1. What kinds of wires and cables are commonly used?
Answer: it can be divided into bare wire, insulated wire, heat-resistant wire, shielded wire, power cable, control cable, communication cable, RF cable, etc.
2. What are the kinds of insulated wires?
Answer: there are several kinds of insulated wires: PVC insulated wires, PVC insulated flexible wires, NBR PVC mixed insulated flexible wires, rubber insulated wires, agricultural underground directly buried aluminum core plastic insulated wires, rubber insulated cotton yarn textile flexible wires, PVC insulated nylon sheathed wires, PVC insulated flexible wires for power and lighting.
3. Where is the cable tray suitable for?
Answer: cable bridge is suitable for general industrial and mining enterprises to lay power cables and control cables indoor and outdoor overhead, and can also be used for Telecom, radio and television departments to set up indoor and outdoor.
4. What are the cable accessories?
A: common electrical accessories are cable terminal box, cable intermediate junction box, connecting pipe and terminal, steel plate wiring slot, cable bridge, etc.
5. What is cable intermediate joint?
Answer: the device that connects the cable with the conductor, insulation shield and protective layer of the cable to connect the cable line is called the cable intermediate joint.
6. What regulations should be followed when selecting the section of power cable?
Answer: the selection of power cables should follow the following principles:
1) The rated voltage of the cable shall be greater than or equal to the rated voltage of the power supply system at the installation point;
2) The continuous allowable current of the cable shall be equal to or greater than the maximum continuous current of the power supply load;
3) The cross section of the core shall meet the stability requirements of the power supply system in case of short circuit;
4) Check whether the voltage drop meets the requirements according to the cable length;
5) The minimum short circuit current at the end of the line shall enable the protection device to operate reliably.
8. What are the biggest features and advantages of the following accessories for heat shrinkable cable head?
Answer: the biggest characteristic of heat shrinkable accessories is that the stress tube is used to replace the traditional stress cone. It not only simplifies the construction process, but also reduces the size of the joint terminal. It is easy to install, time-saving, labor-saving, superior performance and metal saving. The heat shrinkable cable accessories have the advantages of pouring type and dry wrapping type.
9. What inspection work should be carried out before cable laying?
A: the inspection work includes:
1) The support shall be complete and the paint shall be complete.
2) The cable model, voltage and specification meet the design.
3) The cable insulation is good, when there is doubt about the sealing of oil paper cable, it should be judged that it is affected by damp; the direct buried cable and small bottom cable should not pass the DC withstand voltage test; the oil sample of oil filled cable should be qualified.
4) The oil pressure of oil filled cable should not be lower than 1.47mpa.
10. When there is doubt about the sealing of oil paper insulated power cable, how to check whether the cable insulation paper is affected by damp by simple method?
Answer: check the cable insulation paper or put it in cable oil at about 150 degrees. No "hissing" or white foam appears, indicating that it is not damp.
11. What should be indicated on cable signs? What are the writing requirements?
Answer: the sign board should indicate the cable line design number, cable model, specification and starting point, and the cable used in parallel should have the sequence number. The writing should be clear and not easy to fall off.
12. What is the function of cable sheath?
Answer: protect the inner protective layer from mechanical damage and chemical corrosion, and enhance the mechanical strength.
13. What requirements should outdoor cable trench meet?
Answer: the upper part of the cable trench should be slightly higher than the ground, covered with a cover made of concrete. The cable should be laid flat on the support with good drainage pipe.
14. What is the function of cable inner sheath?
Answer: the insulation layer will not contact with water, air or other objects to prevent insulation from moisture and mechanical damage.
15. What is insulation strength?
Answer: in the electric field, when the electric field strength increases to a certain limit, it will be broken down. The electric field strength leading to insulation breakdown is called insulation strength.
16. What are the advantages of crosslinked heat shrinkable cable accessories?
A: This is a new type of material. Compared with other types of accessories now, it has the advantages of superior electrical performance, small volume, small weight, simple installation and material matching. In addition, it also has the ability of weather resistance, anti pollution, flame retardant and self extinguishing.
