Precautions for household wire installation

In home decoration, circuit engineering is the most important, and home circuit belongs to concealed engineering, which is related to people’s quality of life and living standard in the future. Therefore, we must pay attention to circuit problems in decoration to avoid potential safety hazards. Next, Guoyou AAC Cable will share the relevant knowledge of family wire laying to protect the safety of family electricity.

1、 Flame retardant wires shall be selected
In modern families, there are too many household appliances and heavy wire load, which is easy to cause fire accidents. In these aspects, flame retardant wires can meet the power demand of families. At the same time, in case of fire hazard, flame retardant wires can effectively control the spread speed of fire, avoid greater losses caused by the fire of combustibles around wires, and strive for more time for people to evacuate from the fire site to minimize the loss of fire injury.

2、 Use wires of different colors
Color classification shall be done well when laying family lines, and it is more convenient for later maintenance. According to national regulations, red, yellow and green represent live wire, light blue is used for zero wire, and yellow and green are used for ground wire. In future maintenance, electricians can distinguish live wire and zero wire through the color of wires, which is convenient for construction and is also very important for household electricity.
3、 Wire laying and pipe sleeve
According to the ACSR Cables laying regulations, the wire must be protected by insulating sleeve during the laying process, and the joint shall not be exposed. Some irresponsible construction teams will directly bury the wires in the wall without casing protection. This treatment leads to the exposed wire joints, which are easy to be damaged by external forces, so as to reduce the service life of the wires and bury potential safety hazards for people’s life.

Unqualified ABC Cables laying will not only affect our use, but also directly affect our life safety. Choosing a high-quality wire product can reduce the risk from the source. Guoyou high-end wire has excellent performance in high temperature resistance, moisture resistance, durability, energy saving and environmental protection, which is different from ordinary household wires, With professional environmental protection and flame retardancy, consumers are more safe and assured to use. The above is the relevant knowledge of family wire laying. I hope it will be helpful to you

Current situation of power cable and accessories

Power cables and accessories are the key products used for transmission and distribution of electric energy in the main line and distribution network line of power system, mainly including AC power cables and accessories with rated voltage U0 / u 0.6/1kv ~ 290 / kV. Among them, the rated voltage of 1.8/3kv and below is low-voltage power cable, 3.6/6kv ~ 26 / 35kV is medium voltage power cable, 66kV ~ 110kV is high-voltage power cable, and 220kV and above is ultra-high voltage AAC Cable. In recent years, China has promoted the development and application of flexible DC cables, including DC power cables and accessories of various voltage levels within the rated voltage uo10kv ~ 525kv.

Power cables are basically distinguished according to the types of insulating materials. Extruded solid insulated power cables represented by XLPE insulation materials have been widely used. At the same time, there are a small number of oil immersed paper insulated (hereinafter referred to as “Mi cable”) power cables and oil filled (hereinafter referred to as “of cable”) insulated power cables“ During the 13th Five Year Plan period, superconducting power cables and Gil gas insulated lines have also been continuously developed and applied in engineering. PP (polypropylene) thermoplastic insulation material with environmental protection characteristics is known as a new type of ACAR  Cable, which is being developed and applied in engineering demonstration in China.
Power cables are divided into land cables and submarine cables according to use scenarios. In recent years, submarine cables have been rapidly developed and widely used, especially the development of offshore renewable energy (wind power generation), which promotes a large demand for submarine cables.
6kV and above power cables need to be equipped with cable accessories of corresponding voltage level. Cable accessories include terminals and intermediate joints, including wrapping, molding, cold shrinkage, heat shrinkage, prefabrication, combination and other forms.

Power cables, whether land cables or submarine cables, whether AC cables or DC cables, are characterized by a wide range of voltage levels, from 1kV to 500kV. At present, the voltage level tends to be higher; Wide specification range, from 1.5 mm ² To 3500 mm ², At present, the conductor section tends to be larger. Power cable is not only widely used in distribution network, but also an important foundation and indispensable product of power transmission in backbone network (Note: concentrated in urban power supply system). With increasing transmission capacity, operation safety and reliability are becoming more and more important. People not only pay attention to the quality improvement and technical improvement of power cables and accessories, but also study the operation reliability of AAAC Cable system, including electrical factors, mechanical factors, temperature and environmental factors, as well as mutual integration and coordination; It also pays more attention to the economy and long-term operation of power cable system, including transmission capacity, loss, maintenance cost and rapid recovery ability in emergency. Therefore, the power cable system is facing the challenges of quality improvement, operation economy, reliability and durability, involving material innovation, structure innovation and manufacturing process innovation. Facing the new requirements of social progress, urban development and environmental coordination, the challenge of long-distance transmission underground cable with large capacity, low loss, convenient laying, operation and maintenance and intelligent control, as well as the development and application of marine resources and new energy, and the challenge of safe power transmission reliability in complex environments such as seabed.

