Talking about the advantages of prefabricated branch cables

With the strong growth of my country’s national economy, the speed of various infrastructure, capital construction, and real estate development has accelerated. It is a historical necessity to use mining aerial bundled cables(abc) as the main supply, distribution, and trunk lines in various buildings and facilities. Therefore, construction units, design units, and construction units are seeking more advanced, more economical, superior performance, less effective space, and shorter construction period power supply construction technology and methods. It is also under such historical environmental conditions that prefabricated branch cables have entered my country’s architectural electrical stage in strides.

1) In the middle and high-rise buildings, prefabricated branch cables can be widely used in various middle and high-rise buildings such as residential buildings, office buildings, office buildings, commercial buildings, teaching buildings, scientific research buildings, etc., as the main and trunk cables for power supply and distribution use;

2) In airports and ports, it is used as the main cable for airport runway lighting, port terminal lighting, and power supply and lighting in building facilities;
3) It can be used as lighting power supply in tunnels; it can be used as lighting and power supply network in mines;
4) In the transformation and construction of urban power grids, as the main, kydl_yyyb trunk line mining cables can be buried or overhead;
5) In the modern standard factory building, it is used as the main and trunk cable for mining;
6) In various buildings, facilities, buildings, halls, halls, venues, and even sports facilities, swimming pools, etc., it can be used as main and trunk mining aerial bundled cables BS 7870.
7) Prefabricated branch cables can be used in various other occasions where mining cables are used, such as main and trunk lines of power systems such as ships and ships.

Pre-branch cables have many advantages:

1) The cost of insulation treatment of branch joints is greatly reduced;
2) On-site construction costs are greatly reduced;
3) On-site construction cycle and time are greatly shortened;
4) Reduced on-site construction personnel and equipment; reduced technical requirements for construction personnel;
5) Not restricted by the space and environmental conditions of the construction site;
6) The insulation performance of the branch connector is consistent with that of the cable body, with superior insulation performance and high reliability;
7) It has higher seismic, waterproof and fire resistance performance;
8) The power supply is safe and reliable, and the one-time effective opening rate can reach 100%;
9) Wide application range, many varieties and specifications;
10) Users can conveniently choose cables of various specifications, models, cross-sections, and lengths as the main and branch cables;
11) It has more intuitive maintenance operability.

Causes of fire accidents on overhead cables

Now the use of Aerial Bundle Cable has become more and more extensive, but with its popularity in the national power supply lines, some of its safety problems have gradually attracted people’s attention, especially in recent years, the  cable fire accidents reminds people to pay more attention to when using this kind of cable. So, what are the causes of fire accidents of overhead cables?

1. The nominal conductor cross section of cable core does not meet the requirements. Generally, the specified nominal interface is larger than the actual cable produced, and the cable whose nominal value deviates from the standard will have larger unit current density. In its working process, the cable is easy to cause fire accident because it can not generate heat normally.

2. (ABC)XLPE  Insulated cable production process is poor. Although not every manufacturer is like this, it is inevitable that some businesses in the market will not operate strictly according to the standards in the process of cable production in order to seek personal interests. Even some businesses will use some low-quality products to make rough, resulting in the final production of the cable because the quality is not up to standard, causing fire in the process of use.

3. The material of the cable is impure or unqualified. The core wire of the cable is generally made of some copper or aluminum conductive materials, and many businesses often use unqualified or insufficient purity materials in the production process, which will lead to the reduction of power due to the presence of more impurities. Therefore, the materials used as core wires must be some high-quality electrolyte materials, mainly copper and aluminum.

4.Improper transportation. Most cables are subject to strict quality inspection before leaving the factory, but in the process of transportation, due to the lack of proper protection measures, it is squeezed and collided, resulting in the damage of insulation layer or the breakage of internal core wire

5. The composition of the insulating material does not meet the requirements or the processing is poor. We know that the outside of the cable is generally wrapped with a kind of insulating material. If the quality of the insulating material is unqualified, it will reduce its own withstand voltage performance in the process of use, and will form unqualified resistance value. In addition, long-term use will also shorten its service life, it is easy to have some short-circuit faults and cause fire.

