الفهرس 
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Abstract
The experimental study presented in this thesis gives the results of breakdown voltage measurements in transfor¬mer oil and liquid paraffin under direct voltages for both uniform and non-uniform electrode geometries. The effects. of dissolved gases, additives, eleotrode material, polarity of the point electrode and the manner of polarity reversal on the breakdovrn voltage of the liquid were examined for gap lengths varying from 50 to 800 microns.
Both air and oxygen when dissolved in transformer oil affected the breakdown voltage and shifted the cJJDssover point in the breakdown voltage - gap length characteristics for both polarities of the point electrode. With liquid paraffin, nitrogen seemed to have no effect, while oxygen shifted the crossover point to a smaller gap in case of etched aluminium sphere but had no effect in the case of a stainless steel electrode.
For point ~to- sphere electrodes and transformer 01+, the breakdown voltage was found to depend on the manner by which the polarity reversal was carried out. With liqlrld paraffin, however, the test results showed that there was no such effect indicating that the formation of homocharges depends on the type of liquid.
The effect of different molar concentrations of methylnaphthalene as an additive on the breakdown voltage of the liquid paraffin for both uniform and non - uniform field configurations has also been studied. The results indicate the presence of an optim~~ additive concentration corresponding to a maximum increase in the breakdown volt¬age and a maximum deerease in the cross-over gap length.
The ’discussion of the results is based on the pr~ pagation of a corona discharge from the point electrode and the possibility of ,formation of a backstreamer from the sphere electrode.
The influence of the additive is explained in terms of.~ the formation of a negative space char@B whioh effeotiv¬ely quenohes the propagation of initiating streamers. The quenching effectiveness depends on the a4ditiveconcent1’ation.