Effect of oil pressure on insulation strength

The effect of high oil pressure upon the electrical strength of cable insulation has been subjected to a series of tests which are reported in this paper. These tests show that an increase in pressure will result in an increase in the breakdown voltage, the magnitude depending upon the time duration of the test. Although in the long time tests breakdown voltage was doubled by pressure increased from 1 to 6 atmospheres, no improvement was secured with impulse tests by a pressure increase up to 11 atmospheres.