Numerical study of partial discharges apparition in XLPE insulation of high voltage cables

The cavities are inherent shortcomings of XLPE insulation used in electrical cables. Their effects are to tamper the dielectric properties of the insulating material. Indeed partial discharges occur in these cavities for relatively weak electric fields. The purpose of this work is to determine by simulation, the distortions caused by cavities on the electric field distribution in the insulating layer of cable. The computation method used to determine the electric field is based on numerical resolution of Laplace equation using the finite differences method. The threshold of partial discharges ignition in gaseous cavities contained in XLPE insulation of 30 kV cable is studied. The computation of the critical field by the approached expression of Paschen permits us to elucidate the harmfulness caused by a cavity according to its size and its position.