PS-II

 Important QUestions for GTU Exam

1. Write voltage and current relationship of transmission line using A, B, C, D parameters. Write    expression of A, B, C, D parameter in terms of Y and Z for medium transmission line and long transmission line.

2. Derive equation of voltage and current of long transmission line

3. Explain Reactive power compensation of transmission line in brief.

4. A surge of 120 kv traveling in a line of natural impedance of 600 Ω arrives at a junction with two lines ofimpedances 900Ω and 300Ω respectively. Find the surge voltages and currents transmitted into each

branch line.

5.Determine the efficiency and regulation of a 3-phase, 120 km, 50Hz transmission line delivering 30MW

at 0.866 p.f. lagging,66 KV to a balanced load. The line parameters are as follows: R = 0.1Ω/km/phase, L

=1mH/km/phase, C=0.99μF/phase. Use nominal T model of transmission line

6. Derive ABCD constant for medium transmission line using nominal π representation

7. Explain factors deciding selection of circuit breaker.

8. Prove that positive sequence impedance and negative sequence impedance of fully transposed

transmission line are always equal.

9.One conductor of a 3-phase line is open. The current flowing to the delta connected balanced load through the line R is 10A. With R phase as reference and assuming phase B as open, find the symmetrical components of the line currents.

10. Differentiate symmetrical and unsymmetrical faults. List various unsymmetrical faults

11. Three impedances of 5-j10Ω, 6+j5Ω and 3+j15Ω are connected in star to R,Y and B lines of a 3300V, 3- phase, 3-wire supply. The phase sequence is RYB. Calculate the line current IR

12. Describe analysis of line to ground fault at a point of power system using symmetrical components and sequence network. Calculate the value of fault current.

13. Draw and Explain zero sequence network of transformer for Y-Y, ∆-∆, ∆-Y, Y-∆ connection with and

without neutral grounded

14. Discuss the significance of zero sequence circuit. Why should Zn appear as 3Zn in zero sequence

equivalent circuit?

15. Explain the phenomena of corona, Give reasons for following: The disruptive critical voltage is less than visual critical voltage.

16. Find the critical disruptive voltage and the critical voltages for local and general corona on a three phase overhead transmission line, consisting of three stranded copper conductors spaced 2.5 m apart at the corners of an equilateral triangle. Air temperature and pressure are 21 ˚C and 73.6 cm Hg respectively. The conductor diameter, irregularity factor and surface factor are 10.4 mm, 0.85, 0.7 and 0.8 respectively