VTU Electrical and Electronic Engineering (Semester 7)
Computer Techniques in Power System Analysis
May 2016
Total marks: --
Total time: --
INSTRUCTIONS
(1) Assume appropriate data and state your reasons
(2) Marks are given to the right of every question
(3) Draw neat diagrams wherever necessary


1(a) Explain the terms:
(i) Tree
(ii) Co-Tree
(iii) Tree branch path incidence matrix with an example.
10 M
1(b) For the power system shown below. Select ground as reference and a tree for which the link elements are 1-2, 1-4 , 2-3 and 3-4. Write the basic cut set and basic loop incidence matrix. Verify the relation Cb=BTl !mage
10 M

2(a) Consider the power system network shown below; Image
The data is given below;
Line No. Between lines Line impedance  

Off nominal

turns ratio

1 1-4 0.08+j0.37 0.007 -
2 1-6 0.123+j0.518 0.010 -
3 2-3 0.723+j1.05 0 -
4 2-5 0.282+j0.64 0 -
5 4-3 0+j0.133 0 0.909
6 4-6 0.097+j0.407 0.0076 -
7 6-5 0+j0.30 0 0.976
12 M
2(b) From the ZBUS for the power system shown below. Select node (i) as reference. The line reactances are marked in pu. !mage Fig.Q2(b)
8 M

3(a) Explain with the help of a flow chart Gauss Seidel method of load flow analysis in a power system.
10 M
3(b) Compute the line flows and line losses for a 3-Bus power system network shown below. The data obtaied from load flow is as follows;
ElementNo. Bus From To R X Bus No |V| δ
1 1-2 0.02 0.04 1 1.05 0.0
2 1-3 0.01 0.03 2 0.9818 -3.5°
3 2-3 0.02 0.025 3 1.00125 -2.665°

:!mage
10 M

4(a) In a two bus system shown in Fig.Q4 (a). The bus 1 is slack bus with V=1.0∠0degree pu and bus 2 is a load bus with P = 100 MW, Q =50 MVAr. The line impedance is (0.12+j0.16) pu on a base of 100 MVA. Using Newton Raphson load flow method compute |V2| and δ2 upto on iteration. !mage
10 M
4(b) Explain the algorithm with Fast Decoupled lead flow analysis clearly stating all the assumptions made
10 M

5(a) What is meant by economic load scheduling? Explain the Hydro and Thermal unit input-output curves.
10 M
5(b) A power plant has three units with following cost characteristics:
F1=0.05p2p1+21.5P1+800Rs./hr;
F2=0.10P2p2+27P2+500Rs/hr
F3=0.07P2P3+16P3+900Rs/hr
Find the optimum scheduling and total cost in RS./hr for a total load demand of 200 MW. Given that Pimax =120MW: Pimin=39MW: where i = 1,2,3
10 M

6(a) Explain optimal sheduling of hydro-thermal plants and also explain its problem formulation.
10 M
6(b) Figure shown in Fig.Q6(b) is having two plants 1 and 2 which are connected to the buses 1 and 2 respectively. There are two loads and 4 branches. The reference bus with a voltage of 1.0∠0degree pu is shown in the diagram. The branch currents and impedances are as follows:
Ia=(2-j0.5)pu;
Ib=(1.6-j0.4)pu;
Ic(1-j025)pu;
Id=(3.6-j0.9)pu;
Za=Zb=(0.015+j0.06)pu;
Zc=Zd=(0.01+j0.04)pu Calculate the loss coefficients in the system in pu.
10 M

7(a) Explain the computational algorithm for obtaining the swing curves using Runge Kutta method.
10 M
7(b) Explain the load models employed in multi-machine stability analysis with neat sketch.
10 M

8(a) Explain Milne's predictor corrector method of for solving the swing equation of multi-machine system.
10 M
8(b) Explain the swing equation and its importance in stability studies.
10 M



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