Mechanical forces in insulating liquids subjected to high electrical fields

The thesis presents an experimental investigationof the forces and pressures acting on an air bubbleinjected in transformer oil, under different test con-ditions.’-- The gap configuration consisted of. a sphere-plane electrode system, the sphere had a diameter of11.2 mm and the circular plane had a diameter of 30 mm.The sphere electrode was drilled along a diameter, andby the novel test cell used it was possible to injecta controlled air bubble in the liquid at the surfaceof the sphere electrode.The test cell and experimental technique wassuitably designed to measure the internal pressure ofthe air bubble, and hydrostatic pressure above it.The values of internal pressure Pi and the hydrostaticpressure Ph were recorded under different test conditions.The effects of hydrostatic pressure, applied voltage andgap setting were studied for both alternating and directapplied voltages of different polarities.A family of relationships between the.internalpressure of the bubble and the hydrostatic pressure atdifferent applied voltage were obtained for five gapsettings, under A.C. and D.C. reverse poLaity voltages.