wire and cable

Damaged ABC cable sheath may not be a quality problem

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In the severe cold in winter, many construction workers will find such a problem when laying and installing Aerial Bundled Cable: ABC cable products with good quality usually have some hardening of the wire body and peeling off of the insulation coating. In view of these phenomena, many construction workers think that the wire and cable products themselves have quality problems, but in fact, the insulation of the cable products is damaged or peeled off, which is not necessarily the product quality problem. Next, let’s take a look at the reasons and preventive measures for the damage and fall of the cable sheath.

  1. The cable sheath is damaged or peeled off, which may be caused by the cold weather in winter. The outer skin of wire and cable products is mostly ordinary plastic (PVC) or rubber. When they are in a sub-zero environment, they will become hard, especially in the north. In winter, the outdoor temperature is often below zero, and the surface temperature may be more Low, if the wire and cable product is placed outdoors or directly on the ground, the entire wire and cable product line will become hard and brittle, causing the outer skin to fall off and be damaged under a slight external force.
  2. Can (ABC) HD 626 S1 Standard sheath be used if it is damaged?
    Try not to use it. The reason is: the sheath of the cable plays a protective role. If the cable is used directly without the protection of the sheath, it will soon cause leakage. Therefore, try not to use the cable sheath if it is damaged or falling off. If you must use the cable, you need to Take some protective measures, such as: for outdoor cables, you need to use waterproof insulating tape first, and then use heat shrinkable tubing, just fine; if it is used for high-voltage lines, you need to deal with the damaged insulation skin, generally high-voltage Wrap a certain number of turns with tape to make it fully meet the 10KV high-voltage cable insulation requirements; for severely damaged cables with partial discharge phenomena, a section of the partially damaged high-voltage cable should be discarded, and it should be done in a partially damaged place. High pressure connector.
  3. Measures to prevent damage and fall off of the cable sheath in winter:
    (1) When the cable is shipped out of the factory, warm and protective measures are required, such as: use enclosed transportation tools to prevent the product from being directly exposed; padded the product with a layer of soft cushion, such as bedding or other soft foam. (2) Cable storage: When arriving at the destination or the construction site, the product supplier should send personnel to supervise to prevent rough operations when the product is unloaded; try to store the product indoors, and at the same time lay a place on the surface of the storage. Layer isolation layer, such as wood, bedding, foam, etc., to prevent the product from freezing and damp.(3) Cable laying: you should choose to work under the condition of warmer temperature in the middle and afternoon, or do some protection for the cable, especially when laying the cable through the pipe, make sure that the inside and outside of the pipe are smooth in advance, so as not to scratch the wires. .

Well, the above is the introduction about the “causes and preventive measures of cable sheath damage and shedding”, I hope everyone can understand.

Matters needing attention in the production of ACSR Cable

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1. Greasy dirt on the wire surface
Overhead ACSR cables used for overhead transmission lines are often questioned by customers or even returned due to surface quality problems. This phenomenon is mainly caused in the drawing process. The main reasons are as follows:
(1) The size of the finished wire drawing die is too large, the compression is relatively small, and the working area of ​​the wire drawing die is short, which is not enough to remove the oil on the surface of the wire;
(2) The temperature of the lubricating grease is too low, the viscosity is large, and it is not easy to play, causing the drawing oil to adhere to the surface of the aluminum wire;
(3) The thread rubbing felt at the exit of the finished mold is too dirty;
(4) When stranding the wire, the stranding machine body or the traction wheel is too dirty;
(5) There is too much water under the traction wheel.
For the above reasons, in order to avoid the generation of oil stains on the wire surface, select a suitable wire drawing die and adjust the temperature of the lubricating grease during wire drawing; frequently replace the wire rubbing felt, and keep the stranding equipment and mold clean and free of oil when stranding the wire.


