Influence of Cofield liquid flow on the breakdown strength of mineral oil under highly nonuniform fields

This paper reports the effect which forced flow velocity has on the breakdown strength of transformer oil using a needle point opposite a meshed plane electrode and direct voltages. Tests were carried out for gaps 100-700 μm and flow velocities 0-280 m/s; the direction of flow was from the point electrode to the plane electrode. Measurements were carried out on degassed oil, O₂-saturated oil, SF₆-saturated oil and oil with 0.1 molar 1-methylnaphthalene as additive, for both polarities of the point. The results are presented in the form of plots of the nominal field at the point versus gap length for different oil velocities.