Factors that cause power cables to overheat

AAAC Condutors are the basic facilities for transmitting electrical energy to every household or unit. Without it, we can enjoy modern life without electricity. However, precisely because it is placed in our work and living environment, it also brings certain hidden dangers to our lives, lives and work. There are countless fires caused by overheating of AAAC cables, whether at home or abroad, so what causes the overheating of wires and cables to cause fires? The following wire and cable manufacturers will give you a good introduction to what are the factors that cause the wire and cable to overheat? So everyone can be on guard.
1. The cable conductor resistance does not meet the requirements, which will cause the cable to overheat during operation. There is also improper cable selection, the conductor cross-section of the cable used is too small, and overload occurs during operation. After long-term use, the heating and heat dissipation of the cable will be unbalanced and cause overheating.

2. The partial sheath of the armored cable is damaged, which will cause slow damage to the insulation performance after water enters, resulting in a gradual decrease in insulation resistance, and overheating during cable operation.
3. When the cables are installed too densely, the ventilation and heat dissipation effect is not good, or the cables are too close to other heat sources, which affects the normal heat dissipation of the cables, and may also cause the cables to overheat during operation.
Fourth, the joint manufacturing technology is not good, the crimping is not tight, resulting in excessive contact resistance at the joint, and also causing the cable to overheat. The insulation performance between phases of the cable is not good, resulting in low insulation resistance and overheating during operation.

See what acsr conductor manufacturers mentioned above, as long as we usually choose a regular manufacturer when buying cables, buy high-quality wires and cables, and equip them with appropriate cables according to the actual situation of the project or project. The wiring installation is scientific and reasonable. Then it will not easily cause the cable to overheat or even cause a fire.
The above are the factors that cause the overheating of the wires and cables, do you understand it? Hope it helps you.

What are the functions of ACSR cables?

There are too many types and specifications of cables, and if you explain them carefully, it will be very cumbersome. Therefore, today we mainly understand one of them: “flexible fireproof cable”. If you are not a professional, this may sound strange. But it is obvious from the name that this is a flexible cable. This kind of cable has the function of fire prevention; also known as mineral insulated cable, it has the advantages of good flexibility, excellent shielding performance, corrosion resistance, strong practicability, and long service life. It is widely used in demanding occasions.
Flexible fireproof cable function
1. Good flexibility: the cable can be coiled on the cable tray with a bending radius ≤ 20D (D is the outer diameter of ACSR  cable).
2. Large cross-section: the cross-section of single-core cable can reach 1000mm, and the cross-section of multi-core cable can reach 240mm.
3. Long continuous length: Whether it is a single-core cable or a multi-core cable, its length can meet the requirements of the power supply length, and each continuous length can reach 1000m.
4. Corrosion resistance: Organic insulated fire-resistant cables sometimes need to wear plastic pipes or iron pipes, plastic pipes are easy to become brittle, iron pipes are easy to rust, fire-resistant cables with copper sleeves do not need to wear pipes, and copper sleeves have good corrosion resistance此图像的alt属性为空;文件名为abc-cable-full-form.jpg
5. Good shielding performance: Put the fireproof cable on the same shaft as the information cable and control cable. Under the shield of the copper sheath, it will not interfere with the information transmitted by the signal cable and control cable.
6. Excellent fire resistance: its fire resistance not only meets the requirements of the national standard GB12666.6 A 950℃ and 90min, but also meets the test requirements of A grade 650℃ 3h, B grade 750℃ 3h and C grade 950℃ British bs6387-1994 3 hours specified in At the same time, it can withstand the water spray and mechanical shock during the combustion process.
7. Safe and reliable: fireproof cables can usually supply power in flames, reducing fire losses, especially for personal safety, which is particularly reliable. Its copper sheath is an excellent conductor and is the best grounding PE wire. Continuous use within the range improves the sensitivity and reliability of grounding protection.
8. Long service life: Inorganic insulating materials are resistant to high temperatures and not easy to age. Its service life is many times that of organic insulated cables.
Each side of the flexible fireproof cable has a relatively large advantage, and it will also have a higher utilization rate for different environments. If you need to use cables and wires in your life, you can look at one of the advantages of flexible fire-resistant cables and see if they can be used and needed. Of course, we must also grasp the comprehensive consideration of psychological choices when buying, the most appropriate is the best.

