The main use for semi-conducting compounds are as electrical screening (or shielding) in medium voltage cables up to 36kV.  These screening layers are put next to the conductor and on the outside of the insulation; their purpose being to contain the electrical field within the insulation and to eliminate any electrical discharges adjacent to the insulation.
A typical construction of a triple extruded insulated MV Cable consists of a screening layer “bonded” to the CU or AL conductor, then an insulation layers followed by a second screening layer.  Semi-conducting compounds also have the effect of filling in the interstices of the conductor giving a smooth surface for the insulation.  This reduces the electrical flux lines around each individual wire that make up the conductor, which can reduce the stress by 10-15%.

We have below two types of Semi con compounds.

–        Inner Semi con compound (bonded to the insulation)

–        Outer Semi con compound (Either bonded or strippable ease of insulation)