Carbon Black Effect on Electrical Performance of Semi-Conducting Layers for Power Cables

The purpose of semiconducting layer is to smooth out the electromagnetic field, eliminate excessive voltage stress attributed to irregularities and voids between conductor and insulation, reduce vented trees at the interface between the insulation and the semi-conducting shield and avoid partial discharge .The semiconducting layer is typically formed from polymers(Poly vinyl chloride or Ethylene propylene rubber or Polyethylene or Cross-linked polyethylene).The polymer is blended on conducting carbon black to enhance the semiconducting layer which can reflect on increasing the performance of the power cable life by which saving both energy and money can be obtained. The aim of this paper is to improve the electrical performance of the Poly vinyl chloride as a semiconducting layer in power cables to increase the life expectancy of the power cable. Blends of PVC with CB were prepared with 0%, 20%, 25%, 30%, 35%, 40%, 45% and 50% by weight percentages concentration. Dielectric strength of the blends was tested with and without silicon rubber (SiR) layer in normal conditions. Also dielectric strength of blends was tested after being exposed to thermal aging for 24, 96 and 168 hrs, in high temperatures (70°C and 90°C). The mechanical characterization showed that the composite polymer enhanced by using carbon black in the tensile strength and the percentage elongation at break.