The shield should be uniformly conductive and electrically insulated. High-voltage power cables of 6kV and above generally have conductor shielding and insulating shielding, and part of the shielding layer of low-voltage cables. There are two types of shielding layers: semiconductor shielding and metal shielding.
1. Conductive shielding and conductive shielding are usually arranged on the outer surface of the wire core and the outer surface of the insulating layer, which are called the semiconductor shielding layer inside and outside the semiconductor shielding layer.
The semiconductor shielding layer consists of a thin semiconductor material of low resistivity and thickness. The purpose of the semiconductor shielding layer is to make the electric field on the outer surface of the inner wire of the core uniform, to avoid the unevenness of the conductor surface and the generation of air gaps in the stranded wire core, so that the conductor and the insulating layer generate partial discharge. The semiconductor shielding layer and the outer surface of the insulating layer are in very good contact, potential and metal ferrules, avoiding insulation defects such as surface cracks and partial discharges on cables with metal sheaths.
2. Metal shielding layer For low-voltage power cables without metal sheaths, in addition to the semiconductor shielding layer, a metal shielding layer should be added. The metal shielding layer is usually made of copper or copper wire around the package, and it mainly plays the role of shielding the electric field.