| Gas Insulated Switchgear(GIS) has been widely used in urban power grid and extra/ultra high voltage power grid because of its compact structure, small occupation area, convenient maintenance and so on. Meanwhile, SF6 insulation gas has excellent resistance to electrical strength, stable chemical properties, as well as non-toxic and harmless characteristics. In the normal operation of the equipment condition, SF6 is not easy to decompose. However, due to the internal equipment inevitable existence of insulation defects, under normal operating voltage, in defect of local high field forcing triggered partial discharge. With the further deterioration of the fault, the partial discharge will be converted into a more serious spark discharge or even arc discharge. Once the equipment inside the spark discharge failure, which means that the equipment insulation performance has dropped very seriously. If the fault does not detect and eliminate harmful gases produced in the equipment, it will have a serious impact on people and the environment. Therefore, It is necessary to deeply study the decomposition characteristics of SF6 spark discharge.Under the action of spark discharge, SF6 will first be cracked into low fluorine sulfide, and these low fluorine sulfur compounds are very easy to react with the trace moisture and oxygen in the air chamber to form a variety of gas decomposition products. The influencing factors of the decomposition characteristics of SF6 spark discharge are: spark discharge energy, trace moisture, micro oxygen, metal electrode materials, gas pressure, solid insulation material, adsorbent, etc.. GIS chamber pressure will change with the changes in the ambient temperature, and different voltage levels, SF6 gas insulation equipment, there are differences in the inflation pressure. At present, there is no research on the decomposition characteristics and mechanism of SF6 spark discharge under atmospheric pressure. Therefore, this paper build the SF6 spark discharge in decomposition experiment platform, under the influence of a lot of pressure SF6 discharge decomposition experiment, gaseous products of decomposition were quantitatively analyzed by Gas Chromatography and Gas Chromatography / Mass Spectrometry.The work carried out in this paper and the research results obtained are:(1) Based on SF6 decomposition experiment device of spark discharge on the existing laboratory, improved control of discharge frequency relay, the control of spark frequency was more stable. With the gas chamber pressure, discharge spark voltage required will increase. Through the improvement of the existing equipment, improve the insulation performance of the whole experiment platform. Meanwhile, The spark discharge failure of SF6 gas was simulated on the modified spark discharge experiment platform, and the products were analyzed qualitatively and quantitatively by gas chromatograph and gas chromatograph mass spectrometer. The results show that the breakdown of SF6 gas insulation under the fault of the spark discharge will occur, and the generation of CO2, SOF2, SO2F2, SOF4, SO2 and CF4 and other characteristics of decomposition products.(2) Under six different gas pressures, the acquisition and analysis of the decomposition products of SF6 spark discharge is completed. The volume fraction of the decomposition product is sorted by the large to small: SOF2 > CO2 > SO2F2 > SOF4 > SO2 > CF4. In the analysis of the change trend of the characteristic ratio c(SO2F2)/c(SOF2) of the spark discharge products, it is known that the data has a certain dispersion. But the general trend is: with the rising of pressure, the ratio of the first gradually increased and then decreased. The product characteristic ratio c(CF4)/c(CO2) of the variation of the law, the data have a certain dispersion. But in general, as the pressure rise decreased in an inverted S type.(3) The higher the gas chamber pressure, the lower the effective gas production rate of SOF2, SO2F2, SOF4 and CO2. The effective gas production rate of CF4 and SO2 has a certain dispersion with the increase of air pressure. Establish mathematical model of exponential type, to correct the effect of pressure on the feature decomposition product SOF2, SO2F2 efficient production of the gas rate, and verify the correctness of the mathematical model. In order to improve the accuracy of fault diagnosis, the pressure correction method is provided for the fault diagnosis by using SF6 spark discharge characteristic component in the future. |
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