Why can’t aluminum wire cable and copper wire cable connect?

1. Copper and aluminum have different potentials. The part in contact with copper and aluminum will accelerate the oxidation of the aluminum wire due to the galvanic cell reaction. To join together, a copper – aluminum transition wire clip or transition wire pipe must be used.
2. This is a question of chemistry, the chemical properties of metals are relatively lively and not lively, such as gold, never rust, which means gold chemical inertness, easy to rust iron, iron is lively than gold, if two metal together will accelerate active metal oxide, aluminum and copper, aluminium is lively, two kinds of cable connection, will accelerate aluminum oxidation (rust), affect the use.
3. When copper and aluminum conductor are directly connected, the contact surface of the two metals is easy to form electrolyte under the action of moisture in the air, carbon dioxide and other impurities, thus forming a galvanic cell with aluminum as the negative pole and copper as the positive pole, so that aluminum produces electrochemical corrosion, resulting in the increase of the contact resistance between copper and aluminum.

In addition, due to the great difference between the elastic modulus and thermal expansion coefficient of copper and aluminum, after repeated cold and hot cycles (power on and power off) in operation, a large gap will occur at the contact point, which will affect the contact and also increase the contact resistance. The increase of contact resistance will cause the temperature to rise during operation. At high temperature, corrosion and oxidation will be intensified, resulting in a vicious cycle, which further deteriorates the quality of the connection, and finally leads to the occurrence of accidents such as smoke and burning when the temperature of the contact point is too high.

Question: Why are copper and aluminum wire clips used when connecting copper and aluminum wires?
1. The gray white material generated in the place where the copper wire and aluminum wire are connected is aluminum oxide for a little longer time. The contact resistance at the connection will increase and generate heat, resulting in on-off circuit and easy to cause building fire. So use a special copper – aluminum transition clamp. Avoid unnecessary trouble!
2. If copper wire and aluminum wire are directly hinged together, the joint is easy to oxidize, leading to increased resistance and more likely to burn out. The real reason for this damage is that aluminum is much more active than copper, and many micropotentials (i.e. microbatteries) will be generated on the copper-aluminum bonding surface, which will cause microerosion and increase the contact resistance over time. For ordinary homework, it is more reliable to connect the copper before the tin.
3. In the power system, copper and aluminum are directly connected, and electrochemical corrosion will occur when flowing through the current. Therefore, copper and aluminum should be used for transition, or tin sheets should be placed in the middle of the contact surface, and a layer of conductive paste should be applied when possible. Ordinary family connection, can be linked to copper wire tin aluminum wire, can avoid electrochemical corrosion.

Final conclusion: When the customer chooses the water pump, please look for the copper wire motor. There is a huge difference between the two. The details are as follows:
In fact, it can be summarized into two main points:
I. Price.
The price is undoubtedly cheaper than that of aluminum wire motors. Because of this, in some price wars, the products of aluminum wire motors are more than twice as cheap as those of copper wire motors, which also prompts the mass purchase of middle and low level consumers.
Ii. Quality.
Regardless of the quality of wire performance, service life, copper wire motor is superior to aluminum wire. In addition, in production, the motor embedded aluminum wire due to the quality of brittle, low toughness, easy to break, compared with the same thickness of copper wire qualified rate is lower by 30%.

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.

How to prevent wire and cable damage?

Wires and cables are easily affected by the external use environment. Careless protection will easily lead to hardening of the wire body, peeling off of insulation skin and other phenomena. Many users will mistakenly believe that the product quality has problems, which in fact has a great relationship with the temperature. The outer skin of electric power cable and wire products is mostly ordinary plastic or rubber. When the environment is below zero, the wire body of the whole electric wire and cable products will become hard and brittle, which may lead to the peeling and damage of the outer skin under the action of slight external forces. Cables may be damaged if not properly transported.

