75 common problems of wire and cable

1. What types of commonly used wires and cables are divided by purpose?

Answer: According to the purpose, it can be divided into bare wire, insulated wire, heat-resistant wire, shielded wire, power cable, control cable, Communication Cable, and radio frequency cable.

2. What are the types of insulated wires?

Answer: The common insulated wires are the following: PVC insulated wire, PVC insulated cord, nitrile PVC mixture insulated cord, rubber insulated wire, agricultural buried aluminum core plastic insulated wire, rubber insulated cotton yarn Textile cords, PVC insulated nylon sheathed wires, PVC insulated cords for power and lighting, etc.

3, cable bridge for what kind of occasion?

Answer: Cable trays are suitable for general laying of power cables and control cables for Indoor and Outdoor use by industrial and mining companies. They can also be used for indoor and outdoor installations in telecommunications, broadcasting and television departments.

What are the cable accessories?

Answer: The commonly used electrical accessories include cable terminal junction boxes, cable intermediate junction boxes, connecting pipes and terminals, steel wiring slots, and cable trays.

5, what is the cable middle connector?

Answer: The device that connects the cable with the cable conductor, insulation shield and protective layer to connect the cable circuit is called the cable intermediate connector.

6, what is the main electrical wiring?

Answer: The main electrical connection is the connection mode of the main electrical equipment and busbars in power plants and substations, including the main busbars and plant power systems according to certain functional requirements.

7. What rules should be followed when selecting the section of a power cable?

Answer: (1) The rated voltage of the cable should 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 should be equal to or greater than the maximum continuous current of the power supply load; (3) The cross section of the core must meet the short circuit of the power supply system. Time stability requirements; (4) Verify that the voltage drop meets the requirements based on the cable length; (5) The minimum short-circuit current at the end of the line should enable the protective device to operate reliably.

8. What are the advantages of cross-linked polyethylene cable and oil-paper cable?

Answer: (1) Easy to install, because it allows a small minimum bending radius and light weight; (2) Not subject to line drop restrictions; (3) Good thermal performance, allowing high operating temperature and large transmission capacity; (4) Cable accessories Simple, all dry structure; (5) Simple operation and maintenance, no oil leakage problem; (6) Low price; (7) High reliability and low failure rate; (8) Less manufacturing process, simple process, economic benefits Significant.

9. What are the requirements for the clamp of a fixed AC single-core cable? why?

A: The fixture should be composed of no iron to form a closed magnetic circuit. This is because when the cable core passes current, magnetic lines are generated around it. The magnetic force line is proportional to the size of the current through the core. If magnetic materials such as iron are used, according to Electromagnetic induction shows that eddy currents will be generated in the iron parts to cause the cables to heat up and even cause damage to the cables. Therefore, it is not allowed to use iron pieces as fixing fixtures for single-core AC cables.

10. What are the biggest features and advantages of the following heat shrinkable cable head accessories?

A: The most important feature of the heat shrinkable attachment is to replace the traditional stress cone with a stress tube. It not only simplifies the construction process, but also reduces the size of the terminal of the joint. It is easy to install, saves time and labor, has superior performance, and saves metal. The heat-shrinkable cable attachment is a combination of a pouring type and a dry bag type, which combines the advantages of both types of accessories.

11. What inspections should be performed before the cable is laid?

Answer: (1) The bracket should be complete and painted. (2) The cable model, voltage, and specifications meet the design. (3) The cable is well insulated. When there is doubt about the sealing of the oil-paper cable, it should be judged by moisture; the buried cable and the small-bottom cable should pass the DC voltage test and pass the test; the oil sample of the oil-filled cable should pass the test. (4) The oil pressure of the oil-filled cable should not be lower than 1.47 MPa.

12. When there is doubt about the oil-paper-insulated power cable seal, how to use a simpler method to check whether the cable insulation paper is damp?

A: Ignite or place the cable insulation paper 150

Check the cable oil at about 2°C, no “click” or white foam appears, indicating that it is not wet.