How much do you know about the difference between RV and BVR

Both BVR and RV are indispensable decoration wires in the decoration industry. They have good flexibility, high conductivity, abrasion resistance, aging resistance, and very reliable safety and reliability. They are also multi-strand flexible wires commonly used in the market. . So, what is the difference between these two kinds of wires? What are the similarities?
Similarities between the two
1. Both are copper core PVC insulated flexible wires, which are composed of multiple strands of thin copper wires twisted together;
2. The structure of the product is all composed of conductor and PVC insulation layer
3. All copper core conductors are single core
4. In terms of colors, both have multiple colors-red, yellow, black, blue, etc.

The difference between BVR and RV
1. The executive standards of the two are different: the executive standard of BVR wire is GB/T 5023.3-2008, and the executive standard of RV wire is GB/T 3956 category 5;
2. The voltage levels of the two are different: the rated voltage of BVR is 450/750V, and the rated voltage of RV is 300/300V;
3. Purpose: BVR is mostly used for wiring wires. It is used in soft occasions. In many cases, it can be used instead of BV wire. RV wire is mostly used as the internal connection wire of various electrical equipment. Security equipment and instrumentation are also often used. It is used, so the RV line is softer, so it is called “electronic line”.

Wire specifications
4. The diameter of the core is different: the diameter of the copper wire that composes the conductor is different for the wire of the same specification; for example, the wire of the same 2.5mm2, BVR is made of 19 thin copper wires of 0.41mm twisted together, and RV is made of 49 A 0.25mm thin copper wire is twisted together.
5. Temperature: The maximum working temperature of conventional BVR wire is 70°C, and that of RV wire is 80°C. Of course, if you have special requirements, you can choose the high temperature resistant type.

Optical fiber cable signal error-free transmission distance increased to 5890 kilometers

Recently, researchers from University College London demonstrated a new method of processing optical fiber cable signals. Researchers claim that this method can double the error-free transmission distance of signals through submarine fiber optic cables. Because the new method does not need to strengthen the signal, it has the potential to cut the cost of long-distance optical fiber communications.

This research, funded by the British Engineering and Physical Sciences Research Council, improves the transmission distance by eliminating the interaction between different optical channels via a fiber optic cable.

Research leader Robert Maher said: “By eliminating the interaction between optical channels, we can double the error-free signal transmission distance from 3190 kilometers to 5890 kilometers. This is also the largest distance increase reported in the system architecture. .”
“The challenge is to design a technology that can simultaneously capture a group of optical channels with a single receiver, called a super channel.” Maher added.

Researchers use a 16QAM (quadrature amplitude modulation) super channel, which contains a set of frequencies. These frequencies can be encoded using amplitude, phase, and frequency to create a high-capacity optical signal. Utilizing a high-speed super receiver and a new signal processing technology developed by the team that can receive all channels without errors, the super channels can then be detected.

Now, the researchers plan to test new methods for dense super channels that are commonly used in digital cable television (64QAM), wired modems (256QAM), and Ethernet connections (1024QAM).

Polina Bayve, Professor of Optical Communications and Networking, added: “We are very pleased to report this important discovery, which will improve PV wire communications. Our method can greatly increase the efficiency of data transmission, almost double the signal transmission distance, which may greatly reduce the existing The cost of business systems. One of the biggest global challenges we face is how to maintain communications under the prosperous Internet demand. Overcoming the capacity limitations of fiber optic cables is the key to solving the problem.”

How to distinguish the quality of photovoltaic line?