Basic cable performance test

1. Inspection method
Routine test: It is an experiment conducted by the manufacturer on all finished cables. Its purpose is to check whether the quality of the product meets the requirements of the technical conditions in order to find accidental defects in the manufacturing process. It is a non-destructive experiment, such as the DC resistance of the wire and the insulation resistance time. And withstand voltage test, partial discharge detection, etc.
Type test: It is the manufacturer who regularly conducts comprehensive performance inspection of the product, especially for a new product before it is finalized for mass production, or the structure, material and main process of a product have changed, which may affect the performance of the cable Time. Pass type test: It can be tested whether the product can meet the requirements of operation, and can be compared with the old product. Such as thermal aging performance of insulation and sheath, long-term stability test of power cable, etc.
Acceptance test: It is an acceptance test performed on the cable after the cable is installed and laid in order to check the installation quality and find possible damage during the construction. Such as withstand voltage test after installation.

2. Test items
2.1 Measurement of DC resistance of wires
The conductive core of the wire and cable mainly transmits electric energy or electric signal. The resistance of the wire is the main indicator of its electrical performance. When the AC voltage is applied, the core resistance is larger due to the skin effect and the adjacent effect surface than when the DC voltage is applied, but the difference between the two is very small when the electric eye frequency is 50Hz. The current standard stipulates That can only require the detection of whether the DC resistance or resistivity of the core exceeds the value specified in the standard. Through this inspection, certain defects in the production process can be found: such as wire breakage or partial single wire breakage; Meet the standard; the length of the product is incorrect, etc. For aerial bundled cables 1418 standard, you can also check whether it will affect the allowable current carrying capacity of wire and cable products during operation.
There are single-arm DC resistance method and double-arm DC bridge method to measure the DC resistance of conductors. The accuracy of the latter is higher than that of the former. The test procedure is also more complicated than the former.

2.2 Test of insulation resistance
Insulation resistance is an important indicator reflecting the insulation characteristics of wire and cable products. It is closely related to the product’s electrical strength, dielectric loss, and the gradual deterioration of insulating materials under working conditions. For communication cables, low insulation resistance between wires will also increase loop attenuation, crosstalk between loops, and long-distance power supply leakage on conductive cores. Therefore, insulation resistance should be higher than the specified value.
Defects in the process can be found by measuring the insulation resistance, such as the insulation is dry and impermeable or the sheath is damaged and damp; the insulation is contaminated and conductive impurities are mixed in; the insulation layer is cracked due to various reasons. In the operation of aerial bundled cables(abc) sans1418, the insulation resistance and leakage current are often tested as the main basis for continued safe operation.
At present, in addition to the ohmmeter (shaking meter), the current measurement of the insulation resistance of wires and cables is the galvanometer comparison method and the high resistance meter method (voltage-current method).

How to identify poor quality Aerial Bundled Cable

1. Look closely at the label printing, the handwriting is blurred and the address is unknown. It means to look at the printed words on the label and the insulating skin. If there are typos, or the printing is of different shades, or the words are blurred, pay attention to it.
2. Use your fingernails to mark and flick the line , and the line will be cut off. Refers to the use of nails to scratch and pinch the insulating skin. The ones that can be scratched or pinched are generally inferior threads.

3.Twist the insulation skin with your hands, and the color will fade and the characters will be of poor quality. Refers to rubbing the insulating sheath with your fingers. Some inferior insulated wires are easy to fade, especially the red wire. This problem occurs. After rubbing, the color of the thread is left on the finger or the words printed on the thread are wiped off Generally inferior quality Aerial Bundled Cable

4. Repeatedly bend the insulated wire and break (ABC)SANS 1418 Standard three to four times. Refers to repeated bending of insulated wires. Inferior wires are generally of poor quality, and the insulation layer will break after bending 3 to 4 times.


