Surface charge dynamics studied by the temporal evolution of the corona charging current

• The effect of a layer of dielectric placed on the surface of ground electrode on Corona discharges were investigated.
• A FEM-based numerical model was developed to study the surface charge decay process.
• The surface charge decay may follow different mechanisms depending on the applied stress.

The decay of surface charges deposited on the dielectric material by the partial discharge (PD) activity has a great impact on the repetition of partial discharges. In this work, the effect of dielectric placed on the surface of ground electrode in a needle-plane configuration on the discharge activity was investigated, with the application of a periodic negative step voltage. The charge decay mechanisms on a corona charged dielectric surface were investigated based on a comparison between experiments and a FEM-based numerical model. The comparison indicates that the surface charges may decay due to different mechanisms depending on the applied stress.