High Voltage Engineering — Summer 2018

Explain streamer theory of breakdown in gases.

Aten stage Cockroft-Walton circuit has all capacitors of 0.06 μF. The secondary voltage of the supply transformer is 100 kV at a frequency of 150 Hz. If the load current is 1 mA, determine:

Percentage voltage regulation (ii) Percentage ripple (iii) Optimum number of stages for maximum output voltage (iv) Maximum output voltage.

Define Townsend’s first and second ionization coefficients. Obtain current growth equation due to first and second ionization.

Draw & explain Marx circuit and modified Marx circuit of multistage impulse generator. Discuss differences between these two.

Describe the working of a Van de Graff generator with a neat sketch.

What are “Treeing” and “Tracking”? Explain and compare the two processes in solid dielectrics.

Explain corona discharges, due to non-uniform field, in detail.

List out the theories for breakdown in Liquids. Explain Cavitation and bubble theory in detail.

Define and explain the following terms with necessary figure:

Statistical time lag, ii) formative time lag, iii) total time.

Explain how a sphere gap can be used to measure the peak value of voltages. What are the parameters and factors that influence such voltage measurement?

Describe the principle of rotating vane type generating voltmeter with schematic diagram. List out advantages and disadvantages of Generating Voltmeter.

Explain capacitance voltage transformer with its basic structure, schematic representation and equivalent circuit.

Explain with neat diagram the principle of operation of an electrostatic voltmeter. Discuss its advantages and limitations for high voltage measurement.

Draw and Explain the layout of H.V. voltage laboratory. What are the precautions to be taken for the safety?

Explain liquid insulation purification system with neat diagram.

Explain the lightning mechanism including leader and return stroke with appropriate figures.

What is non-destructive testing of materials? Explain the partial discharge measurement method with suitable diagrams.