Decomposition characteristics of SF6 under creeping discharge on solid insulator

Abstract

The decomposition compound analysis of SF 6 in GIS is an effective method to diagnose the partial discharge (PD) caused by the insulation defect. Creeping discharge on solid insulator is a major kind of fault in gas insulated switchgear. It is significant to develop the research on the decomposition characteristics of SF 6 under creeping discharge on solid insulator. SF 6 decomposition was investigated with the GIS-defect-simulating apparatus, where partial discharge energy and charge were monitored by the on-line insulation diagnosis system PD check combining with pulse current method. The gas sample was measured by the Gas Chromatography (GC), and the SF 6 decomposition characteristics under different applied voltage, gas pressure and moisture contents (adsorbent) were analyzed. The results show that the typical decomposition products are CO 2 , CF 4 , SOF 2 and SO 2 F 2 . Meantime, increasing the applied voltage will increase the discharge energy and charge, so as to increase the yield of decomposition products. But the discharge energy decreases with the increased pressure of SF 6 , thereby decreasing the yield of decomposition products. In addition, the increase of moisture content (200 µL/L – 1500 µL/L) has inhibition effect on the yields of CF 4 . The adsorbents 5A, KDHF-03, and F-03 limit the yield of CO 2 , SOF 2 and SO 2 F 2 apparently, while they show no adsorption to CF 4 . Finally we discuss the relationship between the discharge energy and SF 6 decomposition products and feature extraction under creeping discharge on solid insulator. The concentration ratios of (SOF 2 +SO 2 )/(SO 2 F 2 ) and (SOF 2 +SO 2 +SO 2 F 2 )/(CF 4 +CO 2 ) lie in the ranges, 2 – 6, and 0.75 – 2.75 respectively.