Analytic calculation of partial discharge threshold in a gaseous cavity within high voltage cable insulation

The quality of electricity transmission and distribution strongly depends on the behavior of insulating systems. The presence of faults in the high voltage cable, generated during its manufacture or installation, can cause network perturbation ranging from simple partial discharge to the power line decommissioning by total electric discharge. The occurrence of gaseous cavities in the insulation of high voltage cable is the origin of partial discharges because of the electric stress elevation. The determination of this electric field is usually calculated by numerical solving the Laplace equation. The originality of this paper is to establish an analytical model based on the capacitive equivalent circuit of partial discharges who allows estimating the conditions of initiation of these partial discharges using Paschen criterion. The proposed model facilitates the calculation of the threshold voltage of partial discharge and reduces the computation time required by numerical methods. This inception voltage depends on the size of the cavity, its position, conductor radius, thickness of inner semi-conducting layer, type of insulation and its thickness.