# Power Systems (Test 2)

## Gate Exam : Ee Electrical Engineering

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Q.1
A solar energy installation utilize a three – phase bridge converter to feed energy into power system through a transformer of 400V/400 V, as shown below. The energy is collected in a bank of 400 V battery and is connected to converter through a large filter choke of resistance 10Ω.
The kVA rating of the input transformer is
A. 53.2kVA
B. 46.0kVA
C. 22.6kVA
D. 19.6 kVA
Explaination / Solution: Workspace
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Q.2
A power system with two generators is shown in the figure below. The system (generators, buses and transmission lines) is protected by six overcurrent relays R1 to R6. Assuming a mix of directional and nondirectional relays at appropriate locations, the remote backup relays for R4 are A. R1,R2
B. R2,R6
C. R2,R5
D. R1,R6
Explaination / Solution:
No Explaination.

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Q.3
A power system has 100 buses including 10 generator buses. For the load flow analysis using Newton-Raphson method in polar coordinates, the size of the Jacobian is
A. 189 x 189
B. 100 x 100
C. 90 x 90
D. 180 x 180
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Q.4
The bus admittance matrix of a three-bus three-line system is If each transmission line between the two buses is represented by an equivalent π-network, the magnitude of the shunt susceptance of the line connecting bus 1 and 2 is
A. 4
B. 2
C. 1
D. 0
Explaination / Solution: Workspace
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Q.5
The inductance and capacitance of a 400 kV, three-phase, 50 Hz lossless transmission line are 1.6 mH/km/phase and 10 nF/km/phase respectively. The sending end voltage is maintained at 400 kV. To maintain a voltage of 400 kV at the receiving end, when the line is delivering 300 MW load, the shunt compensation required is
A. capacitive
B. inductive
C. resistive
D. zero
Explaination / Solution: Workspace
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Q.6
The figure shows a two-generator system supplying a load of PD = 40 MW, connected at bus 2. The fuel cost of generators G1 and G2 are : and the loss in the line is where the loss coefficient is specified in pu on a 100 MVA base. The most economic power generation schedule in MW is
A. B. C. D. Explaination / Solution: Workspace
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Q.7
The sequence components of the fault current are as follows: Ipositive = j1.5 pu, Inegative = –j0.5 pu, Izero = –j1 pu. The type of fault in the system is
A. LG
B. LL
C. LLG
D. LLLG
Explaination / Solution:

I1 = I2 + I0

So LLG fault

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Q.8
A source is supplying a load through a 2-phase, 3-wire transmission system as shown in figure below. The instantaneous voltage and current in phase-a are Van = 220sin(100πt)V and ia = 10sin(100πt)A, respectively. Similarly for phase-b the instantaneous voltage and current are Vbn = 220cos(100πt)V and ib = 10cos(100πt)A, respectively. The total instantaneous power flowing form the source to the load is
A. 2200 W
B. 2200sin(100πt)W
C. 440 W
D. 2200sin (100πt)cos(100πt)W
Explaination / Solution: Workspace
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Q.9
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 bus voltage is 1 pu. The inertia constant of the generator is 5 MW-s/MVA 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
A. 53.5
B. 60.2
C. 70.8
D. 79.6
Explaination / Solution:  Workspace
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Q.10
A 3-bus power system is shown in the figure below, where the diagonal elements of Y-bus matrix are Y11 = -j12pu, Y22 = -j15pu and Y33 = -j7pu The per unit values of the line reactances p, q and r shown in the figure are
A. p = -0.2, q = -0.1, r = -0.5
B. p = 0.2, q = 0.1, r = 0.5
C. p = -5, q = -10, r = -2
D. p = 5, q =10, r = 2  