B.Tech-B.Tech Electrical and Electronics Engineering 5th Sem Transmission and Distribution of Electrical Power 5E3127(Rajasthan Technical University-2012)
5E3127
B.Tech. V Sem.{Main/Back) Exam. Dec. 2012
Electrical and Electronics
5EX5 Transmission and Distribution of Electrical Power
Common for EE
Time: 3 Hours
Maximum Marks: 80
Min. Passing Marks: 24
UNIT - I
Q.1(a) (i) Distinguish between a feeder and a distributor. Draw single line diagram representing elements of a transmission system.
(ii) State and explain Kalwin's law. Discuss its limitations.
(iii) What are the basic considerations which Influence the design of distribution system? [8]
(b) Write short note on Radial, Ring Main and Interconnected system. [8]
OR
Q .1 (a) Discuss the various factors which affect the choice of the most economical voltage for a transmission system. [8]
(b) (i) What is meant by the terms feeders, distribution and service mains. Why the distribution by A. C. consider superior to that by D.C.? [4]
(ii) A 2- conduction cable one Km in length is required to supply a constant load of 200A throughout the year. The cost of cable is Rs(100+40) per meter where a is the area of the cross section of the conductor cm square. The cost of energy is l0P per KWH and interest and depreciation charges amount to 10%. Specific resistivity of copper is l.85 r Ω-cm. Find the cross - section area 'a'? [4]
UNIT-ll
Q.2 (a) Develop an expression for lag of a transmission line conductor suspended between supports at equal heights, assuming the curve taken up by conductor to be a parabola. [8]
(b) (i) Describe the string chart and its use. [3]
(ii) A transmission line conductor at a river crossing is supported from two towers at height of 50m and 80m above water level The horizontal distance betweenthe towers is 300 meter. If the tension in the conductor is 2000 kg. Find the clearance between the conductor and water at a point midway between the towers. Weight of the conductor per meter is 0.844 kg. Assume that the conductor takes the shape of parabolic curve. [5]
OR
Q.2 (a) A transmission line conductor at a river crossing is supported from two towers at height of 30m and 90m above water level The horizontal distance between the tower is 270 m. If the tension in the conductor is 1800 kgf and the conductor weight is 1kgf per meter, Find the clearance between the conductor and the water at a point midway between the towers. Assume parabolic configuration. [8]
(b) Discuss the various types of line supports. [8]
UNIT-III
Q.3 (a) (i) Write short note on skin,proximity effects. [4]
(ii) Draw phasor diagrams for a nominal π circuits and nominal T circuit of transmission line. Derive expressions for sending end voltage and curreot in each case. [4]
(b) Derive the expression for the inductance for condnctor of 3- phase line. The conductors are placed at the corners of an equilateral triangle. [8]
OR
Q .3 (a) How is the inductance of a single phase two wire line calculated? Describe the process how you will calculate the inductance of each conductor here due to internal and external flux linkages. [8]
(b) Discuss the concept of geometric means distance. How is this concept used to find inductance of composite conductor line. [8]
UNIT-IV
Q .4 (a) (i) Derive the expressions for A,B,C and D constants of a long transmission line in terms of line parameters. [4]
(ii) Explain Ferranti effect in detail with the help of phasor diagram. [4]
(b) (i) Explain the phenomenon of corona. What are the factors affecting corona? [4]
(ii) A 3-phase 220 k:v, 50Hz, transmission line consists of 2cm radius conductors spaced 25m apart in equilateral triangle formula. If the temperature is 20°Cand atmospheric pressure 75cm, m = 0.80, Detenninethe corona loss per Km of line. [4]
OR
Q.4 (a) What is meant by visual critical voltage and disruptive corona voltage? Explain bliefly the method adopted to avoid or reduce corona. [8]
(b) Write short notes on interference of power lines with communication circuits. [8]
UNIT-V
Q.5 (a) (i) A 3- phase line is Supported by suspension string having three units. The voltage across the unit nearest to the line is 20 KV and that acrossthe adjacent units is 15 KV Find
(I) Ratio of capacitance of joints to capacitance of disc
(II) System line voltage
(III) String efficiency [8]
(b) What is string efiiciency? Why is it necessary to have a high string efficiency? How can it be achieved. [8]
OR
Q.5 (a) (i) Name the different types of insulators used in power systems along with the use of each insulator and explain pin type insulator in detail. [4]
(ii) A suspension string has 3 units. Each unit can with stand a maximum peak voltage of 11KV The capacitance of each point and metal work is 20% of the capacitance of each disc. Find:
(i) Maximum line voltage for which string can be used.
(ii) String efficiency [4]
(b) (i) Describe general construction of cable. What are necessary requirement of cable? [4]
(ii) Derive a formula for electric stress in single core cable. Where is stress maximum? Where is it minimum? [4]
| Earning: ₹ 6.90/- |
