On the characteristics of flexible fireproof cable

Flexible fireproof cable, also known as “inorganic mineral insulated cable”, is developing rapidly in China because it is softer and easier to install than mineral insulated AAC Cable.

An electrical arc crossing two blue, copper wires on a green and black gradient background.

Product model
1. Bttw copper core rolled copper sheath: flexible inorganic mineral insulated fireproof cable, rated voltage 750V;
2. Yttw copper core rolled copper sheath: flexible inorganic mineral insulated fireproof cable, rated voltage 750V;
3. Yttwg copper core smooth copper sheath: flexible inorganic mineral insulated fireproof cable, rated voltage 500V;
4. Yttwv copper core rolled copper sheath: PVC outer sheath, flexible inorganic mineral insulation fireproof cable, rated voltage 750V;
5. Dw-yttwy copper core rolled copper sheath: low smoke halogen-free polyolefin outer sheath flexible inorganic mineral insulation fire-proof cable, rated voltage 750V.
Product advantages
1. Excellent fire performance: the fire resistance rating not only meets the national standard gb12666.6 class a 950 ℃ 90min, but also meets the British bs6387-1994 class a 650 ℃ 3H; Grade B: 750 ℃ for 3 h; C class 950 ℃ 3 h test requirements; At the same time, it can also withstand water jet and mechanical impact during combustion;
2. Long continuous length: whether single core or multi-core cable, its length can meet the need of power supply length, and each continuous length can reach 1000m;
3. Large cross section: the cross section of single core cable can reach 1000mm, and that of multi-core cable can reach 240mm;
4. Good flexibility: the cable can be coiled on the cable reel with bending radius ≤ 20d (D is the outer diameter of the cable);
5. Smoke free and non-toxic when burning: the insulation adopts inorganic materials (non combustible body), which will not produce any harmful gas when burning, and will not produce secondary pollution, so it is an environmental protection and green products

6. Large overload capacity: the cable not only has large current carrying capacity, but also has large overload capacity. According to the wiring requirements, usually the surface temperature of the cable is less than or equal to 70 ℃. If the wiring is not touchable or in contact with combustible building materials, the temperature of the cable sheath can be increased to 105 ℃, and the long-term working temperature of the flexible fire-proof cable can reach 250 ℃ under overload;
7. Corrosion resistance: sometimes the organic insulation fire-resistant cable needs to wear plastic pipe or iron pipe. The plastic pipe is easy to be aged and brittle, and the iron pipe is easy to rust. The fire-resistant cable has copper sheath, so it does not need to wear pipe, and the copper sheath has good corrosion resistance;
8. Good shielding performance: when the fire-proof cable is laid in the same shaft with the information and control wires, it will not interfere with the information transmitted by the signal and control wires and cables under the shielding of the copper sheath;
9. Safety and reliability: the fire-proof cable can supply power normally in the flame, start the fire-fighting equipment, reduce the fire loss, and is particularly reliable for personal safety. Its copper sheath is an excellent conductor and the best grounding PE line, which is continuous to the full length of the cable, greatly improving the sensitivity and reliability of grounding protection;
10. Long service life: inorganic insulating material has high temperature resistance and is not easy to aging. Its service life is many times higher than that of organic insulating cable. Under normal working condition, its service life can reach more than 100 years;
11. Simple installation: the transportation and installation of flexible fire-proof cable, including installation accessories, is similar to ordinary cable, which is relatively simple;
12. Low installation cost: due to advanced manufacturing technology and simple installation, the comprehensive cost of flexible fire-proof cable is significantly lower than that of mineral insulated cable under the same conditions.
structural style
According to the requirements of the cable application, the outer copper sleeve can be longitudinally wrapped and welded

without rolling.
1. Conductor: stranded copper conductor;
2. Insulation: synthetic mica tape;
3. Filling: inorganic materials;
4. Copper sleeve: longitudinal package welding and rolling.
Scope of application
1. Power supply for fire fighting equipment and fire elevator in various buildings;
2. Power supply of equipment and lighting system in important buildings or densely populated buildings;
3. Places with high ambient temperature, such as steel works, smelters, glass works, etc;
4. Important inflammable and explosive occasions, such as power supply of petrochemical, coal mine and other equipment;
5. Places requiring special cleaning and sanitation, such as hospitals, food factories and other power supply equipment;
6. Power supply for important military, national defense, aviation and satellite base equipment;
7. Power supply for important equipment of power plant and nuclear power plant.

Can fire resistant cables really not burn?

Nowadays, cables have become essential items in our daily life and production, followed by accidents caused by wires and cables, especially the explosion of wires and cables after burning, which is easy to cause casualties. Every year, there are many fire accidents caused by various wires and cables, and the outer sheath of ordinary wires and cables is mostly plastic rubber products, These materials will release a lot of smoke and toxic gases after they are burned in the fire. Once the cable burns and explodes, it will also cause serious harm to the surrounding residents and the environment.

Why do some cables catch fire or even explode? There are many reasons for cable fire, and the most common five are summarized as follows: short circuit, overload, breakdown, cable head burning, and external fire source. Generally, the insulation layer of the cable is damaged, which leads to short circuit and causes the burning of the outer sheath material of the cable. If the cable is overloaded for a long time, serious heating phenomenon will occur, If it is an old cable running at this time, it is easy to break down and cause a fire.
Another common reason is the burning of the cable head. If the surface of the ACSR Cable head is damp or dirty, the porcelain bushing of the cable head is broken and the distance between the outgoing lines is too small, which leads to flashover and fire, causing the surface insulation of the cable head and the insulation of the outgoing line to burn. Of course, another reason is that the external fire source burns the cable, causing the cable burning or even explosion.

