How to choose the anti-theft alarm cable

The alarm system based on the professional bus form is currently the most widely used, and the aerial bundled cable SANS 1418  is also the most complicated, so I will focus on the discussion here.

RVV2*0.3 (signal cable) and RVV4*0.3 (2-core signal + 2-core power supply) cables are generally used between the front-end detector and the alarm controller, and the two aerial bundled cables ASTM B231 are generally used between the alarm controller and the terminal security center. As for the core signal wire, as for the use of shielded wire or twisted pair or ordinary sheathed wire, it needs to be determined according to the requirements of various brands of products. The thickness of the wire diameter is determined according to the distance and quality of the alarm controller and the center. First of all, determine the location of the security center and the distance between each alarm controller. The farthest distance cannot exceed the length specified by various brands, otherwise it will not meet the requirements of the bus; the entire alarm area is relatively large, the bus must not meet the requirements Under the conditions, the alarm can be divided into several areas. In each area, determine the installation location of the sub-control center to ensure that the bus in the area meets the requirements, and determine the location of the general management center and the sub-management center, and determine the sub-control center to the general management The communication method of the center is to adopt RS232-RS485 conversion transmission or adopt RS232-TCP/IP to use the integrated wiring system of the community for transmission or the management software of the sub-management center to use TCP/IP network to forward to the general management center.The power supply of the alarm controller generally adopts local power supply instead of centralized power supply in the control room. The line is relatively short. Generally, RVV 2×0.5” or more specifications can be used. Configure according to the actual line loss. Perimeter alarm and other public area alarm equipment power supply Generally, the centralized power supply mode is adopted and the line is longer. Generally, the specifications above RVV2*1.0″ are adopted, and the configuration is based on the actual line loss. The grounding of all power cable must be unified.

Different types of alarms (such as perimeter alarm, public area alarm bus and household alarm bus separately) should not use the same bus. The installation location of the junction box should be easy to operate, and the high-quality junction interface is used to handle the connection between the bus and the bus, which is convenient for maintenance. And debugging; it is recommended that the bus and other lines take charge of the wiring. The bus weakening bridge should be kept away from other lines according to the weak current standard to avoid causing unshielded non-twisted pair audio lines and other high and low frequency interferences such as video intercom systems.

the advantages of overhead insulated cables

The Aerial Bundled Cable series products are composed of pressed copper, aluminum (aluminum alloy) conductors, inner shielding layer, weather-resistant insulating material and outer shielding layer. They have both the power transmission characteristics of power cables and the strong mechanical properties of overhead cables. Compared with bare wires, this product has the advantages of small laying spacing, high safety and reliability, and excellent resistance to atmospheric aging
  1. Uses of overhead insulated cables Overhead insulated cable products are a new series of products for power transmission through overhead transmission lines, and are preferred for power grid construction and transformation of 10kV transmission lines. It is the most suitable series of products for line maintenance and safety. Soft copper core products are suitable for the lower leads of transformers.
  2. Overhead cable implementation standards
  3. 1KV overhead insulated cable: GB12527-90 is equivalent to the International Electrotechnical Commission IEC60502, IEC227;
  4. 10KV overhead insulated cable: GB14049-93 is equivalent to the International Electrotechnical Commission IEC60502. Overhead insulated cable Third, the characteristics of (ABC) HD 626 S1 Standard
  5. Rated voltage: 0.6/1KV, 10KV;
  6. The long-term allowable working temperature of the cable: 70°C for PVC insulation and 90°C for XLPE insulation.
  1. When short-circuited (the longest time is no more than 5 seconds), the maximum temperature of the cable: 160°C for PVC insulation, 150°C for high-density polyethylene insulation, and 250°C for cross-linked polyethylene insulation;
  2. The ambient temperature during cable laying is not lower than -20℃;
  3. Allowable bending radius of cable: (1) Cables with rated voltage below 1KV: cable outer diameter (D) less than 25mm should not be less than 4D, cable outer diameter (D) of 25mm and above, should not be less than 6D;
  1. (2) The rated voltage of 10KV cable should not be less than 20 (D+d). Where: D—the actual outer diameter of the cable, d—the actual outer diameter of the cable conductor. Overhead fixed laying of soft copper core products is used for transformer down-conductor; when laying cables, a certain distance between cables and trees should be considered, and frequent contact between cables and trees is allowed during cable operation. For overhead fixed laying and cable erection, a certain distance between the cable and the tree should be considered, and frequent contact between the cable and the tree is allowed when the cable is running. Overhead fixed laying; When installing cables, consider keeping a certain distance between cables and trees. When cables are running, only short-term contact between cables and trees is allowed.