2. The wire surface is scratched
Since there are sharp metal objects in the wire drawing equipment and  ACSR Cable drawing die or the wire stranding equipment and the wire stranding die, it is easy to cause surface scratches when the wire is drawn or the wires are stranded. This kind of defect firstly affects the surface quality of the wire, and secondly, corona occurs due to the unevenness of the conductor when the wire is running. Therefore, once the surface scratches are found, the cause should be investigated immediately from the equipment or mold.
3. Wire scratches
Continuous scratches on wires are the most common cause of corona, and corona is one of the most important causes of power loss in power systems. In order to avoid the occurrence of wire scratches, the following aspects should be controlled in production: firstly, consider the conductor itself. First, ensure that the aluminum rod is not damp. The aluminum rod is damp, causing aluminum chips to stay in the working area of ​​the drawing die hole, and the lubricating oil cannot be used. All enter the work area, resulting in the drawn aluminum wire is not round and not smooth. Second, ensure that the drawing oil is clean and free of moisture. In the process of drawing, the drawing oil is in a high temperature state when it enters the work area from the lubricating area. If it contains a certain amount of moisture, the lubricating oil will be diluted and the lubricating effect will be greatly reduced, resulting in wire scratches and aluminum wire breakage.


Secondly, from the perspective of production, the following issues should be paid attention to:
In the drawing process:
(1) Check whether the mold of the wire drawing machine is placed accurately;
(2) Check whether the drawing drum has a groove after friction, and whether there is a crimping phenomenon;
(3) Check whether the surface finish of the lubrication area of ​​the drawing die meets the requirements, and whether there is blockage by aluminum chips.
In the stranding process:
(1) Check the sensitivity of the top of the spool;
(2) Check whether the tension of the spool is uniform;
(3) Check whether the single wire is slightly crimped or the wire is uneven;
(4) Check whether the single wire is in the groove of the guide wheel during twisting.
4. Loose wires and serpentine bends
(1) Adjust the pay-off tension of the wire reel when twisting the wire. The tension depends on the accumulation of experience in normal work. Generally, experienced operators should be able to adjust the tension to the appropriate requirements;
(2) When selecting the parallel mode first, the diameter of the parallel mode is required to be 0.3-0.5mm smaller than the outer diameter of the stranded wire;
(3) Adjust the back-twisting device to make the single wire “S” before twisting, so as to eliminate the internal stress generated by the single wire during the twisting process;
(4) Minimize the number of stops during the stranding process. It is best to produce the same stranded wire at the same fixed speed to prevent uneven speeds or parking/driving.
(5) Check in advance to use the steel core for stranding to ensure that there is no looseness; when the wire is stranded, the steel core should maintain a sufficient constant pay-off tension.

What are the common installation methods of cable tray?

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Bridge, also known as cable bridge, is composed of support, tray, cover plate and installation accessories. In a computer room project, compared with expensive and high-tech hardware and software, the bridge is very insignificant and rarely paid attention to, but it is also an indispensable part of the whole wiring project. Today, let’s talk about the process and common installation methods of bridge during construction.

1、 Common installation methods of bridge:
1. Horizontal hoisting (lifting frame)
It is applicable to the hoisting of trough and tray bridges with width < = 100mm
2. Horizontal hoisting (cross arm)
It is applicable to the hoisting of trough and tray bridges with width > 100mm
When the width is less than 600mm, the through wire suspender shall be used
Width > = 600mm, use angle steel suspender
3. Horizontal wall (supporting arm)
It is applicable to the horizontal installation of bridge against the wall
4. Vertical wall (horse stool / word stand)
It is ACSR Cables to the vertical installation of bridge along the wall
2、 Installation and construction process of cable tray:
Installation process flow of cable tray
1. Positioning and setting out → embedded iron parts or expansion bolts → support, hanger and bracket installation → bridge installation → protective grounding installation
2. Determine the position from the beginning to the end according to the construction drawing, mark the direction along the drawing, find the horizontal, vertical and curved connection, snap lines or draw lines along the bridge direction on the walls, ceilings, floors, beams, plates, columns, etc., and draw the positions of supports, hoists and brackets with uniform span.


