A Study of Internal Discharges in Cable Insulation

A study has been made of discharges occurring in voids. A sample of convenient size is described. A method of mea suring the discharge pulse has been developed which reduces the inductance of the circuit to a minimum. As a result it has been found that the pulses have rise times of the order of 1 ns which is shorter than previously anticipated. Extremely fast discharges may be counted. A method of counting pulses larger than some predetermined magnitude is presented. Where one surface of the void is a semiconductor, the positive and negative pulses are shown to decrease at different rates. Evidence of pulse shape due to discharge in a void can be determined by instrument.