13. What should be indicated on the cable signboard? What are the requirements for writing?

Answer: The cable design number, cable type, specification and starting point should be indicated on the signboard. The serial cable should be used in parallel. Requires clear writing and easy to fall off.

14. Where should the orientation mark of the buried cable be located?

Answer: At both ends of the cable, the cable connectors at 50 to 100 meters in the straight line section change the direction of the cable at the corners.

15. To make yellow ribbons for cable joints, black glass lacquer tapes, and alkali-free glass ribbons, etc., how to handle the tide before construction?

Answer: (1) Constant temperature drying method: The insulating tape is rolled into a small roll with a diameter of 25 to 30 mm, placed in a constant temperature drying oven at 110 to 120°C for 4 to 5 hours, and then removed by cooling and placed in a dry sealed tube.

(2) Oil immersing and expelling tide method: Put a small coil of insulating tape into the cable oil at a constant temperature of 120-130°C, and keep a distance of 30mm from the bottom of the pot. After a certain period of time, the oil surface will no longer produce foam, then it will be taken out and stored. In tanks with cable oil, the oil level should exceed all enclosed objects and seal it.

16. What is the role of the cable sheath?

A: The inner sheath is protected from mechanical damage and chemical corrosion, enhancing mechanical strength.

17, outdoor cable ditch should meet what requirements?

Answer: The upper part of the cable trench should be slightly higher than the ground. Covers should be covered with concrete. The cable should be laid flat on the bracket and have a good drain.

18. What is the role of the sheath in the cable?

Answer: The insulation layer will not be in contact with water, air or other objects to prevent the insulation from moisture and the insulation layer from mechanical damage.

19, when using wire cutters should pay attention to what?

A: Before use, be sure to check the insulating handle insulation is intact, use wire cutters can not be cut over the specifications allow the metal wire, and the use of wire cutters instead of a hammer to beat the tool to avoid damage.

20, what is the dielectric strength?

A: In the electric field, when the electric field strength increases to a certain limit, the insulation material will be broken down. This electric field strength that causes insulation breakdown is called the insulation strength.

21, crosslinked heat shrinkable cable accessories What are the advantages?

A: This is a new type of material. Compared with other types of accessories nowadays, it has the advantages of superior electrical performance, small size, low quality, easy installation, and matching materials. It also has weather resistance, anti-fouling properties, flame-retardant self-extinguishing, etc. ability.

22. What is the role of the cable sheath?

A: The inner sheath is protected from mechanical damage and chemical corrosion, enhancing mechanical strength.

23, outdoor cable ditch should meet what requirements?

Answer: The upper part of the cable trench should be slightly higher than the ground. Covers should be covered with concrete. The cable should be laid flat on the bracket and have a good drain.

24. What is the role of the sheath in the cable?

Answer: The insulation layer will not be in contact with water, air or other objects to prevent the insulation from moisture and the insulation layer from mechanical damage.

25. What should I pay attention to when using wire cutters?

A: Before use, be sure to check the insulating handle insulation is intact, use wire cutters can not be cut over the specifications allow the metal wire, and the use of wire cutters instead of a hammer to beat the tool to avoid damage.

26. What are the considerations for selecting the section of the power cable?

A: The following aspects should be considered:

(1) The operating current allowed by the cable for a long period of time; (2) Thermal stability in the event of a short circuit; (3) The voltage drop on the line must not exceed the permissible operating range.

27. What are the requirements for the mechanical strength of the cable conductor connection point?

A: The mechanical strength of the connection point is generally lower than the tensile strength of the cable conductor itself. For the fixedly installed power cable, the tensile strength of the connection point is not lower than 60% of the tensile strength of the conductor itself.

28. What are the main properties of the insulation material of power cables?

A; should have the following main properties: (1) high breakdown strength; (2) low dielectric loss; (3) very high insulation resistance; (4) excellent resistance to discharge performance; (5) have a certain degree of softness Sex and mechanical strength; (6) Long-term stability of insulation properties.