3. Embedded iron parts or expansion bolts
(1) The self-made processing of embedded iron parts shall not be less than 120mm × 80mm × 6mm, and the diameter of anchor round steel shall not be less than 10mm.
(2) Closely cooperate with the construction of civil structure, keep the plane of embedded iron parts close to the formwork, and fix the anchor round steel on the reinforcement in the structure by binding or welding; After the concrete formwork is removed, the plane of embedded iron parts is exposed, and the support, hanger or bracket shall be welded on it for fixation.
(3) Select the corresponding expansion bolt and drill bit according to the load borne by the support; After the bolts are embedded, the supports or hangers can be directly fixed on the metal expansion bolts with nuts and corresponding washers.
Bridge installation
1. When the length of steel cable tray in straight section exceeds 30m, and the length of aluminum alloy or FRP cable tray exceeds 15m, expansion joints shall be set, compensation devices shall be set at the crossing of expansion joints, and bridges with expansion joints can be used.
2. The bolts between the bridge and the support and the bolts of the bridge connecting plate are fastened without omission, and the nuts are located outside the bridge. When the aluminum alloy bridge and the steel support are fixed, there are mutual insulation and anti electrochemical corrosion measures, and asbestos pad can be used generally.
3. The cable tray laid in the shaft and crossing different fire zones shall be provided with fire isolation measures according to the design requirements. The ABC Cable tray laid in the electrical shaft can be fixed with angle steel
When the cable tray passes through the firewall and fire floor, fire isolation measures shall be taken to prevent the fire from spreading along the line; For the fire separation wall and plate, the opening shall be reserved in cooperation with the civil construction, and the edge protection angle steel shall be embedded at the opening. During construction, L50 shall be used according to the number of layers and cables laid × fifty × 5. The angle steel shall be used as the fixed frame, and the fixed cabinet shall be welded on the edge protection angle steel at the same time; The frame can also be installed in the wall and slab during masonry or concrete pouring in civil construction.


Grounding of bridge
When the design allows the use of bridge system to form grounding trunk circuit, the following requirements shall be met:
1. The metal cable conduit led in or out of the metal cable tray and its support must be reliably grounded (PE) or connected to neutral (pen), and must comply with the following specifications:
(1) The total length of metal cable tray and its support shall be connected with grounding (PE) or neutral (pen) trunk line at least 2 places, so that the whole tray is an electrical path.
(2) The two ends connected between non galvanized AAAC Cable trays shall be connected with copper core grounding wire, and the minimum allowable cross-sectional area of grounding wire shall not be less than 4mm2.
(3) The two ends of the connecting plate between galvanized cable trays may not cross the grounding wire, but the two ends of the connecting plate shall not be less than 2 connecting and fixing bolts with anti loose nuts or anti loose washers.
2. The connection resistance between the end of tray and ladder shall not be greater than 0.00033 Ω, and shall be tested with equipotential bonding tester (continuity meter) or micro Ω meter. The test shall be carried out on both sides of the connection point. The connection resistance at both ends of the whole bridge length shall not be greater than 0.5 Ω or determined by the design, otherwise the grounding point shall be added to meet the requirements. The coating shall be removed from the grounding hole, and the flat pad on one side of the bolt in contact with the coating shall use a special grounding washer with claw.
3. The expansion joint or soft connection shall be connected with braided copper wire. When another grounding main line is laid along the whole length of the bridge, the tray and ladder of each section (including non-linear section) shall be reliably connected with the grounding main line at least at a small point; Spring washers shall be installed at the connection of grounding parts to avoid loosening.

Harm and Countermeasures of wire joint heating

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The phenomenon of wire joint heating is generally manifested in that there is peculiar smell around the wire joint, which can be smelled. This is because the heat of wire joint makes the outer insulation layer smell; Secondly, the ACSR Cables joint is smoking, red, the outer insulation layer is black, fire, or even broken. What are its hazards, causes and countermeasures?

1. Harm
Hot wire connection will not only cause a lot of power loss, but also seriously affect the normal operation of electrical equipment. At least, the working current in the line will increase and the service life of electrical equipment will be shortened. At worst, it will suddenly interrupt the ongoing production, scientific research, medical surgery and other activities, and lead to fire and electric shock accidents, resulting in incalculable losses.