5. Use fire to ignite the wire insulation and spontaneously ignite away from the open flame. It refers to the inferior wire that ignites the insulating layer and can ignite spontaneously after leaving the open flame.

6. ​​Aluminum and copper are commonly used for wire cores, and the color becomes darker and lighter. It means to look at the color of the core, the color of inferior thread is gray and without metallic luster.

7, finely measure the inner diameter and outer diameter, and look at the pine when weighing. It means that if it is not determined by the above 6 methods, the outer diameter and core diameter of the insulated wire can also be measured. The allowable error is ±10%. If the measured value exceeds the allowable error, it is basically a low-quality insulated wire.

The difference between fire-resistant cable and flame-retardant cable

Flame retardant wire and cable, its flame retardant means that when a wire and cable fire accident occurs, it can block and delay the spread and extension of the flame along the wire and cable, and minimize the expansion of the wire and cable fire range. This type of cable has a self-defense after fire. The characteristics of extinguishing. Generally, it can be understood that when the wire and cable product catches fire by itself or by an external heat source, after the fire source subsides, the wire and cable product no longer burns, or the burning time is very short.

Fire-resistant wire and cable means that in a wire and cable fire accident, the wire and cable product can maintain normal operation for a certain period of time while the external flame is still burning, maintain the integrity of the wire and cable circuit and maintain the normal operation of the line equipment.

Both fire-resistant cables and flame-retardant cables are suitable for wiring of control, signal, protection and measurement systems with a rated voltage of 750V and below.
The structure and materials of fire-resistant cables are different from those of flame-retardant cables. The basic structure of flame-retardant cables is:
(1) The insulating layer is made of flame-retardant materials.
(2) The sheath and outer sheath are made of flame-retardant materials.
(3) The wrapping tape and filling are made of flame-retardant materials.

Fire-resistant cables usually add a fire-resistant layer between the conductor and the insulating layer, so theoretically, a fire-resistant layer can be added to the structure of the flame-retardant cable to form a flame-retardant and fire-resistant cable. Because of the fire-resistant layer of fire-resistant cables, multi-layer mica tapes are usually used to wrap the wires directly. It can withstand long-term burning, even if the polymer at the place where the flame is applied is burned, it can ensure the normal operation of the line.

Selection of cables in normal operation of the wiring system

The entry test of the wiring system is mainly divided into aerial bundled cable(abc) astm b230 test, jumper test, module test and external crosstalk test. Module testing is currently mainly used in laboratory technology models due to its complex technology, mainly facing manufacturers of wiring systems, while the other three are common approach testing techniques for wiring systems.

So how to check these factors qualitatively and quantitatively before construction? The following article will be divided into cable test, jumper test and alien crosstalk test to do a detailed introduction.

1. Pre-construction test: FCL cable test

At present, most data center cabling systems are composed of optical fiber and twisted pair. Optical fiber is mainly used to connect storage devices and servers; twisted pair cables are mainly used for physical connection with switching devices and servers and interconnection of switching devices.

The use of twisted pair cables accounts for 70% to 80% of data center cabling systems. The quality of the twisted pair itself directly affects the quality of the data center cabling system. Ensuring the quality of the twisted pair is the key to improving the quality of the cabling system.

Taking into account the requirements of the data center transmission rate, most of the first parties will require the project implementation party to use well-known brands or cables with good reputation on the market. However, the market is full of aerial bundled cables b230 of various brands, the price gap is very large, and the quality is also far behind. When customers order twisted pair cables, this situation often occurs. The customer requires a certain brand of cable, and the merchant often asks which brand of cable is needed: the quality is average, the better or the best? The best is of course the most expensive, and most likely to be a real brand line.

If the quality is average or better, it may be imitated by some small domestic factories. Although the core technology of twisted-pair cable is in the hands of some large manufacturers, imitation is easy to achieve only from the basic appearance of the cable. If it is not for professionals, it is difficult to see the difference between large-brand products and fake cables in appearance. It is also one of the reasons for the proliferation of false lines. A large part of the price difference is the use of materials. In order to save material costs, many informal manufacturers will add some aluminum and iron to the copper core.