In recent years, China’s cable industry has made great progress in the above fields, but there is also a lot of room for improvement, improvement and promotion. In the manufacturing field, the integration of fine management, informatization, equipment automation and digitization of power cable manufacturing to realize high-quality intelligent manufacturing and development is still on the road. In the application field, there is still a big gap between the construction of high-voltage, large capacity and long-distance underground and submarine transmission networks and the development and application of corresponding materials and high-end equipment and the technical level of advanced countries.

Simple repair method after cable line failure?

After the cable line breaks down (including the breakdown during preventive test), it must be repaired immediately to avoid a large amount of water invading and expanding the scope of damage.
The elimination of faults must be thorough and clean. Otherwise, although it can be used after repair, it will still cause faults in the future, resulting in repeated repair and greater losses.
to repair the fault, the damp part of the ACSR Cable must be removed, and the insulating agent or insulating layer must be checked for carbonization. This paper introduces several simple fault repair methods.

(1) single phase grounding of cable line (without tripping): the conductor damage caused by this kind of fault cable may be local. If it is a mechanical damage, only the AAC Cable insulation is damaged, the conductor is slightly singed, and the land near the fault point is relatively dry, it can generally be repaired locally. The cable core can not be sawed off, only the damaged part of the conductor can be treated smoothly, and the insulation can be wrapped and sealed.
(2) breakdown of cable joint in preventive test: because the voltage of preventive test is high and the insulation strength of the joint decreases gradually during operation, such faults often do not make the ACAR Cable subject to water intrusion. In this case, the connector can be disassembled to check whether the cable conductor is intact and whether the insulation is damp. Check 1 ~ 2 layers of insulating paper on the peelable surface of the oil paper cable, wash with hot oil, and completely remove the moisture if any.

(3) if the indoor cable terminal is broken down in the pre-test, it can also be disassembled and partially repaired. The process is similar to reinstallation, but requires moisture removal. Generally, there is some residual wire left at the terminal part, so the sheath can be appropriately cut for another section, and the operation is more convenient than dismantling the joint.

Is the zero line current greater than the live line?

In low-voltage distribution system, the current of zero line is smaller than that of live line. This is because when the three-phase load is balanced, the three-phase current is completely offset, and the zero line current is zero; However, when the AAC Cables consumption of three-phase load is unbalanced, the three-phase current cannot be completely offset, then the unbalanced current will return to the transformer through the zero line.
In three-phase four wire distribution system, the current of zero line is generally smaller than that of live line, which is the consensus of all people in the industry. However, more and more facts make people subvert this concept.
One day in class, a student called to ask me a question.
Some time ago, he received the installation of wall advertising lines in a building. All the advertising light boxes around the building are illuminated with fluorescent lamps, nearly 1200.
The power supply of the advertising light box is led from the distribution box by four wires (three 25 square meters and one 16 square meters), and 1200 fluorescent lamps are evenly distributed in three-phase lines.
After connection, the power on test is normal and the acceptance is passed. But after a while, it was found that the zero line was burnt out. At that time, I thought the zero line was too small, and then I replaced it with a 25 square one. ACSR Cables was like this for some time. Before long, the zero line burned out again.
The customer is very dissatisfied. If this problem is not solved again, he may not get the balance payment.
I calmed his emotions while thinking. According to my many years of experience, this situation is most likely due to excessive zero line current due to harmonics.
I asked him to measure the current of each wire, and finally measured it with a clamp meter. He was stunned!
The three-phase live line current is almost 90a per phase, but the zero line current reaches an amazing 158a.
In fact, the phenomenon of excessive zero line current is becoming more and more common. Why is there still current on the zero line when the three-phase power load is balanced, and the current reaches more than 150% of the phase line current?
This is caused by harmonics.
We all know that the alternating current we use now is sinusoidal alternating current with frequency of 50Hz.
The waveform of sinusoidal alternating current is as follows:

sinusoidal alternating current
When sinusoidal alternating current is mixed with higher frequency clutter, this is called harmonic.
The figure mixed with harmonics is as follows:

The picture is a sinusoidal alternating current waveform mixed with harmonics
In the above figure, red is our normal sinusoidal AC waveform, in which green and blue are harmonic waveform.
AC non sinusoidal signals can be decomposed into linear combinations of sinusoidal components of different frequencies. When the frequency of the sine wave component is the same as that of the original AC signal, it is called the fundamental wave. Harmonic, in a narrow sense, refers to the electric quantity whose frequency is an integral multiple of the fundamental wave contained in the current. Generally, it refers to the Fourier series decomposition of periodic non sinusoidal electric quantity, and the electric quantity generated by other currents greater than the fundamental wave frequency. Broadly speaking, since the effective component of AC power grid is a single frequency of power frequency, any component different from power frequency can be called harmonic. When the frequency of the sine wave component is a non integer multiple of the frequency of the original AC signal, it is called fractional harmonic, also known as fractional harmonic or interharmonic. For any compound periodic vibration function y (T), it is expressed by Fourier series decomposition: the first term is called mean or DC component, the second term is fundamental wave or basic vibration, the third term is called second harmonic, and so on, or the following harmonics are collectively referred to as higher harmonic.
Harmonic generation
When the current waveform of three-phase alternating current is sine wave, they differ by 120 ° and have the same amplitude. The result of vector superposition on the zero line is that the sum is zero.
However, if the current on the phase line is pulsed and the difference is 120 °. Then, the pulses superimposed on the middle line are staggered, so they cannot be offset, and the current of the zero line is superimposed.
Since most modern electrical equipment contain rectifier circuits, even if the three-phase load is balanced, there will be a large current on the zero line.
The harm of excessive zero line current is very serious, mainly due to two reasons,
First, the cross-sectional area of the zero line is not larger than that of the phase line. The current exceeding the phase line will inevitably cause the zero line to overheat and burn out;
Second, when the zero line is disconnected, because the three phases are not completely balanced, the voltage of each phase will be inconsistent and the three-phase equipment can not work normally. The ABC Cable of one phase with less power will rise; The voltage of one phase with more electricity will be reduced. Single phase equipment on one phase of voltage rise will be damaged; Single equipment on one phase with reduced voltage cannot work normally.

Why do low-voltage power cables use four cores?

The low-voltage power grid in urban residential areas generally adopts the three-phase four wire system. The four core cable used in the low-voltage power grid, except for the three-phase conductor, is called the neutral wire. It can pass through the unbalanced current of three-phase AC and has the function of protective grounding. Three core cable and one conductor cannot be used as neutral wire to connect to three-phase four wire low-voltage power grid, because in this case, part of the three-phase unbalanced current will pass through the armor of three-core ABC Cable, which will heat the armor layer and reduce the current carrying capacity of the cable.

The measured load data of low-voltage power grid in some sections show that the difference of three-phase load may be several times. Due to the unbalanced power load of household appliances and the different timing of household appliance load, the three-phase load is unbalanced, which is difficult for the power department to grasp and manage. At the beginning of the 20th century, in some low-voltage power grids in urban residential areas, accidents of ACSR Cable damage caused by neutral line overload occurred from time to time, especially the low-voltage cable insulated with polyvinyl chloride (PVC), sometimes even burning out the PVC insulation of the whole cable due to overheating. After analysis, the cause of the accident is that when the unbalanced current of the power grid is too large, the neutral line of the low-voltage cable is seriously overloaded due to too small section. Therefore, the power department requires cross-linked polyethylene as the insulation of low-voltage cables, and appropriately increase the cross-section of low-voltage cables. At the same time, the cable factory is required to produce four core low-voltage cables with equal cross-section. Under the condition of extremely unbalanced three-phase load, the cable neutral line can have sufficient ability to pass through unbalanced current.

