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1. What is the bending radius of the cable?
Cables must be actively or passively subjected to bending during the manufacturing, transportation, and installation and construction processes. When the cable is bent, the degree of bending is directly related to the bending radius of the cable.
1. The bending radius of the cable: Normally, we regard the bent cable as an arc, and the radius of the circle where the arc is located is the bending radius of the cable in the bending state.
2. The minimum bending radius of the cable: Due to the cable material and structural characteristics, the cable has a certain limit to withstand bending. The cable bending radius under this limit is the minimum bending radius of the cable.
2. The influence of too small cable bending radius on the cable
1. The effect of bending on the conductor
The cable conductor is made up of multiple single-core wires twisted at a certain pitch. The number of single wires and the pitch of the conductor determine the stability of the conductor during bending. Excessive bending will cause the conductor to become loose and loose. The protrusion directly affects the performance of the semi-conductive layer and insulating layer of the outer conductor.
2. The influence of cable bending on insulation
When the cable is bent with a certain bending radius, the insulation at the bend will undergo tensile deformation. When the bending exceeds the allowable minimum bending radius, it may cause insulation damage.
3. The effect of bending on metal shielding
Usually medium voltage cables are shielded by copper tape. When the cable is bent too much, the metal tape will wrinkle or curl, which will easily lead to insulation damage.www.rfcable.com.cn/en
Precautions for installation of flame-retardant and fire-resistant cables
The characteristics of flame-retardant and fire-resistant cables: have the function of self-extinguishing, and can maintain the normal operation of the electrical circuit for a period of time under burning conditions. Therefore, the installation of flame-retardant and fire-resistant cables can effectively control major disasters caused by cable fire and prolonged combustion, thereby improving the fire protection level of electric lines. So, what matters should be paid attention to when installing flame-retardant and fire-resistant cables?
1. When laying cables in the same pipeline, it is not advisable to configure both flame-retardant and fire-resistant cables and ordinary non-fire-resistant cables.
2. When the number of cables to be installed is small, fire-resistant paint, tape, etc. can be added to the cables.
3. Places with high safety performance requirements, such as oil tank farms, important wooden structure public buildings, dense wire tunnels, hospitals, shopping malls, etc., need to be equipped with Class A flame-retardant and fire-resistant cables.
4. In industrial buildings, important circuits such as fire protection, alarm, emergency lighting, breaker operation DC power supply, and emergency shutdown power supply for generating sets and other important circuits need to be equipped with Class A flame-retardant and fire-resistant cables.
5. When too many cables are laid in the same pipeline, the cables need to be laid in the fire-resistant trough box.
6. In order to reduce the failure rate of wire connectors in fire accidents, the number of connectors should be reduced as much as possible during installation to ensure that the lines can work normally in a fire. If branch wiring is needed, fire-proof the joints should be done.http://www.rfcable.com.cn/en
Special cables are cables that have special uses and can be used on specific occasions. Special cables are a series of products with unique properties and special structures. Compared with ordinary wires and cables with a large quantity and a wide range, special cables have the characteristics of higher technical content, stricter use conditions, smaller batches, and higher added value. Special cables often adopt new structures, new materials, new design calculation methods and new production processes.
Second, the characteristics and classification of special cables
Special cables have special functions due to their special use occasions or specific use conditions, such as high temperature or severe cold resistance, strong acid and alkali resistance, termite resistance, low noise, superconducting, waterproof, soft and wear-resistant, and environmental protection. . So far, special cables are mainly divided into four categories: high temperature resistant wire and cable, special structure and specific purpose wire and cable, functionalized wire and cable, and new green and environmentally friendly wire and cable.
Third, the diversified development direction of special cables
The development direction of special cables is diversified. The military industry has a large demand for light-weight and high-temperature-resistant cables. In terms of construction, fire-resistant and high-temperature resistant wires and cables and low-smoke, halogen-free and environmentally friendly wires and cables can effectively prevent fire and safety accidents. In fields such as medicine and national defense that require small signal measurement, low-inductance and low-noise wires and cables are needed. For oil platforms, deep well survey cables, heating and temperature control cables, and submarine integrated cables are needed. In urban power distribution, substations, power plants and other occasions that need to transmit large currents over short distances, superconducting cables are required. In terms of industrial intelligence, super-flexible, wear-resistant and easy to move drag chain cables are needed. In the application of locomotives and AC motors, frequency conversion cables are required.www.rfcable.com.cn/en
Five principles of circuit wiring in home decoration
Circuit wiring is an important part of home decoration. The quality of home decoration circuit wiring directly affects our future life, and will also affect our future circuit maintenance and transformation. Do you know how home decoration circuit wiring should be implemented and what wiring principles should be followed?
1. Principles of circuit design: walk on the top without walking on the ground, on the top without walking on the wall, and on the wall without walking on the ground.
2. The principle of circuit grouping: according to the circuit application in the home, carry out strong and weak current grouping, keep the distance between strong and weak current groups at 30-50 cm; group the circuits into living room, kitchen, bedroom and other applications according to the spatial layout of the family;
3. Circuit positioning principle: According to the placement of household electrical appliances, the layout of switches, the positioning of sockets, etc., carry out the planning and layout of the circuit.
