Detection and measurement of discharges in gaseous cavities in solid dielectrics under impulse voltage conditions

A technique for detecting and measuring internal discharges in solid dielectrics under impulse-voltage conditions has been developed. The test object forms one arm of a capacitance bridge which is fed with 1/50μs voltage impulses having peaks of up to 15kV. The bridge is connected through a pulse transformer and a bandpass filter to valve amplifiers and a cathode-ray oscillograph, on which are displayed the voltages arising from internal discharges. Calibration is effected by feeding known voltages into the circuit from a pulse generator.The technique has been used in an experiment on a cylindrical air-filled cavity of known dimensions in polythene. It is considered that it will be of value in studying gaseous-discharge phenomena and processes that can lead to the breakdown of a wide range of solid insulating materials.