Quantitative measurements of corona on high voltage cables for space and high altitude applications

High voltages in space and high altitude airborne equipment require highly reliable interconnections which makes the use of high voltage cables necessary. While it is possible to use sealed pressurized cables, the possibility of a leak means that the cable may pass through critical pressure while energized and failure may result. A flexible solid cable has an inherently higher reliability if the ordinary modes of failure can be eliminated. The most important modes of failure of high voltage cables are catastrophic dielectric breakdown and degradation due to corona discharges. The life of the cable is determined by the rate of corona degradation which is a function of the corona intensity in general, and in particular of the energy density of the corona in the largest voids. These modes of failure assume special significance for cables operating at high altitudes or in space vacuum due to the possibilities of exposing the series airgaps in voids or interfaces to low gas pressure. In accordance with Paschen's law, discharges will occur in these gas layers at much lower voltages and, thus, lead to corona at voltages which are lower than operating values.