The addition of some other cheap metals such as aluminum makes the transmission of high-frequency signals a big obstacle, especially affecting the transmission rate. There are also some technological differences. For example, the twisted pair has 4 pairs of cores. In order to reduce the crosstalk between each other and balance the interference between the pairs, it is required that the pitch of each pair of cores is not consistent. The higher the frequency of transmission, the greater the mutual interference between pairs. The twisting rate of twisted pair cables of different levels is completely different, and this technology is also one of the core technologies of well-known wiring production brands.

The so-called “general certain brand”, “better certain brand” or “real brand line” can not be judged by the naked eye when customers purchase cables. Due to the lack of understanding of the wiring market or the asymmetry of information, Party A cannot know the quality of the abc cables used before installation.

Therefore, there will be some bad party B winning the bid at a low price, and at the same time using some fake brand-name cables in order to maximize profits. Therefore, Party A needs some effective means to supervise Party B, and Party B also needs to prove the quality of the materials used by Party A.


How to distinguish between national standard wires and inferior non-standard wires

Before moving into a new house, everyone will check the house first, but most citizens will focus on the structure of the house, and they rarely care about the wires inside the walls. If the house is compared to a person, then the wires hidden in the walls are the vital “arteries”. The wires for home improvement not only concern the normal daily life of the family, but also the safety of the family’s relatives. Inferior wires may cause short circuits, Electric shock, damage to electrical equipment, and even fire, causing casualties. Nowadays, a large number of non-standard wires and low-quality counterfeit wires are flooding the building materials market. Some low-quality wires are broken as soon as they are twisted, making it easier to distinguish. But some low-quality wires are exquisite in workmanship, and at first glance they seem to be even better than the national standard! How to distinguish between national standard wires and inferior non-standard wires? Huaxing Cable‘s professional electrician technicians suggest that you should never think about saving money when buying home improvement wires. The quality of the wires not only affects the service life and safety of household appliances associated with them, but also affects the life safety of our family members. Now let the professional electrician technician of the cable explain to you how to distinguish between the national standard wire and the inferior non-standard wire!

The first step in identifying wires: look at the wire signsThe national standard wire label is the product qualification certificate. Take the wire qualification certificate as an example, it is printed with: wire product trademark, wire product name, wire manufacturer name, wire production site, cable manufacturer contact number, CCC certification and aerial bundled cable b230 factory number, wire model specification , National standard, rated voltage, length of wire, cross-sectional area of ​​wire conductor, production date, inspector’s seal. At the same time, well-known brand wire manufacturers generally have anti-counterfeiting labels that cannot be imitated! Each coil of the aerial bundled cable(abc) b231  has an anti-counterfeit QR code and a barcode, double anti-counterfeiting, just like our ID number

Inferior non-marking signs do not have the above content or are incomplete, and even if they have, they cannot be investigated. The following low-quality line signs are taken as an example; the trademark and company name are all virtual, although the factory address is available, but not specific, there is no way to find the phone number, the model column is blank, and the specification column is only marked 2.52. The formal marking should It is the number of conductor cores × conductor diameter, that is, 1×1.78 mm. The inspector’s seal is printed together with the other contents of the sign, which means that there is no need for inspection at all, and there is no anti-counterfeiting label.

The second step is to look at the copper wire conductor

Qualified copper core wires should be oxygen-free copper, purple-red, shiny, and soft to the touch.

The fake and inferior copper core wire is purple-black, yellowish or white, with many impurities, poor mechanical strength, poor toughness, and it will break with a little force, and there are often disconnections in the wire. The picture below is a low-quality copper-clad copper wire.

The third step is to look at the insulation material

The insulating layer of the national standard wire is made of high-quality insulating plastic, which has a certain degree of mechanical strength and flexibility, and cannot be torn easily. The insulating layer of high-quality wires has a certain flame retardancy. Peel off a section of the national standard wire insulation layer and ignite it with a lighter. After leaving the open flame, it can self-extinguish, and the smoke is light and has a light smell.

