
No Explaination.

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Q.6
An independent voltage source in series with an impedance Zs = Rs + jXs delivers a maximum average power to a load impedance ZL when
A. ZL = Rs + jXs
B. ZL = Rs
C. ZL = jXs
D. ZL = Rs - jXs
Explaination / Solution:

According to maximum Power Transform Theorem
ZLZ= (Rs - jXs)

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Q.7
The synchronous generator shown in the figure is supplying active power to an infinite bus via two short, lossless transmission lines, and is initially in steady state. The mechanical power input to the generator and the voltage magnitude E are constant. If one line is tripped at time t1 by opening the circuit breakers at the two ends (although there is no fault), then it is seen that the generator undergoes a stable transient. Which one of the following waveforms of the rotor angle δ shows the transient correctly? A. B. C. D. Explaination / Solution: Workspace
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Q.8
A 3-bus power system network consists of 3 transmission lines. The bus admittance matrix of the uncompensated system is If the shunt capacitance of all transmission line is 50% compensated, the imaginary part of the 3rd row 3rd column element (in pu) of the bus admittance matrix after compensation is
A. -j 7.0
B. -j 8.5
C. -j 7.5
D. -j 9.0
Explaination / Solution:  Workspace
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Q.9
A balanced (positive sequence) three-phase AC voltage source is connected to a balanced, star connected load through a star-delta transformer as shown in the figure. The line-to-line voltage rating is 230 V on the star side, and 115 V on the delta side. If the magnetizing current is neglected and then what is the value of in Ampere? A. 50 ∠30°
B. 50 ∠ − 30°
C. 50 √3 ∠30°
D. 200 ∠30° 