Power Systems (Test 4)

Gate Exam : Ee Electrical Engineering

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Power Systems

Power Systems
| Power Systems |
Q.1
A 50Hz synchronous generator is initially connected to a long lossless transmission line which is open circuited at the receiving end. With the field voltage held constant, the generator is disconnected from the transmission line. Which of the following may be said about the steady state terminal voltage and field current of the generator?

A. The magnitude of terminal voltage decreases, and the field current does not change.
B. The magnitude of terminal voltage increases, and the field current does not change.
C. The magnitude of terminal voltage increases, and the field current increases.
D. The magnitude of terminal voltage does not change, and the field current decreases.
Answer : Option A
Explaination / Solution:
No Explaination.


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Q.2
A balanced star-connected and purely resistive load is connected at the secondary of a stardelta transformer as shown in figure. The line-to-line voltage rating of the transformer is 110V/220V. Neglecting the non-idealities of the transformer, the impedance ‘Z’ of the equivalent star-connected load, referred to the primary side o the transformer, is:

A. (3 + j 0) Ω
B. (0.866 – j 0.5) Ω
C. (0.866 + j 0.5) Ω
D. (1+j0)Ω
Answer : Option D
Explaination / Solution:
No Explaination.


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Q.3
Consider a three-phase, 50Hz, 11kV distribution system. Each of the conductors is suspended by an insulator string having two identical porcelain insulators. The self-capacitance of the insulator is 5 times the shunt capacitance between the link and the ground, as shown in the figure. The voltage across the two insulators are

A. e1 = 3.74 kV, e2= 2.61 kV
B. e1 = 3.46 kV, e2= 2.89 kV
C. e1 = 6.0 kV, e2= 4.23 kV
D. e1 = 5.5 kV, e2= 5.5 kV
Answer : Option B
Explaination / Solution:
No Explaination.


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Q.4
. Consider a three-core, three-phase, 50Hz, 11kV cable whose conductors are denoted as R, Y and B in the figure. The inter-phase capacitance (C1) between each pair of conductors is 0.2µF and the capacitance between each line conductor and the sheath is 0.4.µF. The per-phase charging current is 

A. 2.0 A
B. 2.4 A
C. 2.7 A
D. 3.5 A
Answer : Option A
Explaination / Solution:
No Explaination.


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Q.5
In the following network, the voltage magnitudes at all buses are equal to 1 p.u., the voltage phase angles are very small, and the line resistances are negligible. All the line reactances are equal to j1 Ω.

The voltage phase angles in rad at buses 2 and 3 are
A.
B.
C.
D.
Answer : Option C
Explaination / Solution:
No Explaination.


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Q.6
For the power system shown in the figure below, the specifications of the components are the following:
G1 : 25 kV, 100 MVA, X = 9% 
G2: 25 kV, 100 MVA, X = 9% 
T1: 25 kV/220 kV, 90 MVA, X = 12% 
T2: 220 kV/25 kV, 90 MVA, X = 12% 
Line 1: 220 kV, X = 150 ohms
Choose 25kV as the base voltage at the generator G1, and 200 MVA as the MVA base. The impedance diagram is 
A.
B.
C.
D.
Answer : Option B
Explaination / Solution:
No Explaination.


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Q.7
In the following network, the voltage magnitudes at all buses are equal to 1 p.u., the voltage phase angles are very small, and the line resistances are negligible. All the line reactances are equal to j1 Ω.
If the base impedance and the line-to line base voltage are 100 ohms and 100kV respectively, then the real power in MW delivered by the generator connected at the slack bus is
A. -10
B. 0
C. 10
D. 20
Answer : Option C
Explaination / Solution:
No Explaination.


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Q.8
Out of the following plant categories (i) Nuclear (ii) Run-of-river (iii) Pump Storage (iv) Diesel The base load power plants are
A. (i) and (ii)
B. (ii) and (iii)
C. (i), (ii) and (iv)
D. (i), (iii) & (iv)
Answer : Option C
Explaination / Solution:
No Explaination.


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Q.9
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
A. V
B. V2
C. 1/V2
D. 1/V
Answer : Option C
Explaination / Solution:



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Q.10
How many 200W/220V incandescent lamps connected in series would consume the same total power as a single 100W/220V incandescent lamp?
A. not possible
B. 4
C. 3
D. 2
Answer : Option D
Explaination / Solution:
No Explaination.


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EE Electrical Engineering