52130-mt----dielectric And Insulation Engineering

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Code No: 52130/MT M.Tech. – I Semester Supplementary Examinations, September, 2008 DIELECTRIC AND INSULATION ENGINEERING (Power Systems (High Voltage)) Time: 3hours

Max. Marks:60 Answer any FIVE questions All questions carry equal marks ---

1.a) b)

Clearly explain the design procedure of power cable insulation. Explain the factors that are taken into account while designing the insulation of capacitors.

2.a)

Derive an expression for maximum thermal voltage and show that the voltage is independent of thickness of the specimen. State clearly the assumptions made. Discuss about applications of various organic materials as insulators.

b) 3.a) b) 4.a) b)

5.a) b) 6.a) b)

Explain the phenomenon of electrical conduction in liquids. How does it differ from that in gases. What are the factors that influence conduction in pure liquid dielectrics and commercial liquid dielectrics. What is “Vacuum” and “high Vacuum” ? How does conduction takes place in Vacuum under high Electric fields? How does “Break down” occur in Vacuum? Explain briefly the factors affecting the break down and the mechanisms involved in it? Explain the streamer theory of break down in air at atmospheric pressure. Explain about “penning effect” when referred to gaseous discharges. Discuss about break down in Non-Uniform fields. Describe how the Vacuum break down is different from normal break down of a gas. Contd…2.,

Code No: 52130/MT

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7.

Explain about break down of commercial liquids. a) Suspended particle theory b) Bubble theory.

8.a) b)

What is a composite dielectric and what are it’s properties? Describe the mechanism of short term break down of composite insulation. ******