So, how to prevent damage to power lines and cables? You are advised to take the following precautions:
I. Pay attention to protective measures during ex-factory transportation: Protective measures are required when products are ex-factory loaded onto the means of transport. Such as the use of closed means of transport, to prevent direct exposure of the product; A soft cushion, such as a bedclothes or other soft foam, applied to a product; Handle with care when loading, do not load roughly, and avoid excessive bending.
2. Pay attention to prevent mechanical damage when unloading: When arriving at the destination or the construction site, the product supplier had better dispatch personnel to supervise and prevent the product from causing mechanical damage due to rough operation behavior during unloading.
3. Indoor storage and laying isolation layer: It is better to store the products indoors, and at the same time lay an isolation layer on the stored ground, such as wood boards, bedding, foam, etc., to prevent the products from being exposed to cold and moisture. Pay attention to prevent the products from being scratched by the wires and cables in direct contact with the ground.
4. Pay attention to control the temperature and prevent scratch during installation of the product: it is better to choose to work under the condition of warm temperature in mid-afternoon. If possible, you can warm up the product in advance with the heater and other equipment before use, so that the product can achieve the best performance. If it is buried, can be laid in the cable trench with a protective layer, such as cloth, foam, etc. If you are wearing a tube, make sure the inside and outside of the tube is smooth in advance, so as not to scratch the wire. Iron pipe should pay special attention to the purchase of qualified iron pipe, low quality iron pipe tube may have a lot of sharp raised points, it is very likely to scratch the cable skin.

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.

Quality inspection index of wire and cable

The inspection of wire and cable has always been an important part of national standard wire and cable. The higher the quality inspection department of a wire and cable enterprise is, the better the quality of the wire and cable produced by the enterprise is and the more trustworthy it is. And the more stringent the third-party quality inspection department is, the more conducive to the development of the industry.

1.Measurement of dc resistance of wire

The conductor cores of electric wires and cables mainly transmit electric energy or electrical signals. Conductor resistance is the main index, its electric performance of the ac voltage effect when the wire core resistance due to the surface of skin effect and proximity effect than dc voltage function, but when the electric frequency of 50 hz and small lines of standard specifies requirements that are only now the core of dc resistance or the resistivity is more than standard value, through the inspection can be found in the process of production of certain defects, such as broken wire or part of the single fracture; Traverse section does not meet the standard; Incorrect length of product, etc.

2. Test insulation resistance

The insulation resistance is an important index to reflect the insulation characteristics of wire and cable products, which is closely related to the electrical resistance, dielectric loss, and the gradual deterioration of insulation materials in the working state. For communication cables, if the insulation resistance between wires is too low, it will also increase circuit attenuation, cross-talk between circuits and long-distance power supply leakage on the conducting wire core, etc., so the insulation resistance shall be higher than the specified value.

3. Measurement of capacitance and loss factor

When the cable is applied with an AC voltage, a current flows through it. When the amplitude and frequency of the voltage are constant, the capacitive current is proportional to the capacitance of the cable (Cx). For ultra high voltage cables, the current of the capacitance may be comparable to the rated current, which becomes an important factor limiting the cable capacity and transmission distance. Therefore, the capacitance of the cable is also one of the main electrical performance parameters. By measuring the capacitance and the loss factor, it can be found that the insulation is affected by moisture, the insulation layer and the shielding layer fall off and other kinds of insulation deterioration phenomenon. Therefore, the measurement of capacitance and TAN delta is always carried out in the cable manufacture or operation.

4. Insulation strength test

The insulation strength of wire and cable refers to the ability of the insulation structure and material to withstand the action of electric field without breaking down. In order to check the quality of wire and cable products and ensure the safe operation of the products, all types of insulation wires and cables generally need to conduct insulation strength tests. The insulation strength test can be divided into pressure test and breakdown test. The voltage of time is generally higher than the rated working voltage of the test product. The specific voltage value and withstand voltage time are stipulated in the product standard. Through the withstand voltage test, the reliability of the product operation under the working voltage can be tested and serious defects in insulation can be found, as well as some shortcomings of the production process can be found

5. Aging and stability test

The aging test is a stability test that can maintain stable performance under the action of stress (mechanical, electrical, thermal). Thermal aging test: The simple thermal aging test is to test the characteristics of the test product under the action of heat aging. The test product is placed in an environment with a certain value above the rated working temperature, so as to obtain a shorter life at a higher temperature.

