1.a) Explain the concept of GMR and GMD.
b) Calculate the inductance and reactance of each phase of a three phase 50 Hz overhead line which has conductors of 2.5 cm dia. The distance between the three phases are 5 cm between a and b, 4 cm between band c and 3m between c and a. Assume that the phase conductors are regularly transposed. [15]
2.a) Explain under which circumstances we will consider T-representation and -representation for transmission lines. Π
b) For a 3φ 400kv line A = D= 0.86, B= 13.2Ω, C= 0.002 mho, obtain the regulation when the line is delivering 120 MVA AT 0.8pf tag. [15]
3. Explain the terms surge impedance, surge impedance loading and velocity of propagation of waves w.r.t the transmission lines. [15]
4.a) Mention the advantages of Bewley’s lattice diagram.
b) A surge of 110 kv travels on a line of surge impedance 500Ω and reaches a T junction. The surge impedances of the branch lines are 450 and 50.Determine the reflected and refracted values of currents and voltages. [15] ΩΩ
5.a) Explain about the Ferranti effect occurring in transmission lines. How to overcome this effect?
b) A 3φ equilaterally spaced transmission line has a total corona loss of 55 kw at 110kv and a loss of 110 kw at 120 kv. What is critical disruptive voltage between lines? What is the corona loss at 125 kv. [15]
6.a) Explain about various types of insulators used for overhead transmission lines.
b) Describe how static shielding improves string efficiency in transmission lines.
[15]
7.a) Derive the equation for sag when the two supports are at equal heights.
b) Explain how stringing chart is useful in erecting the transmission line. [15]
8.a) Describe the constructing and working principle of a 3 core belted cable.
b) Explain the relative advantages and disadvantages of various types of grading procedures adopted in under ground cables. [15]
b) Calculate the inductance and reactance of each phase of a three phase 50 Hz overhead line which has conductors of 2.5 cm dia. The distance between the three phases are 5 cm between a and b, 4 cm between band c and 3m between c and a. Assume that the phase conductors are regularly transposed. [15]
2.a) Explain under which circumstances we will consider T-representation and -representation for transmission lines. Π
b) For a 3φ 400kv line A = D= 0.86, B= 13.2Ω, C= 0.002 mho, obtain the regulation when the line is delivering 120 MVA AT 0.8pf tag. [15]
3. Explain the terms surge impedance, surge impedance loading and velocity of propagation of waves w.r.t the transmission lines. [15]
4.a) Mention the advantages of Bewley’s lattice diagram.
b) A surge of 110 kv travels on a line of surge impedance 500Ω and reaches a T junction. The surge impedances of the branch lines are 450 and 50.Determine the reflected and refracted values of currents and voltages. [15] ΩΩ
5.a) Explain about the Ferranti effect occurring in transmission lines. How to overcome this effect?
b) A 3φ equilaterally spaced transmission line has a total corona loss of 55 kw at 110kv and a loss of 110 kw at 120 kv. What is critical disruptive voltage between lines? What is the corona loss at 125 kv. [15]
6.a) Explain about various types of insulators used for overhead transmission lines.
b) Describe how static shielding improves string efficiency in transmission lines.
[15]
7.a) Derive the equation for sag when the two supports are at equal heights.
b) Explain how stringing chart is useful in erecting the transmission line. [15]
8.a) Describe the constructing and working principle of a 3 core belted cable.
b) Explain the relative advantages and disadvantages of various types of grading procedures adopted in under ground cables. [15]
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