Construction of measurement system of PD phenomena in medium vacuum region of vacuum interrupter

Vacuum interrupter (VI) is an alternative device that contributes to reduce usage of SF₆ gas insulated apparatus in the future. For the past research, we have investigated the partial discharge (PD) phenomena and determined the gas pressure in VI based on PD patterns from 1 Pa to kPa order. We revealed that the pressure below and above 260 Pa were attributed to Townsend and Streamer-like discharge, respectively. We realized that it is also important to identify the PD phenomena and determine the gas pressure of VI based on PD at the pressure where the PD starts to occur, which is at the left side of Paschen curve (below 1 Pa order) for detection purposes. Thus, this paper presents the construction of PD measurement system for investigating PD phenomena in medium vacuum region of VI. The measurement system was confirmed free from unwanted corona discharge. We also identified the partial discharge inception voltage (PDIV) and PD pulse waveform from 0.2 to 5 Pa. The PDIV was identified to follow the left side of Paschen curve. In addition, the occurrence PD in medium vacuum of VI could be characterized as Townsend-like discharge.