60 HZ Behaviour of Vaccum Insulation in High Voltage Switchgear

Vacuum has special properties which make it a potentially good insulating medium for the power industry but high voltage 60 Hz performance data is lacking. Experimental data is presented on the 60-Hz behaviour of vacuum insulation for gap lengths 0.5 to 2.0 cm between metal electrodes in a dynamically pumped system operating at 10-6 torr. The results are compared with the dc characteristics of vacuum insulation for similar test conditions. Prebreakdown phenomena and protrusion formations under 60 Hz voltage stress appear to be distinctly different. Specific recommendations are set out to guide further research effort, and to meet the particular requirements of vacuum insulation for high voltage power apparatus.