29, mechanical laying cable, traction strength requirements?

A: For copper core cables, when pulling the head, the allowable traction strength is 70N/cm; for the aluminum core cable, when the head is pulled, the traction strength is allowed to be 40N/cm; if the wire mesh sleeve is used for traction, the lead protection Set cable allowable strength is 10N/cm;

Lead sheathed cable is 40N/cm.

30. What are the regulations for cable protection tubes?

Answer: (1) When the cable needs to wear a protective tube, the inner diameter of the pipe should not be less than 1.5 times the outer diameter of the cable, and the inner diameter of the concrete pipe, clay pipe, asbestos, cement pipe should not be less than 100mm; (2) The bending radius of the cable tube Should comply with the requirements of the bending radius of the cable to be penetrated; (3) Each pipe should not exceed three bends at most, and no more than two right-angle bends.

31, how to measure the outer diameter of the cable jacket?

A: At the five points evenly distributed around the jacket circumference, the jacket outer diameter and its average value are measured. The average outer diameter is the outer diameter of the jacket.

32, how to connect different sections of copper cable?

Answer: The copper cables with different cross-sections can be connected by using open weak copper back-ends and connected by soldering. Copper can also be connected by pure copper rods according to different cross-section requirements and connected by crimping.

33. What are the advantages of power cables and overhead lines?

Answer: (1) Operation is reliable. Because it is installed in a hidden place such as underground, it is damaged by external force, there is less chance of failure, and the power supply is safe. It will not cause any harm to the human body; (2) The workload of maintenance is small and does not need to be frequent. Inspection; (3) No erection of towers; (4) Helps increase power factor.

34. What are the indoor and outdoor prefabricated terminal installation steps?

Answer: (1) Place the cable in position, fix it, clean the surface according to the predetermined position, and remove the sheath with reference to the instruction manual. If special requirements are required, the length of the outer sheath stripping can be adjusted, and the copper strip and the outer sheath can be installed separately. 2 ground lines.

(2) From the outer jacket mouth up to take the required size, remove the excess cable, insert the heat shrinkable three-finger sleeve to the root of the three prongs and heat shrinkage from the middle, the upper part of the fingertips to measure the specified size (35kv to 350 ~ 380mm ). Remove the excess copper tape (retain 20mm), and then keep the semiconductor at a predetermined position, crimping the outlet terminal seal.

35. What check should be done after the bus device is completed?

Answer: The following inspections shall be carried out: (1) The processing, preparation and welding of metal components shall comply with the requirements; (2) The bolts, washers, and split pins of all parts shall be complete and reliable; (3) The preparation of busbars and the mounting brackets shall comply with The regulations stipulate that the electrical distance between phases and earth meets the requirements; (4) Porcelain pieces, iron pieces and gluing joints shall be complete, the oil-filled casing shall be free from oil seepage, and the oil level shall be normal; (5) The paint shall be complete, the correct color phase shall be obtained, and the grounding shall be good. .

36, cable bracket processing should meet the requirements?

Answer: (1) The steel should be straight, no obvious distortion, the blanking error should be in the range of 5mm, the incision should be no curling, burrs;

(2) The brackets should be firmly welded without any significant deformation. The vertical distance between the cross braces and the design deviation should not exceed 5 mm;

(3) The metal stent must be treated with anti-corrosion treatment. When it is located in hot and humid areas, salt, fog, and chemically corroded areas, it should be designed for special anti-corrosion treatment.

37. List your familiar cable racks.

A: Tailor-welded E-frames, assembled E-frames, bridged cable racks, cable trays, hook-type brackets, single cable brackets, etc.

38. What requirements should be fulfilled for laying cables?

Answer: The following requirements should be met:

(1) In terms of safe operation, all kinds of external damage should be avoided as much as possible, and the reliability of power supply for the cable line should be improved; (2) Economic considerations should be considered from the perspective of the least investment; (3) The construction of the cable route must be easy Work and maintenance after commissioning.

