1. Prefabricated accessories The materials used are generally silicone rubber or ethylene propylene rubber. The geometric structure method, that is, the stress cone, is mainly used to deal with the stress concentration problem. Its main advantages are excellent material properties, easier and faster installation, installation without heating, good elasticity, and greatly improved interface performance. It is the main form adopted by medium and low voltage and high voltage cables in recent years. The disadvantage is that the outer diameter of the insulation layer of the cable is required to be high, and the usual interference is 2 to 5 mm (that is, the outer diameter of the cable insulation is larger than the diameter of the inner hole of the cable accessory by 2 to 5 mm), the interference is too small, and the cable The accessories will fail; the interference is too large, and the installation of cable accessories is very difficult (high process requirements). Especially on the intermediate joint, the problem is prominent, the installation is not convenient, and it often becomes the point of failure. In addition, the price is more expensive. The key technical issues in its use are: the size of the accessory and the size of the cable to be installed must meet the specified requirements. In addition, it is also necessary to use silicone grease to lubricate the interface for easy installation and to fill the air gap at the interface. Prefabricated accessories generally rely on their own rubber elasticity to have a certain sealing effect, and sometimes sealants and elastic clamps can be used to enhance the seal.
2. Cold-shrinkable accessories are generally made of silicone rubber or ethylene-propylene rubber. Cold-shrinkable accessories generally use geometric structure method and parameter control method to deal with the problem of electrical stress concentration. The geometric structure method, which uses the stress cone to alleviate the concentrated distribution of the electric field, is better than the product of the parameter control method. Like prefabricated accessories, the material has excellent performance, can be installed without heating, and has good elasticity, which greatly improves the interface performance. Compared with prefabricated accessories, its advantage is that it is more convenient to install, only need to be in the correct position Pull out the lined core tube of the cable accessory to complete the installation. The materials used are better than prefabricated accessories in terms of mechanical strength, and the requirements for the outer diameter of the cable insulation layer are not very high, as long as the inner diameter of the cable accessories is 2mm smaller than the outer diameter of the cable insulation (this is the same as the prefabricated accessories) Type accessories require 2 ~ 5mm deviation - editor) can fully meet the requirements. Therefore, the construction and installation of cold-shrinkable accessories are more convenient. Its biggest feature is that the installation process is more convenient and quick, and its working performance is the same as that of prefabricated accessories after it is installed in place. The price is comparable to that of prefabricated accessories, slightly higher than that of heat-shrinkable accessories, and is the most cost-effective product. The key technical issues in its use are the same as those of the prefabricated accessories. In addition, cold-shrinkable accessories can be divided into factory-expanded and field-expanded in terms of expansion status. Generally, cold-shrinkable accessories with a voltage level of 35kV and below are mostly factory-expanded, and the effective installation period is within 6 months. , the longest installation period shall not exceed two years, otherwise the service life of the cable accessories will be affected. The cold-shrinkable accessories with a voltage level of 66kV and above are mostly field-expandable, and the installation period is not limited, but special tools are required for installation. Special tools can be provided by general accessory manufacturers. The installation is very convenient and the installation quality is reliable.
