The Role Of Shielding In Multi-core Cables

The so-called "shielding" in the cable structure is essentially a measure to improve the electric field distribution. The multi-core cable conductor is made of stranded wires, and an air gap is easily formed between it and the insulating layer. The surface of the conductor is not smooth, which will cause electric field concentration.

Add a shielding layer of semi-conducting material on the surface of the conductor, which is equipotential with the shielded conductor and is in good contact with the insulating layer, so as to avoid partial discharge between the conductor and the insulating layer. This layer of shielding is also called the inner shielding layer. There may also be gaps at the contact between the insulating surface and the sheath. When the cable is bent, the insulating surface of the oil-paper cable is likely to cause cracks. These are all factors that cause partial discharge. A shielding layer of semi-conductive material is added on the surface of the insulating layer, which has good contact with the shielded insulating layer, and is equipotential with the metal sheath, so as to avoid partial discharge between the insulating layer and the sheath.

Multicore cable shielding layer can also play a role in grounding protection. If the cable core is damaged, the leaked current can flow along the shielding layer like a grounding grid, which plays a role of safety protection.