6. Thermal stability test

The thermal stability test is to evaluate the insulation stability by measuring some sensitive performance parameters after the cable is heated by current and subjected to a certain voltage during a certain period of heating. Insulation stability test can be divided into long-term stability test or short-term accelerated aging test.

Advantages of environmental protection cable

With the increasing level of urbanization, people’s work and life rhythm is accelerating, and people’s awareness of safety and environmental protection is also increasing. Wires and cables are closely related to the lives of residents, and consumers are increasingly demanding the safety and environmental performance of wires and cables.
Wire and cable companies have also begun to attach importance to the development and production of environmentally friendly wires and cables. So what is environmentally friendly wires and cables? Do you need to use environmentally friendly wires and cables in ordinary home decoration? Let’s take a look at environmentally friendly wires and cables.
What is an environmentally friendly cable?
Environmentally friendly wire and cable means that it does not contain heavy metals such as lead, cadmium, hexavalent chromium, mercury, etc., and does not contain bromine-based flame retardants. It has been tested by SGS recognized testing agencies for environmental performance and meets the EU Environmental Protection Directive (RoSH) and is higher than its index Claim.
The environmentally friendly wire and cable does not produce harmful halogen gas or corrosive gas after burning, and generates less smoke during combustion, does not pollute the soil, and will not cause harm to the environment after the wire and cable are discarded. The low-smoke halogen-free flame-retardant cable we often say is a kind of environmentally friendly wire and cable.

What are the advantages of environmentally friendly wires and cables? What characteristics?
Environmental protection and no pollution:
The insulating materials and sheath materials used for environmentally friendly wires and cables are green and environmentally friendly materials, and do not contain heavy metals such as lead, hexavalent chromium, mercury, and cadmium that have harmful effects on the environment. So that it will not pollute the soil and the surrounding environment. And after harsh toxicity experiments, the mice were safe under the specified experimental conditions.
Has good low-smoke and halogen-free characteristics:
Environmentally friendly wire and cable materials do not contain halogens such as chlorine, bromine, and fluorine. Under emergency conditions (such as electrical accidents and fires), they do not produce harmful or corrosive gases, and emit less smoke during combustion. Can minimize the harm to the human body to ensure the user’s own health and safety.
Has good flame retardancy:
The flame-retardant and fire-resistant performance of environmentally friendly wires and cables fully complies with national standards. Wire and cable are not easy to burn and do not ignite when an electrical fire occurs. At the same time, under continuous combustion, they can ensure the normal operation of the circuit system for a certain period of time, and can greatly reduce the wires. The flame spread after the cable burns.

Environmentally friendly wires and cables can be recycled and reused or buried or incinerated after being discarded without harming or destroying the environment.
With high light transmittance:
The smoke produced when the environmental protection cable is burning is extremely thin, which is helpful for the victims to distinguish the safety exit and the firefighters’ firefighting work quickly. The light transmittance of environmental protection cables is greater than or equal to 60%, which is much higher than that of traditional flame retardant cables.
With strong waterproof and anti-corrosion performance:
The use of environmentally friendly materials with special molecular structure ensures ultra-low water absorption and special ultraviolet absorbers, which can prevent the weathering speed and degree of wire and cable exposed to the outside to a certain extent, while slowing the speed of wire and cable aging and extending the cable The service life can be up to 70 years.