17. What are the main properties of insulating layer material of power cable?
Answer: it should have the following main performance:
1) High breakdown strength;
2) Low dielectric loss;
3) High insulation resistance;
4) Excellent discharge resistance;
5) It has certain flexibility and mechanical strength;
6) The insulation performance is stable for a long time.
18. What are the regulations on traction strength when laying cables mechanically?
Answer: for copper core cable, the allowable traction strength is 70N / cm when pulling the head; for aluminum core cable, the allowable traction strength is 40n / cm; if steel wire mesh is used for traction, the allowable strength of lead sheathed cable is 10N / cm; for lead sheathed cable, it is 40n / cm.
19. How to measure the outer diameter of cable sheath?
Answer: measure the outer diameter of the sheath and its average value at five points evenly distributed on the circumference of the sheath. The average outer diameter is the outer diameter of the sheath.
20. How to connect copper core cables with different cross sections?
Answer: copper core cables with different cross sections can be connected with open weak back copper connecting pipes by tin welding method, or copper pipes with different cross-section requirements can be connected with pure copper rods to form copper connecting pipes by crimping method.
21. The application of wires and cables can be divided into three categories:
1) Power system
The wire and cable products used in power system mainly include overhead bare wire, bus bar (bus), power cable (plastic cable, oil paper force cable (basically replaced by plastic power cable), rubber sheathed cable, overhead insulated cable), branch cable (replacing part of bus), electromagnetic wire and electric equipment wire and cable for power equipment.
2) Information transmission system
The wires and cables used in information transmission system mainly include local telephone cable, TV cable, electronic cable, RF cable, optical fiber cable, data cable, electromagnetic wire, power communication or other composite cables.
3) Mechanical equipment and instrument system
In addition to overhead bare wires, almost all other products are applied, but mainly power cables, electromagnetic wires, data cables, instrument cables, etc.
22. Wire and cable products are mainly divided into five categories:
1) Bare wires and bare conductor products
The main characteristics of this kind of products are: pure conductor metal, no insulation and sheath layer, such as steel reinforced aluminum stranded wire, copper aluminum bus bar, electric locomotive line, etc.; the processing technology is mainly pressure processing, such as smelting, calendering, drawing, stranding / pressing stranding, etc.; the products are mainly used in suburban, rural, user main line, switch cabinet, etc.
2) Power cable
The main features of this kind of products are: the insulation layer is extruded (wound) outside the conductor, such as overhead insulated cable, or several core stranded (corresponding to the phase line, neutral line and ground wire of power system), such as overhead insulated cable with more than two cores, or additional sheath layer, such as plastic / rubber sheathed wire and cable. The main process technologies include drawing, stranding, insulation extrusion (wrapping), cabling, armor, sheath extrusion, etc. the different process combinations of various products have certain differences.
Products are mainly used in power generation, distribution, transmission, transformation, power supply lines in the power transmission, through the current (dozens of a to several thousand a), high voltage (220 V to 500 kV and above).
3) Wires and cables for electrical equipment
The main characteristics of this kind of products are: various specifications, wide range of applications, and more use voltage of 1kV and below. In the face of special occasions, new products are constantly derived, such as fire-resistant cable, flame retardant cable, low smoke and halogen-free / low smoke and low halogen cable, termite proof, rat proof cable, oil / cold resistant / temperature resistant / wear-resistant cable, medical / agricultural / mining cable, thin-wall wire, etc.
4) Communication cable and optical fiber
With the rapid development of communication industry in the past 20 years, the product also has an amazing development speed. From the simple telephone and telegraph cable in the past, it has developed to thousands of pairs of voice cable, coaxial cable, optical cable, data cable, and even combined communication cable.
This kind of product structure size is usually small and uniform, and the manufacturing precision is high.
5) Electromagnetic wire (winding wire)
It is mainly used in various motors, instruments and meters.
Wire and cable derivatives / new products:
The derivative / new products of wire and cable are mainly produced by adopting new materials, special materials, changing product structure, improving process requirements, or combining different varieties of products due to different application occasions, application requirements, convenience of equipment and requirements for reducing equipment cost.
