JNTU
JNTU B.Tech III POWER SYSTEMS ANALYSIS Previous Question Paper (May - 2019 - R16)
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.
Part A
What are the advantages of ZBUS building algorithm?
Answer
The ZBUS building algorithm allows for the direct construction of the bus impedance matrix without requiring matrix inversion, which is computationally efficient for large systems. It also facilitates easy modification of the network, such as adding or removing lines or buses, by updating only specific elements of the matrix.
Write the Bus Incidence Matrix for the graph shown in figure 1.
Answer
The Bus Incidence Matrix (A) is constructed by assigning +1 to the node where the current leaves, -1 where it enters, and 0 otherwise for each branch. For a graph with n nodes and b branches, the matrix is of size n x b. In a reduced incidence matrix, one row (corresponding to the reference bus) is removed.
What is the necessity of power flow studies?
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Explain the significance of Slack bus.
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Compare the Newton-Raphson method with decoupled load flow method.
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Write the power system characteristics used in decoupled method.
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Write the applications of Series reactors.
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Give the zero sequence network of: Y-Y and ∆ - Y transformers.
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List the various methods of improving transient stability.
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Discuss the limitation in equal area criterion for the study of power system stability.
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Part B
Derive the expression for bus admittance matrix YBUS in terms of primitive admittance matrix and bus incidence matrix. Form the YBUS by using singular transformation for the network shown in Figure 2 including the generator buses.
Derive the expression for bus admittance matrix YBUS.
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Form the YBUS by using singular transformation.
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For the network shown in Figure 3, determine the modified ZBUS if the line 4 is removed from the network.
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Develop load flow equations suitable for solutions by N-R method using rectangular coordinates when both PV and PQ buses are present.
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For a three bus power system shown in Figure 4, perform the load flow solution at the end of first iteration using Gauss-Seidel iterative method.
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Develop the power flow model using Decoupled method and explain the assumptions made to arrive at the Fast Decoupled load flow method. Draw the flow chart.
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For the network shown in figure 5, obtain the complex bus bar voltages at bus (2) at the end of first iteration, using Fast Decoupled method.
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Derive an expression for the fault current for a line to ground fault at the terminals of an unloaded generator.
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A 25 MVA, 13.2 kV alternator with solidly grounded neutral has subtransient, negative and zero sequence reactances of 0.25, 0.35 and 0.1 p.u. respectively. Determine the fault current and line-to-line voltage for a single line-to-ground fault.
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Differentiate between steady state stability and transient stability of a power system. Discuss the factors that affect steady state stability and transient state stability.
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Explain the point by point method of solving the swing equation. Compare this method with the equal area criterion method.
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