Mineral insulated cable

BTTZ mineral insulated cable
1.BTTZ cable structure
Its structure is: 1. Solid conductor;  2. Magnesium oxide mineral insulation; 3. Copper sheath.
2. Performance characteristics of BTTZ cable
The advantages of BTTZ cable are: it is a non-combustible cable with excellent waterproof performance and radial waterproof and moisture-proof function.
The disadvantage of BTTZ cable is: (1) first of all it is not suitable for moving occasions, copper pipe once damaged insulation performance will rapidly decline, and the insulation performance under high temperature will rapidly decline, so the project should not be used in large quantities; (2) Secondly, this cable due to magnesium oxide insulation is easy to absorb moisture, cable longitudinal moisture-proof requirements and from metal sheath damage is particularly important, end sealant, will seriously affect the service life; (3) In addition to the manufacturing process also limited the cable manufacturing length, resulting in increased joint, joint waterproof treatment is also very difficult, often because of the joint water, resulting in unqualified insulation resistance.

YTTW mineral insulated cable

1.YTTW cable structure
(1)Copper conductor. (2)High temperature (1375℃) will not burn the inorganic (mineral) insulation with insulation. (3)Outer copper sleeve.
2.YTTW cable performance characteristics
Advantages: metallic sheathed inorganic mineral insulated cable. Is a flexible fire cable.

1. Fire resistance
Copper and magnesium oxide, two materials used in mineral insulated cables, are inorganic. This cable does not burn or assist combustion and can continue to operate under conditions close to the flame. The copper sheath melts at 1083 ° C, while the magnesium oxide insulation solidifies at 2800 ° C.
2. High operating temperature
Mineral insulated cables can withstand continuous operating temperatures up to 250℃. However, in an emergency, the cable can continue to operate for a short period of time at temperatures close to the melting point of the copper sheath.
3. Long life
The inorganic materials used in mineral insulated cables can ensure the cables have stability, long service life and fire resistance.

Shortage: YTTW cable, first of all, its sheath USES copper sheath, with copper increased production costs. The cable with a larger section is still hard and not flexible enough, so the larger section (greater than 630mm2) cannot be produced and cannot meet the requirements of large current of the system.

Comparison of YTTW cable and BTTZ cable performance
1. YTTW– Flexible fire cable;
BTTZ– Rigid fireproof cable.
2. YTTW– Unlimited cable manufacturing length;
BTTZ– Cable is limited by manufacturing process, conductor section is small, manufacturing length is short.
3. YTTW– Meet the requirements of design and construction acceptance specifications;
BTTZ– It is mandatory to meet the requirements of “No joints in the middle of cable Lines” in Cable Design Code for Power Engineering, “Avoid intermediate joints” and “Reduce cable joints” in Electrical Design Code for Civil Buildings and “Code for Construction and Acceptance of Cable Lines in Electrical Installation Engineering”.

Damp damage to cables

Although the summer heat, but the rain is also very much, especially in the rainy season, is wet, there are a lot of products because of the improper storage, all be affected with damp be affected with damp, the late is certainly will affect the use, wire and cable, not to mention was electricity is not able to touch water, if be affected with damp be affected with damp the use will not only influence, will certainly bring us some harm, so let’s to find out what are the dangers of cable to be affected with damp be affected with damp.


1. When the new whole cable leaves the factory, both ends of it are sealed with plastic sealing sleeve. However, after it is used for a period at the construction site according to the actual situation, the rest part is simply wrapped with plastic cloth for the fracture.
2.During cable laying, it is often necessary to cross roads, Bridges and culverts, etc. Due to weather or other reasons, a lot of water is often accumulated in the cable trench. During the laying process, it is inevitable that the cable end will be immersed in water, and water will enter the cable due to the loose wrapping or damage of the plastic cloth; In addition, sometimes the outer sheath and even the steel armor will be scratched during the traction and tube penetration. This phenomenon is particularly prominent when mechanical traction is used.
3. After the completion of cable laying, due to the limitation of on-site construction conditions, the cable ends that have not been sealed are exposed to the air for a long time, or even immersed in water, so that a large amount of water vapor enters into the cable.
4.During the production of cable ends (including terminal ends and intermediate joints), due to the negligence of the construction personnel, the newly treated cable ends sometimes accidentally fall into the water on the site.
5. During the normal operation of the cable, if breakdown occurs for some reason, the water in the cable trench will enter the cable interior along the fault point; In civil construction, especially in the use of large construction machinery construction sites, due to a variety of human factors caused by cable damage or breakdown accident, also common. When such an accident occurs, the insulation of the cable is severely damaged, which can also cause water to the cable.

