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B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER

2010 Fifth Semester

Electrical and Electronics Engineering EE 2303 — TRANSMISSION AND DISTRIBUTION

(Regulation 2008) Time : Three hours Maximum : 100 Marks

Answer ALL questions

PART A — (10 × 2 = 20 Marks)

1. State the disadvantages of HVDC transmission.

2. Which factors affect sag in the transmission line?

3. Define skin effect.

4. What are the advantages of using bundled conductors?

5. What is Ferranti effect?

6. What is shunt compensation?

7. Define string efficiency.

8. What is the necessity of grading of an under ground cable?

9. List the various substation equipments.

10. Why are transmission lines 3 phase 3 wire circuits while

distribution lines are

3 phase 4 wire circuits?

PART B — (5 × 16 = 80 Marks)

11. (a) Discuss in detail the various equipments used in HVDC

converter

station.

Or

(b) An overhead line has a span of 336 m. The line is supported ,at a

water

Crossing from two towers whose heights are 33.6 m and 29 m above

water level. The weight of conductor is 8.33 N/m and tension in the

conductor is not to exceed 3.34 × 104 N. Find (i) Clearance between

the

lowest point on the conductor and water (ii) horizontal distance of this

point from the lower support.

12. (a) Derive the expression for inductance of a three phase line with

unsymmetrical Spacing.




Or

(b) A 220 KV, 50 Hz, 200 Km long three phase line has its conductors

on the

corners of a triangle with sides 6 m, 6m and 12 m. The conductor

radius

is 1.81 cm. Find the capacitance per phase per km, capacitive

reactance

per phase, charging current and total charging Mega volt-amperes.

13. (a) What is a nominal ? (pi) circuit? Find the ABCD constants for

nominal

? Circuit.

Or

(b) Write short notes on :

(i) Shunt compensation. [Marks 8]

(ii) Series compensation. [Marks 8]

14. (a) Discuss briefly on the following :

(i) Pin Type insulator. [Marks 8]

(ii) Suspension Type insulator. [Marks 8]

Or

(b) Derive the expression for the Insulation resistance, capacitance,

Electric

stress and dielectric loss of a single core cable.

15. (a) Explain briefly the various types of bus bar arrangements in a

substation.

Or

(b) Discuss briefly each of the following :

(i) Feeders. [Marks 4]

(ii) Radial distribution. [Marks 6]

(iii) Ring main distribution. [Marks 6]




B.E./B.Tech. DEGREE EXAMINATION, NOVEMBER/DECEMBER 2011.

Fifth Semester

Electrical and Electronics Engineering

EE 2303 — TRANSMISSION AND DISTRIBUTION

(Regulation 2008)

Time : Three hours Maximum : 100 marks

Answer ALL questions.

PART A — (10 × 2 = 20 marks)

1. List out the advantages of high voltage A.C. transmission.

2. What is meant by stringing chart?

3. What is the need of transposition?

4. Define the term critical disruptive voltage.

5. Distinguish between attenuation and phase constant.

6. What is meant by Ferranti effect?

7. What are the advantages of string insulators?

8. What are the methods of grading of cables?

9. What are the various methods of earthing in substations?

10. Define the terms feeders and service mains.

PART B — (5 × 16 = 80 marks)

11. (a) (i) What are the various types of HVDC links? Explain them in detail. (10)

(ii) Explain the principle of operation of compensators used for Voltage

Control. (6)




Or

(b) A transmission line conductor at a river crossing is supported from

two towers at a height of 50 and 80 metres above water level. The

horizontal distance between the towers is 300 metres. 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 conductor per metre = 0.844 kg. Derive the formula used. (16)

12. (a) Find the inductance per phase per km of double circuit 3 phase line

shown in Fig. (12. a). The line is completely transposed and operates

at a frequency of 50 Hz. (16)

Fig. (12.a)

Or

(b) (i) Derive the expression for the voltage induced in communication

lines due to the current in power lines. (8)

(ii) Explain the various factors affecting the corona loss. (8)




13. (a) A balanced 3 phase load of 30 MW is supplied at 132 kV, 50 Hz and

0.85 P.F. lagging by means of transmission line. The series

impedance of a single conductor is (20 + j52) ohms and the total

phase-neutral admittance is 315 × 10–6 mho. Using nominal-T

method, determine :

(i) The A, B, C and D constants of the line.

(ii) Sending end voltage.

(iii) Regulation of the line. (16)

Or

(b) A 3 phase line having an impedance of (5 + j20)� per phase delivers

a load of 30 MW at a power factor of 0.8 lag and voltage of 33 kV.

Determine the capacity of the phase modifier to be installed at the

receiving end if the voltage at the sending end is to be maintained at

33 kV. Assume the shunt admittance is neglected. (16)

14. (a) A 3 phase overhead transmission line is being supported by three

disc insulators. The potentials across top unit and middle unit are 9

kV and 11 kV respectively. Calculate (i) the ratio of capacitance

between pin and earth to the self-capacitance of each unit. (ii) the

line voltage and (iii) string efficiency. (16)

Or

(b) With neat diagrams explain constructional features of various types

of cables. (16)




15. (a) Draw the circuit arrangement and explain the various elements of

the following bus-bar arrangements. (16)

(i) Single bus scheme.

(ii) Double bus-bar scheme

(iii) Main and transfer bus-bar

(iv) Mesh scheme.

Or

(b) A 3 wire d.c. distributor is fed at one end at 220V between wires and

middle wire as shown in Fig. (15.b). The numbers between section

indicate the resistance of the respective section. Calculate the voltage

between middle wire and outer at each load point. (16)

Fig. (15.b)




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