So in order to reduce the loss caused by cable burning, fire-resistant cable is designed. Fire resistant cable is the general name for the characteristics of flame-retardant cable and fire-resistant cable. They all have certain fire-resistant characteristics, but many people can’t distinguish the concepts of flame-retardant cable and fire-resistant cable. From its use characteristics, fire-resistant cable can replace flame-retardant cable, But flame retardant cable can not replace fire resistant cable. This is because the working principles of the two are different.
The working principle of flame retardant cable depends on the flame retardant effect of halogen. There is also a halogen-free flame retardant cable. It uses water to reduce the temperature, but the working principle of fire-resistant cable is different from that of flame-retardant cable. The material of fire-resistant cable contains a kind of mica material, which has very high fire resistance and can ensure normal use in the fire.
Understanding the difference between the two working principles, it can be seen that flame-retardant cable is also afraid of fire, just because there are flame-retardant materials, which can strangle the fire in the cradle, while fire-resistant cable is different, its own fire-resistant layer structure, can also maintain normal work in the fire, so in many cases, fire-resistant cable can be used to replace flame-retardant cable.

So the flame-retardant cable and fire-resistant cable will not burn? The flame-retardant cable has a high degree of non combustion characteristics, small combustion range, and can automatically extinguish after the fire disappears. But the flame-retardant cable itself will burn, not completely non combustion. Similarly, fire-resistant cable is the same, and it will burn. Flame retardant cable reduces the temperature through the flame-retardant effect of special materials, while fire-resistant cable relies on its unique fire-resistant layer to ensure that it can work normally in the fire, so fire-resistant cable is better than flame-retardant cable in some occasions.

Common rubber cable classification, process, cable rubber material introduction!

Rubber insulated wire and cable has experienced more than 100 years of development. It is the oldest variety of all wire and cable products. Rubber insulated wire and cable are mostly used in the occasions of harsh working conditions and moving. With the development of rubber industry, various kinds of synthetic rubber have been developed continuously, such as silicone rubber, neoprene rubber, rubber already made rubber, etc., which greatly improved the performance of rubber insulated wires and cables. Besides the inherent advantages of natural rubber, it also increased the oil resistance, cold resistance and heat resistance. Thus, the rubber insulated wire and cable are more abundant and widely used.

Common rubber sheath cable products

Rubber insulated wires and cables are widely used, most of which are used in electrical equipment, and are the products with the widest range, the most varieties and the largest production volume. According to its different purposes, it can be roughly divided into:
General rubber wire and cable; Lead in connection of motor and electric appliances; Cables for rolling stock; Rubber sheath flexible cable; Rubber sheathed soft cable for mining; Marine cables; Cables for geological exploration and petroleum industry; Rubber insulated power cable and rubber insulated control cable.
Common rubber insulated cables include: general rubber sheath soft cable, rubber sheath soft cable, rubber cable, welding machine cable, diving motor soft cable.
1. General rubber sleeve soft cable
The general rubber sheath soft cable is widely used in industrial and agricultural and daily electrical as the mobile power line connecting electrical devices. It can be used in various outdoor and outdoor environments. According to the external force, the products are divided into two types: medium and heavy:
1. Medium sized cable: it should be flexible enough to facilitate movement and bending. The AAC Cable is light in weight and small in outer diameter. It is very convenient to use and does not bear external force.
2. Heavy cable: it shall be able to bear the effect of large mechanical external force (extrusion and impact). The sheath has high mechanical properties, good wear resistance and elasticity, and it should also have certain softness and easy to bend and move.
The general rubber sleeve flexible cable moves frequently, and is often subjected to bending, twisting, friction and other mechanical external forces in use. All requirements of the cable are soft and wear-resistant. And often contact with oil, outdoor cable also can withstand the sun, so also requires that this kind of cable has the sun aging resistance and oil resistance and moisture resistance.

2. Rubber sleeve soft cable for mining
Rubber sheathed soft cable is widely used in coal mines and other mines. There are a lot of combustible and combustible materials such as gas and dust in the mine. The electrical safety requirements are very strict, and the mine is humid and may have corrosive substances. The cable moves frequently and is often impacted by bending, twisting, dragging and smashing. The cable used in the open air and field can also bear the function of sunlight, so the requirements for mine cables are very strict. The conductor core shall be highly flexible and shall be twisted with small pitch with thin soft copper wire. The insulation shall have high electrical resistance and mechanical strength. It is required that the cable is soft, wear-resistant, impact resistant, can be bent frequently, and also has good flame retardant performance. The sheath of cable is much thicker than that of general rubber sheath soft cable to increase the impact resistance and crush resistance of cable.
3. Electric welding machine cable
The cable of electric welding machine is characterized by low voltage, high current and frequent movement. It is often subjected to torsion, bending and dragging in use. The use environment may be acid, alkali, oil, etc. Therefore, the conductor core of electric welding machine cable shall be very soft, the insulation shall be flame retardant, and the sheath shall have the properties of wear-resistant and oil-resistant and atmospheric aging. See the table below for the production capacity of common electric welding cables.
4. Waterproof rubber sleeve soft cable
Waterproof rubber sleeve soft cable is mainly used for connecting power supply to submersible motor or submersible pump with AC voltage of 450/750v and below, and also can be used in oil pollution occasions.

