# Sathyabama University Question Papers BE

## Power system Analysis Fifth Sem

Answer All the Questions

1. What is the need for system analysis in planning and operation of

power system?

2. What are the advantages of per unit system?

3. What is primitive matrix?

4. What is bus admittance matrix?

5. What is the reason for transients during short circuits?

6. Draw the equivalent sequence network for a line-line bolted fault

in a power system.

7. What is P-Q bus in power flow analysis?

8. What is the reason for transients during short circuits?

9. Write the swing equation and explain the term involved in it.

10. Give the expression for critical clearing time.

PART – B (5 x 12 = 60)

Answer All the Questions

11. Draw the reactance diagram for the power system shown in

fig.11. Neglect resistance and use of 100MVA, 220Kv in 50W

line. The ratings of the generator, motor and transformer are

given below.

Generator : 40MVA, 25kV, X” = 20%

Synchronous motor : 50MVA, 11kV, X” = 30%

Y – Y Transformer : 40MVA, 33/220kV, X = 15%

Y – D Transformer : 30MVA, 11/220kV, (D/Y), X=15%

(or)

12. Draw the structure of an electrical power system and describe the

components of the system with typical values.

13. Find bus admittance matrix for the given network. Determine the

reduced admittance matrix by eliminating node 4. The values are

marked in p.u.

(or)

14. Find the bus impedance matrix for the reactance diagram is

shown in fig. all the impedances are marked in p.u.

15. A generator is connected through a transformer to a synchronous

motor. The subtransient reactance’s of generator and motor are

0.15 p.u and 0.35 p.u respectively. The leakage reactance of the

transformer is 0.1 p.u. All the reactances are calculated on a

common base. A three phase fault occurs at the terminals of the

motor when the terminal voltage of the generator is 0.9 p.u. The

output current of generator is 1 p.u. and 0.8 p.f leading. Find the

subtransient current in p.u. in the fault, generator and motor. Use

the terminal voltage of generator as reference vector.

(or)

16. Derive the expression for fault current in Line-to-line fault on an

unloaded generator in terms of symmetrical components.

17. Derive load flow algorithm using Gauss-Seidel method with flow

chart and discuss the advantages of the method.

(or)

18. Derive load flow algorithm using Newton-Raphson method with

flow chart and state the importance of the method.

19. Derive Swing equation used for stability studies in power system.

(or)

20. Explain the modified Euler method of analyzing multimachine

power system for stability, with neat flow chart.