What is the performance difference between cold-shrinkable cable accessories and heat-shrinkable cable accessories?

1, Seal

Since most of the cable accessories are in outdoor overhead, direct buried and other environments, waterproof and moisture-proof has become one of the keys to ensure the safety of cable accessories, and its sealing function and method should be considered.

At present, there are generally two sealing methods:

One is to seal with asphalt or epoxy resin, the process is chaotic, difficult to control, and not conducive to protection.

Another new method is to use high-elastic sealant, which is simple in process, reliable in function, and convenient to protect equipment, which has become the mainstream of application. To use this new method, we must first consider the function of the sealant. Because the quality and function of the sealant directly affect the sealing function of the joint.

The fully cold-shrinkable power cable accessories are actually elastic cable accessories, that is, using the elasticity of liquid or solid silicone rubber itself, expand in the factory in advance, put plastic and support strips, and remove the support strips to the designated direction on site to shorten naturally.

This kind of skill is a cold shrinkage technique, and this kind of accessory is a cold shrinkable cable accessory. Therefore, this cold-shrinkable cable accessory has outstanding elasticity, which can prevent the cable from expanding and contracting due to the uneven atmospheric environment and the uneven working load of the cable, that is, the insulating space created by the breathing of the cable.

The disadvantage of heat-shrinkable cable accessories is that they are not flexible and cannot breathe with the cable.

Therefore, the fully cold shrinkable cable accessories are the best choice for areas with large temperature differences and large climate and environmental impacts!

2, Insulation

The insulation requirements of the cable accessories should meet the insulation between phases and the opposite insulation.

The relative insulation is silicon rubber and heat-shrinkable insulation materials. Generally, the insulation function is also based on the insulation target of the material unit, and the thickness of the combined material meets the requirements.

Cold-shrinkable cable accessories, the general function index is 24kV/mm, and the planned working thickness should meet the thickness of 12mm, which can withstand the test of lightning shock and overvoltage.

The heat-shrinkable cable accessories are made of a variety of composite materials and have a heat-shrinking function after irradiation processing. The unit insulation index is 1.8-2.0kV/mm, and the planned thickness is 3-4mm thicker than the silicone rubber material. Relative insulation is a safe distance to prevent the charge from climbing from a high potential to a low potential.

Cold-shrinkable silicone rubber material has excellent elasticity. As long as the planning is reasonable, its strong resilience can satisfy the holding force. Regardless of whether the environment is thermal expansion or cold contraction, cold-shrinkable cable accessories ensure that the cable is hugged tightly to prevent moisture inhalation and ensure a safe internal creepage distance. At the same time, theoretically, the inner climbing distance of all cold-shrinkable cable accessories is only 70mm, but for safety reasons, the planned working distance is still 90mm.

The shortening temperature of heat shrinkable cable accessories is 100℃-140℃. Only in the equipment can the temperature meet its shortening conditions. When the temperature is low, because the thermal expansion coefficient of the cable is different from that of the heat-shrinkable material, the environment below 80°C may delaminate, so cracks will appear, allowing water and moisture to enter under the action of respiration, thereby destroying the insulation of the system , This is a small disadvantage of heat shrinkable materials.

3, Electric field

When processing the electric field of cold-shrinkable cable accessories, several methods are used to change the electric field dispersion by using stress cones, and certain shapes and accurate R-viewpoint processing are adopted. This method is relatively simple to control and check and can be completed in the factory.

The electric field treatment method of heat-shrinkable cable accessories is to change the electric field distribution through linear parameters. It is necessary to rely on two important parameters:

Volume resistance, 108-11Ω.

The dielectric constant is 25.

Due to the chaotic production process and large changes in environmental factors, it is relatively difficult to control the stability of parameters, which will affect the quality stability of the product.

Therefore, cold-shrinkable cable accessories and heat-shrinkable cable accessories are completely different in the process itself. Working under normal conditions, both meet safety requirements. However, as the environment changes, cold shrinkage is indeed more advantageous than heat shrinkage. Of course, the price of cold contraction is much higher than that of heat contraction.