Abstract
The research on decomposition characteristics of SF6 and its by-products have great significance to the operation, maintenance, condition assessment and fault diagnosis of power equipment. In this paper, the particle composition models of SF6, SF6/polytetrafluoroethylene (PTFE), SF6/PTFE/O2, SF6/PTFE/H2O, and SF6/PTFE/O2/H2O were established by using Gibbs free energy minimization method, and the effects of trace H2O and O2 impurities and PTFE vapour on SF6 by-products were studied by the models. In order to verify the correctness of the simulation results, a series of breaking experiments were carried out on a 40.5 kV SF6 circuit breaker, and a gas chromatograph was used to detect and analyse the SF6 by-products. It was found that when PTFE vapour is involved in the arc plasma, the main by-product after arc quenching is CF4, and the molar fractions of C2F6 and C3F8 are very low. When O2 is involved, the main by-products are SOF2, SO2 and SO2F2, and a small amount of CO and CO2 was also produced. When H2O is involved, the main by-products in simulation are SOF2, SO2 and HF, and a small amount of SO2, CO2, CO, SO2F2 and H2 was also produced. The experimental results are in good agreement with the above results.
Highlights
The arc plasma model cannot be used to study the comprehensive effects of trace H2O, O2, and PTFE vapour on SF6 by-products
CoTnhcilsupsiaopnesr established the arc plasma models of SF6 (12 particles are considered), SF6/PThFiEs p(2a4perpaersttiacblelisshaerde thcoenasricdeprleads)m, aSFm6/oPdTeFlsE/oOf 2SF(364(1p2aprtairctliecslesaraere ccoonnssiiddeerreedd)), SSFF66//PPTTFFEE/H(224Opa(4r3ticpleasratircelecsonasriedecroends)i,dSeFr6e/dP)T, FaEn/dOS2F(63/4PTpFarEti/cOle2s/Har2eOco(4n3sidpearretdic)l,eSsFa6r/ePTcoFnE-/ sHid2eOre(d4)3 bpyarutiscilnegs athre cGoinbsbisdefreed)e,naenrdgySFm6/inPimTFizEa/tOio2n/mHe2Otho(4d3. pTahretiecflfeescatsreocfotnrascide eHre2dO) abnyduOsi2nigmtphueriGtiiebsbasnfdrePeTeFnEervgaypomuirnoimn itzhaetiSoFn6 bmye-tphrod.ucTthseweefrfecsttsuodfietdra. cIne Hor2dOeratnodveOr2ify the correctness of the simulation results, a series of breaking experiments were carried out on a 40.5 kV SF6 circuit breaker, and a gas chromatograph was used to detect and analyse the SF6 by-products
It was found that the experimental results are in good agreement with the simulation results
Summary
The high voltage SF6 circuit breaker will inevitably produce a high temperature and high energy arc in the process of breaking currents It will cause SF6 to decompose and form SF6 arc plasma. In terms of the experiments, Boudene et al studied the decomposition products in detail under the condition of voltage of 60 kV, a current of 4.5 kA and arcing time 40–80 ms They found that the gas production rate of SOF2 and SO2F2 and arc energy is almost linear [10]. The arc plasma model cannot be used to study the comprehensive effects of trace H2O, O2, and PTFE vapour on SF6 by-products. It seriously limits the reliability of the calculation results. It was found that the simulation results are in good agreement with the experimental results
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