2. Cause
(1) The connector is not tightened during equipment installation and repair. When the current passes through, it may generate heat, even redness, smoke, fire and disconnection. ABC Cables, switches and electrical appliances are connected through wire posts. Due to careless construction, no washer is added on the terminal post and the Gong cap is not tightened, which will also increase the contact resistance. For example, in a hotel, because of this reason, the conductor heated and melted, and the molten beads fell on the cardboard box below, causing a fire.
(2) The connector will also loosen after long-term operation. Some joints are of good quality during installation, but they will become loose due to thermal expansion and cold contraction or long-term vibration. For example, for copper aluminum joints in long-term operation, if there is no silver plating or tin hanging on the contact surface, the contact surface produces serious electrochemical corrosion and generates oxide film, which increases the resistance at the joint and is very easy to become a hot spot.

(3) For contacts with small current, the current increases suddenly due to the sudden change of the system, resulting in contact heating;
(4) In case of short circuit fault of the system, the over-current makes the contact with insufficient capacity or defective contact ignite instantly, etc.
Therefore, the contact heating is mainly caused by the increase of contact resistance.
3. Countermeasures
If the connector is well connected, the heating of the connector is prevented, and the heating problem of the AAAC Cable connector will not appear, so it does not need to be handled. Therefore, the wire joint shall be firm, tight and beautiful without overlap, bending, crack and concave convex; The mechanical strength of the joint shall not be less than 80% of the mechanical strength of the conductor; The insulation strength of the joint shall not be lower than that of the conductor. During installation and maintenance, the joints of wires shall be reduced as much as possible. Conductors with too many joints shall not be used. For joints of movable lines and outdoor lines, special attention shall be paid to the provision that only one joint is allowed between two adjacent wire stems.

What are the measures to speed up cable fault repair?

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The speed of cable fault repair directly affects the economic benefits and social image of cable operation Department, and it is also an important symbol to measure the comprehensive management level of AAC Cable operation Department. The repair of cable fault, from receiving the cable fault repair order, checking data, measuring faults, finding fault points, troubleshooting, repairing faults to restoring power transmission, requires the cooperation of all departments. In case of problems or delay in a certain department or construction link, the speed of cable fault repair will be affected. In order to speed up cable fault repair, the following measures are taken:
(1) establish an efficient fault emergency repair command system, and be responsible for commanding emergency repair and coordination of various departments. According to the number of AAAC Cable faults, a fault emergency repair command center or a fault emergency repair dispatching center can be set up.

(2) provide reliable and effective communication equipment to enable the command center to obtain the repair information in time, maintain smooth communication with the emergency repair site, and the material and logistics departments can understand the information of the emergency repair site in time.
(3) formulate a standardized emergency repair software package, and clarify the standard process of emergency repair and the work standards of each department.
(4) provide a skilled emergency repair team and establish a 24-hour emergency repair duty system.

(5) advanced and fast means of transportation shall be equipped. All departments undertaking ABC Cable fault repair shall be equipped with engineering rescue vehicles approved by the government traffic management department.
(6) provide sufficient and orderly accident spare parts and effective and fast means of transportation.
(7) make public commitments to the society and accept social supervision.
Note: in addition, due to the sharp increase in the scale of cables and channels, perfect basic information (especially channel location information and joint location information), experienced skilled personnel and effective fault finding equipment are also the key elements to speed up cable fault repair.