3.5 number of power cable cores
3.5.1 when the neutral point of 1kV and below power supply is directly grounded, the number of cable cores of three-phase circuit shall comply with the following provisions:
1. When the protective conductor is connected with the exposed conductive part of the power receiving equipment for grounding, the following provisions shall be met:
1) For TN-C system, when the protective conductor and neutral conductor share the same conductor, 4-core cable shall be selected;
2) For TN-S system, when the protective conductor and neutral conductor are independent, 5-core cable should be selected; When the provisions of article 5.1.16 of this standard are met, it can also be composed of 4-core cable and another protective conductor laid close to the phase conductor;
3) When TN-S system is not equipped with neutral conductor or the circuit does not need neutral conductor to be led to the power receiving equipment, 4-core cable should be selected; When the provisions of article 5.1.16 of this standard are met, the 3-core cable can also be composed of another protective conductor laid close to the phase conductor.
2 for TT system, when the protective grounding of the exposed conductive part of the power receiving equipment is independent of the neutral point grounding of the power supply system, 4-core cable shall be selected; When the neutral conductor is not provided or the circuit does not need the neutral conductor to be led to the power receiving equipment, 3-core cable should be selected.
3 for TN system, when the exposed conductive parts of power receiving equipment are reliably connected to the public grounding grid distributed in the whole plant and station, 3-core cables should be selected for motors and other electrical equipment that are fixedly installed and do not need neutral conductors.
4 when the section of phase conductor is greater than 240mm2, single core cable can be selected, and the section of neutral conductor and protective conductor of its circuit shall comply with the provisions of articles 3.6.9 and 3.6.10 of this standard.
3.5.2 when the neutral point of 1kV and below power supply is directly grounded, the number of ACAR Cable cores of single-phase circuit shall comply with the following provisions:
1. When the protective conductor is connected with the exposed conductive part of the power receiving equipment for grounding, the following provisions shall be met:
1) For TN-C system, when the protective conductor and neutral conductor share the same conductor, 2-core cable shall be selected;

2) For TN-S system, when the protective conductor and neutral conductor are independent, 3-core cable should be selected; When the provisions of article 5.1.16 of this standard are met, it can also be composed of 2-core cable and another protective conductor laid close to the phase conductor.
2. For TT system, when the protective grounding of exposed conductive parts of power receiving equipment is independent of the neutral point grounding of power supply system, 2-core cable shall be selected.
3 for TN system, when the exposed conductive parts of power receiving equipment are reliably connected to the public grounding grid distributed in the whole plant and station, the fixed electrical equipment should use 2-core cable.
3.6 conductor section of power cable
3.6.9 when the neutral point of 1kV and below power supply is directly grounded, the section of cable neutral conductor or protective grounding neutral conductor of three-phase four wire system shall not be less than the minimum section required for continuous operation according to the maximum unbalanced current of the line; The circuit affected by harmonic current shall comply with the following provisions:
1. For the circuit with gas discharge lamp as the main load, the neutral conductor section shall not be less than the phase conductor section.
2 when there is high-order harmonic current, the current of neutral conductor shall be calculated and the effect of harmonic current shall be included. When the neutral conductor current is greater than the phase conductor current, the cable phase conductor section shall be selected according to the neutral conductor current. When there is harmonic current in the three-phase balance system, and the materials of neutral conductor and phase conductor in 4-core or 5-core cable are the same and the section is the same, the reduction coefficient of cable ampacity shall be determined according to the provisions of table 3.6.9.

Realize the “perspective” management of underground cables

Based on the underground cable informatization model developed by China Electric Power Research Institute, the “perspective” management of underground cables can significantly improve the design, construction, operation and maintenance and management level of underground ACAR Cable lines.

Firstly, this technology can make the route planning and design of underground cable engineering more reasonable. Using three-dimensional technology, technicians can check the underground ABC Cable project and the laying of surrounding pipelines at any time, carry out the calculation and analysis of electromagnetic environment, structural load and safe distance, so as to realize the safe, effective and rational utilization of underground space.
Secondly, the technology can guide accurate construction. Due to its concealment, the maintenance difficulty, cost and time of underground cable are greater than those of overhead transmission line, but the biggest difficulty is the accurate location of fault point. With the help of three-dimensional digitization and sensor technology, the operation of underground cable lines can be monitored in the remote control center, the fault can be monitored and warned in real time, the construction team can be guided to locate the fault quickly and accurately, avoid repeated ground excavation, save construction time, and ensure the safe use of electricity and normal life of residents.

