Flow electrification in power transformers: electrical modeling

A charge zone named electrical double layer exists at a solid-liquid interface. The liquid flow induces a phenomenon called flow electrification: it generates a streaming current (caused by the convection of charges present in the liquid) and a potential rise in the solid (if this one is insulated from the ground). These potentials may reach values high enough to produce electrical discharges and provoke accidents. Although this phenomenon has been identified a long time ago, its physical description rests unknown (production and displacement of charges, equilibrium, etc.). As part of the research program of Electricite de France, a prototype sensor dedicated to flow electrification characterization at the interface between pressboard and oil has been developed with the University of Poitiers. In this paper we propose to use an electrical analogy to model these processes in the prototype. This electrical model is based on the analysis of experiences carried out with the sensor.