# Sathyabama University Question Papers

# Power system Analysis BE Fifth Sem

Answer ALL the Questions

1. Write equation for converting the p.u impedance expressed in one

base to other base.

2. Define steady state stability limit.

3. Explain bus classification in power flow analysis with their

known and known quantities.

4. What is the need for acceleration factor?

5. Write equations to determine sequence components for

unbalanced system of currents.

6. Draw the equivalent sequence network diagram for a single phase

to ground fault in a power system.

7. Write the swing – equation and explain the term involved in it.

8. State equal area criterion.

9. Define load factor and plant capacity factor.

10. Draw the incremental fuel rate curve for thermal power stations

and how to draw the incremental fuel cost from it.

PART – B (5 x 12 = 60)

Answer All the Questions

11. (a) List out the advantages of per unit computations. (2)

(b) The reactance of a generator is designated X” is given as 0.2

per unit based on the generator’s name plate rating of 20 KV, 500

MVA. Find X” on the new base of 22 KV, 100 MVA. (4)

(c) A single – phase transformer is rated 110/440 V, 2.5 KVA.

Leakage reactance measured from the low-voltage side is 0.06W.

Determine leakage reactance in per unit.

(or)

12. Draw the reactance diagram using a base of 100 MVa, 220 KVin

50 ohm line.

Generator: 40 MVA, 25 KV, X” = 20%

Motor : 50 MVA, 11 KV, X” = 20%

Star – Star transformer: 40 MVA, 33/220 KV, X = 15%

Star – Delta transformer: 30 MVa, 11/220 KV, X = 15%

13. Derive load flow algorithm using Gauss – Seidal method with

flow chart.

(or)

14. Explain the step by step computational procedure for the Newton

– Raphson method of load flow studies.

15. Develop the sequence network for a double line to ground (LLG)

fault.

(or)

16. A 15 MVa, 6.9KV, generator unloaded star connected, has +ve,

-ve zero-sequence reactance of 25%, 25% and 8% respectively. A

reactor with 6% reactance based on the rating of the generator is

placed in line from neutral to ground. A line to line fault occurs at

terminals of the generator when it is operating at rated voltage

and disconnected from the system. Find the initial symmetrical

rms line and ground wire currents and line to neutral voltages, if

the fault does not involve ground.

17. Derive Expression for critical clearing angle.

(or)

18. Write the computation algorithm for obtaining swing curves

using modified Euler’s method.

19. Describe the computer approach to economic load dispatch with

flow chart.

(or)

20. The fuel cost characteristics of two generators are obtained as

under. F1 = 1000 + 50P1 + 0.01 P1

2 Rs/hr.

F2 = 2500 + 45P2 + 0.005 P2

2 Rs/hr.

If the total load to be supplied is 1000 MW, find optimal load

division between two generators.