39, the production of cable terminations or intermediate joint insulation material which?

Answer: There are insulating adhesives, insulating tapes, insulating tubes, insulating gloves, and insulating resins.

40. Briefly describe the general operating procedures for cable head production.

Answer: (1) Preparation before production: Including ○1 reading installation instructions; ○2 viewing site; ○3 stock preparation; ○4 cable trial tide; ○5 pre-production testing. (2) Manufacturing process of joints: Including ○1 to cut off excess cable; ○2 Stripping of cable protective layer; ○3 Conductor connection; ○4 Winding insulation (or shrinking pipe); ○5 Installation of joint housing; ○6 Perfusion insulation Agent; ○ 7 sealing treatment.

(3) Post-production electrical testing.

41. What are the requirements for the processing of cable protection tubes?

Answer: (1) The nozzle should be free of burrs and sharp corners, and the nozzle should be made into a trumpet shape. (2) After the cable pipe is bent, there shall be no cracks and significant indentations. The degree of bending shall not be greater than 10% of the outside diameter of the pipe; the bending radius of the cable pipe shall not be less than the minimum allowable bending radius of the cable penetrated. . (3) The metal pipe shall be painted with anticorrosive paint or leaching on the exterior, and the galvanized pipe shall be painted with anticorrosive paint on the zinc layer.

42. What are the requirements for the arrangement of cables?

Answer: (1) Power cables and control cables should not be placed on the same floor support.

(2) For high and low voltage cables, the strong and weak electric control cables should be arranged hierarchically in order. The general situation should be from top to bottom, but when more than 35kv high voltage cables are introduced into the panel, the bend radius can be met from below. Configuration.

43. What are the common equipments for laying cables?

A: (1) Air compressors are mainly used to damage the road surface and prepare for laying cables later; (2) Electric winches or cable traction machines are mainly used to pull cables; (3) Cable conveyors are used with hauling machines. To overcome the great friction and to reduce the damage to the cable; (4) cable tray payout bracket; (5) roller device; (6) anti-snapping, reducing the occurrence of wire rope distortion; (7) cable drum brake device; (8 )Tonometer.

44. What are the requirements for the installation distance of the bracket in the cable trench?

A: The cable is fixed on the wall of the cable trench and the tunnel. When the horizontal device is installed, when the outer diameter of the cable is equal to or less than 50mm, one support should be added every 1m. The cable with an outer diameter larger than 50mm should be supported every 0.6m. The triangular single cable is fastened with a strap every 1m. When it is vertical, it is fixed every 1~1.5m.

45, how to deal with the power cable and control cable in the same bracket installation?

A: The power cables and control cables should not be laid in the same bracket. When there are few cables and the control cables and power cables are laid in the same bracket, separate partitions are used.

46, cable trench laying method is what?

Answer: The method of laying cables in cable trenches is similar to that of buried cables. In general, the pulleys can be placed in the trenches. After the application is completed, the cables are placed on the bottom of the trenches or brackets, and cable labels are tied on the cables.

47. How to install the grounding cable in the cable tunnel?

Answer: The whole length of the tunnel and ditch should be installed with a continuous grounding wire. The grounding wire should be connected to all the supports, and the two ends should be connected to the grounding electrode. The specifications of the ground wire should meet the design requirements. In addition to insulation requirements, cable lead packages and armored equipment shall all be connected to each other and to the grounding cable. The cable racks and grounding cables shall be painted with antirust paint or galvanized.

48. What are the requirements for fire blocking of cable holes?

Answer: For larger cable penetration holes, such as cables running through the floor, when using fire blocking materials to block, according to the actual situation, first apply four to six layers of fire protection coating on the cable surface, the length from the hole below 1.5m, and then Refractory materials are used to process the fireproof plugging material with certain strength. It is guaranteed to be solid after plugging and easy to replace and disassemble when replacing the cable. The plugging is dense and non-porous to effectively block the fire and block fire.

49, commonly used low-voltage power cables according to the different insulation and protection layer, which can be divided into several categories?

