AU Solved Paper

AU Solved Paper [41000]

May - 2018

Transmission and Distribution

Semester - IV (EEE) (Regulation 2013)

 

[Time          : Three Hours]    

[Maximum Marks : 100]

 

Answer ALL questions

PART A - (10 × 2 = 20 Marks)

 

Q.1    What are the advantages of FACTS controllers ?

[Refer Two Marks Q.16 of Chapter - 7]

Q.2    What are the advantages of an interconnected system ?

[Refer Two Marks Q.45 of Chapter - 7]

Q.3    What is meant by proximity effect ?

[Refer Two Marks Q.13 of Chapter - 1]

Q.4 What are the methods adopted to reduce corona loss ?

[Refer Two Marks Q.8 of Chapter - 3]

Q.5 What is Ferranti effect ?

[Refer Two Marks Q.6 of Chapter - 2]

Q.6 What is surge impedance loading ?     

[Refer Two Marks Q.8 and Q.18 of Chapter - 2]

Q.7 State the advantages of suspension type insulators.

[Refer Two Marks Q.5 of Chapter - 5]

Q.8 What are main requirements of the insulating materials used for cable ?

(Refer Two Marks Q.13 of Chapter - 6)

Q.9 What is sag template ?

[Refer Two Marks Q.8 of Chapter - 4]

Q.10 What is gas insulated substation ?

[Refer Two Marks Q.18 of Chapter - 8]

 

PART B - (5 × 13 = 65 Marks)

Q.11 a) Draw and explain the structure of modern power system with typical voltage levels.

[Refer section 1.2]

OR

b) Discuss the advantages of HVDC transmission over HVAC transmission in detail.

[Refer section 7.25.2]

Q.12 a) Determine the inductance of a single phase transmission line consisting of three conductors of 2.5 mm radii in the 'go' conductor and two conductors of 5 mm radii in the, return, conductor. The configuration of the line is as shown in Figure below.

[Refer example 1.21.2]

OR

b) A three-phase, 50 Hz, 132 kV overhead transmission line has conductors placed in a horizontal plane 4 m apart. Conductor diameter is 2 cm. If the line length is 100 km, calculate the charging current per phase assuming complete transposition.

[Refer example 1.29.3] [9]

Q.13 a) Determine the efficiency and regulation of a 3-phase, 100 km 50 Hz transmission line delivering 20 MW at a.pf. of 0.8 lagging and 66 kV to a balanced load. The conductor are of copper, each having resistance 0.1 ohm per km, inductance 1.117 mH per km and capacitance 0.9954 µF per km. Neglect leakage and use nominal n-method.

[Refer example 2.8.6]

OR

b) Derive the expression for voltage and current at any point 'x' from the receiving end of a long transmission line.

[Refer section 2.11]

Q.14 a) In a 33 kV overhead line, three are there units in the string of insulators. If the capacitance between each insulator pin and earth is 11 % of self-capacitance of each insulator, find the distribution of voltage over 3 insulators and string efficiency.

[Refer example 5.5.4]

OR

b) i) Derive the expression for the capacitance of a single-core cable.

[Refer section 6.7]         [8]

ii) A single core cable has a conductor diameter of 1 cm and internal sheath diameter of 1.8 cm. If impregnated paper of relative permittivity 4 is used as the insulation calculate the capacitance for 1 km length of the cable.

[Refer example 6.7.7]

Q.15 a) A transmission line conductor having a dia of 19.5 mm weights 0.85 kg/m. The span is 275 meters. The wind pressure is 39 kg/m2 of projected area with ice coating of 13 mm. The ultimate strength of the conductor is 8000 kg. Calculate the maximum sag if the factor of safety is 2 and ice weights 910 kg/m 3.

[Refer example 4.4.8]

OR

b) Explain the following neutral grounding methods.

i) Solid grounding [Refer section 8.13.1]   [6]

ii) Resistance grounding [Refer section 8.13.2]    [7]

 

PART C - (1 x 15 = 15 Marks)

Q.16 a) A 2-wire d.c. street mains AB, 600 mm long is fed from both ends at 220 V. Loads of 20 A, 40 A, 50 A and 30 A are tapped at distances of 100 m, 250 m, 400 m and 500 m from the end A respectively. If the area of X-section of distributor conductor is 1 square centimeter, find the consumer voltage. Take p = 1.7 x 10-6 ohm-cm.

[Refer example 7.11.8]

OR

b) A single phase distributor 'AB' 300 m long supplies a load of 200 A at 0.8 pf lagging at its far end 'B' and a load of 100 A at 0.707 pf lagging at 200 m from sending end point A. Both pf are referred to the voltage at the far end. The total resistance and reactance per km (go and return) of the distributor is 0.2 ohm and 0.1 ohm. Calculate the total voltage drop in the distributor.

[Refer example 7.13.1]