The insulating layer of inferior non-standard wire is made of recycled plastic, which has poor insulating ability, which can easily cause the insulating layer to be broken down by current and leak. Great harm to the life safety of users! Inferior wires can be distinguished from the insulating layer with a little attention. Pull off a section of the insulating layer. As shown in the figure below, if the color of the cross section is white, it is the inferior wire. Fold a certain part of the wire several times in succession. If the color of the folded part turns white, it can be judged. It is a low-quality wire. Use a lighter to carry out the igniting experiment, it can still burn after leaving the open flame, and the smoke has a strong smell. Cut a section of the wire insulation layer to see if there are visible pores in the section of the insulation layer and whether the core is located in the middle of the insulation layer. What is not in the center is the eccentricity caused by the low craftsmanship. The presence of pores indicates that the wire insulation material used is unqualified. Severe eccentricity is most likely to leak electricity on the thinner side, and air holes also affect the compressive strength of the wire.

The advantages of copper core cable and aluminum core cable are compared

Copper core cables have more advantages than aluminum core cables:

1. Low resistivity: the resistivity of aluminum core aerial bundled cable BS 7870 is about 1.68 times higher than that of copper core cable.

2. Good ductility: the ductility of copper alloy is 20-40%, the ductility of electrical copper is more than 30%, while aluminum alloy is only 18%.

3. High strength: the allowable stress at room temperature, copper is 7~28% higher than aluminum. Especially the stress at high temperature, the difference between the two is even greater.

4. Anti-fatigue: Aluminum is easy to break after repeated bending, while copper is not easy. In terms of elasticity index, copper is also about 1.7-1.8 times higher than aluminum.

5. Good stability and corrosion resistance: The copper core is resistant to oxidation and corrosion, while the aluminum core is susceptible to oxidation and corrosion.

6. Large current carrying capacity: Due to the low resistivity, the copper core cable of the same cross section is about 30% higher than the allowable current carrying capacity (the maximum current that can pass) of the aluminum core cable.

7. Low voltage loss: Due to the low resistivity of the copper core cable, the same current flows in the same section. The voltage drop of the copper core cable is small. Therefore, the same transmission distance can ensure higher voltage quality; in other words, under the allowable voltage drop condition, the copper core cable can reach a longer distance, that is, the power supply coverage area is large, which is beneficial to network planning and reduces The number of power supply points.

8. Low heating temperature: Under the same current, the copper core cable with the same cross section has much smaller heat than the aluminum core cable, which makes the operation safer.

9. Low energy consumption: Due to the low electrical resistivity of copper, it is obvious that copper cables have low power loss compared to aluminum cables. This is conducive to improving the utilization rate of power generation and protecting the environment.

10. Anti-oxidation and corrosion resistance: The performance of the connector of the copper aerial bundled cable(ABC) B231 is stable, and there will be no accidents due to oxidation. When the connector of aluminum core cable is unstable, the contact resistance will increase due to oxidation and heat will cause accidents. Therefore, the accident rate is much greater than that of copper core cables.

11. Convenient construction: The copper core is flexible and the allowable bend radius is small, so it is convenient to bend and easy to pass through; the copper core is fatigue-resistant, repeated bending is not easy to break, so the wiring is convenient; the copper core has high mechanical strength and can withstand relatively The large mechanical pulling force brings great convenience to construction and laying, and also creates conditions for mechanized construction.

12. Cheap price: Copper pole is 3.5 times the price of aluminum pole, and the proportion of copper is 3.3 times that of aluminum. Therefore, aluminum core cables are much cheaper than copper core cables, and are suitable for low-cost projects or temporary electricity use.

13. The cable is very light: the weight of the aluminum core cable is 40% of the copper core cable, and the construction and transportation costs are low.

14. Anti-oxidation and corrosion resistance: Aluminum quickly reacts with oxygen in the air to form an oxide film, which can prevent further oxidation. Therefore, aluminum wire is a necessary material for high-voltage, large-section, and large-span overhead power transmission.

