Development of partial discharge detection and diagnostic methods of vacuum circuit breaker

There is a possibility of partial discharge (PD) occurrence due to an abnormality of the insulation and the aging of the vacuum circuit breaker (VCB) in cubicle-type gas insulated switchgear (C-GIS). PD may contribute to a risk that leads to breakdown in the worst case, and cause failure of the equipment. Thus, knowing the characteristics of the PD internal VCB is required. In this work, a development of PD detection and diagnostic method of VCB is introducedA model VCB consisting of a vacuum interrupter (VI) was connected in series with a transformer. The internal pressure of VI was set by a turbo molecular pump via flexible hose, insulating tube and leak valves. The internal pressure of VI was verified up to 10^-2 Pa by a digital metal ionization gauge. The diagnostic method was studied using a number of sensors with different specification. We have used detection resistance, horn antenna, transient earth voltage (TEV) sensor and three different frequency bands to detect PD signals.