Basic process flow of plastic wire and cable manufacturing

1. Copper and aluminum single wire drawing
Copper and aluminum rods commonly used in electric wires and cables are used to reduce the cross section, increase the length and increase the strength by drawing machine through one or several die holes of drawing dies at room temperature. Wire drawing is the first process of each wire and cable company. The main technological parameter of wire drawing is die matching technology.
2. Monofilament annealing
When heated to a certain temperature, copper and aluminum single wire can be recrystallized to improve the toughness and reduce the strength of single wire, so as to meet the requirements of wire and cable for conducting wire core. The key of annealing process is to prevent oxidation of copper wire.


3. Stranding of conductors
In order to improve the softness of wires and cables and facilitate laying and installation, the conductor core is made of several single strands. The twisted form of conductor core can be divided into regular twisted and irregular twisted. Irregular skewing can be divided into bundle skewing, concentric wringing, special skewing, etc.
In order to reduce the area occupied by the conductor and reduce the geometry size of the cable, the compact form is adopted while the conductor is twisted, so that the ordinary circle is changed into semicircle, sector, tile and compact circle. This conductor is mainly used in power cables.
4. The insulation extrusion
Plastic wire and cable mainly adopts extruded packing solid insulation layer. The main technical requirements of plastic insulation extrusion are as follows:
4.1. Eccentricity: the deviation value of extruded insulation thickness is an important symbol to reflect the level of extrusion technology. Most product structure size and deviation value are clearly stipulated in the standard.
4.2. Smoothness: the surface of the extruded insulation layer shall be smooth, and the surface shall not be rough, scorched, or contaminated
4.3. Density: The cross section of the extruded insulation layer should be compact and strong, and no visible pinholes should be allowed, so as to eliminate the existence of bubbles.


5. Cabling
In order to ensure the shape of multi-core cable and reduce the shape of cable, it is generally necessary to twist the cable into a round shape. The mechanism of stranded is similar to that of conductor stranded. The technical requirements of cable forming are as follows: first, the twisted bending of the cable caused by the turning over of the abnormal insulation core is eliminated; The second is to prevent the insulation layer from being scratched.
Most of the cables are completed with two other procedures: one is filling, which ensures the completeness and stability of the cables after cabling; One is binding to ensure that the cable core is not loose.
6. The protective layer
In order to protect the insulation core from being armored, it is necessary to properly protect the insulation layer. The inner sheath is divided into extruded inner sheath (isolation sleeve) and wound inner sheath (cushion layer). The wrapping cushion replaces the binding belt and is carried out synchronously with the cabling process.


7. Armoured
For laying underground cable, it may bear certain positive pressure during work. Internal steel tape armored structure can be selected. When cables are laid under both positive pressure and tension (such as in water, vertical shafts or in soil with a large drop), the structural type with internal steel wire armor should be selected.
8. Outer sheath
The outer sheath is the structural part that protects the insulation layer of electric 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, moistureproof, waterproof immersion, prevent the cable from burning capacity. According to the different requirements of cable extrusion machine directly extrusion plastic sheath.

