Experimental determination of space charge density associated with flow electrification phenomenon: Application to power transformers

At the solid/liquid interface, a charge zone called the Electrical Double Layer (EDL) appears. It is constituted of two zones of opposite sign, one in the solid and another one in the liquid. When a liquid flows through a pipe, an axial streaming current is generated. This current is due to the convection of the charges coming from the electrical layer in the liquid. The experimental methods for the determination of space charge density have been clearly identified in the case of fully-developed EDL. On the contrary, there is a need for further exploration in the case of a non-fully developed EDL. The purpose of this paper is to calculate the fully developed space charge density at the wall by streaming electrification experiments which are conducted in the case of non-fully developed EDL. Moreover, it introduces a simplified procedure for the experimental determination of space charge density as a function of liquid flow velocity. This procedure can be conducted for the investigation of flow electrification phenomena in transformers with oil/metal configuration.