Electric strength of liquid-filled plastics tape insulation

The paper describes electrical-breakdown experiments performed on thin, flat packs of plastics film impregnated with mixtures of dielectric liquids of different composition. Using this technique, it is possible to distinguish the direct effect of the ratio of the liquid and solid relative permittivities on the electric strength of the composite from the characteristics of particular materials. It is shown that the impulse electric strength of the composite depends only on the stress in the liquid at the breakdown site and its electric strength, but, for mineral oil or silicone oil alone, the composite may have a considerably greater electric strength than expected on this basis. The magnitude of the increase is governed by the solid.