1. The material has excellent electrical properties. The material used in cold shrink cable accessories is silicone rubber, which has extremely high elasticity, good insulation properties, anti-leakage, hydrophobicity, weather resistance, and UV aging resistance.
The material used in heat shrinkable cable accessories is rubber-plastic composite material (polymer). The material itself has no elasticity and only has an "elastic memory" function.
2. The electrical stress control unit has stable performance. The electrical stress control unit of the cold shrink cable joint is a geometric type: that is, the stress cone, which relies on geometric curves to improve electric field distortion. Its shape has been formed in the company, so the performance of the electrical stress control unit is stable.
The electrical stress control unit of heat shrinkable cable accessories is a parametric type, that is, the electrical stress control unit is made of a material with a high dielectric constant and a volume resistivity between insulating materials and semi-conductive materials. The special parameters of this material are difficult to control and are prone to change during the molding and construction process, resulting in unstable performance of the electrical stress control unit.
3. The structural type is more ideal. The stress cone and insulation part of the cold shrink cable joint are prefabricated as a whole in the factory through high-temperature and high-pressure molding processes. During installation, you only need to put the accessories on the processed cables. The product quality can be controlled in the factory, and the on-site installation workload is small.
The structure of heat shrinkable cable accessories is made of pipes: stress tubes, internal and external insulating pipes, and semi-conductive pipes. There are inevitably small air gaps between various pipes, especially the partial discharge performance of the intermediate joints is difficult to guarantee.
4. Installation is more convenient: no need to use fire. Due to structural limitations, heat-shrinkable cable accessories are not suitable in some fire-prohibited situations; cold-shrinkable cable accessories are not subject to this restriction. No fire or other special tools are required during installation. You only need to pull out the skeleton in the main body or insert the main body by hand.
5. The interface features are good. The material used in cold shrinkable cable accessories is high elastic silicone rubber, and the accessory is an elastomer. After installation, the accessory is always tightly clamped on the cable and becomes one with the cable. At the same time, it exerts greater pressure on the interface, has good interface characteristics, and has good partial discharge performance.
Since the material of the heat-shrinkable cable accessory is heated and has no elasticity at room temperature, after installation, the bending and rubbing of the cable will cause the heat-shrinkable cable accessory to detach from the cable; during the operation of the cable, changes in the ambient temperature will also cause a gap between the heat-shrinkable accessory and the cable, resulting in poor interface performance between the accessory and the cable, resulting in poor partial discharge performance in actual operation, especially at the 35kV voltage level.
6. Reliable sealing performance. The cold-shrinkable cable accessories are made of highly elastic silicone rubber material. After installation, the accessories and the cable become integrated. When the cable expands and contracts due to temperature, the accessories will also expand and contract accordingly. They will always be tightened on the cable and have 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 cable accessories are installed, when the temperature drops, the cables will shrink (thermal expansion and cold contraction). The shrunk heat shrinkable parts have a stable structure and are no longer elastic, so they lose elastic compression force on the cables. The sealing depends entirely on the sealant, and the sealing performance is unreliable.
7. Comparison of materials and production costs. The material cost of the domestic cold-shrinkable intermediate head (outdoor) is 6-7 times that of the heat-shrinkable type, and the material price is about 6,500 yuan (there are some differences depending on the specifications); the material price of the domestic heat-shrinkable terminal head (outdoor) is 4-5 times that of the heat-shrinkable type, and the material price is about 3,000 yuan (there are some differences depending on the specifications). Other consumable materials are not much different. The production cost (that is, the labor cost for production) of cold shrink cable accessories is slightly greater than the production cost of heat shrink heads.
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