Introduction to ABC Cable

1. The main features of overhead insulated conductors (ABC cables) have good insulation performance.
Overhead insulated conductors have an extra layer of insulation and have superior insulation performance than bare conductors, which can reduce the distance between lines, reduce the insulation requirements for line supports, and increase the number of circuits erected on the same pole. Overhead insulated (ABC) cable uses and characteristics-Jianzhenda Cable|Jianzhenda Wire and Cable|Jianzhenda-Jianzhenda Cable has good insulation performance. Overhead insulated conductors have an extra layer of insulation and have superior insulation performance than bare conductors, which can reduce the distance between lines, reduce the insulation requirements for line supports, and increase the number of circuits erected on the same pole. Good corrosion resistance.
2. The specification core of the overhead insulated wire. There are two types of overhead insulated wires: aluminum core and copper core. In the distribution network, aluminum core applications are more, mainly because aluminum is lighter and cheaper, and has low requirements for line connectors and support parts. In addition, the original distribution lines are mainly steel core aluminum stranded wires. The aluminum core wire is used to facilitate the connection with the original network. In actual use, aluminum core wires are often used. Copper core wire is mainly used as the down conductor of transformers and switchgear. Insulation Materials. There are two types of insulation protection layers for overhead insulated wires: thick insulation (3.4mm) and thin insulation (2.5mm). The thick insulation allows frequent contact with trees during operation, and the thin insulation allows only short-term contact with trees. The insulating protective layer is divided into cross-linked polyethylene and light polyethylene, and the insulating properties of cross-linked polyethylene are better.
3. The laying method of overhead insulated wires is a single conventional laying method.
This erection method is to use the current conventional cement poles, iron accessories and ceramic insulator accessories with bare conductors, and erect according to the bare conductor erection method, which is more suitable for the area where the old line is reconstructed and the corridor is sufficient. A special insulating bracket is used to suspend the wires for single laying. This method can increase the number of circuits erected, save the line corridors, and reduce the cost of the line unit.
4. The application area of ​​overhead insulated wires is suitable for places with many trees.
Lines erected by bare conductors are often shielded by the erection and maintenance of lines and greening and forestry in areas with many trees. The use of overhead insulated wires can reduce tree felling (early erection and operation and maintenance stages), solve many problems, and reduce conflicts with greening and forestry departments, protect the ecological environment, beautify the city, and reduce the line Ground Fault. Used in areas where there is a lot of metal dust and pollution. In old industrial areas, metal processing companies often have metal dust flying in the wind due to environmental protection failures. In polluted areas of thermal power plants and chemical plants, short circuits and ground faults in overhead distribution lines have been caused. The use of overhead insulated wires is a better way to prevent short-circuit grounding of 10 kV distribution lines. Suitable for salt spray areas. The salt spray corrodes the bare wires very seriously, which greatly reduces the tensile strength of the bare wires. In the event of wind and rain, the wires will break, causing short circuit grounding accidents and shortening the service life of the wires. The use of overhead insulated wires can better prevent salt spray corrosion.
5. Design and construction of ABC conductors. The insulated wires and the steel core aluminum stranded wires are in the same specification, and the current carrying capacity of the insulated wires is smaller than that of the bare wires. After the insulated wire is added with the insulating layer, the heat dissipation of the wire is poor, and its current-carrying capacity is almost a grade lower than that of the bare wire. Therefore, when designing and selecting, the insulated wire should be selected a larger gear. At the same time, the strain clamp is directly clamped on the wire insulator. In order to prevent excessive wire tension from cracking or peeling of the insulation layer, the maximum working stress of generally insulated wires is about 41N/mm2. Wire arrangement and pitch. The conductor arrangement of overhead insulated lines is