Thirdly, the technology can realize cross departmental and cross professional data sharing and collaborative office. To ensure the construction and safe operation of a power cable project line, it requires the cooperation of multiple departments such as planning, design, construction, supervision, operation and maintenance and management, and the joint efforts of multiple professionals such as system, electrical, structure and survey. For departments and disciplines with upstream and downstream relations, the three-dimensional digital model can directly realize data sharing; For the work that needs to be completed through multi-party intelligent negotiation, three-dimensional visual discussion can be carried out based on the same underground cable information model to realize collaborative office, which is conducive to the improvement of project construction quality and efficiency.

At this stage, 3D digital technology has been applied in various fields of underground cable construction to varying degrees. However, to expand to the whole process of underground AAAC Cable line construction, go deep into the business needs of all parties and cross domain data sharing, we still need to continue to carry out in-depth research on digital application; Based on the established digital design system of power cable engineering, cetca will continue to explore the application research of the whole life cycle of underground cable engineering construction, so as to provide technical support for the construction of big data center of power transmission and transformation engineering.

Does the fireproof cable really not burn?

Fireproof cable has become an indispensable item in our daily life and production, followed by accidents caused by wires and cables, especially when wires and cables explode after combustion, it is easy to cause casualties. Every year, all kinds of wires and cables cause accidents. The fire accident continues. Most of the shells of ordinary wires and cables are plastic and rubber products. These materials will release a lot of smoke and toxic gases after the fire. Once the ABC Cable burns and explodes, it will also cause serious damage to the surrounding residents and environment.

Why do some cables catch fire or even explode? There are many reasons for AAAC Cable fires. Xiaobian summarized five common situations: short circuit, overload, breakdown, burning of cable head and external fire source. Generally, the insulation layer of the cable is damaged, resulting in cable short circuit. The outer sheath material will burn and severe heating will occur if the cable is overloaded for a long time. If the old cable is running at this time, it is easy to break the line and cause a fire.
Another very common reason is that the cable head is burned. If the surface of the cable head is wet or dirty, the ceramic sleeve of the cable head will break and the conductor is too small, which will cause arcing and fire, thus insulating the surface of the cable head and causing the conductor. Of course, another reason for the burning of the insulation layer is that the external fire source burns the cable, causing the cable to burn or even explode.
Therefore, in order to reduce the loss caused by cable burning, a fireproof cable is designed. Fireproof cable is a general term for the characteristics of flame retardant cable and fireproof cable. They all have certain flame retardancy, but many people can’t distinguish flame retardancy. The concept of cable and fireproof cable. In terms of its characteristics, fireproof cable can replace flame-retardant cable, but flame-retardant cable cannot replace fire-retardant cable. This is because they work differently.

The working principle of flame retardant cable is realized through the flame retardant effect of halogen, as well as halogen-free flame retardant cable. It uses precipitated water to reduce the temperature, but the working principle of fireproof cable is different from that of flame retardant cable. The material of fireproof cable contains a kind of mica material, which has high fire resistance and can be used normally in fire.
After understanding the working principles of the two, it can be seen that the flame-retardant cable is also afraid of fire, but due to the use of flame-retardant materials, it can stifle the fire in the communication base, and the flame-retardant cable is different. It has a fireproof layer structure. Normal operation can be maintained even in a fire, so in many cases, fireproof cables can be used instead of flame retardant cables.

Will flame retardant cables and fireproof cables not burn? Flame retardant ACAR Cables are highly nonflammable, with small combustion distance, and can be extinguished automatically after the fire source disappears, but the flame retardant cables themselves will still burn and cannot burn completely. Burning. Similarly, fireproof cables are the same and will burn. Flame retardant cables reduce the temperature through the flame retardant effect of special materials, and flame retardant cables rely on their unique flame retardant layer to ensure that they can work normally in fire. Therefore, flame retardant cables are better than flame. In some cases, flame retardant cables are used.

How to train cable line operators?

The operation of cable line is a highly professional work. The technical training of AAAC Cable operators should focus on cultivating various basic skills. The learning contents mainly include:
1) basic knowledge of electrical theory;
2) structure and characteristics of power cable;
3) cable laying and manufacturing methods of joints and terminals;
4) understand the cable line design, power system operation diagram and assembly drawing of joint process;
5) performance, processing and storage methods of various common insulating materials;
6) high altitude operation skills on poles and towers;
7) cable test technology;
8) be familiar with safety and quality management procedures and systems (including urban construction, public utilities, transportation and other relevant regulations);
9) computer and other related skills.
in addition to the necessary classroom explanation and on-site practice, these basic skills should be carried out in combination with the on-site conditions. Cable line operators must be trained in the above basic skills, have certain on-site work experience, and then learn the professional knowledge of ACSR Cable operation in order to be competent for the operation of cable line.