The technological process of rubber insulated wires and cables

Rubber insulated wire and cable is a kind of wire and cable with various structures. The process is different, but it can be divided into two basic processes for its typical products: one is the processing of rubber rubber: rubber plastic refining, adding coordination agent, mixing, extrusion and vulcanization. The second is the processing process of wire and cable products, and the production process of rubber insulated wires and cables.
Rubber processing: according to the rubber formula, the preparation and weighing (ingredients), rubber plastic refining, mixing, extrusion and other processing processes of raw materials and auxiliary materials are collectively referred to as rubber processing.
Vulcanization of rubber: vulcanization is the process of crosslinking the molecular chain to form a solid mesh structure by chemical or other methods.
Rubber processing process guidance:
1. Rubber formula composition and the role of each material!
2. The cooperation and processing of natural rubber
3. Rubber raw material inspection, mixing processing and rubber refining equipment detailed explanation!
4. Rubber formula design basis

Introduction of common rubber materials for electric wires and cables

1、 Natural rubber
It is divided into cigarette and crepe glue, and used in the industry of wire and cable. The main components are rubber hydrocarbon (the basic chemical composition is isoprene, c5h8)
1. High mechanical strength
2. Excellent electrical insulation performance
3. Good elasticity
4. Good cold resistance
5. Good process performance
It has the advantages of heat resistance, oxygen aging, ozone resistance, oil resistance, solvent resistance, long burning and limited source.
2、 Styrene butadiene rubber
It is formed by polymerization of two monomers, butanediethylene and styrene. Domestic soft butane-30a is commonly used, which is equivalent to international model 1500 and 1503.
1. The electrical insulation performance is better, but not as good as natural rubber
2. The aging performance of heat-resistant oxygen is better than that of natural rubber, but the ozone resistance is worse than that of natural rubber
3. It has some elasticity, but it is not as good as natural glue
4. The wear resistance is better than that of natural rubber, but the resistance to flexibilities and cold resistance is not as good as that of natural rubber
5. Poor processing performance, small adhesion, large shrinkage, difficult to roll and squeeze
In the electric wire and cable, the styrene butadiene rubber and the natural glue are used in a certain proportion.

Ethylene, propylene copolymer, ethylene propylene diene rubber and EPDM
1. Excellent electrical insulation performance
2. Good heat resistance
3. Excellent ozone resistance
4. Good weather resistance
5. Good cold resistance
6. Good chemical corrosion resistance
4、 Neoprene
Chloroprene polymer, divided into general (GN), 54-1 (W) and special type, general purpose for wire and cable industry and 54-1 type.
1. Good mechanical properties
2. Excellent aging resistance
3. It has special non – delay and excellent oil resistance
4. Poor electrical insulation performance
It is easy to self sulfur in storage period, and it is easy to cause early vulcanization (i.e. coke burning) and roll dip in industry. Because of its poor insulation performance, it is not generally used as insulation, only used for low-voltage rubber insulated wires.
Because of its excellent ozone resistance, atmospheric aging resistance, superior non flame resistance and high mechanical properties, it is widely used in the sheath of marine cables and mine cables.
5、 Nitrile rubber
It is made of butadiene and acrylonitrile, and is divided into general NBR and special NBR by use.
The hot NBR and cold NBR were divided by polymerization.
According to the different content of propylene, there are bunitrile-18 (propylene content is 18%), nitrile-26 (propylene content is 26%), nitrile-40 (propylene content is 40%), soft and hard.
Nbr-18 and NBR-26 are commonly used in the wire and cable industry.
1. It has excellent oil resistance and solvent resistance. The higher the content of acrylonitrile, the better its oil resistance.
2. General physical and mechanical properties
3. Good heat resistance
4. Good water resistance and low permeability
5. Can be used in combination with other rubber or plastic to improve the performance of rubber.
The higher the content of acrylonitrile, the worse the cold resistance, the less brittle the temperature is about-20 ℃. It is not suitable for insulation because of its poor ozone resistance and poor process performance. It can be used as oil resistant electrical insulation sheath, such as motor lead out, oil mine cable, marine cable sheath, etc.
6、 Chlorosulfonated polyethylene rubber
It is a derivative of polyethylene. According to the different chlorine content and molecular weight of polyethylene, chlorosulfonated polyethylene 20, chlorosulfonated polyethylene 30, chlorosulfonated polyethylene 40, chlorosulfonated polyethylene 45 are divided. In the wire and cable industry, chlorosulfonated polyethylene 20 and chlorosulfonated polyethylene 40 are generally used.
1. Good physical and mechanical properties
2. It has good heat resistance and can be used continuously at 120 ℃
3. Excellent ozone resistance, sunlight resistance and atmospheric aging resistance, no crack in outdoor exposure for six years
4. It has good fire resistance, second only to fluororubber and neoprene
5. Excellent chemical resistance
6. Good oil resistance
7. It has good corona resistance and radiation resistance
8. It has good process performance and can be used with other rubber.
The high compression deformation and poor low temperature performance are the most promising rubber in synthetic rubber. Oxo sulfonated polyethylene 40 is commonly used in insulation and coating. The oxygen sulfonated polyethylene 20 can be used as insulation for low voltage wires.

