Study On Discharge And Gas Generation Characteristics Of Typical Defects In Oil-impregnated Paper Bushing

With the continuous growth of power load demand and the large-scale construction of UHV power grid,higher insulation qualtiy levels are put forward for the reliability level of power equipment.Oil-immpregnated paper(OIP)bushing is one of the common outlet components of power transformers,many failures have occurred,causing serious consequences.The defect of OIP bushing has become one of the main factors affecting the safe operation of power transformer.OIP bushing is one of the few power equipment with both internal and external insulation problems,and its defect types are varied.At present,there is a lack of experimental research on solid models designed for different defect types from the practical point of view,and the characteristics of initial discharge and gas generation of typical defects of OIP bushing are not clear yet.Therefore,the existing bushing defect diagnosis methods cannot meet the actual bushing defect diagnosis requirements,and it is urgent to carry out research on the deterioration process and characteristics of typical bushing defects to provide a basis for bushing defect diagnosis.In order to study the characteristics of discharge and gas generation of typical defects of OIP bushing,five models of typical defects were designed from the practical point of view:discharge between metal tubes,surface discharge of porcelain insulator,X wax in capacitor core,partial discharge of capacitor core and overheating of current-carrying connectors.A test and research platform for bushing typical defects has been established,which has the functions of online partial discharge detection and gas chromatography analysis of oil extraction,the characteristics of initial discharge and gas generation under five typical defects of OIP bushing were studied,the discharge and gas generation rules under different defects were analyzed and summarized,and the diagnostic criteria for different defects were proposed:The discharge between metal tubes can be judged by the stable percentage of H2 in total hydrogen and hydrocarbon at about 70%and CH4/H2 at about 0.43,and there is no contact between the metal tubes;when there is contact between metal tubes,the proportion of total hydrocarbon of C2H2 increases significantly while the content of other hydrocarbon gases does not increase significantly.The discharge is random,and the discharge phase is distributed in the whole power frequency cycle;the surface discharge defects of porcelain insulators can be judged by the presence of C2H2 and C2H6,the percentage of H2 in the total hydrogen and hydrocarbon is stable at about 80%,CH4/H2 is about 0.24,CO2/CO continues to decrease,and the discharge phase distribution ranges from 0-120°,150-300°,and 330-360°;the partial discharge of capacitor core can be judged by the fact that the characteristic gas is H2,the percentage of H2 in the total hydrogen and hydrocarbon is more than 80%and continues to increase,and the CO2/CO increases first and then decreases;the overheat of current carrying connectors can be judged by The characteristic gas is CO2,and the slow rise of CO2/CO when the temperature is about 200℃;when the temperature exceeds 500℃,the contents of gas components increased obviously except for C2H2,and CO2/CO continued to decrease to less than 2;the X-wax in the capacitor core defect can not be judged by the discharge and chromatographic characteristics.