What is the cable shielding layer and the classification of the cable shielding layer

What is the cable shielding layer? The so-called "shielding" in the cable structure is essentially a way to improve the electric field dispersion. The cable conductor is formed by twisting multiple strands of wires. It is easy to form an air gap between it and the insulating layer. The appearance of the conductor is not smooth, which will cause electric field concentration.

A shielding layer of semi-conductive material is added to the surface of the conductor, which is equipotential with the shielded conductor, and has an outstanding touch with the insulating layer, and then prevents some discharge between the conductor and the insulating layer. This layer of shielding is also called the inner shielding layer. There may also be gaps where the insulation surface and the sheath touch. When the cable is twisted, cracks are easily formed on the insulation surface of the oil-paper cable. These are all factors that cause some discharge.

A shielding layer of semi-conductive material is added to the surface of the insulating layer, which has an outstanding touch with the shielded insulating layer, and is equipotential with the metal sheath, and then prevents some discharge between the insulating layer and the sheath.

　　
Cable shield classification

The shielding layer of the cable In order to uniform the conductive core and the insulating electric field, the medium and high voltage power cables of 6kV and above generally have a conductor shielding layer and an insulating shielding layer, and some low-voltage cables do not have a shielding layer. There are two types of shielding layers: semi-conductive shielding and metal shielding.

1. Semi-conductive shield

The semi-conductive shielding layer is generally arranged on the outer surface of the conductive core and the outer surface of the insulating layer, which are called inner semi-conductive shielding layer and outer semi-conductive shielding layer, respectively. The semi-conductive shielding layer is composed of semi-conductive materials with low resistivity and thin thickness. The inner semi-conductive shielding layer is to uniform the external electric field of the core and prevent the formation of conductors and insulation due to the uneven surface of the conductor and the air gap caused by the stranding of the cores. Some discharges. The outer semi-conductive shielding layer and the insulating layer have a good touch. , And equipotential with the metal sheath to prevent some discharge from the metal sheath due to defects such as the appearance of the cable insulation crack.
　
2. Metal shield

Regarding the medium and low voltage power cables without metal sheath, in addition to the semi-conductive shielding layer, a metal shielding layer must be added. The metal shielding layer is generally made of copper tape or copper wire, and it is mainly used for shielding