The product structure of signal cable industry in China has been adjusted well. With the EU issued ROHS directive, the development and large-scale adoption of ecological environmental protection wire and cable has become an international trend. With the increasing awareness of environmental protection, the application of halogen free low smoke cross-linked polyolefin insulated wire and cable will gradually expand.

Focusing on technological innovation and focusing on Sustainable Utilization of raw materials, only by reducing environmental pollution can we effectively improve the utilization of resources and reduce costs. It can be predicted that which enterprises do well in this area, becoming the leader of the wire and cable industry will be just around the corner.

In order to uniformly guide the wire core and insulation electric field, the middle and high voltage power cables of 6kV and above generally have conductor shielding layer and insulation shielding layer, and some low voltage cables do not have shielding layer. There are two kinds of shielding layer: semi conductive shield and metal shield.

(1) semi conductive shield

The semi conductive shield layer is usually arranged on the outer surface of the conductive wire core and the outer surface of the insulating layer, respectively called the inner half conductive shielding layer and the outer semi conductive shielding layer.  Semi conductive shielding layer is composed of semi conductive material with low resistivity and thinner thickness. The inner semi conductive shielding layer is used for the uniform surface electric field of the wire core, so as to avoid the partial discharge of the conductor and insulation due to the unsmooth surface of the conductor and the air gap generated by the wire core stranding. The outer semi conductive shielding layer is well contacted with the outer surface of the insulating layer, and the metal sheath has equal potential to avoid partial discharge with the metal sheath due to the cracks on the insulation surface of the cable.

(2) metal shield

For the medium and low voltage power cables without metal sheath, besides the semi conductive shielding layer, the metal shielding layer must be added. The metal shielding layer is usually wrapped by copper strip or copper wire, mainly shielding the electric field.

Commonly used auxiliary materials for wire and cable include: filling materials, separation materials, shielding materials in 3 categories.

1. filling materials, including: polyester fiber, cotton yarn, PP rope. The purpose is to keep the cable round, reduce the amount of rubber material, reduce the cost, and increase the cable strength. Polyester fiber is commonly used in the wire with higher bending requirements.

2. separate materials, including paper, polyester belt, PP belt, foam Talc / mica powder, silicone oil, DOP, B.T.A.

(1). The core of tissue, polyester belt, foam PP belt, line cable wrapping tape or charge to be longitudinal wrapping tape, can make the wire round, to ensure open skin.

(2). Talc / mica powder by extrusion and coating the surface of PVC core PVC when heated, easy to stick together, the use of talc / mica powder can be isolated, ensure open skin and adhesion control.

(3). Silicone oil, spraying insulation extrusion, mainly to improve the adhesion between conductor and insulation, and can ensure the insulation between the outside to open the skin.

(4).DOP is used between conductors and insulation to improve the adhesion between conductors and insulation.

(5).B.T.A., the solution is applied to the conductor surface when it is insulated. The main function is to prevent the bare copper wire from oxidation.

3. shielding materials, including: aluminum foil tape (often with a row of interference, ground wire) braided wire, cable wire. Shielding can effectively prevent mutual interference inside and outside the shield layer.