European cable joint, PT cable joint
●1. Design principle of cross-linked cable head
First of all, the design principles of all cross-linked cable heads should follow the principle of restoring the cable body structure. Therefore, the design concept of its connector should comply with China's GB12706-4 and IEC60502-4:1997 electrical standards, and must meet its electrical, physical and chemical properties to ensure the long-term normal operation of the cable head and the safe operation of electrical equipment.
●2. Basic requirements for high-voltage cable heads
Cable terminal: It is a component that connects cables to other electrical equipment. The terminal joint material is called a cable accessory. Cable accessories should be as safe for long-term operation as the cable body and have the same service life as the cable. Good cable accessories should have good wire core connections, mainly small and stable connection resistance, and can withstand the impact of fault current; after long-term operation, the contact resistance should not be greater than 1.2 times the resistance of the cable body with the same length.
High voltage cable head manufacturing process
●3. The commonly used processes are:
A. Cold shrink cable head terminal
B. Heat shrinkable cable head terminal
C. Special plug-in equipment for cable heads (usually connected to the special socket of the equipment, often used in special environments, such as tunnels and other environments where the operating environment is complex and inconvenient to make cable accessories, and the voltage level is low)
D. Junction box (cable connection or cable divided into two or three, 10kV junction box)
Flameproof high voltage cable connector LBG2-500/3300
Explosionproof and intrinsically safe high-voltage combination switch
High voltage cable junction box BHG1-4O0A/10KV-(2)3G
Differences between processes
(1) The difference between cold shrink and heat shrink:
a. Sealing:
Cable terminals have high requirements for waterproofing and moisture-proofing. Fully cold-shrinkable power cable accessories are actually elastic cable accessories; they have good "elasticity" and can avoid thermal expansion and contraction of the cable caused by the atmospheric environment and the load level during cable operation. That is, the gaps between insulation caused by "cable breathing" cause breakdown accidents. The biggest disadvantage of heat shrinkable accessories is that they are not elastic and cannot breathe with the cable. Fully cold-shrinkable accessories are more suitable than heat-shrinkable cable terminals for areas with large temperature differences and large impacts from climate environments.
b. Insulation:
1) Cold shrink accessories are made of a variety of composite materials and have heat shrink function after irradiation and processing. Its unit insulation index is 1.8-2.0kV/mm. The cable is cold-shrinkable and has relatively good insulation.
2) The shrinkage temperature of the heat-shrinkable cable head is 100℃-140℃. When the temperature is low, because the thermal expansion coefficient of the cable is different from that of the heat-shrinkable material, it is entirely possible for delamination to occur in an environment below 80℃, resulting in cracks. Water and moisture will then enter under the action of breathing, destroying the insulation of the system. Heat shrink has higher installation requirements.
c. Electric field
The geometric method is applied in the electric field treatment of the cold shrink cable head, and the electric field distribution is changed through the stress cone, which is solved by using the R angle of a certain geometric shape. This method is easier to control and test. This can be ensured and implemented at the factory. The electric field treatment method of heat-shrinkable cable ends is to use the linear parameter method to change the distribution of the electric field, which must rely on two important parameters: a volume resistance, 108-11Ω; b dielectric constant is 25; due to its complex production process and large changes in environmental factors, it is difficult to control the stability of the parameters, so it will have an impact on the quality stability of the product.
d. Economical and practical
Cold-shrinkable cable accessories have higher performance than heat-shrinkable cable accessories, and the production process and materials are more complex and more demanding than heat-shrinkable cable accessories. This results in cold-shrinkable cable accessories being more expensive than heat-shrinkable cable accessories. The prices of cold-shrinkable cable accessories of different brands are also very different. According to the service life of the cable and the use environment, cold-shrinkable cable accessories or heat-shrinkable cable accessories with better quality grade and brand should be selected. Currently, cold-shrinkable cable accessories are usually used for cable joints with long service life.
(2) Special plug-in equipment and junction boxes for cables
These two high-voltage cable wiring methods have greater limitations, are more expensive than the first two, and are rarely used in power systems; however, the wiring technology requirements are lower than the first two; cable plug-in equipment often generates heat due to the large gap between the copper rod and the plug-in space. These two types of equipment are mostly used in mining enterprises. The use of these two types of equipment in special environments can avoid the possibility of breakdown due to reduced insulation performance during the high-voltage cable joint process.
Hengyuan Technology cable joint series includes: European cable joints, American cable joints, cold shrink cable heads, cold shrink cable joints, cable plug-in heads