4. Circuit grooving principle: The principle of horizontal and vertical grooving should be followed, and horizontal grooves should be opened as little as possible; if there are no more than 3 inflection points on the line, the shortest line should be planned and then grooved .
5. The principle of circuit buried pipe: circuit wiring generally adopts the method of concealed buried pipe. There are two types of wire pipes: cold-bent pipe and PVC pipe. Cold-bend pipes can be bent but difficult to break. It is recommended as the preferred choice for buried pipes.
Adhering to the five principles of circuit wiring in home decoration can enhance the safety of life electricity and provide convenience for future circuit maintenance and transformation.http://www.rfcable.com.cn/en
2. Overload operation: Due to long-term overload operation, the operating temperature of the cable far exceeds the maximum allowable temperature during normal heating, which makes the insulation material of the cable aging and dry, so it is easy to break down and cause the wire to catch fire.
3. Excessive contact resistance: The contact resistance is too large due to poor contact at the junction of line and line, line and switch, and line and other electrical equipment. When strong current passes, it will also cause local heating and high temperature and cause line fire.
4. Leakage: The quality problems of the wire, such as poor insulation performance or friction or scratches in the laying of the wire, will cause the wire to leak. The electric spark and high temperature caused by the leakage will cause the wire to catch fire.
Prevention of wire fire:
1. Short-circuit prevention: Use safe fuse electrical switches and select flame-retardant cables with high safety factors. When a short-circuit fault occurs on the electrical circuit, the fuse will blow and cut off the current, and the flame-retardant cable has its own self-extinguishing performance, which greatly reduces the spread of fire.
2. Overload prevention: Do not pull wires randomly. When using high-power electrical appliances, consider the acceptable range of wires and cables. for
To prevent aging and breakdown of insulating materials during overload operation, it is recommended to use wires and cables with better aging resistance and lower eccentricity.
3. Prevention of excessive contact resistance: The electrical wiring must be installed in strict accordance with the electrical installation regulations. If necessary, please ask a professional electrician.
Set up the line.
4. Leakage prevention: choose wires and cables with good insulation material quality and strong bending resistance. In addition, regular
Check electrical wiring and equipment, etc.www.rfcable.com.cn/en
Talking about the naming principle of wires and cables
The naming of wire and cable is usually related to its application occasion, category, material, and purpose. In order to facilitate memory, the naming of most wire and cable products usually needs to follow the following three principles:
1. Content principle: The product name should contain the following content.
(1) Product application occasion or classification name; (such as power cables, control cables, marine cables, wind engine cables, etc.)
(2) Product structure material or type (types include steel tape armor, steel wire armor, double aluminum tape, etc.);
(3) Important features or additional features of the product. Sometimes in order to emphasize a certain feature of the product, it can be written before the product name or before the corresponding structural description. Such as: flame-retardant, fire-resistant, termite-proof, corporate standards, etc.
2. Order principle: The description of product structure materials should be named in the order of conductor --> insulation --> inner sheath --> outer sheath --> armor type.
3. Abbreviation principle: for example, aluminum conductors are not allowed in automobile wires and flexible wires, so the conductor materials are not described.
Examples of product names are as follows:
1. The name of the cable: rated voltage 8.7/15kV flame-retardant copper core XLPE insulated steel tape armored PVC sheathed power cable, in which the content of the name is interpreted as:
"Rated voltage 8.7/15kV"-use occasion/voltage level
"Flame retardant"-emphasized features
"Copper Core"-Conductor Material
"Cross-linked polyethylene insulation"-insulating material
"Steel tape armor"-armor layer material and type
"Polyvinyl chloride sheath"-inner and outer sheath materials (the inner and outer sheath materials are the same, the inner sheath material is omitted)
"Power cable"-the name of the product category
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Isolation sleeve: The focus is on the word isolation. The isolation is between two different metals, such as the three-core YJV22 structure. There is a layer of PVC between the copper strip and the steel strip. At this time, the PVC plays the role of isolation. From chemical and physical From the perspective of consideration, the activities of copper and iron are different, and when they are in contact with each other, they will accelerate the oxidation of copper. Therefore, the isolation sleeve must be squeezed and cannot be wrapped, because there are gaps in the wrapping, which may cause mutual contact.
Lining layer: copper wire shielding, copper tape armoring, single-core power cable-this structure also has PVC between the shielding layer and the armoring layer, but since the two metals are of the same kind, they will not accelerate oxidation, so PVC does not need to be used. To the isolation effect, so in this case it is not called an isolation sleeve, but an inner liner. In addition, the inner liner may be wrapped.
Cushion: Generally, the word "wrap tape" is added in front of the cushion. This is used in many standards to describe its function. When the cable is armored, it is used together with the inner lining to strengthen the inner lining. The role of.
The inner lining can be squeezed or wrapped, while the isolation sleeve can only be squeezed. For cables with specifications above 10mm2, wrapping can save material costs. When the metal layer under the armor is different from the armor material, a layer of isolation sleeve must be squeezed to separate it. At this time, the isolation sleeve can replace the inner lining. Since the cores of medium voltage power cables are shielded by copper tape, and the cores of low voltage cables are unshielded, this is why we usually see why medium voltage armored cables have to squeeze the inner lining (isolation sleeve), while low voltage armored cables The reason to wrap the inner liner.www.rfcable.com.cn/en