Although aluminum core cables are cheap, copper cables have outstanding advantages in cable power supply, especially in the field of underground cable power supply. The underground power supply using copper core cables has the characteristics of low accident rate, corrosion resistance, high reliability, and convenient construction and maintenance. This is why copper abc cables are mainly used in underground power supply in China.

Three problems with cable insulation

It can be seen from the structure of the cross-linked polyethylene cable that there is a layer of outer semiconductor and copper shielding outside the main insulation layer of the cable. If this layer of outer semiconductor layer and copper shielding does not exist in the cable, then the core and core of the three-core cable Will an insulation breakdown occur during the period?

In the three-core cable terminal head, there must be a small section of the cable whose outer semiconductor and copper shielding layer have been stripped off, so is this small section of cable a weak link?
Can you overcome this problem by stripping less of the semiconductor and copper shielding layer (preserving the longer outer semiconductor and copper shielding layer as much as possible)? What is the disadvantage of keeping the longer outer semiconductor and copper shielding layer? The so-called “shielding” in the cable structure is essentially a measure to improve the electric field distribution. The cable conductor is formed by twisting multiple wires. An air gap is easily formed between it and the insulating layer. The surface of the conductor is not smooth, which will cause electric field concentration.Add a shielding layer of semi-conductive material on the surface of the conductor, which is equipotential with the shielded conductor and in good contact with the insulating layer, so as to avoid partial discharge between the conductor and the insulating layer. This layer of shielding is the inner shielding layer; Similarly, there may also be gaps at the contact between the insulating surface and the sheath, which is a factor causing partial discharge. Therefore, a shielding layer of semi-conductive material is added to the surface of the insulating layer. It has good contact with the shielded insulating layer and is in contact with the metal shield. The sheath is equipotential, so as to avoid partial discharge between the insulating layer and the sheath. This layer of shielding is the outer shielding layer; for extruded insulated cables without metal sheaths, in addition to the semi-conductive shielding layer, copper tape must be added Or the metal shielding layer wrapped with copper wire, the role of this metal shielding layer is to pass capacitive current during normal operation; when the system is short-circuited, it acts as a channel for short-circuit current and also plays a role in shielding the electric field.

It can be seen that if this outer semiconductor layer and copper shield do not exist in the ABC cable, the possibility of insulation breakdown between the core and the core of the three-core cable is very high. The main purpose of stripping off a small section of the shielding layer when making cable terminations or connectors is to ensure the creepage distance of the high voltage to the ground. The stress on the shielding fracture is very concentrated, which is a weak link! Appropriate measures must be taken for stress treatment. (Use stress cone or stress tube, etc.)

The length of the shielding layer is stripped to ensure the creepage distance; the basis is to enhance the creepage resistance of the insulating surface. Excessive stripping of the shielding layer will increase the difficulty of construction, and it is completely unnecessary to increase the cost of cable accessories.

Medium and low voltage cable accessories are currently used more products

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 abc 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 adopted by 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 to facilitate installation and fill the air gap of 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 sealing.

3. Cold shrinkable accessories

The material used is generally silicone rubber or ethylene propylene rubber. Cold-shrinkable accessories generally adopt geometric structure method and parameter control method to deal with the problem of electric stress concentration. The geometric structure method that uses the stress cone to relieve the concentrated electric field distribution is better than the product of the parameter control method.

Like prefabricated accessories, it has excellent material properties, can be installed without heating, and has good flexibility, which greatly improves the interface performance. Compared with prefabricated accessories, its advantage is that it is more convenient to install and only needs to be in the correct position. The installation can be completed by pulling out the inner lining core tube of the cable accessory. The material used is 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 less than the outer diameter of the cable insulation 2mm (the data is like this, this The type attachment requires a deviation of 2~5mm (Editor) to 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 quicker. After the installation is in place, its working performance is the same as the prefabricated accessories.

The price is equivalent to that of prefabricated accessories, and slightly higher than heat shrinkable accessories. It is the most cost-effective product.