Answer any three including Q1 which compulsory Q1. Answer all the questions. a) Define string efficiency. Explain how to improve string efficiency. b) What is sag? What are the factors affecting sag. c) Explain conductor vibration. What are the different types of conductor vibrations? d) Discuss and compare the cost of investment in ac and dc transmission showing the graph. e) What are the advantages of DC transmission? Q2. A stress crossing overhead line has a span of 150m over the stream. Horizontal wind pressure is 20 Kg/m 2 and the thickness of the ice is 1.25cm. Diameter of the conductor is 2.80 cm and weight is 1520Kg/Km, and an ultimate strength of 12900Kg. Use a factor of safety of 2 and 912Kg/m 3 for the weight of ice. Determine weight of ice in Kg/m, total vertical load on conductor in Kg/m and the vertical sag in m. Q3. In a 33Kv overhead line, there are three units in the string of insulators. If the capacitance between each insulators and earth is 11% of self capacitance of each insulator, find (i) the distribution of voltage over 3 insulators and (ii) the string efficiency. Q4. A two-wire dc distributor AB 300m long is fed at both ends A and B. The distributer supplies uniformly distributed load of 0.25A/m and concentrated loads of 40A at C and 60A at D. The distances AC and BD are 120m each. The top resistance of distributor is 0.1 ohm/100m. Both A and B are maintained at 300V. Find the currents fed at A and B and potentials of points C and D.

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Answer any three including Q1 which compulsory

Q1. Answer all the questions.

a) Define string efficiency. Explain how to improve string efficiency.b) What is sag? What are the factors affecting sag.c) Explain conductor vibration. What are the different types of conductor vibrations?d) Discuss and compare the cost of investment in ac and dc transmission showing the graph.e) What are the advantages of DC transmission?

Q2. A stress crossing overhead line has a span of 150m over the stream. Horizontal wind pressure is 20 Kg/m2 and the thickness of the ice is 1.25cm. Diameter of the conductor is 2.80 cm and weight is 1520Kg/Km, and an ultimate strength of 12900Kg. Use a factor of safety of 2 and 912Kg/m3 for the weight of ice. Determine weight of ice in Kg/m, total vertical load on conductor in Kg/m and the vertical sag in m.

Q3. In a 33Kv overhead line, there are three units in the string of insulators. If the capacitance between each insulators and earth is 11% of self capacitance of each insulator, find (i) the distribution of voltage over 3 insulators and (ii) the string efficiency.

Q4. A two-wire dc distributor AB 300m long is fed at both ends A and B. The distributer supplies uniformly distributed load of 0.25A/m and concentrated loads of 40A at C and 60A at D. The distances AC and BD are 120m each. The top resistance of distributor is 0.1 ohm/100m. Both A and B are maintained at 300V. Find the currents fed at A and B and potentials of points C and D.