ANALYSIS OF ELECTRIC FIELD IN CROSS-LINKED POLYETHYLENE INSULATED CABLES WITH TYPICAL DEFECTS OF SEMICONDUCTING SHIELD

The study of electric field in the cross-linked polyethylene insulation of medium-voltage cable (10 kV) with typical defects of semiconducting insulating layers is carried out by computer modeling. The defects are associated with the technological faults, operating conditions, electrical and environmental aging. The model is built as a quasi-electrostatic approximation for the axial-symmetric representation of the cable. The volume defect with the loss of cable sealing and with the destruction of the metal screen and part of main insulation, when the electric field spreads into the surrounding medium, is also considered. The non-uniform distribution of the electric field in the insulation, the nature of field variation and the level of field enhancement depending on the defects are analyzed. The results of the numerical study ground the causes of polyethylene insulation aging as well as the risk of the considered defects for the dielectric strength of the insulation and its reliable long-term operation. References 17, figures 3.