On the Creepage Over Solid Insulation in Air and Oil

Abstract

The creeping spark discharge over solid insulation in air and transformer oil is investigated for the case:-
(I) With the electrodes on the same side of the glass plite.
(II) With the electrodes placed on opposite sides of the glass plate.
In the case (I), the spark discharge in oil does not always creep over the solid insclation as in air, but passes at intervals into oil, diverging some disance from the surface.
In the case (II), in air, the spark discharges on both sides more distinetly creep along the surface of the solid in ultaion, somewhat restraining each other. In oil, however only in the positive side it creeps over the solid insuhtion, and in the negafive side it onguas in oil far apart from the surface.
Such a difference in character of creeping discharge in oil compared with chat in air seems to depend on the deficiency of free electron and the lack of homogeneily in oil.