A New Scheme for Residual CF4 Detection in Gas-Insulated Switchgear Using Plasma-induced CF4 Decomposition into CO2

This paper presents a new scheme for the detection of residual carbon tetrafluoride (CF
4
) gas in gas-insulated switchgear (GIS) for its diagnosis. For the diagnosis of GIS, the decomposition gas species including CF
4
generated by partial discharges or breakdown are analyzed. Accumulation of the gas species indicates the history of the failure of GIS. However, most of the gas species are removed by an absorbent placed in a GIS vessel. The only CF
4
stays in GIS vessel for the long term. In this study, it is aimed to develop an easy and rapid CF
4
detection method. Because direct detection of CF
4
is difficult, an indirect detection method of CF
4
is proposed, in which CF
4
is processed by non-thermal plasma (NTP). In this paper, the conversion of CF
4
using dielectric barrier discharge (DBD) was examined. The infrared absorption band among SF
6
, CF
4
, and CO
2
was observed by Fourier transform infrared (FT-IR) spectroscopy. The amount of CO
2
generated in the case of CF
4
(10,000 ppm) and O
2
(10,000 ppm) diluted in Ar or SF
6
was analyzed. In the case of Ar dilution, CO
2
gradually increased with increasing time of DBD application by using a compact CO
2
NDIR sensor. In the case of SF
6
dilution, CO
2
, CO, O
2
, and SO
2
were detected by using a portable gas analyzer. The latter case showed a higher CO
2
generation rate of 400 ppm/hr, whereas the other showed 50 ppm/hr. In addition, a zeolite-filled column was installed for removing SO
2
from the processed gas.