basically the same as that of bare conductor lines, which can be divided into: triangular, vertical, horizontal, and multi-loop erection on the same pole. The span of overhead insulated lines should be controlled at 50m. The distance between phases of insulated wires. Due to the good insulation performance of overhead insulated wires, the distance between phases is smaller than that of bare conductor lines, but the distance between vertical and triangular arrangements is not less than 0.3m; the distance between horizontal arrangements is not less than 0.4m. The vertical and horizontal distances of two circuit lines erected on the same pole shall not be less than 0.5m. The clearance distance between the jumper, the down conductor and the adjacent lead wire and low-voltage line, and the clearance distance between the overhead insulated wire and the pole wire or frame shall not be less than 0.2m. Connection of insulated wires. The connection of the insulated wire is not allowed to be twisted, and the insulated wire should not be connected within the span as much as possible. It can be connected when the tension rod is jumper. If you really want to connect within the span, within a span, each wire cannot exceed one socket, and the distance between the connector and the fixed point of the wire should not be less than 0.5m. Insulated wires of different metals, different specifications, and different twisting directions are strictly forbidden to make load-bearing connections within the pitch. The connection point of the insulated wire should be wrapped with an insulating cover or self-adhesive insulating tape. Sag of insulated wire. After the conductor is erected, considering the influence of plastic elongation on sag, the sag reduction method should be used to compensate. The percentage of sag reduction is 20% for aluminum or aluminum alloy core insulated wires and 7% to 8% for copper core insulated wires. When the wire is tightened, the insulated wire should not be overdrawn. After the wire is tightened, the sag of each phase wire in the same gear should be consistent. Fixing of insulated wires. Insulated wire and insulator are fixed with insulated wire. For pin-type or rod-type insulators, the straight rod adopts the top groove tying method, and the direct angle rod adopts the side groove tying method, which is tied to the side groove of the outer corner of the line. The screw-type insulator is bound in the side groove, and the insulating wire and the contact part of the insulator should be wound with insulating self-adhesive tape. Construction and erection of insulated wires. The construction and erection of insulated wires is different from overhead bare wires. It does not allow the wires to damage the insulation layer during the construction process. Pay attention to the protection of the insulation layer during construction, and try to avoid contact and friction between the wire insulation layer and the ground and tower accessories. Overlap of insulated conductors and drop wires. The connection of jumper wires and drop wires of insulated wires is different from that of bare wires, because insulated wires need special wire strippers to strip the insulation layer. The process is more complicated and the requirements are stricter. The jumper connection can be connected by a parallel groove clamp or a connecting pipe. The lead wire can be connected with a parallel groove clamp or a T-shaped clamp. At the same time, wrap the interface with an insulating cover or insulating self-adhesive tape. Coordination of ordinary fittings and insulated wires. Overhead insulated wires have special line fittings, which can insulate the entire line. Considering the cost of the circuit, ordinary accessories can also be combined to reduce the cost of the circuit. Since the insulated wire has an extra layer of insulation, the wire diameter is larger than that of the bare wire. When using ordinary fittings, the wire fixing fittings and connecting fittings should be enlarged. The tension clamp should be clamped together with the protective layer of the wire to prevent the overhead insulated wire from peeling off, which affects its mechanical and insulation properties.
The use of insulated wires instead of bare wires is a technological advancement measure to achieve insulation of distribution lines, which can better improve the reliability, stability and safety of power supply, save line maintenance and management costs, and help improve the economic benefits of power supply enterprises. Compared with overhead bare wires, overhead insulated conductors have better performance, and the cost is not too high. In rural power grids, depending on local conditions, it is beneficial to use overhead insulated conductors in some areas.

