Research on the characteristics of partial discharge gas generation in typical defects of oil immersed current transformers

During the operation of oil-immersed current transformers, they gradually deteriorate due to various factors. In order to study the relationship between partial discharge and gas generation characteristics under different typical defects, this paper measures the unit-time discharge energy, unit-time apparent discharge quantity, pulse repetition rate, and gas generation rate during the discharge development process of three typical defects: protrusion defect, surface defect, and gas gap defect. The study reveals that the generation of hydrocarbon gases and hydrogen in the oil mainly depends on discharges with an apparent discharge quantity above 300 pC. Among the discharge characteristics, the unit-time discharge energy and unit-time average discharge quantity significantly impact the gas generation rate. It is found that the content of C₂H₂ and C₂H₄ in the oil for protrusion and surface defects increases significantly with discharge intensity, while CH₄ and H₂ show significant changes for gas gap defects. Additionally, an approximately linear relationship exists between discharge energy per unit time, pulse repetition rate, and the rate of characteristic gas generation for both protrusion and surface defects, as well as for gas gap defects. These findings provide a reference for diagnosing current transformers and highlight the critical role of discharge characteristics in gas generation dynamics.