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
PVC and XLPE
What are the measures to speed up cable fault repair?
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.
What is the reason for the problem of high voltage cable?
ACSR Cable is the bridge between power supply equipment and electrical equipment, which plays the role of transmitting electric energy. It is widely used, so faults often occur. The following briefly analyzes the causes of common problems of YJV high-voltage cable. According to the causes of faults, they are roughly divided into the following categories: Manufacturer’s manufacturing reasons, construction quality reasons, design reasons of design unit and external force damage.
1、 Reasons for construction quality there are many cases of high-voltage cable system failure caused by construction quality. The main reasons are as follows:
1. The site conditions are poor, the environment and process requirements of cables and joints are very high when they are manufactured in the factory, and the temperature, humidity and dust on the construction site are not easy to control.
2. During cable construction, small slip marks will inevitably be left on the insulation surface, and semi-conductive particles and sand particles on abrasive cloth may also be embedded in the insulation. In addition, moisture will be absorbed in the insulation due to insulation exposure in the air during joint construction, which will leave hidden dangers for long-term safe operation.
3. The installation did not strictly follow the process construction or the process regulations did not consider the possible problems.
4. DC withstand voltage test is adopted for completion acceptance, resulting in the formation of reverse electric field in the joint, resulting in insulation damage.
5. Due to poor sealing treatment. The intermediate joint must adopt the sealing structure of metal copper shell plus PE or PVC insulation and anti-corrosion coating, and the lead seal is dense during on-site construction, so as to effectively ensure the sealing and waterproof performance of the joint.
2、 The manufacturer’s manufacturing reasons are divided into cable body reasons, AAAC Cable joint reasons and cable grounding system reasons according to different parts.
1. Reasons for cable joint manufacturing high voltage cable joints used to be wrapped, molded, molded and other types, which requires a large amount of work to be made on site. Moreover, due to the limitations of on-site conditions and manufacturing process, there will inevitably be air gaps and impurities between insulating tape layers, so problems are easy to occur. The commonly used types in China are assembled type and prefabricated type. The cable joint is divided into cable terminal joint and cable intermediate joint. No matter what type of joint, the cable joint failure generally occurs at the fracture of cable insulation shield, because this is the part where the electrical stress is concentrated. The reasons for the cable joint failure due to manufacturing reasons include manufacturing defects of stress cone body, insulation filler problems, oil leakage of sealing ring and so on.
2. Cable grounding system cable grounding system includes cable grounding box, cable grounding protection box (with sheath protector), cable cross interconnection box, sheath protector, etc. The common problems are mainly due to the poor sealing of the box and the water inflow, resulting in multi-point grounding and excessive induced current of the metal sheath. In addition, unreasonable parameter selection or poor quality of sheath protector and unstable zinc oxide crystal are also easy to cause sheath protector damage.
3. The reasons for the manufacture of the cable body generally include insulation eccentricity, uneven insulation shield thickness, impurities in the insulation, protrusions in the internal and external shields, uneven crosslinking degree, cable moisture, poor sealing of the cable metal sheath, etc. some conditions are more serious, and faults may occur in the completion test or shortly after putting into operation, Most of them exist in the form of defects in the cable system, causing serious hidden dangers to the long-term safe operation of the ABC Cable.
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.
Introduction to the characteristics of btly flexible mineral insulated cable!
Btly is also called gn-al, ng-a and ng-a (btly)
Btly is a flexible mineral insulated cable with copper tube sheath replaced by aluminum tube sheath.
This product is the first in China and there is no prototype in the world. Compared with bttz series metal sheathed AAC Cable, the product can achieve continuous large length and multi-core cable within 240mm, which overcomes the disadvantage of too many joints. However, the product has complex structure, large outer diameter and weight, and its electrical performance is weaker than that of bttz, yttw and bbtrz cables. The fire resistance of aluminum protective sleeve is relatively weak, and it is prone to electrical corrosion. It is difficult to deal with the aluminum copper transition of the joint, and the requirements for the installation process capacity are still very high.
