Overheating decomposition characteristics of epoxy dielectrics in SF6 atmosphere

In this paper, the thermal decomposition characteristics of epoxy resin in SF
₆
was studied using simultaneous thermal analysis (TG/DSC) and gas chromatograph-mass spectrometry (GC-MS). The concentrations of the decomposed gas components were tested, and the method of determining whether the failure of SF
₆
gas insulation equipment is caused by thermal decomposition of the insulating epoxy resin material is proposed. TG-DSC shows that the epoxy resin starts to lose weight sharply at 350 °C, and heating from 350 to 450 °C shows that the main gas products are CO
₂
, SO
₂
, H
₂
S and SOF
₂
. The concentrations of the four gases are significantly higher than where no epoxy resin is present and only pure SF
₆
is injected. The concentrations of SO
₂
F
₂
, CF
₄
and CS
₂
were all kept below 0.5 ppm in the given temperature range. H
₂
S is generated at about 325 °C while it can hardly be detected in the decomposition products of pure SF
₆
without epoxy resin at the same temperature. Based on our observations, it is concluded that when the concentration of CO
₂
reaches 5 times the sum of the concentrations of SO
₂
and H
₂
S, and when the concentration of H
₂
S is higher than 0.5 ppm, failure of electrical equipment occurs by thermal decomposition of epoxy resin will occur.