Effect of Aging on Leakage Current in Oil-Paper Composite Insulation Under Oil Flow Conditions

The oil flow in converter transformers enhances heat dissipation and significantly alters the charge transport behavior within the oil-paper composite insulation. This paper examines the effects of different aging states on the leakage current behavior in oil-paper insulation subjected to different oil flow conditions. Measurements indicated that paper-side leakage current under flowing conditions was notably higher than that under static conditions for both unaged and aged samples. Furthermore, with the aggravation of aging, the leakage current exhibited a significant increasing trend in both static and flowing conditions. These phenomena were interpreted as the flowing oil facilitating interface charge accumulation, thereby intensifying the electric field strength on the paper side and increasing its leakage current. Moreover, aging increases both charge density and carrier mobility, resulting in elevated leakage current.