Different materials are used, such as flame retardant cable, LSZH / LSZH cable, termite proof cable, mouse proof cable, oil / cold / temperature resistant cable, etc;
Change product structure, such as: fire resistant cable, etc;
Improve process requirements, such as: medical cable, etc;
Combined products such as OPGW, etc;
It is convenient to install and reduce equipment cost, such as prefabricated branch cable.
23. List the cable racks you are familiar with.
Answer: tailor welded E-frame, fabricated E-frame, bridge cable rack, cable bracket, hook type bracket, single cable support, etc.
24. What requirements should be met for cable laying?
A: the following requirements should be met:
1) In terms of safe operation, all kinds of external damage should be avoided as far as possible to improve the power supply reliability of cable lines;
2) In terms of economy, we should consider the least investment;
3) In terms of construction, the route of cable line must be convenient for construction and maintenance after commissioning.
25. What are the insulation materials for making cable terminal or intermediate joint?
Answer: there are insulating glue, insulating tape, insulating pipe, insulating gloves, insulating resin, etc.
26. What are the requirements for the arrangement of cables?
1) Power cable and control cable shall not be arranged on the same layer of support.
2) High and low voltage cables, strong and weak current control cables shall be arranged in layers according to the required sequence. Generally speaking, they should be arranged from top to bottom. However, when high-voltage cables above 35kV are introduced into the cabinet panel, they can be configured from the bottom to meet the bending radius.
27. What are the common equipment for cable laying?
1) Air compressor, mainly used to destroy the road surface, for the future cable laying preparation;
2) Electric winch or cable traction machine, mainly used to drag cables;
3) Cable conveyor, with the use of tractor to overcome the huge friction, reduce the damage to the cable;
4) Cable reel setting out support;
5) Roller device;
6) Anti twist, reduce the twist of wire rope;
7) Cable reel brake device;
28. According to the different insulation and protective layer, which types of low-voltage power cables can be divided into?
A: the categories include:
1) Oil impregnated paper insulated lead (or aluminum clad) power cables;
2) Non dripping oil impregnated paper insulated power cable;
3) PVC insulated PVC sheathed power cable;
4) XLPE insulated PE sheathed power cable;
5) XLPE insulated PVC sheathed power cable;
6) Rubber insulated power cable.
29. What are the types of commonly used insulating materials? For example?
1) Inorganic insulating materials: Mica, asbestos, marble, porcelain, glass, etc;
2) Organic insulation materials: resin, rubber, paper, hemp, cotton yarn, etc;
3) Mixed insulating material: a kind of insulating material formed by processing the above insulating materials.
30. How many cable laying methods are there?
A: there are the following:
1) Buried directly in the ground;
2) Installed in cable trench;
3) Installed in underground tunnels;
4) Installed on the internal wall or ceiling of the building;
5) It is installed on the bridge;
6) It is laid in the row pipe;
7) Laid under water.
31. What is cable fault? How many common types are there?
Answer: cable fault refers to the cable insulation breakdown during preventive test or the power failure of cable line caused by insulation breakdown and wire burning during operation. The common faults include ground fault, short circuit fault, broken wire fault, flashover fault and mixed fault.
32. Where are the inner and outer shielding layers of power cables? What materials are used? What's the effect?
Answer: in order to make the insulation layer and cable conductor have better contact, and eliminate the increase of electric field intensity caused by the unsmooth surface of conductor, the inner shielding layer of metallized paper or semiconductor paper tape is generally wrapped on the surface of conductor. In order to make the insulation layer and the metal sheath have good contact, the outer layer of the insulation layer is generally covered with an outer shielding layer. The material of outer screen layer is the same as that of inner screen layer, and sometimes copper tape or braided copper ribbon is also tied outside.
33.What are the advantages of power cable compared with overhead line?
1) Reliable operation, because it is installed in the underground and other hidden places, it is less damaged by external force, has less chance of failure, and the power supply is safe and will not cause harm to people;
2) The maintenance workload is small and frequent inspection is not required;
3) No tower is needed;
4) It helps to improve the power factor.
34. What main stranding machine for cable&Wire?
Tubular stranding machine
Planetary stranding machine
Cable laying up machine
Bow Twister laying up machine
Rigid stranding machine
Cable extrusion line machine
Planetary steel wire amouring machine
SZ stranding machine
Cable screening machine