Solar energy technology will become one of the green energy technologies in the future. Solar energy cable is becoming widely used in China. In addition to the rapid development of government-supported photovoltaic power plants, private investors are also actively building plants and plan to put them into production and sell them globally. Solar modules. Many countries are still in the learning stage. There is no doubt that in order to obtain the best profits, companies in the industry need to learn from countries and companies that have years of experience in solar energy applications. The construction of cost-effective and profitable photovoltaic power plants represents the most important goal and core competitiveness of all solar manufacturers.

How to choose fiber optic cable for us?
1. Outer: Indoor optical cables generally use polyvinyl or flame-retardant polyvinyl. The appearance should be smooth, bright, flexible and easy to peel off. The outer skin of poor quality optical fiber cable is not smooth and easy to adhere to the tight sleeve and aramid inside.

The PE sheath of the outdoor optical cable should be made of high-quality black polyethylene. After the cable is formed, the outer skin is smooth, bright, uniform in thickness, and free of small bubbles. The outer skin of inferior fiber optic cable is generally produced with recycled materials, which can save a lot of cost. The outer skin of this kind of fiber optic cable is not smooth. Because there are many impurities in the raw material, the outer skin of the made fiber optic cable has many very small pits. water.

2. Optical fiber: Regular optical fiber cable manufacturers generally use grade A cores from large factories, and some low-cost and inferior optical cables usually use grade C, grade D optical fibers and smuggled optical fibers from unknown sources. These optical fibers take a long time to leave the factory due to their complex sources. It is often damp and discolored, and single-mode fibers are often mixed in multimode fibers. Generally, small factories lack the necessary testing equipment and cannot judge the quality of the fiber. Because such optical fibers cannot be distinguished by the naked eye, the common problems encountered in construction are: narrow bandwidth and short transmission distance; uneven thickness and cannot be connected to the pigtail; the optical fiber lacks flexibility and breaks when it is bent.

3. Reinforced steel wire: The steel wire of the outdoor optical cable of the regular manufacturer is phosphated, and the surface is gray. Such steel wire does not increase hydrogen loss, rust, and has high strength after being cabled. Inferior fiber optic cables are generally replaced by thin iron or aluminum wires. The identification method is easy-it is white in appearance and can be bent at will when it is pinched in the hand. The optical fiber cable produced with such steel wire has a large hydrogen loss, and after a long time, the two ends of the hanging optical fiber box will rust and break.

4. Steel armor: regular production companies use double-sided brushed anti-corrosion paint longitudinally wrapped pattern steel strips, inferior optical cables use ordinary iron sheet, usually only one side of the anti-rust treatment.

5. Loose tube: The loose tube of the optical fiber in the optical cable should be made of PBT material, which has high strength, no deformation and anti-aging. Inferior fiber optic cables generally use PVC as the sleeve. The outer diameter of such a sleeve is very thin, and it is flattened by pinching it with the hand. It is a bit like a straw for drinking.

6. Fiber paste: The fiber paste in the outdoor optical cable can prevent the fiber from oxidizing. Due to moisture ingress and dampness, the fiber paste used in inferior fibers is very small, which seriously affects the life of the fiber.

7. Aramid: Also known as Kevlar, it is a high-strength chemical fiber that is currently used most in the military industry. Military helmets and bulletproof vests are produced from this material. At present, only DuPont and the Dutch Akzo can produce them, and the price is about 300,000 tons. Indoor optical cables and power overhead optical cables (ADSS) both use aramid yarns as reinforcements. Because aramid costs are relatively high, inferior indoor optical cables generally have a very thin outer diameter, which can save costs by using fewer strands of aramid. Such optical cables are easily broken when they are threaded through the tube. Because ADSS optical cable determines the amount of aramid fiber used in the optical cable according to the span and wind speed per second, it is generally not afraid to cut corners.

