Performance of enhanced insulation system designed for medium voltage cables

Cables insulated with crosslinked polyethylene were first installed in the early 1960´s. The most significant users were Germany, Japan and USA. Typically for new solution, unforeseen problems appeared when technology use became widespread. One of the challenges was water treeing in medium voltage cables. Based on early cable failures intensive work has been made to improve the reliability of XLPE insulation for medium voltage cables. Several important steps have been taken to enhance the performance of medium voltage cables such as; : Removal of foreign materials from polymer matrix : Introduction dry cure process : Introduction extruded semiconductive compounds with triple extrusion : Adoption of water tree retardant compounds (WTR_XLPE) with improved resistance against water trees : Change from PVC to PE jacketing. This paper will focus on insulation materials performance, especially on copolymer WTR_XLPE and its further enhancement.