Rubber matching and processing process guidance:

1. Rubber formula composition and the role of each material!
2. The cooperation and processing of natural rubber
3. Rubber raw material inspection, mixing processing and rubber refining equipment detailed explanation!
4. Rubber formula design basis
5. Production flow chart of Mixing Workshop


Working principle and characteristics of radiation cross-linked wire and cable

1. Explanation of the principle of irradiation:
Irradiation cross-linking is to use the high-energy electron beam generated by the electron accelerator to bombard the insulating layer and the sheath to break the polymer chain, and each broken point becomes a free radical. Free radicals are unstable and must be recombined with each other. After recombination, the original chain molecular structure becomes a three-dimensional network molecular structure to form crosslinks.
Second, the characteristics of radiation cross-linked low-smoke halogen-free wire and aaac cable
1. Large current carrying capacity; after radiation cross-linked cable, after high-energy electron beam irradiation, the molecular structure of the material changes from linear to three-dimensional network molecular structure, and the temperature resistance level is increased from non-crosslinked 70℃ to 90℃, 105 ℃, 125℃, 135℃, or even 150℃, the current carrying capacity of cables of the same specification is increased by 15-50%.
2. The insulation resistance is large; because the radiation cross-linked cable avoids the use of hydroxide as a flame retardant, it prevents pre-cross-linking during cross-linking and the insulation resistance drop due to the absorption of moisture in the air by the insulating layer. Thereby ensuring the insulation resistance value.

3. Long service life and strong overload capacity; due to the high temperature resistance grade and high aging temperature of the radiation crosslinked polyolefin material, the service life of the cable during the cycle of heating is extended.
4. Environmental protection and safety; since the materials used in the abc cables are all halogen-free environmentally friendly materials, the combustion characteristics of the cables meet environmental protection requirements.

5. Product quality temperature: The quality of traditional warm water cross-linked cables is affected by water temperature, preparation process, cross-linking additives and other factors, and the quality is unstable. The quality of irradiated cross-linked cables depends on the radiation dose of the electron beam. The radiation dose is controlled by a computer, and there are no human factors, so the quality is stable.
Irradiation cross-linked low-smoke halogen-free flame-retardant wires and cables are difficult to catch fire and have the ability to prevent or delay the spread of flames. They have strong overload capacity and once caught fire, they have halogen-free, low-smoke, non-toxic, and non-corrosive characteristics. Used in high-rise buildings, hotels, hospitals, subways, nuclear power plants, tunnels, power plants, ore, petroleum, chemical industries, etc.

Cable quality defects and troubleshooting methods

The degree of crosslinking (hot extension) is unqualified
If the degree of cross-linking fails to meet the standard, the thermal-mechanical properties of the aac cable are unqualified and cannot meet the requirement of 90°C working temperature.
The reasons for the unqualified cross-linking degree are the unqualified formula and the improper type and ratio of the compounding agent. The formula should be adjusted to solve the problem; the second is the improper vulcanization process, such as low air pressure, fast line speed, high cooling water level and other factors.
The solution is to first find out what is the reason, which may be one or several reasons at the same time, and eliminate the reasons.

Unqualified structure and appearance
(1) The thinnest point of the insulating layer thickness is lower than the minimum value specified in the standard, or the average thickness is lower than the nominal value. The reasons for the unqualified insulation thickness are the fast line speed, the small amount of glue from the extruder, and the improper selection of molds.
The solution is to reduce the linear speed or increase the speed of the extruder and adjust the size of the die.
(2) Eccentricity
The reason for the eccentricity is that the mold is not adjusted or the suspension control has changed after the recruitment is adjusted.
The solution is to control the drape as stable as possible during driving.
The reason for the appearance of the bamboo-shaped outside of the cable is electrical and mechanical systems that cause the traction speed to be unstable. The second is that the core is too small, or the outer diameter of the acsr conductor full form is uneven.
The troubleshooting method is to check the mechanical and electrical system and eliminate the fault. Properly adjust the size of the core, control the outer diameter of the suburbs and counties to be as uniform as possible, and the stranded wire that exceeds the process regulations can be used.

Scratches on the surface
(1) The cable touches the upper or lower wall or foreign matter in the vulcanizing tube. Therefore, it is required to adjust the degree of suspension, try to make the wire core move in the middle of the cross-linked tube, and find foreign matter, and clean it in time.
(2) There is burnt on the outer edge of the mold sleeve. The solution is to adjust the temperature of the mold sleeve when starting the car to prevent overheating. Once it is found to be burnt, it should be stopped immediately to remove it, or it will not get better by itself.
Most of the impurities in insulating materials and semi-insulating materials are brought in during mixing and during the feeding process of the extruder. Strict attention should be paid to the cleanliness of materials during operation to prevent the mixing of external impurities. Another kind of impurity is scorching lumps, its existence affects the performance and service life of the abc cable, so the temperature is strictly controlled during mixing and extrusion to prevent the occurrence of scorching.