Basic product parameters
Conductor: round copper stranded wire (softer than solid copper rod of BTT).
Insulation: pure phlogopite tape (no longer composed of extruded insulating material, so as to eliminate the generation of carbon particles and improve the electrical stability).
Filling layer: dense filling with mineral compounds.
Sheath: aluminum soft sheath is adopted.
Refractory layer: it is covered with non fusible, non combustible and expandable flame retardant inorganic matter Mg (OH) or Al (OH)).
Outer sheath: low smoke halogen-free or better plastic material.
Metal sleeve: continuously extruded aluminum metal pipe (greatly simplifying bttz copper pipe drawing process)
Mineral insulated cable
Product executive standard
1. BS 6387:1994 performance requirements for ACSR Cables to maintain circuit integrity under flame conditions;
2. GB / t12706.1 extruded insulated power cables and accessories with rated voltage from 1KV (UM = 1.2KV) to 35kV (UM = 40.5kV);
3. Follow the corresponding enterprise standards.
Product use characteristics
Voltage level: 0.6/1kv, working voltage: light load 500V, heavy load 1000V.
Working environment: the long-term working temperature is 90 ℃.
Bending radius: minimum allowable bending radius ≥ 12D.
Btly flexible mineral insulated cable
Product features
1. The fire resistance standard can pass three tests of bs6387: no breakdown under 950 ℃ flame for 3h, water spray for 15min after 30min at 650 ℃ (direct immersion is also acceptable), knocking vibration for 15min under 950 ℃ flame without damage, so as to fully meet the BTT assessment standard in fire resistance performance.
2. The product can produce 1 ~ 37 cores in 1.5 ~ 6 square meters, 1 ~ 5 cores in 10 ~ 240 square meters and single cores in 300 ~ 630 square meters. The length can be delivered in a whole plate without joints according to the needs of users.
3. There is no need to wear another pipe during laying, and it has the same waterproof and anti impact functions as BTT.
4. It has good mouse, ant and radiation protection functions, which can ensure the stability, long service life and durability of the cable.
5. Low working temperature, small line loss, strong overload resistance, long service life and high safety. It is especially suitable for application in projects with environmental protection requirements
6. Explosion proof (the highly compacted insulating material in the AAAC Cable and the cable terminal installed with special sealing sleeve can prevent steam, gas and flame from entering the electrical equipment connected with the cable, so it is used in places with explosion risk and the connection of various explosion-proof equipment and equipment).
7. Corrosion resistance (the metal sheath of BTT (L) series mineral insulated cables has high corrosion resistance. For most devices, it does not need to take additional protective measures; Even where the metal sheath of the cable is vulnerable to chemical corrosion or serious industrial pollution, because the outermost layer of the cable is protected by the plastic outer sheath, it is still safe).
The world’s largest copper mine enters the countdown to strike
Union members of Escondida copper mine, the world’s largest copper mine in Chile, voted against the latest contract offer made by the mine owner and decided to go on strike. Many industries are worried that the global economy will continue to recover from the impact of the COVID-19 pandemic, which could lead to disruption in the supply of ABC Cables, a key metal.
Escondida copper mine is located in Atacama Desert in northern Chile. It is the largest copper mine in the world, and its output accounts for almost 5% of the total global copper supply. BHP Billiton currently manages the copper mine business and holds about 58% of the copper mine. Other investors include Rio Tinto and Mitsubishi Corp.
99.5% of union members reject BHP Billiton’s new contract
The union of Escondida copper mine said in a statement late Saturday that the union voted overwhelmingly against the new contract proposal of the mine owner (BHP Billiton). 2164 miners (about 99.5% of the total) rejected the proposal, and only 11 supported it.
The trade union said that the contract proposal did not include the terms previously required by the trade union: providing one-time bonuses for workers to maintain mine operations during the epidemic, performance-related remuneration and improved career development plans, and enabling workers’ children to enjoy the same educational benefits as those of supervisors.