Harm of harmonics in power system

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1. Hazards to distribution transformer:
For the distribution transformer with the wiring group of yyno, during the three-phase four wire system wiring, the third harmonic current generates harmonic voltage in the original and auxiliary windings of the distribution transformer and causes the neutral point voltage to rise. In addition, because the odd harmonics have the same phase, their phasors on the neutral line are superimposed, so that the phasors of the zero sequence current on the neutral line are superimposed. Therefore, the medium linearity is heated due to the harmonic current.
During three-phase three wire connection, the ACSR Cable sequence harmonic forms the neutral point voltage due to the same phase, which changes the phase voltage.
For the distribution transformer with dyno wiring group, the zero sequence harmonic current forms a circulating current in the winding to heat the distribution transformer winding and reduce the service life of the distribution transformer.
2. Hazards to power cables:
Due to the high frequency rise of harmonic number and the larger cross-sectional area of cable conductor, the skin effect is more obvious, resulting in the increase of AC resistance of conductor and the reduction of allowable current of cable. In addition, the resistance of the cable and the inductive reactance of the line are connected in series with the system, and the capacitor for improving the power factor and the capacitive reactance of the line are connected in parallel with the system. A certain value shows that the inductance and capacitance may vibrate.
3. Hazards to power capacitors:
When there are harmonics in the power grid, when the capacitor is input, the terminal voltage increases, the current passing through the capacitor increases, and the loss power of the capacitor increases. The capacitive reactance of the capacitor is inversely proportional to the frequency. The higher the frequency, the smaller the impedance. Therefore, the harmonic voltage can greatly increase the current of the capacitor. If the allowable conditions of the capacitor are exceeded, the capacitor will be overcurrent and overload, resulting in abnormal heating. Especially when the capacitor is put into the power grid with distorted voltage, it may also aggravate the harmonic of the power grid, that is, harmonic expansion. Partial discharge is induced in the medium. Due to the large voltage change rate and high partial discharge intensity, it can accelerate the aging of the insulating medium, so as to shorten the service life of the capacitor（ http://www.diangon.com/ Copyright) generally speaking, for every 10% increase in voltage, the service life of the capacitor will be shortened by about 1 / 2. When the harmonic is matched with the parameters of the capacitor, it will produce resonance and make the harmonic square. When the harmonic is serious, it will cause bulging, breakdown, group explosion and greater loss of the capacitor.
4. Damage to incandescent lamps:
Incandescent bulb is a widely used lighting fixture. Its life is closely related to the thermal effect of harmonics. The AAC Cable of distortion coefficient shortens the life of bulb, and changing the fundamental voltage has a greater impact than changing the distortion coefficient.


