The movement characteristics of space charge in flowing transformer-oil

Space charge accumulating in oil-paper insulation structure can distort electric field. Transformer-oil, carrying space charge, might change charge transport behavior due to flow properties. In this article, the effect of oil convection on space charge is analyzed by the upstream finite element method based on vector sum. First, the velocity of transformer-oil is obtained by solving Navier–Stokes equations. It is associated with the migration to determine every upstream finite element. And then, the interpolation equation of space charge in flowing fluid is deduced to investigate the movement. Compared to traditional approaches, the velocity of flow is considered to judge the charge transport direction and to update charge density. To consider the temperature effect, a three-electrode experimental system is constructed to measure ion mobility. Finally, a flat rectangular model and a bent oil-path model are built as examples to study the movement characteristics. It is proven that convection makes a significant contribution to charge transport.