BHP Billiton spokesman previously said in an e-mail statement on Friday that “the new offer proposed by the company improves the previous conditions and incorporates new benefits on issues that workers attach great importance to.” However, the trade union statement refuted that the so-called benefits in Escondida’s latest contract offer to the miners were actually based on extending working hours, increasing job requirements and other more demanding conditions for workers.
“We hope that this overwhelming vote will sound a decisive alarm and prompt BHP Billiton to start substantive negotiations to reach a satisfactory agreement – if they want to avoid the most costly long-term trade union conflict in Chile’s history,” the trade union statement said.
Historically, miners at Escondida copper mine also held a strike in 2017, which lasted for 44 days at that time.
Strike Countdown: last chance during government mediation
After the announcement of the AAC Cables of the union vote, BHP Billiton has said it will ask the government to intervene in mandatory mediation.
“The company’s interest is always to reach an agreement with employees, which is why we maintain an open dialogue and occupy all available space for this purpose,” the company said in a statement BHP Billiton did not comment on the Union’s specific request.
Analysts said that according to the local law of Chile, miners must continue to work during the government’s forced mediation, and the mediation period is up to 10 days. Therefore, although the strike has entered the countdown, it is not a certainty at present. In all walks of life, union voting to authorize strikes is often used as a negotiation strategy.
Eleni joannides, an analyst at wood Mackenzie, a commodity consulting firm, said before the union vote: “whether the market and prices will be significantly affected will depend on whether there will be a strike in about 10 days.” She also pointed out that “at current prices, Escondida’s negotiations seem to have affected the market.”
Will the strike push copper prices higher?
Copper is a key raw material for manufacturing wires and motors, and is widely used in many fields such as construction industry. Earlier this year, copper prices soared to a record high as the market expected that the global economy would continue to recover and the energy transformation would require a large amount of copper to produce electric vehicles and renewable energy.
Novel coronavirus pneumonia has been faced with severe challenges before mining operations. BHP Billiton said on July 20 that due to a number of epidemic prevention measures, the operation of several Chilean copper mines including Escondida has not been interrupted, but the number of employees has been reduced. The company reported that copper production at Escondida copper mine is expected to decline by 10% in the current fiscal year. BHP Billiton also said that due to the rising infection rate of the epidemic, the company is expected to face continuous operational challenges in Chile.
Although some analysts, including joannides, believe that the recent rise in copper prices has reflected people’s expectations of the interruption of mine operations, other analysts are still worried that the strike may push copper prices further to record highs. LME copper prices climbed to a six week high of $9924 last week after hitting an all-time high of $10747.50 in May.
Morgan Stanley said that the contract negotiation of Chilean copper mine is a key focus of short-term copper price trend. The bank said that although the copper market is expected to have surplus in 2022 due to output growth exceeding demand, the ACSR Cables will still face copper shortage this year.
Sabrin Chowdhury, an analyst at Fitch solutions in Singapore, also said that the strike risk of Escondida copper mine is driving up the short-term prospect of copper prices. Copper prices will also benefit from severe floods in Central China and the weakness of the US dollar.
Chowdhury pointed out, “whether the strike occurs or not, it will cause panic among investors, because copper stocks on the exchange have fallen sharply in recent weeks. The market is already tight, and the demand exceeds the supply that is trying to return to the pre epidemic level. If the strike does happen, copper prices will reach a new record high, higher than in May“
Causes and treatment of unqualified strand products
1. Scope of application
This specification is applicable to the stranding of copper aluminum strand, steel cored aluminum strand and power ABC Cable conductor core.
