Measurements by residual gas analysis (RGA) inside vacuum interrupters / devices

Abstract

For low and medium voltage applications the vacuum interruption principle has been well established over the past 30 years. Component materials for vacuum interrupters (VI) have to be designed for very low gas content, since this characteristic determines the quality of vacuum inside the VI for at least 30 years of service or shelf life. Vacuum integrity in a "sealed for life" VI is needed and therefore gas pressure measurements on VIs are conducted during production as a quality control process. In order to limit the pressure resolution in the range of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> hPa for a long period vacuum measuring systems are applied to assure the vacuum integrity (tightness) of the VI or vacuum device (VD). Those measurements are performed during production by magnetron (Penning principle) measurements on each VI/VD. In addition, some selected VIs are analyzed by means of residual gas analysis (RGA - mass spectroscopy) for further production control and improvement. This technique is used to detect residual gases, for example: gas sources, and to investigate the diffusion of gases from material into vacuum. The measurements of magnetron and RGA are analyzed and compared herein and a description of how to eliminate gas sources by selection of suitable materials for a VI/VD will be presented.