Electrical Characteristics and Requirements of Extruded Semi-Conducting Shields in Power Cables

An extensive study of conduction mechanism of carbon black dispersion in polyethylene and cross-linked polyethylene has been made in order to create a basis for design of semi-conducting extruded shields. It has been found that an ac resistance-capacitance bridge is a simple and convenient tool for this study. Simplified mathematical equations have been developed which relate electrical parameters of semi-conducting shields as measured by the ac bridge to the physical structure of conducting chains. Requirements and typical properties concerning semi-conducting shields have been discussed.