Internal corona spaces in cables

IN THE DEVELOPMENT of high-voltage cables insulated with thermoplastics or rubber, it is necessary to measure the corona onset voltage. The manometric method detects internal corona by the decrease in air pressure caused by absorption of corona-activated oxygen. The rate of pressure drop increases rapidly with voltage. By connecting a capillary oil manometer to the sample, this pressure drop can be measured. In this study, all voltages are 60 cycles rms.