A simulation method for streaming electrification by direct current field analysis

A simulation method for evaluating potential and electric field distribution in an oil-filled transformer was developed. Potential distribution around the entrance of the oil duct should be carefully considered in view of the risk of static discharge. A large potential may be built up by negative charge current through highly resistive insulators due to charge separation caused by streaming electrification at the pressboard (PB) surface. At steady state in terms of both fluid dynamics and electrical conduction, a flow of the negative charge can be regarded as a constant current source distributed over the PB surface that flow into grounded conductors through resistive materials such as the solid/liquid insulation of PB and oil. As will be presented in another paper in this conference by the authors, the local streaming current can be obtained from the local shearing stress calculated by a fluid dynamics simulator. Using the wall current distribution calculated from the shearing stress model as a distributed current source, the electric field and potential distribution were calculated by a direct current field simulator.