Author: Site Editor Publish Time: 2019-10-29 Origin: Site
Cable joints are also called cable ends. After the cable is laid, in order to make it to be a continuous line, the sections must be connected as a whole. These connection points are called cable joints. According to the production and installation materials, cable joints can be divided into heat shrinkable cable joints and cold shrinkable cable joints, next we will mainly introduce their differences:
The material used in the cold shrinkable cable accessories is silicone rubber, which has advantages of high elasticity, good insulation performance, electric leakage resistance, water repellency, weather resistance and UV aging resistance.
The material used in the heat shrinkable cable accessories is rubber-plastic composite (polymer). The material itself has no elasticity and only has the function of “elastic memory”.
The stress cone and the insulating part of the cold shrinkable cable accessories are prefabricated in the factory by high-temperature and high-pressure forming process. When installing, just install the accessories on the processed cable, and the product quality can be controlled in the factory. The on-site installation workload is small.
The structure of heat shrinkable cable accessories is heat shrink tubing: the stress pipe, the inner and outer insulating pipe, and the semi-conductive pipe. The slight air gap inevitably exists between pipes, and in particular, the partial discharge performance of the intermediate joint is difficult to ensure.
Due to the limitation of the structure, the heat shrinkable cable accessories are not applicable in some cases where the fire is not allowed. The cold shrinkable cable accessories are not limited in this condition, and it is not necessary to use the fire and other special tools during installation, just pull out the skeleton in the main body or insert the body in by hand.
The cold shrinkable cable accessories are integrated with the cable after installation, because they are made of high-elastic silicone rubber material. When the cable is thermally expanded and contracted due to temperature, the accessories will also expand and contract, and they will always tighten to the cable, which ensures it having excellent sealing performance.
The sealing of heat shrinkable cable accessories is mainly achieved by hot melt adhesive and shrinkage compression stress. After the heat shrinkable accessories are installed, the cable shrinks (thermal expansion and contraction) when the temperature drops, while the shrink-wrapped heat shrinkable parts have a stable structure and no longer has elasticity, so that the elastic pressing force is lost to the cable, and the sealing completely depends on sealing glue. Its sealing performance is not reliable.
The material used for the cold shrinkable cable accessories is high-elastic silicone rubber. The accessory itself is an elastic body. After installation, the accessory is always hung tightly on the cable, integrated with the cable, and has a large pressure on the interface, and has good insulation. The partial discharge performance is very good.
Since the material of the heat shrinkable cable accessories is heated and has no elasticity at normal temperature, after installation, the bending of the cable may cause the heat shrinkable accessories to be disconnected from the cable. During the operation, when the ambient temperature changes, there will also be a gap between the heat shrinkable accessories, and then water and moisture will enter, which may damage the insulation of the system.
The electrical stress control unit of the cold shrinkable cable accessories is geometric: the stress cone relies on the geometric curve to improve the electric field distortion. Its shape has been formed in the company, so the electrical stress control unit has stable performance.
The electrical stress control unit of the heat shrinkable cable accessories is a parametric type, that is, the electrical stress control unit is formed by using a material having a high dielectric constant and a volume resistivity between the insulating material and the semi-conductive material, and the special parameters of the material. It is difficult to control and is easy to change during molding and construction, which results in unstable performance of the electrical stress control unit.