Study On SF₆ Decomposition Characteristics Of Free Particle Local Discharge

With the economic and social development,the power system on the equipment reliability and compact requirements continued to increase,GIS instead of the traditional open electrical equipment has gradually become the main direction of power grid construction.Domestic power systems generally believe that GIS is the equipment that has a long maintenance cycle,its safe operation reliability is higher.However,in recent years,based on the statistical data of GIS equipment,we find that GIS reliability is still affected by its insulation failures.The existing research results show that:before the occurrence of GIS equipment insulation failure,local breakdown of GIS equipment leads the generation of partial discharges.Under the action of high electric field energy of PD,SF₆ decomposed,generated compounds such as CF₄,CO₂,SOF₄,SOF₂,SO₂ and H₂S.These compounds are closely related to the PD which inside the GIS,therefore,in this paper,the experimental study of SF₆ decomposition under partial discharge is carried out.The author researched PD events and types in a substation and find the most prone to GIS internal PD defects.Based on the field GIS,the author establish the experimental platform,carried out a series SF₆ decomposition experiments under partial discharge of240 hours,and under five voltage levels.Analyzed the types,contents and rates of SF₆decomposition products with the change of voltage and experimental time,find the type of product that can provide a reference for site GIS status assessment and troubles diagnosis.The research indicated that:the most vulnerable site which lead the partial discharge in the field is the free particle type.Under partial discharge,SF₆ decomposition products are CO₂,CF₄,H₂S and SO_2.These four decomposition products can be used to reflect the seriousness of the discharge in the GIS chamber.The content and generation rate of CO₂,CF₄,H₂S and SO₂ were increased with the increase of the applied voltage and the extension of the experimental time.The relationship between the content and generation rate of the four decomposition products is:SO₂>CO₂>CF₄>H₂S,When CO₂ and SO₂ are generated inside the GIS chamber,substation duty officers need to attract attention,at this time there may be an initial internal insulation fault inside the GIS,they should enhance their tracking methods.The Generation conditions of H₂S and CF₄ is hard,that is,the correspond fault of these two products is more serious.If these two decomposition products are detected in the field GIS chamber,we should enhance their tracking methods and report to the higher authorities,carry out the relevant maintenance work timely.