Factors Affecting the Stability of Semi-Conducting Polyolefin Shielding Systems

In selecting extrudable semi-conducting polyolefins for use as conductor and insulation shields for high voltage power cables, too much emphasis is often placed on initial volume resistivity. An Engineering analysis, covering the electrical, chemical and physical requirements for these shields, reveals that a different balance of properties is desirable for each application and that volume resistivity may be of secondary importance. This paper covers the results of an extensive Laboratory investigation to determine the effects of temperature, time, materials processing, solvents, and electrical tape adhesives on nine commercially available semi-conducting materials, and five experimental variations, and offers a guide for selecting semi-conducting compounds for optimum service performance.