Partial discharge resulting from internal degradation in underground MV cables: Modelling and analysis

A significant cause of underground cable failures is the breakdown of electrical insulation between the conductors due to the internal partial discharge (PD) activity [1]. Failure in cable insulation is generally resulted by a degradation phase which may last several years. Modeling and analysis of medium voltage equipment and partial discharge phenomena are mainly based on electric field analysis. The initiation and propagation of PD activity are subject to the maximum value of electric stress across the degradation of the void. The work presented in this paper considers the electrostatic consequences of the presence of void-defects in MV cables and, in particular, the likelihood of resulting in internal partial discharge. This work is based on Online PD method which widely known as an efficient tool for detecting insulation defects, assessing and monitoring the insulation of high voltage equipment to prevent its in service failure [2 ]. The two-dimensional electrostatic models of three phase Paper Insulated Lead Covered (PILC) cable containing void-defects as an electrostatics problem have been developed using the COMSOL multiphysics finite element environment. Therefore, the calculations of electric stress in void-defects based on electric stress of insulation materials are presented. The present investigation of single event of PD activity will produce an accurate indication of the degradation process and direction of discharge acting on PILC cable insulation. Outcomes will lead to better understanding of PD behavior, improved assessment of plant integrity and successful extension of life expectancy.