What are the common types of aluminum alloy cables

Aluminum alloy cable (abbreviation: alloy cable) is different from the traditional copper core cable. This aluminum alloy cable uses high elongation aluminum alloy material. The pure aluminum is added with iron and other materials, and undergoes a compact stranding process and special Annealing treatment can “squeeze” the voids in the alloy aluminum to reduce the cross-sectional area, so that the cable has better flexibility. The safety performance of this kind of aluminum alloy cable is also better than that of copper core cable. When its surface is in contact with air, it can form a thin and strong oxide layer, which can withstand various corrosions. Even when overloaded or overheated for a long time, the stability of the connection can be guaranteed. To achieve the same electrical performance, the direct purchase cost of aluminum alloy cables is 40% lower than that of copper cables, and the general construction and installation costs can be saved by more than 20%.

1.Aluminum alloy (STABILOY) non-armored AC-XLPE insulated PVC sheathed cable:
AC-XLPE insulated PVC sheathed cable, aluminum alloy non-armoured cable is made of conductor, the cross-section specification is from 10mm² to 400mm², the core is grade compressed strand type, which fully complies with CSA C22.2 NO.38 about ACM alloy conductor Standards, also in line with the latest editions of GB 12706.1 and IEC 60502.1.
Aluminum alloy (non-armoured cables use cross-linked polyethylene insulation with a working temperature of 90℃ and black PVC outer sheath, which have a very wide range of applications where no armored mechanical protection is required. They can be used in non-combustible buildings, such as Feeder lines for lighting, sockets and other equipment in office buildings, hotels, shopping malls and factories.

Aluminum alloy cable is an aluminum alloy conductor specially developed for construction application cables. The safety performance, electrical performance, and mechanical performance of aluminum alloy cables have been tested by the China Quality Certification Center and the National Wire and Cable Quality Supervision and Inspection Center, and all meet the requirements of China’s National Standards (GB). Aluminum alloy cables have been successfully used in North America for more than 30 years and are advanced and mature technologies and products.

2.Self-locking armored cable:
ACWU90 is a highly flexible self-locking aluminum armored, PVC outer sheath, 90℃ cross-linked polyethylene waterproof insulated single-core or multi-core cable, with an equipotential bonding bare conductor. Because of the FT4 grade PVC outer sheath, ACWU90 can be directly laid and buried in the ground, and is suitable for corrosive environments and non-combustible buildings. ACWU90 reduces the construction difficulty and labor cost caused by pipeline wiring.

The alloy cable has been assembled in the factory with a highly flexible self-locking armor and a sealed PVC outer sheath. There is no need for pipelines and accessories and manual procedures such as intensive drawing, buckling and pipe threading. ACWU90 has passed the CSA certification and can be used in open or dark wiring in dry and humid environments, as well as in the first-level hazardous environment in zone 1 and 2, as well as the second and third-level hazardous environments. Laying method: Brackets, ladders, trays and cable clamps can be used for indoor laying. Outdoors can be directly buried, cable trench, cable tunnel and other methods. ACWU90 is equipped with calibration marks per meter to accurately determine the cable length.

Aluminum alloy cable, ACWU90 multi-core cable is made of conductor, and the cross-section specification ranges from 10mm² to 400mm². It is fully compliant with IEC 60502.1 and GB 12706.1 standards, and can also provide various specifications of low-smoke and halogen-free products according to customer requirements. Both AC90 and ACWU90 can be used as user incoming cables. The self-locking armored technology used makes the cables more flexible and easier to install than conventional armored cables. In fixed installation, the bending radius of the self-locking armored cable can be only 6 times the outer diameter of the cable.

