The cable head is installed in the outdoor aerial and directly buried environment, so it is waterproof. Anti tide gas is one of the key factors to ensure the safe operation of the cable head, and its sealing performance and methods should be considered. At present the domestic and foreign first choice is to use a high elastic sealant has the advantages of simple process, reliable performance also makes him become the mainstream of the use, but to consider using this gum glue, because the sealing performance of sealant directly affects the performance of the joints, to choose a can and the cable body surface can materials and accessories surface bonded solid glue, but also to meet the temperature change in different environment can be the perfect use of glue is what is difficult and important.
The cold shrink product is actually an elastic cable attachment, that is to say, the elasticity of the silicone rubber itself is pre - expanded in the factory and put into the bracing bar. Go to the site and put the support strip off to make it shrink naturally. The end of this is the cold shrinkage technique. This is the cold shrink cable accessories accessories, accessories and so this has good flexibility, can avoid the gap between the cable thermal load level is generated in the atmospheric environment, cable operation and contraction due to breakdown caused by accident, and not lack of elastic point itself is the biggest heat shrinkable products fully meet the cable with the same breath, so and the products are used in temperature, affected by the regional climate environmental impact of use is the best choice.
The insulation requirement of the cable head is the two large insulation that meets the relative insulation box between the phase and phase.
Two insulating materials of silicone rubber and heat shrinkable material are usually relatively insulated. The insulation performance usually depends on the thickness of the material and the thickness of the material. The performance index of all cold shrinkable accessories is that the design operation thickness of 24kv/mm should meet 12mm, which can withstand the test of lightning shock and overvoltage. The heat shrinkable accessory is made of many kinds of composite materials. It has thermal shrinkage function after irradiation. Its unit insulation index is feeding 1.8~2.0kv/mm. Therefore, the design thickness is 3~4mm relative to that of silicone rubber material, that is, 15~16mm.
The relative insulation is the safe distance to prevent the charge from climbing to the low potential by high potential. Cold shrink tube silicone rubber material has good flexibility, as long as reasonable design, its strong resilience is enough gripping force, regardless of the environment to ensure the thermal expansion and contraction, tightly wrapped cable bundled parts. In this way, water and moisture are prevented from inhaling, and the safe distance to the inside is guaranteed. Heat shrinkable accessories only in the installation, the temperature is enough to satisfy his contraction condition, when the temperature is low, because the expansion coefficient of thermal expansion coefficient and thermal shrinkage cable of different materials, it is possible to produce delamination cracks, therefore, such water and moisture will breathe into the role of ah, resulting in the destruction of insulation systems. Because of the lack of the elasticity of silicone rubber, it will also affect the safety, which is the weakness of the heat shrinkable product relative to the cold shrink product.
Three. Electric field
Three, the cold shrink attachment is applied in the electric field treatment, and the distribution of electric field is changed by stress cone. It is solved by using certain geometry and precise R angle. This method is easier to control and check. It can be ensured and realized in the factory. The processing method of power plant heat shrinkable accessories is distributed with linear parameter change of the electric field, we must rely on two important parameters: a B volume resistance, dielectric constant, due to the complexity of the production process, the change of environmental factors, so it is difficult to control the parameters of stability, thus affecting the stability of the quality of will.
In the above analysis, the cold shrinkable tube and the heat shrinkable tube are essentially different. But as long as they can meet the safety requirements in normal operation conditions, but with the change of environment, and the cold shrink tube heat shrinkable tube are incomparable advantages and differences; in addition the contraction tube is made of special mould, installed after the completion of the shape is very beautiful, the installation and construction speed; save time; the advantages of anti pollution etc..