Low-voltage cable head production and installation

(1 )Overview

Low-voltage cables have many specifications and models. Take indoor PVC insulated PVC sheath below 1KV as an example to illustrate the production of power cable terminal cable heads.

(2) Construction process

Measure the grounding resistance → strip the cable end → wrap the cable and sheath the terminal end of the aerial bundled cable ASTM b231 → press the cable core wire lug → connect with the equipment

(3) Main construction methods and technical measures

1) Press cable core wire lug

a. Measure the length from the end of the core wire to the depth of the wire nose, add another 5mm, strip the cable core wire insulation, and coat the core wire with petroleum jelly.

b. Insert the wire core into the wiring nose, and use crimping pliers to press the wiring nose. There should be more than two crimping holes. Large-size wiring terminals should be crimped by hydraulic machinery.

c. According to different phases, use yellow, green, red, and four-color plastic tapes to respectively wrap each core wire of the cable to the crimping part of the terminal lug.

d. Fix the cable with the terminal head on the pre-made cable head bracket, and separate the core wires.

e. According to the model of the terminal, use bolts to crimp the cable terminal on the equipment. Pay attention to the bolts from top to bottom or from the inside to the outside. Flat washers and springs should be installed.

2) Telemetry cable insulation

a. Use 1KV shaker to measure the cable, and the insulation resistance should be greater than 10MΩ.

b. After the cable shake test is completed, the core wires should be discharged to the ground respectively.

3) Wrap the cable, cover the cable terminal head cover

a. Strip the outer insulation layer of the aerial bundled cable(abc) b230 standard, and put the lower part of the cable head cover into the cable first.

According to the type and size of the cable head, according to the length and inner diameter of the cable head sleeve, wrap the cable with a plastic tape in a half-stack method. The plastic tape should be tightly wrapped, and the shape should be like a date.

c. Put the upper part of the cable head cover on, butt and cover it tightly with the lower part.

The principle of omission in the model: copper is the main conductor material used in wire and cable products, so the copper core code T is omitted, except for bare wires and bare conductor products. Bare wires and bare conductor products, power cables, and magnet wire products do not indicate major category codes, and electrical equipment wires and cables and communication cables are also not listed, but subcategory or series codes are listed.

Item 7 is a mark for various special use occasions or additional special use requirements, marked with a pinyin letter after “-“. Sometimes in order to highlight this item, write this item to the top. Such as ZR- (flame retardant), NH- (fire-resistant), WDZ- (low smoke and halogen-free, corporate standard), -TH (for hot and humid areas), FY- (termite-proof, corporate standard), etc.

High-voltage cable head manufacturing technology

1. The basic requirements of high voltage cable head

The cable terminal is the component that connects the aerial bundled cable(abc) with other electrical equipment. The cable middle is the component that connects the two cables. The cable terminal and the middle are collectively called cable accessories. The cable accessory should be able to operate safely for a long time like the cable body and have the same service life as the aerial bundled cable SANS 1418 standard. A good cable accessory should have the following properties:

Wire core connection is good: mainly because the connection resistance is small and the connection is stable, which can withstand the impact of fault current; after long-term operation, its contact resistance should not be greater than 1.2 times the resistance of the cable core body with the same length; it should have a certain mechanical strength and resistance Vibration and corrosion resistance; in addition, it should be small in size, low in cost, and easy to install on site.

Good insulation performance: The insulation performance of the cable accessories should not be lower than that of the cable body, and the dielectric loss of the insulating materials used should be low. Structurally, the sudden change of the electric field in the cable accessories can be perfected, and there are measures to change the electric field distribution.