3AC90 type multi-core aluminum alloy self-locking armored aluminum alloy cable:
AC90 is a highly flexible self-locking aluminum armored, 90℃ cross-linked polyethylene insulated single-core or multi-core cable, with an equipotential bonding bare conductor. The AC90 cable is assembled in the factory with high-flexibility self-locking armor, without the need for pipelines and accessories, and manual procedures such as intensive drawing, buckling and pipe threading.
AC90 type has been used in non-combustible buildings, such as office buildings, hotels, shopping malls and factories in the lighting, sockets and other equipment feeder lines, can be used as users on the ground and in dry environments as the incoming cable. AC90 can be installed on the cable tray (perforated tray, non-perforated tray and ladder frame), and can also be laid along the wall and the top by using a bracket or a cable clamp.
AC90 multi-core cables are made of conductors, with cross-sectional specifications ranging from 10mm² to 400mm². It has passed CSA certification and can be used for open or dark wiring in a non-humid environment, and has the same performance as pipeline laying. AC90 is a flame-retardant Class A, low-smoke and halogen-free type, which fully complies with the standards of IEC 60754, GB17650.1 and IEC 60502.1\GB 12706.1.


Treatment method of polyethylene insulated power cable damp and water

In urban power grid renovation projects, cables, especially polyethylene insulated power cables, have been widely used. However, due to the particularity of the cable, there are special requirements for the installation, operation and maintenance of the cable. Moisture or water in the cable reduces the insulation resistance of the cable, which is a few important aspects that cause operation accidents in the cable line.

Causes and hazards of cables being damp
(1) When XLPE insulated cable  is shipped from the factory, both ends of the cable are sealed with plastic sealing sleeves. However, after a section of the cable is used according to the actual situation at the construction site, the remaining part is simply wrapped with plastic cloth to wrap the fracture. Placed in the open air and poorly sealed, over time, water vapor will inevitably seep into the cable.
(2) During cable laying, it is necessary to cross roads, bridges and culverts frequently. Due to weather or other reasons, a lot of water often accumulates in the cable trench. During the laying process, it is inevitable that the cable head will be immersed in water. , Because the plastic cloth is not tightly wrapped or damaged, water enters the cable; in addition, the outer sheath or even the steel armor is sometimes scratched when pulling and piercing the pipe. This phenomenon is particularly prominent when using mechanical traction.

(3) After the cable is laid, the cable head cannot be made in time due to the constraints of the site construction conditions, so that the unsealed cable fracture is exposed to the air for a long time, or even immersed in water, causing a large amount of water vapor to enter the cable.
(4) In the process of making cable heads (including terminal heads and intermediate joints), due to the negligence of the construction personnel, the newly processed cable ends sometimes accidentally fall into the stagnant water on site.

(5) In the normal operation of the cable, if breakdowns such as breakdown occur due to some reason, the water in the cable trench will enter the cable along the fault point; in civil construction, especially when large construction machinery is used It is not uncommon for cables to be damaged or broken down due to various human factors on construction sites in China. When such an accident occurs, the cable insulation is severely damaged, and water can enter the cable.
After the cable enters the water, under the action of the electric field, the aging phenomenon will occur, and finally the cable will break down.

What is Aerial Bundled Cable? What are the main characteristics of overhead cables?

Aerial Bundled Cable is an overhead cable and is commonly used for overhead distribution in place of traditional overhead distribution systems with bare conductors. (ABC) NFC 33-209 Standard cable is also a low-voltage cable that provides higher levels of safety and reliability, lower power losses, and ultimately system economy by reducing installation, maintenance, and operation costs.

Aerial Bundled Cables do not directly hang ordinary oil-paper insulated cables or cross-linked insulated cables on overhead poles, but are a kind of special cable manufactured by a production process similar to cross-linked cables.

