Modelling of flow electrification in a 3D computational fluid dynamics software: application to power transformers

The 3D Computational Fluid Dynamics software ESTET developed at the RandD center of Electricite de France has been used to simulate flow electrification in power transformers. To take into account the phenomena, extensions in ESTET were carried out concerning the introduction of the Poisson equation for electric potential, the migration of fluid particles in electric field, the dissociation-recombination of the ionic species in chemical equilibrium and the electric force in the Navier-Stokes equations. The interfacial charge transfer law is derived from the H. Walmsley's model but involves ionic concentrations of both sides of the interface. Transient and steady state simulations, in good agreement with experimental data, show that some parameter sets lead to great gradients of potential in the pressboard which might be the cause of the hazardous discharges observed in power transformers.