Answer: (1) Oil-impregnated paper insulated lead (or aluminum) power cable; (2) Non-dripping oil-impregnated paper-insulated power cable; (3) PVC insulated PVC sheathed power cable; (4) Cross-linked PVC insulated polyethylene sheathed power cable; (5) cross-linked PVC insulated PVC sheathed power cable; (6) rubber insulated power cable.

50, what are the categories of commonly used insulation materials? for example?

Answer: (1) Inorganic insulating materials: mica, asbestos, marble, porcelain, glass, etc.; (2) Organic insulating materials: resin, rubber, paper, hemp, cotton yarn, etc.; (3) mixed insulating material: using the above insulation The type of insulation material that is formed by the material processing.

51, in which case the use of pipe laying? What are the advantages?

A: The laying of pipes is generally used where they intersect with other buildings, roads or railways, and is sometimes used in areas where buildings are dense. The main advantage is that it occupies less space and can withstand large loads. The cables do not affect each other and are relatively safe.

52. What is the long-term allowable ampacity of the cable?

Answer: The long-term allowable ampacity of the cable refers to the current value when the cable conductor reaches the long-term allowable operating temperature after the heat is stabilized in the cable through the specified current.

53. What factors determine the long-term allowable ampacity of the cable?

Answer: (1) The long-term allowable operating temperature of the cable; (2) The thermal performance of the cable itself; (3) The condition of the cable device and the cooling conditions of the surrounding environment.

54. How to lay cables?

Answer: There are the following: (1) buried directly underground; (2) installed in a cable ditch; (3) installed in an underground tunnel; (4) installed on a building's internal wall or ceiling; (5) Installed on the bridge; (6) laid in the pipe; (7) laying on the bottom.

55, how to connect the cable pipe work?

Answer: When the cable pipe is connected, it must be connected with the buckle and the pipe joint. If welding is adopted, direct butt welding is not allowed. The joint should be covered with a thick pipe and then welded so as to prevent the welding slag from falling into the pipe.

56. When making cable heads, what are the requirements for twisting up and down the cable cores?

Answer: When pulling the core, the paper insulation must not be damaged. The bending radius of the core wire must not be less than 10 times that of the cable core. Special care must be taken in the production, so that the bent part of the core should be evenly subjected to force, otherwise the insulating paper can be easily damaged.

57, a brief description of the plastic cable heat shrinkage sealing method.

A: The heat shrink method is applicable to the sealing of middle and low pressure rubber and plastic cable joints and terminal heads. It can also be applied to non-dripping and viscous impregnated insulated cables. The cross-linked polyethylene type and silicone rubber type heat shrinkable tube that can be uniformly shrunk when heated. The tube is placed over a predetermined adhesive seal, and a hot melt adhesive is applied to the adhesive site. When heated to a certain temperature, the heat shrinkable tube shrinks, and the hot melt adhesive melts. After being naturally cooled, the tube is formed. Good seal seal.

58. What should you pay attention to when bending a cable protection tube with an electric bending machine?

Answer: (1) The bender should be operated by a person who understands its performance and is familiar with the operation knowledge; (2) Must be inspected before use. Buttons, operating handles, travel switches should be intact, and the bender must be reliably grounded; (3) Select the mold that meets the requirements, and determine the required bending radius; (4) There should be sufficient activity range around the construction site; (5) After the idling is normal, the load can be used in operation. During operation, hands and feet are strictly prohibited. Contact with the rotating part; (6) Power failure should be promptly completed after work is completed to release oil pressure.

59. What is the meaning of cable catalog and cable number?

Answer: The cable inventory is the basis for laying out the cable and guiding the construction, operation and maintenance of the file information. Should be included in each cable number, starting point, model, size, length, and statistics of the total length of the classification, control cable should also list the spare core of each cable.

The cable number is a sign of the identification cable, so the whole plant number is not repeated, and there are certain meanings and laws that can express the characteristics of the cable.

