Abstract
C5F10O has been widely studied as a promising environmentally friendly substitute to SF6 in power equipment. Up to now, the environmentally friendly gas insulated equipment developed still uses the same sealing materials as SF6 gas insulation equipment. However, whether these sealing materials are chronically compatible with C5F10O has always been a fundamental problem that perplexes the industry and academia. In this study, a thermally accelerated aging experiment on four rubber materials contacted with C5F10O/N2 was carried out. During the experiment, aged rubbers were analyzed using scanning electron microscopy and x-ray photoelectron spectroscopy to obtain the surface morphology characteristic and element composition. The gas samples were collected periodically and detected through gas chromatography mass spectrometry. Meanwhile, the degradation of the rubbers’ mechanical property is tested to figure out their long-term compatibility with C5F10O/N2 mixtures. Surface analysis of the rubber samples showed that after thermal accelerated aging, F in the form of C–F bonding and metal fluorides were detected on the surface of the ethylene propylene diene monomer (EPDM), nitrile butadiene rubber (NBR), chloroprene rubber (CR), and methyl vinyl silicone rubber (VMQ), which did not exist in origin samples. The main gaseous decomposition products of C5F10O include CO, CO2, C3F6, and C3F7H, and the concentration when coexisting with rubber is significantly higher than that in the control group. The compression performance of aged rubbers all reduced, and the compression performance of EPDM and NBR is better than that of CR and VMQ. The experimental results proved the incompatibility between C5F10O and these four rubbers, while EPDM and NBR showed less deterioration in compression properties and could be more suitable for the C5F10O power equipment.
Highlights
SF6 has been extensively applied in gas insulated switchgears (GISs) due to its excellent insulation and arc extinguishing performance.1–3 the global warming potential (GWP) of SF6 is 23 500 times larger than CO2, making SF6 to become one of the strongest greenhouse gasses
Based on the different morphological characteristics and chemical content analysis of the clean and aged samples, it can be judged that ethylene propylene diene monomer (EPDM), nitrile butadiene rubber (NBR), chloroprene rubber (CR), and VQM will react with C5F10O when coexisting chronically
A thermal accelerated aging experiment on the compatibility between C5F10O and sealing materials is carried out in this paper; according to the results, the following conclusions are drawn: (1) F atoms were detected on the aged rubber’s surface and mainly appeared in the form of the carbon–fluorine bond (C–F) bond and metal fluoride, indicating that the fluorine-containing group generated by the decomposition of C5F10O will interact with the rubber’s molecule and react with the additives inside the rubber to form metal fluorides
Summary
SF6 has been extensively applied in gas insulated switchgears (GISs) due to its excellent insulation and arc extinguishing performance. the global warming potential (GWP) of SF6 is 23 500 times larger than CO2, making SF6 to become one of the strongest greenhouse gasses. Environmentally friendly switchgears employing C5F10O/air as the insulating medium have been developed and applied to engineering. The environmentally friendly GIS still uses the same sealing materials as SF6 equipment. If the sealing materials are not compatible with C5F10O chronically, the consequent gas leakage or gas deterioration will directly affect the insulation performance. C3F7H and C3F6 were found to be newly produced after long-term operation in the C5F10O/air insulated 22 kV switchgear designed by ABB. Is this due to the partial overheating or discharge faults occurring inside the equipment or caused by the incompatibility of C5F10O/air with the metal, solid insulating medium, or sealing materials? The results could contribute to the selection of sealing materials for C5F10O switchgears in future application scenarios
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