2. Principle of electric field distribution

There is a grounded (copper) shielding layer outside each phase core of the high-voltage cable, and a radially distributed electric field is formed between the conductive core and the shielding layer. In other words, the electric field of a normal aerial bundled cable 33-209 is only the electric field from the (copper) wire along the radius to the (copper) shielding layer, and there is no electric field (electric force) in the axial direction of the core wire, and the electric field distribution is uniform.

When making the cable head, the shielding layer is stripped, and the original electric field distribution of the cable is changed, which will produce a tangential electric field (electric force along the axis of the conductor) that is extremely unfavorable to the insulation. The power lines from which the core wires of the shielding layer are stripped are concentrated toward the shielding layer fracture. Then the break of the shielding layer is the most easily broken part of the cable. At the break of the shielding layer where the cable is most likely to break down, we use the concentrated power line (electric stress) to disperse the electric stress control tube (abbreviated as the material with a dielectric constant of 20-30 and a volume resistivity of 108-1012Ω•cm). Stress tube), sleeved at the fracture of the shielding layer to disperse the electric field stress (power line) at the fracture to ensure reliable operation of the cable.

In order to make the cable run reliably, the stress tube is very important in the production of the cable head, and the stress tube can achieve the effect of dispersing electrical stress on the basis of not destroying the main insulation layer. In the cable body, the outer surface of the core wire cannot be a standard circle, and the distance between the core wire and the shielding layer will not be equal. According to the principle of electric field, the electric field strength will also be large, which is also detrimental to the cable insulation. In order to make the electric field uniform within the cable as much as possible, there is a semiconductor layer with a circular outer surface outside the core wire, so that the thickness of the main insulating layer is basically equal, and the electric field is uniformly distributed.

Outside the main insulation layer, the outer semiconductor layer inside the copper shielding layer is also set to eliminate unevenness of the copper shielding layer and prevent uneven electric field.

In order to disperse the electric field stress of the cable at the fracture of the shielding layer as much as possible, the contact length of the stress tube and the copper shielding layer must not be less than 20mm. The length is fixed). If it is longer, the electric field dispersion area (segment) will be reduced and the electric field dispersion will be insufficient. Generally around 20~25mm.

When making intermediate joints, part of the main insulation layer must be stripped off. After the core wire is crimped with a copper tube, it is flattened with filler (round). There are two production methods:

Heat-shrinkable casing: the main insulating casing made of heat-shrinkable material is shrunk, the main insulating casing is externally contracted to the semiconductor tube, and then covered with a metal shield, and finally the outer protective casing.

Prefabricated accessories: The materials used are generally silicone rubber or ethylene propylene rubber. It is a hollow cylinder, the inner hole wall is a semiconductor layer, and the outside of the semiconductor layer is a main insulating material.

Prefabricated installation requires higher and more difficult than heat shrinkable. The hole diameter of the tubular preform is 2~5mm smaller than the outer diameter of the main insulation layer of the cable. The prefabricated pipe of the intermediate joint should be sheathed outside the main insulation layer of the cable at both ends, and the length of each connection with the main insulation layer shall not be less than 10mm. There is no need to sharpen the pencil tip on the main insulation head of the cable (as much as possible to leave the semiconductor layer on the cable core). The surface of the copper pipe should be smooth and packed with proper amount of filler.

Key technical issue: the size of the accessory and the size of the cable to be installed must meet the specified requirements. In addition, it is necessary to use silicone grease to lubricate the interface to facilitate installation, while filling the air gap of the interface to eliminate corona. Prefabricated accessories generally rely on their own rubber elasticity to have a certain sealing effect, and sometimes sealants and elastic clamps can be used to enhance the sealing. The outside of the prefabricated tube is the same as the heat-shrinkable one, the semiconductor layer and the copper shielding layer, the outermost layer is the outer protective layer.