60. How can the current cable laying method be divided into several categories?

A: (1) Artificially laid, that is, employing human-sea tactics, under the coordination and command of one or more people, laying according to regulations;

(2) mechanized laying, that is, the use of rollers, tractors, conveyors, through a synchronous power control, more secure;

(3) The combination of labor and machinery, some sites due to more turns, construction is difficult, full use of machinery is more difficult, so use this method.

61, for the cable conductor connection resistance requirements?

Answer: It is required that the resistance of the connection point is small and stable, and the ratio of the resistance of the connection point to the conductor of the same length and the same cross-section should not be greater than 1 for newly installed terminal heads and intermediate terminals; for the terminal heads and intermediate heads in operation This ratio should not exceed 1.2.

62, Cable Connector and the middle of the design should meet what requirements?

Answer: The requirements that should be met are: (1) high compressive strength and good conductor connection; (2) large mechanical strength and small medium loss; (3) simple structure and strong sealing performance.

63, what is the cable fault? There are several common types?

Answer: The cable fault refers to the breakdown of the cable line due to the breakdown of the cable during the preventive test or the operation of the cable due to the breakdown of the cable or the blow of the cable. Common faults include ground faults, short-circuit faults, breakage faults, flashover faults, and hybrid faults.

64, how to deal with single-phase earth fault cable line?

A: Single-phase earth fault of cable line In general, the damage of the cable conductor is only partial. If it is a mechanical damage and the soil near the fault point is relatively dry, partial repairs are usually performed and a false joint is added. Do not cut the cable core, only the insulation of the fault point can be sealed.

65. What tests and inspections should be conducted before laying power cables?

Answer: Before laying, check whether the cable's type, size and length are in compliance with the requirements. Is there any external damage? The low-voltage cable must have a 1000V megger to measure the insulation resistance. The resistance value should not be lower than 10MΩ. The high-voltage cable should be measured with a 2500V megohmmeter. The resistance generally does not reach 400MΩ.

66. What should you pay attention to when laying cables in the main building?

Answer: (1) Where the control cables leading to the central control room should be laid overhead; (2) 6KV cables should be laid by tunnels or pipes, and the groundwater level can be elevated or laid by pipes; (3) 380V cables when two When the end cable is at zero meter, it is better to use a tunnel, a ditch or a drain pipe. When one end device is on the upper end and the other end is on the lower end, it can be partially laid overhead. When the groundwater level is high, it should be overhead.

67. Where are the inner shield and the outer shield of the power cable? What material is used? What is the role?

Answer: In order to make the insulation layer and the cable conductor have better contact and eliminate the increase of the electric field strength on the surface of the conductor caused by the non-smooth surface of the conductor, the inner shield layer of metalized paper or semiconductor paper tape is generally covered on the conductor surface. In order to make the insulating layer and the metal sheath have better contact, generally the outer layer of the insulating layer is covered with an outer shield layer. The material of the outer screen layer and the inner screen layer are the same, and sometimes the copper tape or the braided copper ribbon is also used.

68. Briefly describe the composition and properties of epoxy resin composites.

A: Epoxy resin composites consist of epoxy resin, hardener, filler flexibilizer, and thinner. Has the following properties:

(1) has sufficient mechanical strength; (2) has excellent electrical properties; (3) has stable electrical properties; (4) has sufficient adhesion with non-ferrous metals; (5) has good corrosion resistance; (6) when used outdoors, Rain, light, moisture and heat.

69. Why should a single-core cable jacket grounded in one end be installed with a reflow line laid along the cable?

Answer: In the cable line grounded at one end of the metal sheath, in order to ensure that the induced voltage in the sheath does not exceed the allowable standard, a conductor laid in parallel along the cable line must be installed, and both ends of the conductor are grounded. This conductor is called back Streamline. When a single-phase ground fault occurs, the ground short-circuit current can flow back to the center of the system through the return line, and the magnetic flux generated by the ground current through the return line cancels the magnetic flux generated by the ground current of a part of the cable conductor and can be reduced. The induced voltage of the sheath in the event of a short circuit.