Procurement and selection of crosslinked cables

Crosslinking cable quality is high, the power frequency breakdown strength can reach 50 kv/mm, tan6 was only 5 x10-4, dielectric constant is 2.3, is the ideal cable insulation, at the same time, the working temperature of crosslinking cable up to 90 c, good heat resistance and weather resistance, and high mechanical properties and chemical properties such as corrosion resistance, in the middle and lower cable products basically have all crosslinking cable. Although the technology of crosslinked cable is different, its insulation quality is completely the same. The selection of different types of cables in common use is introduced as follows:


(1) 1 kv three core aluminum core is 70 mm ‘cross-linked polyethylene insulated PVC sheathed steel pin cables, models for YJLV22-0.6/1, 3 x70: the types of crosslinking insulation (YJ) can use any kind of crosslinking process, but to use warm water network it best, such as using dry crosslinking, the equipment investment is large, slow production, such as cable again, in the vast product line cable will be fine, or break, if use irradiation crosslinking, due to the bending times too much will make the compression of the cable conductor is impaired, press the copper conductors are easier to damage. When purchasing, it should be taken into consideration that dry crosslinking should be avoided for aluminum cable with small cross section; For large section or copper core cable can not be used to crosslink, warm water crosslink has greater flexibility.


(2) 10 kv three core copper 120 mm ‘crosslinked polyethylene insulated PVC sheathed steel tape armoured cable, models for YJV22-8.7/10, 3 x 120:10 kv level cable is larger, especially copper core cable, can’t irradiation crosslinking process, except for the bending times too much easy to damage the cable, and the insulation cimc tired space charge decreased insulation quality. At present, dry crosslinking technology is the most suitable for the production of 10kV cable, which has stable product quality and reasonable price. However, if the cable quantity is small and the specifications change a lot, dry crosslinking scrap rate is very high, and it is easy to break the cable with a small section, so warm water crosslinking should be used. Warm water crosslinking belongs to the category of low temperature crosslinking, with no insulation thermal stress and good insulation quality. To eliminate the misunderstanding of “certain water content” of warm water crosslinking, with the development of new warm water crosslinking materials, it has a very good development prospect in the field of medium and low voltage cables.
(3)10KV aluminum core 70mm overhead insulated cable, models jKLYj-6 / lO, 1×70:, this type of cable is also in the production of three technologies, using the cross linking technology of amplitude lighting. In order to eliminate space charge, after the cable conductor is grounded for a long time, the cable can be safely used in the overhead cable line of semi-insulated system. The comparison between dry crosslinking and warm water crosslinking is consistent with the above 10kV cable production.
Henan Huaxing wire and cable Co., LTD., 20 years focus on the production and customization of industrial equipment supporting cables, mainly produces power cables, control cables, flame retardant cables, fire-resistant cables, low-smoke halogen-free cables, high-temperature resistance, waterproof and other dozens of series, thousands of specifications of low-voltage cables. The products strictly comply with international standards (IEC), national standards (GB) and Machinery Ministry standards (JB), the implementation of strict production process testing and rigorous factory testing, products through CCC certification and ISO9001 quality management system certification. It is your first choice to buy wires and cables.

Analysis of current situation of wire and cable industry

Wire and cable are used to transmit electrical (magnetic) energy, information and electromagnetic energy conversion wire products. It is widely used in various departments of national economy and provides important supporting facilities for various industries, national defense construction and major construction projects.
China’s wire and cable industry, based on a large number of technology introduction, digestion and absorption and independent research and development, has formed a huge production capacity, product variety satisfaction rate and domestic market share of more than 90%. Large enterprises of wire and cable manufacturing have obvious advantages in market competitiveness and the market develops rapidly.


At present, the market competition in China’s wire and cable industry is fierce, and most small and medium-sized enterprises in China adopt price competition. Wire and cable enterprises lack of development momentum, independent innovation ability is not strong, in the low – and medium-end wire and cable market with relatively low technical added value, price competition is quite common.
As the global wire and cable market matures, wire and cable manufacturing slowdown, growth is not big, falling demand, cable companies relative excess capacity, prices, competition between enterprises, combined with copper, aluminum, plastic and other factors such as main raw materials rose sharply, causing many cable enterprise development difficult.
International cable enterprises occupy the market by means of mergers and acquisitions, external expansion and transfer of production bases, etc., and occupy a large share in the international market.
The relevant personage inside course of study introduces, in recent years foreign capital electric wire and cable enterprise enters, intensified the market competition of domestic electric wire and cable industry further.

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.