General overhead cables are single-core, and can be divided into hard aluminum wire structure, hard drawn copper wire structure, aluminum alloy wire structure, steel core or aluminum alloy core support structure and self-supporting three-core pattern structure according to their different structures. (The core can be hard aluminum or hard copper wire), etc.

main feature
1. High reliability of power supply
The use of overhead cables can greatly reduce various short-circuit faults (especially the common flashover faults of overhead bare wires). Compared with overhead bare wires, the failure rate is 4-6 times lower.
The domestic overhead cable was put into trial operation in Shanghai in 1988. The test overhead cable runs along the dense boulevard of Huaihai Road. After the typhoon season in Shanghai and the high temperature in summer, it runs well, and its power supply failure rate is much lower than that of the original overhead bare conductor. Overhead cables will not produce water trees during use, and the insulation quality of the cables has not significantly decreased after years of operation.
  2. Good power supply safety
The use of overhead cables greatly reduces personal injury and death accidents due to electric shock [3]. The Shanghai Electric Cable Research Institute has set up a special subject to conduct “Research and Test on Personal Safety of Overhead Cable Insulation”. Tests and calculations show that even if the electrically charged cable insulation surface is touched by hand, the induced current is less than 0.1mA (10kV) and 0.2mA (35kV), which is much lower than the 50-100mA lethal standard stipulated by the national electrical safety regulations. It can be seen that when the overhead cable is energized, when the human body or other animals accidentally touch the surface of the cable insulation, as long as the cable does not penetrate, it will not cause harm to humans and animals.

 3. Convenient erection and maintenance
Overhead cables can be erected on any kind of poles or towers, or along walls. Under special circumstances, they can also run through trees and be directly fixed on tree poles with hardware. It can be erected on a single circuit or multiple circuits on the same pole, without requiring a wide “electrical corridor”. In installation, it can be easily erected on the original overhead line, using the original cross arm and porcelain bottle, or a full set of matching hardware and accessories. According to the actual situation of the site, the manufacturer can make special or self-made special fittings, so the construction is extremely convenient. Overhead cables do not need to conduct special inspections, and they will not cause short circuit trip accidents due to tree flashovers, residents littering, or accidental collisions of crane booms, which greatly reduces line maintenance and repair work.

Analysis of XLPE ACWU90 AC90 Cable Waterproof Structure

Cable waterproof structure type:
For XLPE ACWU90 AC90 Cable, there are usually the following waterproof structures:
1. For single-core cables, wrap a semiconducting resistance hose on the insulation shield of the cable, wrap a common water blocking tape outside the metal shield, and then squeeze the outer sheath. The outer sheath material can be ordinary For PVC, HDPE material with radial water blocking function can also be used, depending on other performance requirements of the cable. For three-core cables, in order to ensure the full contact of the metal shield, only the single-conductance resistance hose is wrapped outside the insulating shield, and the water blocking tape is no longer wrapped outside the metal shield. Water blocking filling, inner lining and outer sheath materials are the same as those described in single-core cables.

2. The aluminum-plastic composite tape layer is longitudinally wrapped inside the outer sheath or inner lining layer as a waterproof layer.
3. Squeeze the HDPE outer sheath directly on the outside of the cable.

Cable waterproof structure type:
For XLPE insulated power cables, there are usually the following waterproof structures:
1. For single-core cables, wrap a semiconducting resistance hose on the insulation shield of the cable, wrap a common water blocking tape outside the metal shield, and then squeeze the outer sheath. The outer sheath material can be ordinary For PVC, HDPE material with radial water blocking function can also be used, depending on other performance requirements of the cable. For three-core cables, in order to ensure the full contact of the metal shield, only the single-conductance resistance hose is wrapped outside the insulating shield, and the water blocking tape is no longer wrapped outside the metal shield. Water blocking filling, inner lining and outer sheath materials are the same as those described in single-core cables.

2. The aluminum-plastic composite tape layer is longitudinally wrapped inside the outer sheath or inner lining layer as a waterproof layer.
3. Squeeze the HDPE outer sheath directly on the outside of the cable.
For PVC XLPE Insulated Power Cable, the metal sheath is mainly used to make the cable meet the waterproof requirements. The most important feature of the metal sheath is that it is completely impermeable, so the cable with the metal sheath has very good radial water blocking performance. The main types of metal sheaths are: hot-pressed aluminum sleeve, hot-pressed lead sleeve, welded corrugated aluminum sleeve, welded corrugated steel sleeve, and cold drawn metal sleeve.

