Partial Discharges are the defects found by ultrasound in medium and high voltage installations. They are unwanted electrical discharges that bypass isolation between a conductor and ground. The resulting current flow may cause breakdown and finally lead to the complete failure of the equipment.
The escape of electricity causes an air ionization around which produces a broad sound spectrum, including ultrasound frequencies. The ultrasound components contain rich information useful to distinguish between Corona, Tracking and Arcing defects. The diagnosis is based first on listening to the heterodyned signal. It will greatly facilitated by the analysis of time and frequency signals. The SDT270 ultrasound detector is an ideal tool for this purpose.