The above text is excerpted from the technical Q & A on power cable installation and operation)
[1] Shi Chuanqing, editor in chief. Q & A on power cable installation and operation technology. Beijing: China Electric Power Press, 2007
Requirements for technical training in DL / T 1253-2013 operation specification for power cable lines
7.8 technical training
7.8.1 cable operators shall receive special technical training and pass the examination before they can carry out various operation work, and post assessment shall be carried out at least once a year.
7.8.2 operators shall have the following basic knowledge and skills:
a) Relevant laws and regulations, systems, plans, standards, etc;
b) Basic theoretical knowledge of power cable line;
c) Drawing of cable route map;
d) Finding method of cable fault;
e) Cable test and live detection technology;
f) Various laying methods of ABC Cable lines;
g) Key points of process construction methods of various cable accessories;
h) Work at height on Tower:
i) State evaluation and state management requirements.

Relevant training discussion in the three-year action plan for improving the professional level of high voltage cable 2019-2021:
3. The contradiction between the high requirements for the whole process control of cables and the low level of personnel and equipment is becoming increasingly prominent
With the rapid growth of equipment scale and assets, the business volume of operation and maintenance, maintenance and engineering cooperation of cables and channels is growing rapidly. In order to ensure high reliability power supply of urban power grid, the requirements for the whole process control of high-voltage cables are becoming higher and higher. However, some cable professionals have insufficient skills in inspection, test, maintenance and project acceptance, lack of civil engineering and other professionals, insufficient equipment allocation for test and detection, and there is still a gap with the actual work requirements. At the same time, the training of professionals is still lack of the support of practical training system, and the talent training mode needs to be improved.

What are the advantages of overhead cables over underground cables?

(1) The power transmission is not easily affected by the surrounding environment and has high reliability.
(2) The insulation distance between wires is small, the land occupation is small, and there is no interference with radio waves.
(3) When laying underground, it does not occupy the ground and space, which is not only safe and reliable, but also not easy to expose the target.
Therefore, in densely populated urban areas, large factories, power plants, traffic congestion areas and power grid intersection areas require small floor area, safety and reliability, reduce the impact of power grid on transportation and urban construction, and generally use AAC Cable power supply; In severely polluted areas, cables are often used to improve the reliability of power transmission; For the river crossing and river crossing lines with large span, it is not suitable to erect overhead lines, or cables are also used to avoid the interference of overhead lines to ship navigation or radio; Some national defense and military projects use cables to avoid exposing targets; Some also use cables due to the needs of architectural beauty.
Whenever encountering stormy weather, the high-voltage lines exposed in the air will be affected, resulting in power failure, and the power grid staff will nonstop start to repair and maintain the “injured” power grid. Therefore, some people will ask: since it is easy to be damaged when erected in the air, why not “hide” them underground?

Because if all the high-voltage lines are buried underground, once there is a fault, the power grid staff should first apply for the formalities of digging the ground channel, then work overtime to dig the channel, check the fault section by section, and finally find the fault point before repair. The whole process is time-consuming and labor-consuming. So, is it more appropriate to lay the high-voltage line underground or in the air?


Underground cables: AAAC Cables need to be wrapped in expensive and thick insulating shells.
Overhead wire: high enough to expose the conductor.


Underground cable: difficulty in manufacturing, construction and maintenance.
Overhead wire: it can quickly find and solve faults.


Underground cable: if electric leakage occurs, it will spread around and cause accidents. Therefore, the voltage level will be limited when laying.
Overhead wire: the exposed wire can be erected in the air according to a certain safe distance, because the air is a natural insulating medium. In this way, it can not only reduce the consumption in transportation, but also reduce the risk of electric shock.

To sum up, overhead high-voltage lines have obvious advantages! Therefore, the use of overhead lines in remote mountainous areas has the advantages of fast construction and low cost. However, there is no space for building overhead lines in many parts of the city, so we can only go underground, which saves space and gives consideration to the beauty of the city.

Maintenance contents of cable channel

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.