There may be two reasons for bubbles generated in insulation, one is caused during extrusion. The solution is to select appropriate molds. There are bubbles in the shielding layer. The main reason is that there is moisture in the material. It should be dried before extrusion. The second is insufficient cooling. At this time, the following will appear. A circle of bubbles will appear on the circumference equidistant from the core.
The elimination method is to strengthen the cooling, raise the water level and lower the temperature of the cooling water.
Unqualified cable performance
(1) Unqualified free discharge and dielectric loss
The causes of dissociation discharge and dielectric loss unqualified are very complicated, and they are shielded from the outside. Whether the insulation contains bubbles and impurities is closely related to the performance of the raw materials. The elimination method is to keep the raw materials clean and strictly follow the production process.
(2) Cable insulation breakdown
The main cause of cable insulation breakdown is the mixing of insulating materials and external damage. Due to strict avoidance of external damage, the mixing of impurities should be avoided as much as possible. The semi-finished products are strictly managed to prevent stumbling.
(3) Cushion breakdown
The main reason for the cushion layer breakdown is the steel with burrs, curling, and puncture the cushion. The method of elimination is the use of different quality requirements of the steel belt. The cushion shall be made of plastic tape with a higher hardness, and it shall be ensured The thickness of the cushion.

Smart grid boosts urban green development

In the future, smart cities will not only focus on high-efficiency and intelligent goals, but also include green, environmental protection and low-carbon development goals. The construction of smart grids will promote the green development of cities. With uneven energy distribution, a strong smart grid can greatly improve the grid’s ability to accept clean energy and optimize the allocation of energy resources on a large scale. More and more smart cities in our country are incorporating clean energy into the overall planning of smart cities. Especially abc cables played a huge role in this plan,realize the transformation of the economic development direction and the optimization and upgrading of the industrial structure. The goal is to build a modern and fully internationalized world ecological garden city, and the goal is to build a smart, green, and low-carbon livable city.

In the process of realizing the smart grid to promote urban green development, power cables play a prominent role in the construction of smart grids,the State Grid took the lead in practicing and established the National Wind and Solar Storage and Transmission Demonstration Project. The project is currently the world’s leading new energy comprehensive utilization platform integrating wind power, photovoltaic power generation, energy storage, and smart power transmission. Wind power will reach 1 million kilowatts, the total scale of photovoltaic installations will reach The scale reaches 110,000 kilowatts.

There are many participants in the construction of smart grids. With the construction of smart grids, its R&D and manufacturing levels will continue to improve, and the overall strength of the aaac industry will continue to improve. City-related industries will also develop rapidly and share market shares, creating conditions for smart grid-related industries to enter the international market. In addition, the improvement of the safe and stable operation of the power grid, the improvement of power supply reliability, and the high-quality power supply have also laid the foundation for the rapid growth of traditional industries and the rise of high-tech industries.

The basic process flow of plastic wire and cable manufacturing

1. Copper and aluminum monofilament drawing
Commonly used copper and aluminum rods for wires and cables, at room temperature, use a wire drawing machine to pass through one or several stretch die holes to reduce the cross-section, increase the length, and increase the strength. Wire drawing is the first process of various wire and abc cable companies, and the main process parameter of wire drawing is die matching technology.
2. Monofilament annealing
Copper and aluminum monofilaments are heated to a certain temperature to recrystallize the toughness of the monofilament and reduce the strength of the monofilament to meet the requirements of the wire and cable for the conductive core. The key to the annealing process is to prevent the oxidation of the copper wire.

3. Stranding of conductors
In order to improve the flexibility of the wire and cable and facilitate the laying and installation, the conductive core is made of multiple monofilaments twisted. From the stranding form of the conductive core, it can be divided into regular stranding and irregular stranding. Irregular stranding is divided into bundle stranding, concentric twisting, special stranding and so on. In order to reduce the occupied area of ​​the wire and reduce the geometric size of the cable, the compacted form is adopted while the acsr conductor size is twisted, so that the ordinary circle is transformed into a semicircle, sector shape, tile shape and compacted circle. This kind of conductor is mainly used in power cables.

4. Insulated extrusion plastic wires and cables mainly use extruded solid insulation layer, the main technical requirements of plastic insulation extrusion:
4.1. Eccentricity: The deviation value of the extruded insulation thickness is an important indicator of the level of the extrusion process. Most of the product structure dimensions and deviation values ​​are clearly specified in the standard.
4.2. Smoothness: The surface of the extruded insulating layer must be smooth, and there must be no poor quality problems such as surface roughness, burnt, and impurities
4.3. Density: The cross-section of the extruded insulation layer should be dense and strong, and no pinholes visible to the naked eye are allowed to prevent the existence of air bubbles.
5. Cable
For multi-core cables, in order to ensure the degree of forming and reduce the appearance of the cable, it is generally necessary to twist them into a circle. The stranding mechanism is similar to that of conductor stranding. Because the stranding pitch diameter is larger, most of them adopt the non-back-twisting method. Technical requirements for cable formation: First, to prevent twisting of the cable caused by the overturning of the special-shaped insulated core; second, to prevent the insulation layer from being scratched. Most of the cables are completed with the completion of the other two processes at the same time: one is filling to ensure the roundness and stability of the cable after the cable is formed; the other is binding to ensure that the cable core is not loose.

6. Inner sheath
In order to protect the insulated core from being damaged by the armor, it is necessary to properly protect the insulating layer. The inner protective layer is divided into: extruded inner protective layer (isolation sleeve) and wrapped inner protective layer (cushion layer). The wrapping cushion layer replaces the lashing tape and the cable forming process is carried out simultaneously.
7. Armoured
For cables laid underground, they may be subjected to certain positive pressure during work, and an inner steel tape armored structure can be selected. Cable laying in occasions with both positive pressure and tension (such as in water, vertical shafts or soil with a large drop), the structure type with inner steel wire armor should be selected.
8. Outer sheath
The outer sheath is the structural part that protects the insulating layer of the wire and cable from environmental factors. The main function of the outer sheath is to improve the mechanical strength of the wire and cable, prevent chemical corrosion, moisture, waterproof, and prevent the cable from burning. According to the different requirements of the cable, the plastic sheath is directly extruded by the extruder.