Physical characteristics of aluminum alloy cables

The advantage of aluminum alloy cable over ordinary cables is that under the same volume, the actual weight of aluminum alloy is about one-third of copper. According to this calculation, under the premise of meeting the same electrical conductivity, the length of the aluminum alloy cable with the same weight is twice that of the copper cable. Therefore, the weight of the aluminum alloy cable is about half of the copper cable at the same current carrying capacity. The use of aluminum alloy cables instead of copper cables can reduce the weight of the aerial bundled cable ASTM b231, reduce the installation cost, reduce the wear of the equipment and the cable, and make the installation work easier.

Aluminum alloy power cable is a new type of material power cable created by advanced technologies such as AA-8000 series aluminum alloy material as the conductor, using special pressing technology, annealing treatment, and chain armoring technology.

The difference between aluminum alloy cables and ordinary cables: aluminum alloy cables use AA-8000 series aluminum alloy conductors, while ordinary cables use copper or pure aluminum as cable conductors.

Tensile strength and elongation

Compared with pure aluminum conductors, aluminum alloy conductors have greatly improved tensile strength due to the addition of special ingredients and special processing techniques, and the elongation rate has increased to 30%, making it safer and more reliable to use.

Thermal expansion coefficient

The coefficient of thermal expansion is used to calculate the dimensional change of the material when the temperature changes. The coefficient of thermal expansion of aluminum alloy is equivalent to that of copper. Aluminum connectors have been reliably used for copper and aluminum conductors for many years, and most of the electrical connectors used today are made of aluminum, which is especially suitable for aluminum alloys. So the expansion and contraction of the aluminum alloy conductor and the connector are exactly the same.

Strong weight bearing capacity

Aluminum alloy improves the tensile strength of pure aluminum. Aluminum alloy cables can support a weight of 4000 meters, while copper cables can only support 2750 meters. This advantage is particularly prominent when wiring large-span buildings (such as stadiums).

Armour characteristics

Most commonly used armored aerial bundled cables(abc) b230 standard in China are armored with steel tape, with low security level. When subjected to external destructive forces, their resistance is poor, which is easy to cause breakdown, and the weight is heavy, the installation cost is quite high, and the corrosion resistance is poor. The service life is not long. The metal interlocking armored cable we developed according to American standards uses aluminum alloy tape interlocking armor. The interlocking structure between the layers ensures that the cable can withstand the strong destructive force from the outside, even if the cable is subjected to greater pressure The cable is not easy to be punctured under the impact force, which improves the safety performance. At the same time, the armored structure isolates the cable from the outside world. Even in the event of a fire, the armored layer improves the flame-retardant and fire-resistant level of the cable and reduces the risk of fire. Compared with the steel tape armored structure, the aluminum alloy tape armored structure is lighter in weight and convenient to lay. It can be installed without bridges and can reduce installation costs by 20% to 40%. Different outer sheath layers can be selected according to different places of use, which makes the use of armored cables more extensive.

Talking about the advantages of prefabricated branch cables

With the strong growth of my country’s national economy, the speed of various infrastructure, capital construction, and real estate development has accelerated. It is a historical necessity to use mining aerial bundled cables(abc) as the main supply, distribution, and trunk lines in various buildings and facilities. Therefore, construction units, design units, and construction units are seeking more advanced, more economical, superior performance, less effective space, and shorter construction period power supply construction technology and methods. It is also under such historical environmental conditions that prefabricated branch cables have entered my country’s architectural electrical stage in strides.