5. Damage to motor:
The damage of harmonic to motor is mainly caused by additional loss, mechanical vibration, noise and harmonic overvoltage.
The distorted wave can increase the magnetic saturation of the motor core, especially the magnetic saturation of the core clamp winding, and reduce the fundamental short-circuit impedance. It is generally believed that the magnitude of the Nth harmonic current of the three-phase asynchronous motor can be calculated by the following formula:
6. Impact on electric energy meter:
(1) mechanical watt hour meter is an inductive mechanism. When measuring electric energy, it can be divided into the following three situations:
① The distorted wave power supply provides linear load. At this time, the electric energy meter measures the fundamental wave electric energy and some harmonic electric energy, which will deteriorate the performance of user equipment. In this way, users not only suffer from harmonic pollution, but also pay more electricity charges.
② The sine wave power supply supplies the nonlinear load. At this time, the electric energy meter measures the fundamental wave electric energy minus part of the harmonic electric energy. This shows that users pollute the power grid and pay less electricity bills.
③ The distorted wave power supply supplies nonlinear loads, which is more complicated. The fundamental current flows to the load, while the harmonic current is not necessarily. It may flow to the load or to the power supply, depending on the specific situation. The most direct method is to measure with an instrument.
⑵ the electronic watt hour meter uses an integral circuit, whether the power grid provides harmonic current to the load or negative current
The harmonic current provided by the load to the power grid will be integrated and measured together, which will cause measurement error.
7. Hazards to low voltage switchgear:
For the circuit breaker for power distribution, the full electromagnetic circuit breaker is easy to be affected by the harmonic current, which increases the iron consumption and generates heat. At the same time, it is difficult to trip due to the influence on the electromagnet and eddy current, and the higher the harmonic number, the greater the influence; The thermal magnetic circuit breaker generates heat due to the skin effect of conductor and the increase of iron consumption, resulting in the reduction of rated current and tripping current; For electronic circuit breakers, harmonics should also reduce their rated current, especially for electronic circuit breakers that detect peak values. AAAC Cable can be seen that the above three distribution circuit breakers may misoperate due to harmonics.
For the leakage circuit breaker, because the harmonic will affect the leakage current, the circuit breaker may be abnormally heated and misoperate or refuse to operate. For electromagnetic contactors, the harmonic current increases the temperature rise of magnet components, and the increase of coil temperature reduces the rated current. For the relay, the current should also be reduced due to the influence of harmonic current. They may cause misoperation during operation.
8. Interference to weak current system equipment:
For weak current equipment such as computer network, communication, cable TV, alarm and building automation, harmonics in power system are coupled to these systems through electromagnetic induction, electrostatic induction and conduction to produce interference. The coupling strength of electromagnetic induction and electrostatic induction is directly proportional to the interference frequency, and the conduction is coupled through the common grounding. A large amount of unbalanced current flows into the grounding electrode to interfere with the weak current system.
9. Impact on communication lines:
Generally, the working frequency of audio channel is about 200-400hz, and many harmonics of power supply system are within this frequency range. Because the power levels of power lines and communication lines are very different, the harmonics in the power supply system will cause perceptible, sometimes even unacceptable interference noise.
10. Impact on rectifier, inverter and logic control circuit:
Rectifier devices and thyristor circuits are widely used in various electrical equipment, ranging from rectifier and inverter devices for DC transmission, DC power supply for urban trams, to frequency conversion equipment, television, microcomputer, AC regulated power supply, battery charger and uninterruptible power supply (UPS), https://www.diangon.com/m234091.html On the one hand, these devices open and close different circuits according to a certain law, resulting in harmonic current injected into the power grid and become a harmonic source. On the other hand, the distorted waveform affects the normal operation of them and their loads. The distortion wave will cause the error of the control circuit, cause the ignition angular displacement, and the excessive current change rate and voltage change rate or overheating of the rectifier will cause equipment failure and damage to the rectifier components. These will bring harm to the converter. At the same time, the logic control circuit of some rectifier devices often leads to operation error due to distorted voltage.
11. Influence on fuse melt:
Overheating of the harmonic current in the melt will cause the displacement of its ampere second characteristic curve. Therefore, for the fault with low current, special attention should be paid to the selection of fuse to prevent accidental fusing and power failure, affecting the power supply.
12. Influence of harmonic skin effect:
The alternating current generates alternating magnetic flux through the conductor, and the alternating magnetic flux generates induced electromotive force with the conductor, so that the current density inside the conductor increases from the center to the outside along the conductor section, and the central current density is the smallest, which is commonly known as skin effect. Skin effect not only reduces the current carrying capacity of the conductor, but also increases the loss of the conductor, and this skin effect becomes more serious with the increase of current frequency. In general, the loss caused by skin effect is small at power frequency (50 Hz), while when the harmonic frequency is high, the loss and impact caused by skin effect such as harmonic with fifth harmonic frequency above 250 Hz are very significant. Therefore, the skin effect of harmonics should be considered when selecting conductors, and the conductor section should be increased appropriately.
13. Harmonics are also harmful to human body:
From the perspective of human physiology, when human cells are stimulated and excited, they will fluctuate rapidly or flip reversibly on the basis of cell membrane resting potential. If its frequency is close to the harmonic frequency, the electromagnetic radiation of power grid harmonic will directly affect human brain and heart.
Harm of harmonics to cables
As we all know, harmonic refers to the electric quantity whose frequency is an integral multiple of the fundamental wave contained in the current.
Generally, harmonic generation comes from three aspects: harmonic generation due to low quality of power generation, harmonic generation due to transmission and distribution system and harmonic generation due to electrical equipment. The third point is the main cause of harmonics, such as nonlinear loads, such as rectifier, switching power supply, UPS, frequency converter, inverter, etc. As shown in Figure 1, the harmonic generated by the equipment.

Figure 1 harmonics generated by equipment
The harmonics generated by the above three points have a serious impact on our electrical equipment. For the Xi’an Metro cable mentioned at the beginning of this article. Let’s focus on the harm of harmonics to cables.
Harmonic pollution will increase the dielectric loss, transmission loss, leakage current, temperature rise and partial discharge of dry-type cable, and increase the possibility of single-phase grounding fault.
Because the distributed capacitance of power cable can amplify the harmonic current, when the system load is low, the system voltage increases and the harmonic voltage increases accordingly. The higher the rated voltage level of the cable, the greater the risk of cable medium instability caused by harmonics, and the more prone to failure. As shown in Figure 2, it is cable combustion caused by harmonics.

