A diagnostic technique to detect abnormal conditions of contacts measuring vibrations in metal enclosures of gas insulated switchgear

The diagnosis of abnormal conditions at current-conducting contacts by measuring the metal-enclosure vibrations of gas-insulated switchgear was studied experimentally and theoretically. Vibrations appeared when current flowed through artificially simulated abnormal contacts. Vibration peaks existed at frequencies which were integral values times the current frequency, especially between 400 Hz and 2 kHz. Vibration peak values increased as contact voltage increased above 400 Hz. Contact voltage waveforms in the stable state were distorted and their top peaks became sharp as the contact voltage increased. The reason for the distortion was the temperature rise which accompanied the alternating current change