The functions and advantages of twisted pair cable

Twisted pair cable. Most people don’t know what it is. As the name implies, twisted pair cable literally means to wind two or more separate insulated wires together and make them parallel to each other. Twisted pair wire has the property of eliminating interference. Therefore, cables are suitable for short distance data and voice infrastructure because they reduce the impact of electromagnetic interference on electronic signals. It is also more flexible and easier to install than coaxial cable. Use two types of twisted pair cable: shielded and unshielded. Shielded twisted pair wire (STP) has a thin wire mesh around the wire to protect transmission. Unshielded twisted pair (UTP) does not.

The latter is the more common of the two types, used in Ethernet installations, and is often used in residential and enterprise applications. Shielded cables are used in telephone networks as well as network and data communications to reduce external interference and crosstalk, and are designed to aid grounding. Of the two types of cables, UTP cables are cheaper than STP cables and require less maintenance because they do not rely on external shielding. Although UTP can transmit data as fast as STP cables, they are much more noisy than STP cables. Twisted-pair cables are the most cost-effective choice for coaxial cable and fiber, but they also have lower bandwidth and higher attenuation, i.e., lower performance over longer distances. They also wear out easily and must be maintained regularly. It is best to use twisted pair cables anywhere where there is no strong electromagnetic interference.

Advantages: high cost performance, reliable and easy to install over short distances for best performance

Disadvantages: higher attenuation vulnerable to electromagnetic interference (EMI) low durability (must be maintained regularly)

The global subsea power cable market will grow at a compound annual rate of over 4% from 2020 to 2024

The market for subsea power cables is expected to grow at a compound annual rate of more than 4 percent from 2020-2024, driven largely by surging demand for electricity, according to Technavio.

According to the report, 47 percent of the market growth in the forecast period will come from Europe, with Italy, Denmark and Finland being important markets for European subsea power cables.

Europe is the largest subsea power cable market in 2019, and government support and growing concern about wind power will significantly drive growth in the subsea power cable market in the region during the forecast period.

Offshore wind turbines can produce more energy using fewer turbines than conventional ones. As a result, the Asia-Pacific region will enjoy rapid growth during the forecast period. Thanks to heavy investment in offshore wind projects over the past few years, China and India will account for most of the region’s share of the forecast period.

According to the IEA, demand for electricity will rise by 40 per cent by 2024. Similarly, growing environmental concerns will force economies to use renewable energy to generate electricity. As a result, the number of renewable projects such as wind and tidal power projects is increasing in most countries, which in turn will increase the demand for undersea power cables or submarine cables. The growing demand for intercountry and island connections will be one of the main drivers of market growth. Subsea power grid interconnection projects in France – UK, Belgium – UK and Ireland – UK are under construction.

On the other hand, the growing demand for high-voltage direct current (HVDC) power cables will also drive the market growth. These HVDC cables are more and more popular compared with traditional cables because they are safe and reliable and can transmit power over long distances. These factors will drive the global subsea power cable market to grow at a compound annual rate of over 4% over the forecast period.

From the manufacturers’ point of view, Prysman, Nexans, Sumitomo Electric, Lenny Cable, Ankart Cable, Tengura Cable, Guhe Electrician, LS cable will continue to dominate the global subsea power cable market in the forecast period.

Design and laying of submarine cable

The design of submarine optical cable: anti-corrosion, anti-seepage, but also against sharks, compared with coaxial cable, optical fiber is quite obvious advantages, but its own is quite fragile, so this protection of optical fiber submarine cable peripheral protection structure put forward higher requirements. Specifically, the design of submarine optical cable must ensure that the internal optical fiber is not affected by external forces and the environment. Its basic requirements include adaptability to submarine pressure, abrasion resistance and non-corrosion, etc. It also has to prevent hydrogen from forming inside (and therefore not using aluminum) and hydrogen from outside (preventing gas infiltration). In addition, it must be properly armored to protect it from trawlers, anchors and sharks. When the cable is broken, but also as much as possible to reduce the length of seawater into the cable; At the same time, it can withstand the tension during laying and recovery; Last but not least, the service life of submarine cables is generally required to be over 25 years.