2. Equipment parameters
2.1 equipment name: jlk-500 / 12 + 18 + 24 frame stranding machine
2.2 equipment capacity (technical parameters)
a. Single wire diameter: 1.5 ~ 5mm (copper) 1.8 ~ 5mm (aluminum)
b. Maximum stranded outer diameter: 45 mm
c. Maximum traction speed: 69m / min
d. Maximum speed of frame: 12 discs R / min 173m
18 discs R / min 152 M
24 discs R / min 133 M
e. Equipment stranding pitch: 12 reels mm 56 ~ 962
18 disc mm 64 ～ 1095
24 disc mm 73 ~ 1245
f. Traction wheel diameter: φ 200 mm
g. Specification of pay off panel in frame: PND 500 mm
h. Specification of central pay off panel: pn800 ~ pn1600 mm
1. Specification of take-up reel: pn1250 ~ pn2500 mm
j. Main motor power kw: 75 (DC)
3. Preparation before production:
3.1 check whether all electromechanical equipment and transmission devices are normal, check the lubrication system, and apply pressure to the equipment according to the “oil standard”
Lubricating oil.
3.2 put the production tools and measuring tools (vernier caliper with accuracy of 0.02 mm and micrometer with accuracy of 0.01 mm) in a place convenient for use
A safe place and check whether the measuring tools are accurate.
3.3 according to the production plan, check whether the diameter of the single line is consistent with the process, and whether the single line is bruised, scratched, oxidized, etc,
Unqualified single line shall not be used.
3.4 prepare pressing wheel, die and other molds according to process requirements.
3.5 the take-up reel shall be selected according to the outer diameter, manufacturing length and process requirements of the strand, and the quality of the take-up reel shall be checked. The deformation is serious
Burrs on the edge of the side plate shall not be used.
3.6 the successor must understand the variety, specification and quality of twisted products and make clear the responsibility.
4. Key points of operation
4.1 before start-up, carefully check the correctness of operating parts, the reliability of interlocking mechanism and reel jacking, and the locking mechanism can make
The reel must be tightened and locked reliably, and the fence protection of the whole machine shall be set in place to ensure safety.
4.2 no matter under any circumstances, observe the changes of current, AAC Cables, temperature and other parameters at all parts at any time
In addition, any large fluctuation is dangerous and should be stopped immediately for inspection. Start up after troubleshooting.
4.3 according to the production plan and process requirements, the winding and branching shall be arranged according to the specified structure. When hanging the coil, pay attention to the balance and correct swing of the coil
The setting out direction of the reel shall be the same as that of the reel in a frame. The top clamp shall be screwed first and then locked and fixed with interlocking device,
Prevent accidents. Adjust the tension to achieve basic consistency.
4.4 the single line shall not be scratched or scratched when passing through the single line through the threading hole. The single line must be evenly separated through the threading hole or distribution board
Cross each other.
4.5 when installing the die, it must be aligned with the center, and check whether the die quality is good. The surface of the inner hole of the die or the pressing wheel and the conductor
The surface contact part shall be smooth, otherwise it shall not be put into use.
4.6 adjust the pitch and rotation direction of each section according to the process requirements.
4.7 lead wire: tightly wound outside the steel wire rope with a single wire to form a whole. Then start pulling and guiding from the die base of disc 12
Then 12 coils and 24 coils, gradually add stranded wires outside the core wire, and wind at least 4 turns on the traction wheel according to the branching slot.
Stop the machine when the conductor head is led to the reel. Replace the reel, remove the conductor head, and wrap the head tightly with tape and wire,
Prevent looseness. Insert the head into the threading hole on the disc core / side plate, extend the head for at least 1m, and use homogeneous wire to thread the coil
Wrap the brace for several turns and fix it firmly.
4.8 after the stranding machine is adjusted, the process inspection must be carried out comprehensively again, including the structure, direction, pitch
Start up after the outer diameter and number of strands fully meet the process requirements.
4.9 during the production of sector conductors, the sector height shall be adjusted at a slow speed and the pressure roller height shall be adjusted at the same time. Static pressure adjustment is not allowed
Roll to prevent breakage caused by uneven deformation of single line.
4.10 start up after process adjustment. After the strand reaches the traction wheel, actually measure the process parameters, such as pitch, outer diameter
The sector is high, and each process parameter shall be subject to the actual measurement, and each process parameter shall be filled in the self inspection form.
