Study of Electric Field Grading Types on Medium Voltage Polymeric and Paper Insulated Cables

Cross Linked Polyethylene (XLPE) and Paper Insulated Lead Covered Cables (PILC) are widely used for distribution and transmission of electrical power. For making long distance cable connection, a cable joint is used for connecting two smaller cables. During the installation of such cable joint, external layers around the conductor of cables are stripped, which leads to concentration of electric field at the terminated outer semi conductive layer of the cable. There are various types of field grading options available, such as electrode field grading, epsilon field grading and resistive field grading that are used for controlling this concentration of electric field. In this paper, application of these types of field grading are studied on XLPE and PILC cables. This study was performed with the help of Finite Element Analysis software and High Voltage AC short time test on cables with different types of field grading types installed on them. At the end of this study, it was concluded that electrode grading performs better in comparison with other field grading options, as it results in minimum tangential electric field at surface of cable insulation.