Based on the above requirements, the current design structure of submarine cables usually consists of one or two coating treatments of the fiber in a spiral wrapping around the center, and then reinforcing members (made of steel wire) wrapped around (usually 69 mm in diameter). Specifically, it includes: polyethylene layer, polyester resin or asphalt layer, steel strand layer, aluminum waterproof layer, polycarbonate layer, copper or aluminum tube, paraffin layer, alkane layer, fiber bundle, etc.

Laying process: from relying on the tide to relying on robots

The laying project of submarine optical cable is recognized as one of the most complicated and difficult large-scale projects in the world, which is not difficult to understand why the service life of submarine optical cable is required to reach more than 25 years, because laying once is very troublesome! The laying process of submarine optical cable can be divided into two parts, namely, the laying of shallow sea area and the laying of deep sea area. In the deep sea area, the laying of submarine optical cable has to go through three stages, namely, exploration and cleaning, sea cable laying and burial protection. The laying of submarine cables mainly depends on the cable laying ships and underwater robots. The cable laying ships should pay special attention to the sailing speed and cable release speed, so as to control the water inlet Angle and laying tension of the cable, so as to avoid damaging the fragile optical fibers in the cable due to too small bending radius or too large tension.

As shown in the figure above, this is the laying process of an undersea optical cable. In shallow sea areas, the laying ship stays a few kilometers away from the coast, and the cable placed on the floating bag is pulled to the shore by the shore tractor. Then the floating bag is removed to make the cable sink to the sea floor. In the deep sea, the laying ship is mainly responsible for releasing optical cables, and then the underwater detector is combined with the underwater remote control vehicle for underwater monitoring and adjustment, so as to avoid uneven and rocky areas on the seabed. The robot then proceeded to a three-step operation: first, it created a trench about 2m deep in the sea floor, using high-pressure flushing; The second step is to put the cable into the trench; Third, cover it with the sand nearby.

Special to note here is that a intercontinental submarine cable is difficult to a complete laid, because at present the most advanced optical cable laying ship can only carry 2000 kilometers of fiber optic cable (and now laying rate can only reach 200 km/day), thus laid to segments, and each paragraph “cable docking”, needs to be done in laying the ship, and requires high technology.

Five causes of cable fire and explosion

1. Insulation damage causes short circuit fault
The protective lead cover of power cables is damaged during laying or the cable insulation is damaged by mechanical damage in operation, which causes the insulation breakdown between cables or between the lead cover. The electric arc will cause the insulation materials and the protective layer of cables to burn up.
2. The cable is overloaded for a long time
For a long time in overload operation, the operating temperature of the cable insulation material exceeds the maximum allowable temperature of normal heating, making the cable insulation aging and dry up. This phenomenon of aging and dry up insulation usually occurs in the whole cable line. As the cable insulation ages and dries up, the insulation material loses or reduces the insulation performance and mechanical properties, so it is easy to break down and burn, or even burn up in many places along the whole length of the cable.

3. Insulation breakdown of intermediate connector box
The intermediate joints of the cable connector box are oxidized, heated and glued during operation due to loose pressing, weak welding or improper selection of joint materials; When making cable intermediate joint, the quality of insulating agent in the intermediate joint box does not meet the requirements. During the filling of insulating agent, there will be air holes in the box memory and leakage of moisture into the cable box due to poor sealing and damage. All the above factors can cause insulation breakdown, form short circuit, and cause cable explosion and fire.
4. Cable end combustion
As the surface of the cable head is contaminated by moisture, the porcelain bushing of the cable head is broken and the distance between the lead wires is too small, which leads to flashier fire and causes the surface insulation of the cable head and lead wire insulation to burn.
5. Cable fire caused by external fire source and heat source
Such as oil system fire spread, oil circuit breaker explosion fire spread, boiler pulverized coal system or coal conveying system coal spontaneous combustion, high temperature steam pipeline baking, acid and alkali chemical corrosion, welding spark and other fire, can cause the cable fire.