# BE Transmission And Distribution Fifth Sem

Answer All the Questions
1. Give four advantages of EHVAC Transmission.
2. State Kelvin’s Law? And discuss its limitations.
3. What do you understand by the constants of an overhead
transmission line?
4. What is skin effect? Why is it absent in the d.c. system?
5. List out two advantages and disadvantages of corona.
6. What do you understand by medium transmission lines? How
capacitance effects are taken in to account in such lines?
7. Define Thermal Resistance of a Cable.
8. Define and explain string efficiency. Can its value be equal to
100%.
9. What is a sag in overhead lines?
10. Why are Dampers preferred for high voltage power lines?
PART – B (5 x 12 = 60)
Answer All the Questions
11. What is electric power supply system? Draw and explain a single
line diagram of a typical a.c supply scheme.
(or)

12. (a) What are the advantages and disadvantages of d.c
transmission over a.c transmission? (8)
(b) How will you determine the economic transmission
voltage? (4)
13. Derive an expression for the inductance per phase for a three
phase overhead transmission line.
(a) When conductors are symmetrically placed.
(b) Conductors are unsymmetrically placed but line is
completerly transposed.
(or)
14. (a) A 3-phase, 50Hz, 66kV overhead line conductors are placed
in a horizontal plane as shown in fig (i) the conductor diameter is
1.25cm. If the line length is 100 km, calculate.
(i) Capacitance per phase (ii) Charging current per phase,
assuming complete transposition of line.
• 2m • 2.5m •
(b) Calculate the inductance of each conductor in a 3-phase, 3-
wire system when the conductor are arranged in a horizontal
plane with spacing such that D31 = 4m; D12 = D23 = 2m. The
conductors are transposed and have a diameter of 2.5 cm.
15. (a) Explain the procedure for determining the transmission
efficiency and voltage regulation of a long transmission line. (5)
(b) Determine the sending end voltage for following, using
Normal p method. The transmission line is 120 km long and
delivers 40MW at 132Kv and 0.8 p.f. lagging. (7)