The Effect of High Oil Pressure Upon the Electrical Strength of Cable Insulation

Long time overvoltage tests on oil treated cable samples and short time and impulse tests on oil treated paper sheet samples indicate that an increase in the hydrostatic pressure of the oil will result in an increase in the breakdown voltage. The magnitude of this increase depends on the time duration of the test. A doubling of breakdown voltage was secured by a pressure increase from 1 to 6 atmospheres in the case of the long time (several weeks) while no improvement at all was secured in the case of the impulse tests (several microseconds duration) by a pressure increase up to 11 atmospheres.