Partial discharge detection in gas insulation load breaker switch

This paper aims to discuss the measurement and recognition of partial discharge (PD) signals in gas insulation load breaker switch (GILBS) by using high frequency current transformer (HFCT) and acoustic emission (AE) sensors. Three kinds of fault were made purposely within the GILBS that sealed up with SF₆ gas. Then we increase the voltage onto the GILBS until it produce PDs and measure the signals with HFCT and AE sensors. If PD occurs inside the solid insulators, the phase of the electrical signals detected by HFCT, compared with the 60-Hz power line, will locate in 0°~90° and 180°~270°. If there were aluminum screenings and knobs inside the GILBS or tips on the high voltage side, the signals detected will occur between 90° and 270° due to the discharge in SF₆ gas. Because the discharge occurs at the end of the high voltage side, the electrical signals of the negative half cycles measured by HFCT are larger than those of the positive half cycles. According to the arrival time difference between HFCT sensors measuring and AE sensors measuring, the discharge place can be identified. By comparing with the electricity magnitude measured from the electrical signals, the discharges generate 30 pC (picocoulomb) or so. This detection method can also be applied to the online measurement of gas insulation switchgear (GIS).