Direct burial / pipe laying / pipe laying / cable trench: the four laying methods of cables are learned

1. What should we pay attention to when burying directly? Under what circumstances

In direct burying, it is necessary to consider whether the cable is vulnerable to external force impact and lead to damage.
1. if it is not greatly affected, it can be laid directly.
2. if it may be affected by a large extent, but the strength can be controlled within a certain range, the direct burial of armor can be considered.
3. if the external force is large, the casing shall be protected. You can set up locally (for example, where you pass a road).
Advantages and disadvantages of direct embedded cable laying:
Advantages: easy to lay, saving materials and labor,
Disadvantages: inconvenient maintenance. If maintenance is required, the overlay needs to be excavated. Only recommended where maintenance is not considered or acceptable. When buried directly, yellow sand must be placed on it.
Question 1. how to find the fault point of buried cable grounding?
A: use cable tester.
Question 2 does the cable well need to be buried directly?
Problem added: cables laid in the plant area are buried directly with armored cables. Are cables required at the intersection of the workshop and in the distribution room? Is it necessary to add cables to municipal 10kV cables entering the plant area?
A: cable tray cannot be set for 6 or less cables, and more cable trays are set, which is convenient for replacing and adding cables. Municipal 10kV cable can be directly buried in high voltage distribution cabinet from the terminal post when it enters the factory without good cable.
Q3 how to lay temporary cables on site?
Problem supplement: the new plant of the unit, the construction transformer and high voltage line are far away from the construction center. Because of the steel structure workshop, overhead lines cannot be used to avoid conflict with the installation of steel structure. Only primary distribution boxes leading from transformers to construction sites through low voltage cables can be used and then distributed to secondary distribution boxes of each construction unit on site. How to lay low voltage cables? Is it buried directly or directly on the ground?
A: it is strictly forbidden to lie on the ground directly. Low voltage cable is laid directly.


2. What should be paid attention to when piping? Under what circumstances

Compared with direct burial, the ACSR Cable is more convenient to maintain and increase the line in the later stage. For cables laid through pipes, some spare pipes may be considered to prepare for future maintenance and increase of line capacity.
1. when laying pipelines, cable wells shall be considered when the turning angle of the conductor is large or the distance of straight section is long.
2. cable shaft can be used for the number of cables and the diameter of cable is small.
3. if there are many cables and large diameter, cable manholes shall be considered. Cable wells can be carried out according to the atlas. In addition to the atlas method, many small intersections can also be placed directly with bricks or concrete, and the bottom of the tunnel should be considered.
4. there are more pipes that are pierced by pipes, such as cast iron pipe, steel pipe, polyethylene pipe, nylon pipe and carbon pipe, which can be selected according to the needs. When single core cable is through metal pipe, the influence of eddy current should be paid attention to.

3. What should be paid attention to in the pipe arrangement? Under what circumstances?

The laying of the pipe is mainly used in the areas with more lines and concentrated routes. Relatively speaking, it is more convenient to lay out the pipe and save materials.
Question 1 is the outdoor pipe laying cable, one line of pipe, one cable, or multiple cables can be laid in one row of pipes?
A: only one cable should be worn for each pipe. Except for important places such as power plant and substation, for all circuits of one motor or all circuits of low voltage motor of the same equipment, no more than 3 power cables or multiple control cables can be connected in each pipe.
Question 2. The laying depth of row 2 pipe is not enough, what should be done?
(problem added: how to embed cable bank pipe on the ground less than 1m thick? Below is basement, basement roof is only 70, 80 cm thick, well depth is 1.3m?)
A: if the buried depth is not less than 0.5m in the area without vehicles passing (the cable specification requires 0.5m and the civil code requirement is 0.7m, the cable specification shall prevail here). If there are more vehicles to pass, the protective plate can be added to the discharge pipe. Or use thick wall steel pipe to lay or use cable trench. If the roof of basement is only 70-80 cm of soil covering, the well depth of 1.3m is to reduce the slab of the roof, but this is not significant, because the drainage problem of cable well is difficult to solve, and few people pay attention to it.
Question 3. Strong current discharge pipe and weak current pipe, laying problem?
(problem added: there is an external line in the plant, with more than ten low-voltage and strong current cables, and also weak current (TV, telephone, network) cables. The strong current cables are more than 8, and can not be buried directly. I used the laying of the pipes. But now there is a problem, that is, weak current is also laid through pipes. Can strong and weak current pipes be arranged all the time
A: try not to be in line, when doing small municipal work, try to set strong and weak electric pipes on both sides of the road. If there are occasional intersections, it is recommended to implement the requirements of the specification spacing. Please refer to the atlas, such as laying 05×101-2 underground communication cable.

