Investigation on Potential of Floating Electrode in Modeled Vacuum Interrupter during AC Voltage Application

This paper describes about a charging characteristics of a floating electrode during unipolar AC voltage application. A model sample of Vacuum Interrupter has a floating electrode between two alumina cylinders. Two kinds of sample were prepared which are attached with or without electric field relaxation shield rings at the both side of floating electrode. A real time measurement of charging potential during applying high voltage was conducted using a surface potential meter not to contact the floating electrode.From the results, when a high voltage was applied, a charging potential was observed enough to change the potential of the floating electrode strongly. In the case of sample without shield rings at the floating electrode, the floating electrode was positively charged due to the field electron emission from the floating electrode itself. In the case of sample with shield rings, it was negatively charged due to the influx of electrons into the floating electrode from the high voltage electrode in the early stage of high voltage application. That is caused by the suppression of electron emission from the floating electrode due to the attachment of the shield rings. In addition, these charging potential was suppressed after high voltage conditioning process.