Figure 2 cable combustion caused by harmonics
For the problem cables of Xi’an metro, the impact of harmonics will be more prominent. Unqualified cables and heating caused by harmonics are prone to accidents. This will be more serious in a relatively closed and crowded subway station. Of course, the problem with cable is not just about harmonics.
Therefore, for the safety of our transportation and other aspects, we should not only require from the transmission medium, but also check from the source of power quality. At this time, a device is needed to accurately capture and measure all parameters of power quality, and then analyze them to timely investigate possible potential safety hazards.

Take you to quickly understand the types of flame retardant cables

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Flame retardant wires and cables have unique flame retardant, low smoke emission and harmful smoke suppression properties. What flame retardant properties should AAC Cable materials have?


Type and performance of flame retardant wire and cable
1. General flame retardant wires and cables
Generally, the insulating layer and protective sleeve of flame-retardant wires and cables are generally made of polymer materials containing halogen bulbs (or modified materials added with halogen bulb flame retardant), and polyethylene (PVC) materials are common. The general PVC epoxy resin has higher electrolytic strength, acid resistance, wear resistance and anti-aging properties. The quality and cheap price of the epoxy resin become the raw material of AAAC Cable material which is in great demand in China. However, when PVC burns, hydrogen chloride, carbon monoxide, carbon dioxide, all kinds of fatty hydrocarbons, effective chlorine chemicals and other harmful substances will be released.


2. Low smoke halogen-free flame retardant wire and cable
Low smoke halogen-free cable flame retardant wire and cable can add inorganic nickel hydroxide flame retardant such as aluminum chloride and aluminum hydroxide to the insulating layer and protective wire sleeve materials. The basic principle of flame retardant is the basic principle of condensation phase flame retardant: the water released by the decomposition reaction of aluminum chloride and aluminum hydroxide, at the same time, digest and absorb the heat, reduce the specific temperature of insulating layer and protective wire sleeve materials, and inhibit the dissolution and release of combustible gases. The converted hydroxide is also a fireproof material, which is covered on the surface of the material to improve the working ability of the insulating layer and protective wire sleeve to resist fire, and has the purpose of blocking gas and blocking combustion. Aluminum chloride and aluminum hydroxide are the advantages of flame retardant: no poison, no evaporation, high quality and low price, flame retardant and destructed opium. However, the compatibility with the epoxy resin of the base material is poor. When it is used as a flame retardant, it must be added a lot to achieve a certain flame retardant grade. In addition, it is easy to reduce the forming process performance and structural mechanical properties of the material.


3. Low smoke halogen-free flame retardant wire and cable
Thermosetting polyurethane elastomer materials are often used for the insulation layer and protective sleeve of low smoke halogen-free flame retardant wires and cables. The materials do not contain halogen elements such as fluorine, chlorine, bromine and iodine. Mercury, chromium, cadmium, lead and other heavy metal elements that cause great environmental pollution to the natural environment are removed in the manufacturing process. Acrylic resin is often used. The flame retardant principle of this kind of ABC Cable is the flame retardant principle of final break interchange. Final flame retardant refers to taking away part of the calorific value caused by the combustion of flame retardant materials, resulting in that the materials can not maintain the decomposition reaction temperature, so it can not continuously cause flammable gases, so the combustion will extinguish itself. For example, when the flame-retardant material is subjected to strong heat or burning, it can melt, and when the molten material drops, it can take away most of the calorific value, resulting in slow combustion, which is likely to stop combustion.

Pithy formula and interpretation of common cable selection

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In our daily sales, we may encounter customers asking about ACSR Cable selection in the process of maintenance and repair. As a cable salesman, choosing the right cable for customers is the top priority of this work.
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First, the actual power of the load should be considered, at the same time, the maximum current to be borne by the cable should be calculated, and then the appropriate cable should be selected. The following is the relevant contents sorted out by the editor in AAAC Cable treasure. I hope I can provide some help for my colleagues.

[doggerel]: five out of ten, two out of one hundred, fifty-three out of four, and 75% off for buried casing.
[explanation]: according to the total current required by the insulated conductor, when the total current is less than 10a, the cross-sectional area of the conductor per square millimeter can pass 5A current, if it is more than 100A, it can only pass 2A current per square millimeter, 4A current per square millimeter between 10 ~ 50A and 3a current per square millimeter between 50 ~ 100A. After this calculation, In case of buried or casing laying, the current value that can be passed shall be multiplied by 0.75.
The calculation method given above obtains the allowable current per square millimeter. The selection of the actual specific conductor section should be: first determine the current required by the electrical equipment (including rated current and appropriate margin), then compare the current range in the doggerel according to the required current value, and then the conductor section that should be selected can be obtained by “allowable current per square millimeter” belonging to the range at the required current value.


