Abstract: A sensitive yet non-destructive method and apparatus for detecting the presence of voids contained within dielectric materials is disclosed which comprises applying a voltage across the dielectric material to create an electric field therethrough, increasing this voltage to create a partial electrical discharge and monitoring the field current to detect the voltage at which partial discharge occurs. When the partial discharge is detected, the voltage applied across the test material is recorded. Reference can then be made to mathematical charts and formulas readily available to determine the size and shape of the detected void.

Abstract: The pressure of a gas within an enclosure is measured without making physical contact with the gas by focusing radiation from a laser onto a section of the gas and, while varying the intensity of the radiation, monitoring the section under measurement for electrical breakdown, as indicated by emitted light or suitable breakdown indicia, such as radio noise. The absolute gas pressure at the section of the gas under measurement is determined from a calibration curve relating the intensity of the beam to the pressure at which breakdown occurs for the particular gas being monitored.

Abstract: Before impregnation with fluid a capacitor roll, or a transformer core and coil, is filled with a monomeric gas that is thereafter polymerized, in situ, in a plasma discharge. Formation of solid polymer occurs at the regions of most intense electric field, thereby raising both corona-start and operating voltage for these devices.