4.11 during the normal operation of the machine, the operator shall not leave the post without authorization, and it is found that the equipment is abnormal and the product quality is affected
In case of any problem, stop the vehicle for inspection in time.
4.12 when stopping, turn off the power supply and stop slowly. Emergency stop is allowed under special circumstances.
4.13 if the single line is allowed to have joints, the joints shall meet the requirements of the process card.
5. Precautions and treatment methods
5.1 always observe whether the electromechanical equipment and various instruments are in normal state.
5.2 regularly check whether the outer diameter (or fan height) pitch of the product is consistent with the process requirements, and fill in the self inspection form with the inspection results; If not, stop the vehicle for inspection and start the vehicle after handling.
5.3 pay attention to the surface quality and structural dimension of the line during the replacement of specifications, joints, adjustment plates and normal start-up.
5.4 the sector height of the compacted wire core must be controlled within the range specified in the process documents. If the requirements are not met, the pressure shall be adjusted in time
Wheel.
5.5 the take-up reel shall meet the requirements of users and products.
5.6 the wiring arrangement shall be tight and tidy, and no pressing, disorder, scratch and other phenomena are allowed. The finished product line shall be full if the user has special requirements
Meet user requirements. The distance between the outermost layer and the edge of tooling side plate shall not be less than 50mm
5.7 the length of the downlead shall meet the user’s requirements or the conductor wiring length requirements. After each reel is completed, the process shall be filled in
The product circulation card shall indicate the workshop, machine, model, specification, length, number of sections, shift, production date and product manufacturing information
Kuang et al.
6. After shift work:
6.1 cut off the main power supply after the work is completed.
6.2 report the equipment operation, product quality, problems, product specification and length of the shift to the successor in detail
The handover is clear.
6.3 keep the production process records of the shift, sort out the waste, clean the equipment, sort out the tools and measuring tools, clean the working place and clean the equipment
Do not use the mold temporarily and hand it over to the mold warehouse for storage.
What are the effects of temperature on cable selection?
Whether our colleagues in electrical design or factory electrical maintenance can not open the topic of cable selection, we often see that the AAC Cable selection size of the same equipment under the same power will be different in the work, some may be less than one or two levels, and some friends may be confused by which right? Why do you choose different? Today we will learn how to choose the cable and how to consider it from? What is the effect of temperature on the selection of cables?
1、 Cable selection
(1) Select cable according to temperature rise
We all know that when the conductor passes through the load current, the temperature of the conductor will rise, the conductor has insulation layer, and the conductor temperature shall not exceed the maximum temperature allowed for a long time by the conductor insulation, and the conductor will be damaged after exceeding.
(2) According to mechanical strength
When laying, the conductor has a minimum section allowed according to the laying mode and the distance between the support point and the distance.
(3) Select according to economic conditions
That is, choose the most economical way.
(4) Select by line voltage drop
We all know that when the current passes through the conductor, the voltage drop will be generated in the line due to the existence of line impedance. If the voltage drop is too large, the voltage at the end of the line, that is, the load end is too low, which will cause the equipment to fail to work or affect the equipment life. Therefore, it is required that the voltage drop cannot be too large, so the cable section should be selected reasonably.
(5) Cable selection shall meet the requirements of load protection
When the circuit is in fault, the protective device should act according to the specified time, whether it can operate reliably or not has a great relationship with the cable section. Therefore, we should consider the requirements of reliable action when choosing the ACSR Cable.
(6) Select cable according to the requirements of thermal stability
In case of failure of cable or electrical equipment, the cable shall meet the requirements of thermal stability, and the size of cable section shall be considered in order to meet this requirement. The maximum cross section is the final result by combining the above conditions.
Difference between low voltage cable and medium voltage cable
There are many kinds of AAAC Cables. According to voltage, they can be divided into low-voltage cable, medium voltage cable and high-voltage cable. What we can often touch and use in our life are low-voltage cable and medium voltage cable. How can we distinguish them? Some people say it’s 1kV, others say it’s 10kV. How to distinguish between low voltage cable and medium voltage cable? Now let Dr. Bao popularize science for you.
