ABSTRACT
Electrical insulation materials are utilized to provide protection over the metallic conductors of underground cables. The insulating materials physically enclose the conductor and provide a margin of safety. These materials are composed of either synthetic or natural polymers. The polymeric insulation material selected for use may vary with the voltage class of the cable. For medium voltage cable constructions, compatible polymeric shields are employed between the insulation and the conductor, and over the insulation to grade the voltage stress; these are composed of ®exible polymers blended with conducting carbon black that imparts the semiconducting characteristics. Metallic neutrals or tapes are applied over this cable core, and polymeric jackets are applied on the outside of the cable core.