For example, the rated current of an electrical equipment is 20A. Considering a certain margin, the required current is determined to be 22a. Then, find out that the current range of 22a current in the above doggerel belongs to 10 ~ 50a, and the available current per square millimeter is 4a. Finally, divide 22a by 4a to obtain the conductor section s that should be selected as:
S = 22 / 4 = 5.5 (mm2). According to this value, the conductor with corresponding section can be selected. If the calculated sectional area is not in the conductor section specification series, a slightly larger conductor section can be selected.

Maintenance contents of cable channel

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1. Replace the damaged well cover, cover plate and protection plate, and complete the missing well cover, cover plate and protection plate.
2. Maintain the working shaft stop.
3. Clean up the water and debris in the passage.
4 stairs (ladder) for tunnel maintenance personnel entering and leaving the shaft

5. Maintain the ventilation, lighting, drainage and low voltage power supply system in the tunnel.
6. Maintain fire prevention and isolation facilities and fire fighting facilities in cable trench and tunnel.
7 prune and cut branches and vines with insufficient safety distance around AAAC Cable terminal tower (pole) and T-joint platform.
8 repair the grounding down lead with loose connection, poor grounding, corrosion and other defects.
9 replace the missing, faded and damaged stakes, warning signs and signs, and timely correct the inclined stakes, warning signs and signs.
10. Carry out anti-corrosion treatment for corroded cable support, and replace or repair the missing, damaged and severely corroded support parts.
11. Bailey frame, I-beam and other facilities can be used to protect the cable trench in operation, and the suspension and support protection shall be well done. When the suspension protection is carried out, the cable trench body or row pipe shall be protected as a whole, and direct suspension of bare cables is prohibited.


12. If the cable passage in the green belt or sidewalk is changed to slow lane or fast lane, it should be relocated. Before the relocation, the relevant parties should be required to take reinforcement measures according to the load-bearing road standard to protect the working shaft, drainage pipe and cable trench.
10.2.13 when there are excavators, cranes and other large machinery passing through the non load bearing AAC Cable channel, the relevant parties shall be required to take protective measures such as setting steel plates above, and the protective measures shall prevent noise from disturbing the residents.
10.2.14 if the elevation of the working shaft or trench body is inconsistent with the surrounding due to the change of the environment of the cable passage, the elevation of the working shaft or trench body shall be adjusted by prefabricated shaft or cast-in-place method.

What are the cable maintenance items?

by

1. Manhole and drainage pipe
(1) water samples were taken for chemical analysis.
(2) remove the water in the well and remove the sludge.
(3) paint the iron parts such as cable bracket and hook.

(4) check the well cover and ventilation, and check the well body for settlement and cracks.
(5) dredge the spare pipe hole.

(6) check the condition of ACSR Cables and joints in the manhole to see if there is any oil leakage, whether the insulation gasket on the bracket is in good condition and whether the grounding is good.
(7) check the circuit name plate.
(8) check whether there is electric erosion, and measure the potential and current distribution of cables in the manhole.
2. Cable trench and tunnel
(1) check whether the door lock is normal and whether the access is smooth.
(2) check whether there is water seepage and ponding in the tunnel, remove the ponding and repair the leakage.

(3) check whether the ABC Cable bracket falls.
(4) check whether the insulation gasket between the metal sheath of the cable and connector and the bracket is intact, and whether there is any damage on the bracket; Whether the bracket has fallen off.
(5) check whether the fireproof tape, coating, blocking material and fireproof box are in good condition, whether the fireproof equipment and ventilation equipment are perfect and normal, and record the room temperature.

(6) check whether the grounding condition is good, and measure the grounding resistance if necessary.

(7) clean cable trench and tunnel.
(8) check the cable and cable joint for oil leakage.
(9) check cable tunnel lighting.