Cable waterproof form:
Cable waterproofing methods are generally divided into longitudinal water blocking and radial water resistance. Water blocking yarn, water blocking powder and water blocking tape are commonly used in longitudinal water blocking. Their water blocking mechanism is that these materials contain a material that can swell in contact with water. When water flows from the cable end or from the sheath After entering the defect, this material will quickly expand with water to prevent further diffusion of water along the longitudinal direction of the cable, thus achieving the purpose of longitudinal waterproofing of the cable. Radial water resistance is mainly achieved by extruding HDPE non-metallic sheath or hot pressing, welding, and cold drawing metal sheath.
Cable waterproof test basis:
The cable waterproof test method, the cable longitudinal water resistance performance can be tested and judged by the IEC 60502-1997 ANNEX D (normative) or GB/T 12706.2-2002 Appendix D (standard catalog) water permeability test; and the cable radial water resistance Performance, currently is mainly determined by indirect methods, such as checking whether the HDPE non-metal sheath or non-metal sheath is defective. If these sheaths are determined to be intact, then the cable is considered to have good radial water resistance. performance. However, many users of this method have raised some questions, caused some disputes, and lacked convincing power. Therefore, cable manufacturers and users now urgently need a test method to determine the radial water blocking performance of the cable. This can avoid disputes between manufacturers and users about the cable’s radial water blocking performance due to the lack of a radial water blocking test method.


Types of medium and low voltage cable accessories

The main types of products that are currently used for medium and low voltage cable accessories are heat shrinkable accessories, prefabricated accessories, and cold shrinkable accessories. They have the following characteristics:

1 Heat shrinkable accessories

The material used is generally a blend of polyethylene, ethylene-vinyl acetate (EVA), and ethylene-propylene rubber. This kind of product mainly uses stress tube to deal with the problem of electric stress concentration. That is, the parameter control method is used to relieve the electric field stress concentration. The main advantages are light weight, easy installation, good performance and low price.

The stress tube is a kind of heat-shrinkable tube with special electrical parameters with moderate volume resistivity (1010-1012Ωcm) and large dielectric constant (20-25). The electrical parameters are used to force the stress at the power cable insulation and shielding fracture to evacuate. The stress tubes are more evenly distributed. This technology is generally used in cable accessories of 35kV and below. Because the stress tube will heat up when the voltage level is high and cannot work reliably.

The key technical issues in its use are:

To ensure that the electrical parameters of the stress tube must reach the values ​​specified in the above-mentioned standards, it can work reliably. In addition, attention should be paid to filling the air gap at the fracture of the cable insulation semi-conductive layer with silicone grease to eliminate gas and achieve the purpose of reducing partial discharge. Cross-linked cables will shrink greatly during operation due to poor internal stress handling, so when installing accessories, pay attention to the stress tube and the insulation shield to cover not less than 20mm to prevent the stress tube from separating from the insulation shield during shrinkage. Due to the small elasticity of heat-shrinkable accessories, air gaps may occur at the interface during thermal expansion and contraction during operation. Therefore, the sealing technology is very important to prevent moisture intrusion.

2 prefabricated accessories

The material used is generally silicone rubber or ethylene propylene rubber. The geometric structure method is mainly used to deal with the stress concentration problem. Its main advantages are excellent material performance, easier and faster installation, installation without heating, good flexibility, and greatly improved interface performance. It is the main form used in low-voltage and high-voltage cables in recent years. The disadvantage lies in the high requirements for the outer diameter of the cable insulation layer. The usual interference is 2-5mm (that is, the outer diameter of the cable insulation is larger than the inner hole diameter of the cable accessory by 2-5mm). The interference is too small, and the cable The accessories will malfunction; the interference is too large, and the installation of the cable accessories is very difficult (high process requirements). Especially in the middle 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 necessary to use silicone grease to lubricate the interface for easy installation.