Question 4 outdoor cable concrete pipe laying?
(problem supplement: when drawing the general drawing, all outdoor cables shall be laid by concrete pipe arrangement according to Party A’s requirements. After consulting the atlas (94d164), the following problems were found:
1. due to the influence of other pipelines on site, the manhole shaft of cable drain pipe can not be in accordance with the size shown in the atlas except for straight shaft,
I wonder what reasonable solutions are available?
2. the drainage problem in the manhole. According to the requirements of the people’s regulations, the sump pit is required in the manhole, but it is not known what method is adopted to centralized drainage.
3. the spacing between man hole and well is 150m according to the specification, and the atlas is 50m. I don’t know which one is the rule, or there are other provisions.
4. whether there are other atlas to refer to. Besides standard wells, can you design the shape and size of the well itself.
5. what should be paid attention to in the design and construction of this laying method.)
1. Non standard wells can be designed as required;
2. For drainage in the well hole, if there is any condition for setting drainage pump, drainage pump shall be set. If there is no way to set drainage pump, overflow hole shall be set at the bottom of sump, and it is not sealed with concrete, so that water can be penetrated naturally, but it depends on local groundwater level;
3. The spacing of manhole wells is usually considered according to 50-70;
4. In my opinion, it is unnecessary for small municipal distribution to do well according to the atlas requirements, and it is not standard;

4. What should be paid attention to in cable trench laying? Under what circumstances?

Pay attention to cable trench laying, cables of different voltage levels shall be set up according to different supports, and drainage measures shall be paid attention to in cable trench itself. And consider measures to prevent the entry of mice and other small animals.
Question 1 how many cables need to be laid in cable trenches?
A: according to “measures 2009 6.10 section 8 below recommended to adopt direct burial, 8-12 recommended to use the drainage pipe, 12-18 recommended cable trench, 18 more recommended cable tunnel.” These are all suggestive, and can be combined with actual engineering reference, not so fixed. As for cable trench and cable tunnel, it is not the difference between number of roots, but also the difference between maintenance and importance.
It mainly depends on the factors such as engineering conditions, environmental characteristics and cable type, and the selection of requirements for reliable operation, easy maintenance and reasonable technology and economy. It is uncertain whether there are mandatory index requirements.
Question 2 how to calculate the cable capacity of cable trench laying?
Netizen 1: (considering the cable tray laying, considering that the bridge is in the air, and the cable trench has cover plate, the capacity reduction coefficient is 0.96.)
Netizen 2: (for the coefficient of bearing capacity, refer to GB t16895.15-2002 “bearing capacity of 523 wiring system of Part 5 of electrical installations of buildings”, considering that the coefficient is appropriate to determine the ladder according to the ladder coefficient
Is there a depth requirement for the laying of high voltage cable with length question 3?
A: no requirement, the depth of cable trench is determined by the number of cables and the number of cable types. There are control cables, low-voltage power cables and high voltage power cables, which are generally divided into three layers. Generally, the spacing between each layer is 250-300, so the height can be determined,
Question 4 can be laid along the cable trench through bus duct?
(problem added: first, for high-level hospitals, it is necessary to save money. Oil immersed transformers shall be used for outdoor installation. 15 meters from the building (6m from the road in the middle) and the low voltage distribution room is located underground of the hospital. In order to save investment, I want to use bus duct (3000A load) to lay along the cable trench to the underground distribution room of the house.
A: dense buses meeting the corresponding IP level requirements can be adopted, for example, Siemens’ buses can be submerged underwater. However, the cost of using dense busbars will be higher, preferably dry-type transformers and bus bars should be considered comprehensively. The personal recommendation is to use dry transformers and put them indoors. Maintenance work will be reduced and failure rate will be reduced.
Question 5 how many cables can be laid in the cable tray without support?
A: Generally speaking, it is necessary to support it. If not supported, cable maintenance in the cable trench will be more troublesome. If the project is small and the number of cables is not large, it will not be harmful to set it, but the cooling conditions will be worse and if there is water in the trench, it will also affect the cable.
Q6 can high and low voltage cables be placed in the same cable tray?
(added questions: outdoor cable trench, width 1200mm, support on both sides, 10kV High Voltage Cable on one side, 1kV LV cable and control cable on the other side, please note whether it meets the specification? What should we pay attention to
Answer: cable trenches can be laid together. See setting requirements for specific requirements
Question 7 what is the distance between the cable trench and the road?
A: This is mainly to consider the force of cable trench cover plate. If there is no problem, there is no problem. Usually, it is set on sidewalks or where motor vehicles do not pass.
Should armour cable be used when Q8 is laid in cable trench?
(problem supplement: technical measures say: when laying cables in cable trenches or cable tunnels, cables with anti ant and rodent protection functions shall be considered. But it seems that there is no clear explanation on the standard! Can’t armour be used?
A: embedded cables do not need mandatory armouring and cable trenches will not exist. According to different environmental requirements (if mouse activity in this area is rampant, armor is recommended), there is no mandatory requirement.
Question 9 when placed in layers on the same side of the support, what is the minimum distance between the strong current cable and the weak current cable in the cable tray?
A: separate the weak current cable from the metal plate and ground the metal plate at the same time! It is best to pad the upper bracket with a plate (or metal slot box), then ground the plate and place the weak current cable on the plate (in the slot box).
The voltage levels shall be arranged in “descending order” of power cables from high to low, control and signal cables from strong to weak current and signal cables from communication cables to power sources.

Collected! Six judging methods of cable breakpoint

  When the breakpoint fault occurs in the cable or inside of the cable, it is difficult to determine the location of the breakpoint intuitively due to the wrapping of the external insulation.

