Code No: 126AG
R13
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
B. Tech III Year II Semester Examinations, December - 2019
COMPUTER METHODS IN POWER SYSTEMS
(Electrical and Electronics Engineering)
Time: 3 hours Max. Marks: 75
Note: This question paper contains two parts A and B.
Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B
consists of 5 Units. Answer any one full question from each unit. Each question carries
10 marks and may have a, b, c as sub questions.
PART - A
(25 Marks)
1.a) Is incidence matrix unique for a given network? Justify. [2]
b) Give the performance equation for primitive network in impedance form. [3]
c) Give the limitations of fast decoupled method. [2]
d) Give importance of acceleration factor in Gauss seidal method. [3]
e) Give the objectives for finding fault level at a bus. [2]
f) Give some applications of shunt inductor. [3]
g) Define stability limit in power system. [2]
h) Give significance of synchronousing power coefficient. [3]
i) Suggest suitable methods to improve transient stability. [2]
j) Derive swing equation. [3]
PART - B
(50 Marks)
2.a) Form the YBUS for the system shown in below figure 1, using singular transformation
method.
Figure 1
b) Give the steps for modification of existing bus when a node is added or removed from a
existing bus. [5+5]
OR
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3. Find the ZBUS for the power system network shown in figure 2. All reactance’s are in
p.u values. [10]
Figure 2
4.a) What are the advantages of NR-method over GS-method? Explain.
b) For the system in below figure 3. P2=0.5 p.u., Q2 = -0.2 p.u., P3 = -1 p.u., Q3 = 0.5 p.u.,
P4 = 0.3 p.u., Q4 = -0.1 p.u., and V1 = 1.04 00 p.u. Determine the value of V2 after the
first iteration of Gauss Seidel (GS) method. Line admittances are as shown in the
figure 3. [5+5]
Figure 3
OR
5.a) Explain the fast decoupled load flow algorithm. State assumptions made.
b) What is D.C. load flow method? State its merits and demerits. [5+5]
6.a) The voltages across a 3-phase unbalanced load are Va= 300 Volts, Vb= 300 900 Volts
and Vc = 800 1430 Volts respectively. Determine the sequence components of
voltages. Phase sequence is ABC.
b) Draw the pu impedance diagram for the system shown in figure 4. Choose Base MVA
as 100 MVA and Base kV as 20 kV. [5+5]
Figure 4
OR
7.a) Given Z0 = 0.199<900 per unit; Z1 = 0.175<900; Z2= 0.175<900 calculate the fault
current and line voltages for a Line -Line fault .
b) Compute the fault current and voltages for a Single line-to-ground fault.
c) Compute the fault current and voltages for a Line-to-Line fault. [4+3+3]
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8.a) What is power system stability? Define stability limit of the system.
b) A 50 Hz generator of reactance 1 pu is connected to an infinite bus through a line of
reactance of 0.5 pu. E=1.1 pu and V=1 pu. The inertia constant is 5 MW-sec/MVA. The
generator is loaded to 50% of the maximum power limit. Find the frequency of natural
oscillations. [5+5]
OR
9.a) Discuss briefly various methods to improve steady state stability.
b) What is power angle curve? Assuming a loss less line derive relation for a SMIB
system. [5+5]
10.a) Explain how the use of auto reclousure circuit breakers improve steady state stability.
b) Explain the use of equal area criteria for the study of stability with an example. [5+5]
OR
11. Derive an expression for critical clearing angle for a power system consisting of a
single machine supplying a infinite bus for sudden load decrement. [10]
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