1) In the middle and high-rise buildings, prefabricated branch cables can be widely used in various middle and high-rise buildings such as residential buildings, office buildings, office buildings, commercial buildings, teaching buildings, scientific research buildings, etc., as the main and trunk cables for power supply and distribution use;

2) In airports and ports, it is used as the main cable for airport runway lighting, port terminal lighting, and power supply and lighting in building facilities;
3) It can be used as lighting power supply in tunnels; it can be used as lighting and power supply network in mines;
4) In the transformation and construction of urban power grids, as the main, kydl_yyyb trunk line mining cables can be buried or overhead;
5) In the modern standard factory building, it is used as the main and trunk cable for mining;
6) In various buildings, facilities, buildings, halls, halls, venues, and even sports facilities, swimming pools, etc., it can be used as main and trunk mining aerial bundled cables BS 7870.
7) Prefabricated branch cables can be used in various other occasions where mining cables are used, such as main and trunk lines of power systems such as ships and ships.

Pre-branch cables have many advantages:

1) The cost of insulation treatment of branch joints is greatly reduced;
2) On-site construction costs are greatly reduced;
3) On-site construction cycle and time are greatly shortened;
4) Reduced on-site construction personnel and equipment; reduced technical requirements for construction personnel;
5) Not restricted by the space and environmental conditions of the construction site;
6) The insulation performance of the branch connector is consistent with that of the cable body, with superior insulation performance and high reliability;
7) It has higher seismic, waterproof and fire resistance performance;
8) The power supply is safe and reliable, and the one-time effective opening rate can reach 100%;
9) Wide application range, many varieties and specifications;
10) Users can conveniently choose cables of various specifications, models, cross-sections, and lengths as the main and branch cables;
11) It has more intuitive maintenance operability.

Causes of fire accidents on overhead cables

Now the use of Aerial Bundle Cable has become more and more extensive, but with its popularity in the national power supply lines, some of its safety problems have gradually attracted people’s attention, especially in recent years, the  cable fire accidents reminds people to pay more attention to when using this kind of cable. So, what are the causes of fire accidents of overhead cables?

1. The nominal conductor cross section of cable core does not meet the requirements. Generally, the specified nominal interface is larger than the actual cable produced, and the cable whose nominal value deviates from the standard will have larger unit current density. In its working process, the cable is easy to cause fire accident because it can not generate heat normally.

2. (ABC)XLPE  Insulated cable production process is poor. Although not every manufacturer is like this, it is inevitable that some businesses in the market will not operate strictly according to the standards in the process of cable production in order to seek personal interests. Even some businesses will use some low-quality products to make rough, resulting in the final production of the cable because the quality is not up to standard, causing fire in the process of use.

3. The material of the cable is impure or unqualified. The core wire of the cable is generally made of some copper or aluminum conductive materials, and many businesses often use unqualified or insufficient purity materials in the production process, which will lead to the reduction of power due to the presence of more impurities. Therefore, the materials used as core wires must be some high-quality electrolyte materials, mainly copper and aluminum.

4.Improper transportation. Most cables are subject to strict quality inspection before leaving the factory, but in the process of transportation, due to the lack of proper protection measures, it is squeezed and collided, resulting in the damage of insulation layer or the breakage of internal core wire

5. The composition of the insulating material does not meet the requirements or the processing is poor. We know that the outside of the cable is generally wrapped with a kind of insulating material. If the quality of the insulating material is unqualified, it will reduce its own withstand voltage performance in the process of use, and will form unqualified resistance value. In addition, long-term use will also shorten its service life, it is easy to have some short-circuit faults and cause fire.

Basic cable performance test

1. Inspection method
Routine test: It is an experiment conducted by the manufacturer on all finished cables. Its purpose is to check whether the quality of the product meets the requirements of the technical conditions in order to find accidental defects in the manufacturing process. It is a non-destructive experiment, such as the DC resistance of the wire and the insulation resistance time. And withstand voltage test, partial discharge detection, etc.
Type test: It is the manufacturer who regularly conducts comprehensive performance inspection of the product, especially for a new product before it is finalized for mass production, or the structure, material and main process of a product have changed, which may affect the performance of the cable Time. Pass type test: It can be tested whether the product can meet the requirements of operation, and can be compared with the old product. Such as thermal aging performance of insulation and sheath, long-term stability test of power cable, etc.
Acceptance test: It is an acceptance test performed on the cable after the cable is installed and laid in order to check the installation quality and find possible damage during the construction. Such as withstand voltage test after installation.

