Code No: RT32024 R13 SET - 1
III B. Tech II Semester Supplementary Examinations, October/November - 2020
POWER SYSTEM ANALYSIS
(Electrical and Electronics Engineering)
Time: 3 hours Max. Marks: 70
Note: 1. Question Paper consists of two parts (Part-A and Part-B)
2. Answering the question in Part-A is compulsory
3. Answer any THREE Questions from Part-B
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PART –A (22 Marks)
1. a) How can you select the base quantities? [3M]
b) What is the need of slack bus? [4M]
c) What are the four ways of adding impedance to an existing system so as to modify [4M]
Z-bus matrix?
d) How do you get the short circuit kVA from per unit impedance? [4M]
e) What is the significance of symmetrical components? [3M]
f) What are the methods considered for improving steady state stability? [4M]
PART –B (48 Marks)
2. a) For the power system shown in below figure. Obtain the bus incidence matrix. [10M]
Take ground as reference. Is this matrix is unique? Explain.
b) Describe the step by step procedure for developing single line diagram of a given [6M]
power system.
3. The power system network shown in below network, bus 1 is connected as a slack [16M]
bus of voltage 1.4 ∠0 0 p.u . The line impedances are indicated in the network on
100 MVA base and neglect the line shunt admittance
By using Fast Decoupled method at the end of first iteration, calculate the voltage
magnitude and phase angle at buses 2 and 3.
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Code No: RT32024 R13 SET - 1
4. a) Write an algorithm for the Modification of Zbus Matrix for different cases. [8M]
b) Determine the ZBus using building algorithm for the network shown in below [8M]
figure. The values are in p.u reactance.
5. The plant capacity of a three phase generating station consists of two 8 MVA [16M]
generators of reactance 14.5% each and one 4MVA generator of reactance 9.5%.
These are connected to a common bus bar from which loads are taken through a
number of transformers of 3MVA (step-up) each having 4% reactance. Determine
the MVA rating of the circuit breakers on (i) L.V.side and (ii) H.V.side.
Reactance’s given are based on the MVA of each equipment.
6. a) What do you understand by sequence networks? What is their importance in [8M]
unsymmetrical fault calculations?
b) A 25 MVA, 13.2 kV alternator with solidly grounded neutral has a subtransient [8M]
reactance of 0.25 p.u. The negative and zero sequence reactance’s are 0.35 and
0.1 p.u. respectively. A single line to ground fault occurs at the terminals of an
unloaded alternator; determine the fault current and the line-to-line voltages.
Neglect resistance.
7. a) Derive an expression for steady state stability limit of a short transmission line [8M]
having send end and receiving end voltages Vs and Vr an impedance Z.
b) A 4-pole, 50 Hz, 26 kV turbo alternator has a rating of 100 MVA, p.f 0.8 lag. The [8M]
moment of inertia of rotor is 8000 kg-m2. Determine M and H.
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