Experimental determination of space charge density at solid-liquid interface versus temperature: Application to oil flow electrification in power transformers

A liquid in contact with a solid induces the development of an electrical double layer. Flow electrification is due to the convection by the liquid flow of electrical charges coming from the electrical double layer. The aim of this work is to determine experimentally the space charge density at the wall for a fully developed double layer, and its evolution with temperature. A new experimental method based on current measurements as function of rest time is used to determine this parameter. The experimental set up simulates a power transformer with pressboard and oil as electrical insulation, and where convection of the oil is used for cooling purposes. The flow electrification phenomenon is suspected to be at the origin of electrostatic damages.