SREC EEE PSA A.U QP (May 2011 – May 2015) – Unit - II

DEPARTMENT OF ELECTRICAL AND ELECTRONICS ENGINEERING

Year/Sem : III/V

POWER SYSTEM ANALYSIS [EE 6501]

UNIT – II A.U QUESTIONS (May 2011 – May 2015)

Part – A1. What is Jacobian matrix? (May 2011)

2. What is a slack bus? (May 2011)

3. What are the different types of buses in power systems? What are the quantities specified in each bus? (Nov 2011)

4. How are the disadvantages of Newton-Raphson method overcome? (Nov 2011)

5. What are the informations that are obtained from a power flow study? (May 2012)

6. Compare Gauss-Seidal and Newton-Raphson methods of load flow solutions. (May 2012) (May 2015)

7. What is meant by acceleration factor in load flow studies? (Nov 2012) (May 2013)

8. What are the data required for a load flow study? (Nov 2012)

9. What is the necessity of slack bus? (May 2013)

10. Why do Ybus used in load flow study instead of Zbus? (Nov 2013)

11. What is the role of swing bus in power flow study? (May 2014)

12. At what condition generator bus is treated as load bus? (May 2014)

(Or)

When will the generator bus be treated as load bus? (Nov 2013)

13. What is load flow or power flow study? (Nov 2014)

14. Define voltage controlled bus. (Nov 2014)

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SREC EEE PSA A.U QP (May 2011 – May 2015) – Unit - II

Part – B1. Formulate the power flow equation for n bus system. (04) (May 2014)

2. Give the detailed flow chart for Newton-Raphson method. (12) (May 2014)

Write the step by step procedure for load flow analysis by Newton-Raphson method. (12) (May 2012)

Develop an algorithm and draw the flow chart for the solution of load flow problem using N-R method. (16) (Nov 2014)

3. Describe the step by step procedure for load flow solution from Gauss-Seidel method, if PV and PQ buses are present along with slack bus. (16) (May 2014)

Explain the step by step computational procedure for the Gauss-Seidel method of load flow studies. (16) (May 2011)

Discuss in detail about Gauss-Seidel load flow analysis algorithm and give steps for its implementation when PV buses also present in the system. (16) (May 2013)

4. Compare Gauss-Seidel and Newton-Raphson methods in detail. (06) (Nov 2012)

5. Discuss the various types of buses and their significance. (03) (Nov 2012)

Give the classification of various types of buses in a power system for load flow studies. (06) (Nov 2013)

Write a note on classification of buses. (06) (Nov 2014)

6. Give the advantages and limitations of Newton Raphson method. (06) (Nov 2013)

7. Briefly explain the importance of power flow analysis. (06) (Nov 2011)

8. What is Jacobian matrix? How the elements of Jacobian matrix are computed? (04) (May 2012)

9. State the elements of Jacobian matrix for a system with P-Q buses alone. (07) (Nov 2012)

10. A three bus power system is shown in figure. The relevant per unit line admittance on 100 MVA base are indicated on the diagram and bus data are given in table. Form Ybus

and determine the voltages at bus 2 and 3 after first iteration using Gauss-Seidal method. Take the acceleration factor α = 1.6. (16) (Nov 2013)

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SREC EEE PSA A.U QP (May 2011 – May 2015) – Unit - II

Bus Number

TypeGeneration Load Bus voltage

PG QG PL QL V(p.u) δ deg

1 Slack ? ? 0 0 1.02 0

2 PQ 25 15 50 25 ? ?

3 PQ 0 0 60 30 ? ?

11. The one line diagram of three bus power system is shown in figure.

Bus 1 : Slack bus Especified = 1.05 ∠0 °

Bus 2 : PV bus | E | specified = 1.2 p.u, PG = 3 p.u

Bus 3 : PQ bus, PL = 4 p.u. QL = 2 p.u

Carry out one iteration of load flow solution by Gauss-Seidel method. Take Q limits of

generator 2 as 0 ≤ Q ≤ 4. Take α = 1. (16) (Nov 2011) (Nov 2012)

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SREC EEE PSA A.U QP (May 2011 – May 2015) – Unit - II

12. The figure shows a five bus power system. Each line has an impedance of (0.05 + j 0.15) p.u. The line shunt admittances may be neglected. The bus power and voltage specifications are given in table. (i) Form Ybus

(ii) Find Q2, δ2, V3, V4 and V5 after the first iteration using Gauss-Seidel method. Assume Q2, min = 0.2 p.u and Q2, max = 0.6 p.u. (16) (May 2012)

Bus

PL QL PG QG VBus

Specification

1 1.0 0.5Not

specifiedNot Specified 1.02 ∠0° Slack bus

2 0 0 2 Not Specified 1.02 PV bus

3 0.5 0.2 0 0 Not Specified PQ bus

4 0.5 0.2 0 0 Not Specified PQ bus

5 0.5 0.2 0 0 Not Specified PQ bus

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SREC EEE PSA A.U QP (May 2011 – May 2015) – Unit - II

13. Consider the power system with the following data:

Assume that the bus 2 can supply any amount of reactive power. With a flat start, perform the first iteration of power flow analysis using Newton-Raphson method. (16) (May 2013)

14. Fig. shown below a three bus power system. Bus 1 : slack bus V = 1.05 ∠0 ° p.u, Bus 2 : PV bus |V| = 1.0 p.u, Pg = 3 p.u, Bus 3 : PQ bus PL = 4 p.u, QL = 2 p.u. Carry out one iteration of load flow solution by Gauss-Seidel method. Neglect limits on reactive power generation. (10) (Nov 2014)

15. Figure shows the one line diagram of a simple three bus power system with generation at

buses 1 and 2. The voltage at bus 1 is V = 1 + j0.0 V per unit. Voltage magnitude at bus 2 is fixed at 1.06 p.u with a real power generation of 400 MW. A load consisting of 500 MW and 400 MVAR is taken from bus 3. Line admittances are marked in per unit on a 100 MVA base. For the purpose of hand calculations, line resistances and line charging susceptances are neglected.

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SREC EEE PSA A.U QP (May 2011 – May 2015) – Unit - II

Using Newton-Raphson method, start with the initial estimates of V2

0 = 1.05 + j 0.0 and V3

0 = 1.05 + j0.0, and keeping |V2| = 1.05 p.u, determine the phasor values of V2 and V3. Perform two iterations. (16) (May 2015)

16. In the power system network shown in figure, bus 1 is slack bus with V1 = 1.0 +j0.0 per unit and bus 2 is a load bus with S2 = 280 MW +j60 MVAr. The line impedance on a base of 100 MVA is Z = 0.02 + j0.04 per unit. Using Gauss-Seidel method, determine V2. Use an initial estimate of V2

0 = 1.0 + j0.0 and perform four iterations. Also find S1 and the real, reactive power loss in the line, assuming that the bus voltages have converged.

(16) (May 2015)

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