Power Systems - Online Test
Q1. 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?
Answer : Option A
Explaination / Solution:
Q2. 
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
Answer : Option B
Explaination / Solution:
Q3. 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?
then what is the value of in Ampere?
Answer : Option A
Explaination / Solution:
Q4. A 3-phase transformer rated for 33 kV/11 kV is connected in delta/star as shown in figure.
The current transformers (CTs) on low and high voltage sides have a ratio of 500/5. Find
the currents i1 and i2, if the fault current is 300A as shown in figure.
Answer : Option A
Explaination / Solution:
Q5. In a 100 bus power system, there are 10 generators. In a particular iteration of Newton Raphson load flow technique (in polar coordinates), two of the PV buses are converted to PQ type. In this iteration,
Answer : Option A
Explaination / Solution:
Q6. If the star side of the star-delta transformer shown in the figure is excited by a negative sequence voltage, then
Answer : Option D
Explaination / Solution:
Q7. 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
Answer : Option D
Explaination / Solution:
No Explaination.
Q8. 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
Answer : Option A
Explaination / Solution:
Q9. 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
Answer : Option B
Explaination / Solution:
Q10. 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
Answer : Option A
Explaination / Solution:
