Process problem of fire-resistant cable

As fire-resistant cables are used more and more widely, many manufacturers are producing them, but their quality is often not guaranteed.
Therefore, in general, enterprises in the development of fire-resistant cable products, are the first trial production of a section of products, sent to the relevant national testing institutions, after obtaining the test report, mass production.
For producing fireproof cables, if refractory test pass rate of 99%, fire-resistant cable, fire-resistant cable is 1% of the security hidden danger, the danger of this is 100% dangerous for users, how to solve these problems we will improve the passing rate of fire-resistant cable fire experiment, from raw material, conductor selection, production process control, etc, to do a description:


1. With three kinds of mica, synthetic mica, phlogopite, white mica, their performance is a synthetic mica best quality, white mica, worst for small specifications of the cable must be selected synthetic mica tape around the package, can not use the mica tape stratification, long-term storage of mica tape is easy to moisture absorption, when stored mica tape so must consider the surrounding environment of temperature and humidity.

2. When selecting mica tape wrapping equipment, good stability should be adopted and the wrapping Angle should be between 300 and 400. The mica tape wrapping equipment should be uniform and tight.
3. For a circular wire core with axial symmetry, its mica tape is tightly wound in all directions, so it is advisable to use a circular compact conductor for the conductor structure of fire-resistant cable. The reasons are as follows:


(1) some users put forward stranded conductor for beam soft conductor structure, which requires enterprises from the aspects of the reliability of the cable to use to communicate with the user to circular press conductor, soft cable structure, the complex ground mica tape damage easily, as a fire-resistant cable conductor is not desirable, but some manufacturer that users need to what kind of fireproof cables, manufacturer should meet the demand of users, I think the user after all relevant details of the cable is not very understand, cable is is closely related to people’s life, so the cable manufacturing enterprises must be related to technical issues with the user clear.
(2) The fan conductor is not suitable for use, because the fan conductor of the mica band winding pressure is not uniform distribution, from the point of view of cost of the fan conductor structure section circumference is greater than the circular conductor section circumference, thus increasing the valuable material mica band, although the circular structure of the cable diameter increased. PVC sheath material increased, but the product material compared with the total cost, the overall cost of circular structure cable is still less.
Based on the above description, from the technical and economic analysis, the circular structure of the conductor of fire-resistant power cable is the best.

Indian railways operates zero carbon

In an effort to transform India’s railways into green railways by 2030, the Ministry of Railways has taken a series of major measures to mitigate global warming and combat climate change.
Electrification of railways, improvement of energy efficiency of locomotives, trains and fixtures, green certification of installations/stations, installation of biological toilets in passenger cars and conversion to renewable energy are part of its strategy to achieve zero carbon net emissions, the Ministry said in a statement on Monday.
Indian Railways has completed more than 40,000 km (63 per cent of the wide rail line) of electrification, of which 18,605 km was completed in 2014-2020. Previously, only 3,835 km of electrification was completed between 2009 and 2014.
Indian Railways has set a target of 7,000km electrification by 2020-21. The company plans to electrify all its routes by December 2023. At the same time, the company is focusing on last-mile connectivity and electrification of the missing link. With this in mind, 365 kilometers of major connections have been made during COVID-19.

Indian Railways has also taken a number of initiatives to promote solar power, including efforts to harness 500 megawatts of energy potential through rooftop solar panels.
So far, 100 megawatts of solar power have been tested on the roofs of various buildings, including 900 power stations. In addition, solar power plants with a total installed capacity of 400 megawatts are at different stages of implementation. Bids have been awarded for 245 megawatts, and the plants are targeted for completion by December 2022.


In addition, Indian Railways is trying to generate electricity for train operations through onshore solar installations. Indian railways has 51,000 hectares of land potential for 20GW of onshore solar power plants.
In the wind sector, Indian Railways has so far been commissioning 103-megawatt wind farms. This includes 26 mw in Rajasthan, 21 mw in Tamil Nadu and 56.4 MW in Maharashtra. Indian Railways also plans to build 200 MW of wind power plants in Tamil Nadu, Gujarat, Rajasthan and Karnataka in the next two years. Aware of its role in climate change, Indian Railways has launched other green initiatives such as 100% LED lighting in buildings and stations.

The function of outer sheath of cable

Outer sheath is a protective covering covering the cable sheath (inner sheath), mainly used for mechanical strengthening and anti-corrosion. Common cables have inner sheath as the outer sheath of metal sheath and inner sheath as the outer sheath of plastic sheath.
The outer sheath of the metal sheath is generally composed of three parts: the liner layer, the armor layer and the outer quilt layer. The gasket layer is located between the metal sheath and armor layer, which plays a role of protecting gasket and metal sheath against corrosion. The armor layer is metal belt or metal wire, mainly for mechanical protection, the metal wire can withstand the tension. The metal armor is protected from corrosion by the outer layer. The cushion and outer layer of the village are composed of asphalt, polyethylene tape, impregnated paper, PVC or polyethylene sheath and other materials. According to the different use environment and conditions of various cables, its outer sheath structure is also different, the outer sheath structure of common various types of power cables are shown in the table of various types of cables.


There are two kinds of structure of outer sheath for plastic sheath. One is only PVC or polyethylene sheath without outer sheath. The other is PVC sheath extruding PVC sheath or polyethylene sheath with the same thickness as the inner sheath. Traditional PVC outer sheath Due to the low working temperature of PVC, high voltage crosslinked polyethylene (XLPE) cable with high operating temperature and protective insulation requirements is not suitable, so now high density polyethylene (CHDPE) or low density polyethylene (LLDPE) as the outer sheath has been very common, but no flame retardant. Fire prevention measures or flame retardant cables should be taken when laying. Using HDPE as the outer sheath can improve the insulation level of the sheath. The outer sheath and the corrugated metal sheath should be bonded.

Knowledge of power cord

The components of a power cord are as follows:
1. Copper wire. Copper wire is the core part of power cord. Copper wire is the carrier of current and voltage. The quality of a power cord depends on three points, namely, the density of copper wire, the material of the cord, the amount of copper wire, and the flexibility.
2. Inner sheath. Inner sheath is the material wrapped between the shielding layer and the wire core, also known as insulation sheath. The materials used are generally polyvinyl chloride plastic, polyethylene plastic or low smoke halogen-free. To ensure the safety of our power supply and prevent any leakage between copper wire and air.
3. Outer sheath. Outer sheath is the outermost protective layer (sheath) of the power cord, which plays the role of protecting the power cord. It is characterized by temperature resistance, cold resistance, oil resistance, water resistance, natural light interference, good winding performance, environmental protection, long service life.
Classification of power cord:

Power lines can be classified according to safety certification, the shape of the power cord plug and the standard of electricity consumption in different areas.
1. According to safety regulations, there are UL, CCC, VDE, PSE, SAA, UC, IRAM, IMQ, BSI, KS, PSB, SABS and so on.
2. According to the shape of the power cord plug, it can be divided into two flat power cord, three power cord, two round power cord, straight power cord, bent power cord, etc.
3. According to the standard can be divided into different parts of the electricity, the standard power cord, China standard power cord, European standard power cord, Japan standard power cord, the Australian standard power cord, the Brazilian standard power cord, Argentina standard power cord, power cord, Italy, the British standard power cord, South Korea standard power cord, standard power cord in Singapore, South Africa’s standard power cords, etc.


Manufacturing process:
Copper and aluminum single wire drawing of power cord – single wire annealing of power cord – stranded conductor of power cord – insulation extrusion of power cord – wire forming – Inner sheath of power cord – wire armor – outer sheath of power cord
Tips for identifying:
The identification method of power cord namely five look: look the quality qualification certificate of home appliance; Check the cross section of the wire; Look at the appearance of the power cord; Look at the core of the power cord; Look at the length of the power cord.
Above is a few small knowledge of power cord, hope to be helpful to everybody.

Distinguish between power cables and control cables

Power cable and control cable are widely used in people’s production and life, but many people do not know the difference between the two. Power cables are used in power system mains to transmit and distribute large functional electric energy, while control cables transmit electric energy directly from power distribution points of the power system to power connection lines of various electrical equipment and appliances. Let me show you six tips for distinguishing power cables from control cables:
Rated voltage: The rated voltage of power cable is generally 0.6/1kV and above, and the control cable is mainly 450/750V.
Ii. Insulation and sheath thickness: when producing power cables and control cables of the same specification, the insulation and sheath thickness of power cables are thicker than that of control cables.


Three, look at the implementation of the cable standard. Control cables belong to electrical equipment cables, and power cables are two of the five categories of cables. The standard of power cable is GB12706, and the standard of control cable is GB/T 9330. The flame retardant cable should also meet the technical conditions of IEC337-8 standard.
Four, look at the color of the insulation core: the insulation sleeve of each inner core of low-voltage power cable is generally color-coded; And the color of the control cable insulation core is generally black printed in white.
Five, look at the cable section. Power cable is mainly to transmit power, generally is a large section, control cable section is generally not more than 10 square. Power cable specifications can generally be large, up to 500 square; The control cable section is generally small, the maximum is generally not more than 10 square.
The above is the introduction of the method to distinguish power cable and control cable, hoping to help you better complete the selection of cable.

British-French submarine cable preparation

Crosslake Fiber, a developer and operator of communications networks in North America and Western Europe, revealed its latest submarine cable project, called CrossChannel Fibre, which is a submarine cable system connecting Slough, United Kingdom and Paris, France, with a total length of approximately 550 kilometers.
According to the plan, the system will contain 96 pairs of optical fibers, each pair of optical fibers provides more than 20Tbps of capacity. To support the project, Crosslake Fiber has authorized EGS, the world’s leading ocean survey and service provider, to conduct project maritime surveys.


In addition, Tiger Infrastructure Partners, the capital partner of Crosslake Fibre, has invested additional capital in the Crosslake platform to support the CrossChannel Fiber system.
Mike Cunningham, CEO of Crosslake Fibre, said, “We are very pleased to launch this historic submarine project and provide a new connection in the crucial data center connecting Slough in the English Channel with Paris. This new The optical fiber infrastructure has been optimized to establish the shortest path between the two data, providing users with enhanced technical solutions and greatly reducing operating costs. With the COVID-19 pandemic, the continuous increase in bandwidth demand has continued to increase The submarine cable has never been so important to the function of the Internet backbone.”
According to the plan, the submarine cable system will be put into use in the fall of 2021 (RFS).

Single and multi-core wires

The single-core cable wire is a hard wire (BV wire), and only the wires below 10mm2 have a single core. Multi-core cable wire can be divided into multi-core hard wire (BV wire) and multi-core flexible wire (BVR wire).
For example, 2.5mm2 wire, single-core BV wire is composed of 1 strand of conductor with a diameter of 1.78mm; multi-core BV wire is composed of 7 conductors with a diameter of 0.68mm; multi-core BVR wire is composed of 19 conductors with a diameter of 0.41mm Conductor composition.
For home decoration, it is recommended to use single-core BV cable. In addition to being cheap, there are several reasons.


First, the strongest wire in home decoration is the most external force encountered is tension and pressure. In terms of strength, the single-stranded wire is better than others-during the process of pulling and squeezing the multi-core wire, it is easy to break the copper wire, causing a reduction in the current carrying capacity-especially the thin copper wire with a diameter of 0.41mm .
Second, the current-carrying capacity is large in short-distance, low-frequency, low-voltage, and low-current circuits (no need to consider the skin effect). The current-carrying capacity of a single-core wire is larger than that of a multi-core wire.
PS: If the skin effect is considered, the current carrying capacity of the multi-strand wire will be greater-this is also the reason why there is no single-strand wire for wires above 10mm2.
The BV line is a customized product specially launched for decoration. Compared with the BVR line, the BV line has weaker resistance to bending and anti-skin effects. However, due to the simple production process and low price, it is more suitable for home decoration.

Single core cable
In almost all circuits except for decoration and laying, most of them are BVR lines-the adaptability of BV lines is very poor, especially when frequent bending is required, it has a great impact on the life of BV lines, and the difficulty of wiring will also increase. less.
As for the multi-core BV line, it is a product between the single-core BV line and the BVR line-it has a certain anti-skin effect, but the anti-bending ability is still not enough.
Because the single core wire is too hard, the 4mm2 and 6mm2 wall sockets are not easy to connect and are prone to failure. Home improvement generally chooses 4mm2, 6mm2 to choose flexible wire, 2.5mm and 1.5mm to choose hard wire. The above content is for reference only, please refer to the actual situation.

Fire-resistance cable

Refractory cables refers to a cable that can maintain safe operation for a certain period of time in the case of flame burning. National standard GA 306.2-2007 classifies the fire resistance test into two grades, A and B. The flame temperature of Class A is 950~1000℃, and the continuous fire time is 90min. The flame temperature of Class B is 750~800℃, and the continuous fire time is 90 min. The whole test During this period, the sample shall withstand the rated voltage value specified by the product.
Fire-resistant cables are widely used in high-rise buildings, underground railways, underground streets, large power stations and important industrial and mining enterprises and other places related to fire safety and fire rescue. Therefore, their fire resistance performance has attracted much attention because even 1% of potential safety hazards exist for users It is 100% dangerous.


So how to improve the test pass rate of refractory cables? It should be analyzed from three aspects: raw materials, conductor structure and production process:
1. In terms of raw materials: the material of mica tape is divided into three types: synthetic mica, phlogopite and muscovite. Among them, the performance of synthetic mica is good, and the performance of muscovite is poor. For small-sized cables, synthetic mica tape must be selected for wrapping. It is worth noting that the mica tape stored for a long time is easy to absorb moisture, so the temperature and humidity of the surrounding environment must be considered when storing the mica tape.
2. Conductor structure: a round wire core with axial symmetry, the mica tape is tightly packed in all directions, so the conductor structure of the refractory cable should be a round compact conductor. Other users want to use bundled flexible conductors, but the soft structure bundles and double twisting can easily cause mica tape damage, so it is not desirable. The fan-shaped conductor is also not suitable for use, because the pressure distribution of the mica tape of the fan-shaped conductor is uneven, and the wrapped core passes through the guide wheel, the branch bar and the cable to the edge of the side plate of the tool wheel, and the insulation is squeezed into the back process When the mold core is used, it is easy to be scratched and bumped, which leads to a decrease in electrical performance.


In addition, from a cost perspective, the cross-sectional circumference of the sector-shaped conductor structure is larger than that of the circular conductor, adding valuable material mica tape. Although the outer diameter of the circular structure cable has increased, the amount of PVC sheath material has increased. But the overall cost of round structure fire-resistant cables is lower. Therefore, from a technical and economic point of view, the round structure of fire-resistant cable conductors is the best.
3. In terms of production process: when using mica tape wrapping equipment, the mica tape wrapping is even and tight. All the guide wheels and rods that touch the equipment must be smooth, the wiring is neat, and the tension should not be too large. And the cylinder is flat and smooth.
In summary, refractory cables are particular about raw materials, conductor structure and production technology, and manufacturers should strictly produce in accordance with specifications. When users choose fire-resistant cables, they can also analyze the performance of fire-resistant cables from the above angles.

Single-conductor cable and dual-conductor cable

Cable is made of cable structure, with power as the energy, the use of alloy resistance wire or carbon fiber heating far infrared for electrification and heating, known as carbon fiber floor heating, to achieve the effect of heating or insulation. There are usually single and double conductors, known as heating cables.
The difference between single guide cable and double guide cable
The heating cable can be divided into single conductor and double conductor. There are some differences between them in structure and performance.


Because of the structural characteristics of double guide cable, it is more convenient to install than single guide cable in the construction process. Both ends of the single guide cable need to be connected to the power supply, so the cable tail should be pulled back to the limit when laying. This requirement is difficult to operate under multiple conditions, such as large room area and long cable. Small room area and limited laying area; Room structure is complex, the side wall is not straight line but by a lot of broken lines. Dual guide cables do not need to consider these issues. Since the cable itself is a loop, all wiring is at the same end. In the construction, as long as the wiring terminal connects the power supply without considering the end of the cable, it can be laid at will according to the specific situation, which expands the practicability of cable ground laying.
The difference between double guide cable and single guide cable is obviously that the electromagnetic radiation double guide cable is much smaller than the single guide cable. Why does a single conductor cable have electromagnetic radiation and a double conductor cable does not? This is determined by their internal structure, from the physics can know, the conductor current is the magnetic field, the direction of the magnetic field is determined by the ampere rule. Ampere’s rule: In the case of a straight current, extend your right hand and hold the wire (the wire). The direction indicated by your thumb is the direction of the current, and the direction indicated by your bending four fingers is the direction of the magnetic field induced by the current passing through.
The structure of two kinds of heating cables determines that the failure rate of them is very different. In general, the failure rate of single guide can reach 35%, while the failure rate of double guide is much less than 0.1%, almost without any failure.

Aluminum alloy cable and aluminum core cable

What are the differences between the performance of aluminum alloy cables and aluminum core cables
The performance of aluminum alloy cables and aluminum core cables are different. There are four aspects of corrosion resistance, mechanical properties, electrical conductivity, and creep resistance.
First,Corrosion resistance
Pure aluminum has better corrosion resistance than copper, but aluminum alloy has better corrosion resistance than pure aluminum, because the rare earth and other chemical elements added to aluminum alloy can increase the corrosion resistance of aluminum alloy, especially the electrochemical corrosion resistance. Solve the problem of electrochemical corrosion of pure aluminum at the joint for a long time.

Second, mechanical properties
1. Tensile strength and elongation. Compared with pure aluminum conductors, aluminum alloy conductors, due to the addition of special components and the use of special processing techniques, have greatly improved the tensile strength, and the elongation rate has been increased to 30%, which is safer and more reliable.
2. Bending performance. The bending performance of the aluminum core cable is very poor, and the bending is easy to break. The bending radius of the aluminum alloy power cable is 7 times the outer diameter of the cable, which is far better than the 10 in GB/T12706 “Minimum bending radius during cable installation”. Times -20 times the outer diameter of the cable.
3. Flexible performance. As long as the pure aluminum cable is twisted at a certain angle a few times, the conductor will crack or break, which is easy to cause accidents, and the aluminum alloy power cable can withstand dozens of bends, eliminating the accidents that occurred during the installation and use of pure aluminum cables in the past Hidden dangers have greatly improved safety and reliability.


Three,Conductivity
Aluminum alloy conductor is an emerging conductor material formed by alloying process by adding rare earth, magnesium, copper, iron and other elements to pure aluminum. As we all know, after adding other kinds of alloying elements to aluminum, the conductivity will be reduced, and through the process control, the conductivity can be restored to the level close to pure aluminum, so that it has a similar current carrying capacity as pure aluminum.
Fourth, creep resistance
Pure aluminum has poor creep resistance. The thermal expansion and contraction caused by power on and off will cause a large creep at the connection, and it will relax after a long time. The contact resistance will increase and cause overheating, which may easily cause accidents. The creep resistance of AA8000 series aluminum alloy is 300% of the pure aluminum conductor, which greatly reduces the possibility of cable joint slack and improves the connection status of the conductor.