SHIELDING OF POWER CABLES

Shielding of an electric power cable is accomplished by surrounding the assembly or insulation with a grounded, conducting medium. This confines the dielectric field to the inside of this shield. Two distinct types of shields are used:

metallic and nonmetallic.

The purposes of the insulation shield are to:

1. Obtain symmetrical radial stress distribution with the insulation.

2. Eliminate tangential and longitudinal stresses on the surface of the insulation.
3. Exclude from the dielectric field those materials such as braids, tapes, and fillers that are not intended as insulation.

4. Protect the cables from induced or direct aver-voltages. Shields do this by making the surge impedance uniform along the length of the cable and by helping to attenuate surge potentials