The following is to introduce several methods to judge the breakpoint of wire and cable

The method of no damage cable

Digital multimeter

First, connect one end of the cable with breakpoint to the 220 V live wire, and make the other end suspended. Adjust the gear of the multimeter to AC 2V. Then, starting from the live wire access end of the faulty cable, hold the black pen tightly with one hand, and the red pen slowly slides along the insulation layer of the faulty cable. The voltage of the cable without breakpoint is about 0.445v. When the red probe moves to a certain place, the voltage value displayed by the multimeter drops to 1 / 10 of the normal voltage, that is, 0.04V. At this time, it can be concluded that the breakpoint is 15cm forward of the position (the live line access end).
If the shielding layer of the shielding wire is not damaged, this method cannot be used.

Induction pen method

First, eliminate the power supply of the ACSR Cable around the breakpoint cable, then connect the cable with breakpoint to the live wire, and then use the induction pen to move vertically to the cable slowly. When the AC signal of the induction pen disappears, it can be judged that the breakpoint is at the detection point, and the error is not more than 10cm at most.

Broken line method

For the short cable test break point, the bending method can be used to connect the two ends of the cable to the red and black probes of the multimeter. Bend back and forth from one end of the cable. If the multimeter is on and off at this time, the breakpoint is here. According to this method, it has been checked until the breakpoint( To learn more cable technology, please click here. A large amount of dry goods are waiting for you.)

Methods of repairing damaged cables

Acupuncture discrimination

This method is to use the on-off of the cable to check the breakpoint of the cable. Insert the steel needle into the breakpoint cable section by section, and then use the multimeter to measure the on-off condition in turn. Different points are where the breakpoint is. However, this method will damage the insulation layer, which is easy to cause other problems in the later use of the cable.

Methods of professional instrument testing

1. In addition, for the judgment of underground cable fault point, the audio detector can be used to judge the fault point.
2. The cable fault telemeter can be used to judge the full length of the cable and the short circuit and open circuit points

3. According to the actual situation, different methods are used to determine the breakpoint. The above methods can basically determine the breakpoint of the cable.

from a to z! Low smoke halogen free power cable

What is a low smoke halogen-free ACSR Cable? As the name suggests: low smoke, that is to reduce the production of harmful objects in combustion; Halogen is a kind of toxic gas for human body, and halogen-free means that there is no release of toxic gas, usually for cables in case of fire.

Low smoke and halogen-free AAC Cable can also be called environmental protection cable. Most of the low smoke and halogen-free cables are used in hospitals and places with strict requirements for environmental sanitation.


The identification of low smoke and halogen-free power cable mainly lies in the identification of insulating materials

1 combustion method

Judge whether the material is easy to burn, whether it is flame retardant wire zrbv or flame retardant power cable zryjv… According to whether it is burning, identify its flame color; Whether smoke is smoke or not, how much smoke is judged, whether it is low smoke halogen-free power cable wdz YJV, and the color of smoke can be distinguished, such as: smoke is clear smoke or soot smoke; Whether there is drop of sol, if there is any, it is necessary to see whether the sol continues to burn; And what kind of smell it produces when burning.


When it is softened and deformed by fire, it has zouqu thin layer, a small amount of coke, micro coke has flavor and non flammability.


Green flame light cover, softens white smoke and has hydrochloric acid taste, self extinguishing plastic; Put in the water and sink.


Blue light cover, the combustion zone is melted transparent, with the smell of glue dropping and candle; put in water and float up.


Blue light cover, the combustion zone is melted transparent, with the drop of adhesive and kerosene taste; put in water and float up.


Black smoke, with drop of adhesive, no coke ash, nitrogen and oxygen compound flavor, ductility.


Blue light cover, melting, hair burning, self extinguishing.

Silicone class:

Tasteless, thick white smoke, white residual ash, self extinguishing.

2. Low smoke halogen-free power cable specific gravity method

Density comparison method, that is, based on the density of water, plastic materials are placed in water. If they sink, the density of plastic is larger than that of water. If it floats up, it is smaller than water. This method can be used in conjunction with other methods

The above two kinds of cables are simple to test the flame retardant power cable, flame retardant wire, low smoke halogen-free power cable and low smoke halogen-free wire.

Machine settings for low smoke halogen-free wire and cable

The machine for low smoke halogen-free wire and cable is 55 l dense training; Double wrist feeding with 120 single screw; Hydraulic plate automatic network change; Push pull type counter blower head; The grinding surface is hot for air cooling – the first cyclone separator – the second cyclone separator – the extended air-cooled vibrating screen – the bin; It is necessary to use a compact drill to make m (OA) 3 and EVA of base material more compatible; If only double screw is used, it will be bad to disperse; The advantage of double wrist feeding is that the material is mixed again when feeding; This is very guarantee for the quality of the material; The output of this configuration is about 350 kg / h; Many large factories now adopt this production process.

There is also a machine configuration for low smoke halogen-free wire and cable:

The machine is 55 litre compact drill; Add 65 double screw to the conical double feeder; Automatic change of hydraulic plunger; The air-cooled grinding surface is hot—— The first cyclone separator – the second cyclone separator – the extended air-cooled vibrating screen – the bin; The output of this configuration is about 250 kg per hour.

There is also a configuration of low smoke halogen-free wire and cable: dense drill and cone double feed and double-stage granulation; The price of this equipment is high.