1、 Voltage level
According to different voltage levels, cables are habitually divided into low voltage power cables (3KV and below), medium voltage power cables (6kV ~ 35kV), high voltage power cables (66kV ~ 220kV) and ultra-high voltage power cables (above 220kV).
2、 Application and laying
Low voltage cable
Low voltage cables are used to transmit and distribute electric energy, mainly used in urban underground power grid, outgoing lines of power stations, internal power consumption of industrial and mining enterprises, and power transmission under river and sea water; It has the characteristics of reliable operation, no pole, no occupation of the ground, no hindrance to the view, less external influence and so on. The common laying methods include direct buried laying, AAC Cable trench laying, tunnel laying and wall laying.
■ medium voltage cable
MV cables are mostly produced as part of power generation and distribution networks for many applications such as utilities, petrochemicals, transportation, wastewater treatment, food processing, commercial and industrial markets. The common laying methods are underground direct buried laying; Laying of protective pipe (steel pipe, plastic pipe, row pipe, etc.); Laying of cable structures (cable trench, tunnel or working shaft, etc.); Laying in other public facilities (public facilities such as roads, railway bridges, tunnels or underground shopping malls, wharves, trestle roads, etc.); Underwater laying, etc.
3、 Observe the appearance
■ insulating materials
Low voltage power cable insulation material can be: PVC, cross-linked polyethylene;
Medium voltage power cable insulation material: cross linked polyethylene.
■ number of cable cores
The number of low-voltage power cable core is divided into: 1, 2, 3, 4, 5 core, 3 + 1 core, 3 + 2 core, 4 + 1 core
The number of medium voltage power cable core is divided into: 1 core, 3 core (so this kind of cable is mainly used for trunk transmission, 3-phase balance).
Minimum specification
The minimum specification of low voltage power cable is 1.5mm ²；
Minimum specification of medium voltage power cable: 3.6/6kv: 10mm ², 6/6kV, 6/10kV：16mm ², 8.7/10kV, 8.7/15kV：25mm ², 12/20kV：35mm ², 18/30kV：50mm ²， 21/35 kV、26/35 kV: 50mm ²。
Color discrimination
Low voltage power cable cores are distinguished by different insulation colors, color lines or digital marks;
The core of medium voltage power cable shall be distinguished by ribbon.
Conductor structure
The conductor of low voltage power cable can be round non compact, round compact and irregular compact;
The conductor of medium voltage power cable must be round and tightly pressed（ At present, the medium and low voltage power cables produced by our company all adopt circular compact structure
Basic structure of cable
The basic structure of low voltage power cable is conductor + insulation + filling + wrapping + outer sheath;
The basic structure of medium voltage power cable is conductor + three-layer coextrusion (conductor shielding, insulation, insulation shielding) + copper tape shielding + filling + wrapping + outer sheath.
Low voltage cable and medium voltage cable have different uses due to different voltage levels, composition, structure, etc. when choosing, you can choose according to your own actual situation.
Operation and maintenance of protective layer protector
In order to reduce the induced overvoltage of the metal sheath of single core AAAC Cable lines of 110kV and above, a protective layer protector should be installed between the ungrounded end of the metal sheath and the earth.
In case of system trip or line lightning stroke, special patrol shall be conducted for cable sheath protector.
The valve plate of protective layer protector may be damaged during power frequency overvoltage. The damage degree of the valve plate is related to the overvoltage of the protective layer. If the valve plate is damaged, it should be replaced.
At present, zinc oxide sheath protector is widely used in high voltage ABC Cable lines, and its residual work ratio is 2.5 ~ 4.0. Insulation resistance monitoring should be carried out for sheath protector, which can usually be tested at 500V / min.
The cross transposition box should be cleaned once a year, and the underground transposition box should also be checked for ponding.