2. Test items
2.1 Measurement of DC resistance of wires
The conductive core of the wire and cable mainly transmits electric energy or electric signal. The resistance of the wire is the main indicator of its electrical performance. When the AC voltage is applied, the core resistance is larger due to the skin effect and the adjacent effect surface than when the DC voltage is applied, but the difference between the two is very small when the electric eye frequency is 50Hz. The current standard stipulates That can only require the detection of whether the DC resistance or resistivity of the core exceeds the value specified in the standard. Through this inspection, certain defects in the production process can be found: such as wire breakage or partial single wire breakage; Meet the standard; the length of the product is incorrect, etc. For aerial bundled cables 1418 standard, you can also check whether it will affect the allowable current carrying capacity of wire and cable products during operation.
There are single-arm DC resistance method and double-arm DC bridge method to measure the DC resistance of conductors. The accuracy of the latter is higher than that of the former. The test procedure is also more complicated than the former.

2.2 Test of insulation resistance
Insulation resistance is an important indicator reflecting the insulation characteristics of wire and cable products. It is closely related to the product’s electrical strength, dielectric loss, and the gradual deterioration of insulating materials under working conditions. For communication cables, low insulation resistance between wires will also increase loop attenuation, crosstalk between loops, and long-distance power supply leakage on conductive cores. Therefore, insulation resistance should be higher than the specified value.
Defects in the process can be found by measuring the insulation resistance, such as the insulation is dry and impermeable or the sheath is damaged and damp; the insulation is contaminated and conductive impurities are mixed in; the insulation layer is cracked due to various reasons. In the operation of aerial bundled cables(abc) sans1418, the insulation resistance and leakage current are often tested as the main basis for continued safe operation.
At present, in addition to the ohmmeter (shaking meter), the current measurement of the insulation resistance of wires and cables is the galvanometer comparison method and the high resistance meter method (voltage-current method).

How to identify poor quality Aerial Bundled Cable

1. Look closely at the label printing, the handwriting is blurred and the address is unknown. It means to look at the printed words on the label and the insulating skin. If there are typos, or the printing is of different shades, or the words are blurred, pay attention to it.
2. Use your fingernails to mark and flick the line , and the line will be cut off. Refers to the use of nails to scratch and pinch the insulating skin. The ones that can be scratched or pinched are generally inferior threads.

3.Twist the insulation skin with your hands, and the color will fade and the characters will be of poor quality. Refers to rubbing the insulating sheath with your fingers. Some inferior insulated wires are easy to fade, especially the red wire. This problem occurs. After rubbing, the color of the thread is left on the finger or the words printed on the thread are wiped off Generally inferior quality Aerial Bundled Cable

4. Repeatedly bend the insulated wire and break (ABC)SANS 1418 Standard three to four times. Refers to repeated bending of insulated wires. Inferior wires are generally of poor quality, and the insulation layer will break after bending 3 to 4 times.

 

5. Use fire to ignite the wire insulation and spontaneously ignite away from the open flame. It refers to the inferior wire that ignites the insulating layer and can ignite spontaneously after leaving the open flame.

6. ​​Aluminum and copper are commonly used for wire cores, and the color becomes darker and lighter. It means to look at the color of the core, the color of inferior thread is gray and without metallic luster.

7, finely measure the inner diameter and outer diameter, and look at the pine when weighing. It means that if it is not determined by the above 6 methods, the outer diameter and core diameter of the insulated wire can also be measured. The allowable error is ±10%. If the measured value exceeds the allowable error, it is basically a low-quality insulated wire.