70. What inspections should be performed on the acceptance of cable lines?

Answer: (1) The cable specifications should conform to the regulations, the arrangement should be neat, no damage, complete signs, correctness, and clarity;

(2) The fixed bending radius of the cable, the relevant distance and the wiring of the metal sheath of the single-core power cable shall meet the requirements;

(3) The cable terminal and the middle head are not leaking oil, and the installation is firm. The oil pressure of the oil-filled cable and the setting value of the meter should meet the requirements;

(4) good grounding; (5) the correct color of the cable terminal, complete metal parts such as brackets;

(6) There should be no debris in the cable trench, in the tunnel and on the bridge, and the cover is complete.

71, What are the requirements in the process of positive sequence impedance measurement of cable lines?

A: The AC resistance of the cable conductor and the phasor of the same three inductive reactance of the cable are called the positive sequence impedance.

The positive sequence impedance of the cable line can be measured directly on the cable reel. Generally, lower voltage is used for measurement. Therefore, a step-down transformer is required to perform step-down, and the buck is star-connected. The capacity is generally more than 10 kVA. For wider voltage regulation range, the AC power supply should be relatively stable during measurement to ensure that the current reaches the specified requirements during measurement. The actual voltmeter reading must be the voltage of the cable end, and the test current is preferably close to the long-term allowable ampacity of the cable. For each meter value, the three tables are read at the same time after closing the current.

72, cable should pay attention to what is in the process of loading and unloading?

Answer: (1) In the process of transportation and loading, cables and cable trays should not be damaged. It is forbidden to push the cable tray directly from the vehicle. Cables should not be transported flat and stored flat.

(2) Before transporting or rolling cable trays, it must be ensured that the cable trays are securely fastened, and the oil conduits between the oil-filled cables and the pressurized oil tanks should be fixed and not damaged. The pressure oil tanks should be firm and the pressure indications should meet the requirements.

73, cable fire prevention measures?

Answer: (1) Flame-retardant cables; (2) Fire-proof cable trays; (3) Fire-proof coatings; (4) Fire-proof partitions and fire dampers at cable tunnels, mezzanine exits, etc.; (5) Aerial cables Should avoid the oil pipeline, explosion-proof door, otherwise there should be to take some of the pipe or insulation fire prevention measures.

74, what are the requirements of the cable pipe?

Answer: (1) The distance from the top of the pipe to the ground is 0.2m in the factory, 0.5m under the sidewalk, and 0.7m in the general area;

(2) Well pits should be installed in the direction of change and at the branches, and pits should also be provided when the length exceeds 30mm;

(3) The depth of the pit is not less than 0.8m, and the diameter of the manhole is not less than 0.7mm; (4) The drainage pipe should have a slope of inclination of 0.5% to 1% of the pit.

This article is reproduced from http://. Com. Cn Wire and Cable Factory

75, control the secondary circuit wiring should meet the requirements?

Answer: (1) According to the diagram, the wiring is correct; (2) The electrical connection of the wire should be firm and reliable; (3) The wire inside the panel should not have connectors, and the core wire should be free of damage; (4) The end of the cable core The circuit number should be marked, the number should be correct, the writing should be clear and not easy to decolorize; (5) The wiring should be neat, clear and beautiful, and the wire insulation should be good and non-destructive; (6) Each side of each terminal should be a wire Up to two.

Cable Construction Logical No. Of Pairs Wire Diameter Conductor dimension

Insulated wire diameter Core Dimension shielded Shielding jacket diameter Nom O. D Electrical property Electrical characteristis Frequency Frequency decay max Attenuation Return loss min Echo Loss

Near-end cross-talking Min Next Worst Pair Far-end cross-talking min Worst Pair

1, wire and cable products are mainly divided into five categories:

(1) Bare wire and bare conductor products

The main features of this type of product are: pure conductive metal, non-insulating and sheathing layers, such as ACSR, copper and aluminum busbars, electric locomotive lines, etc.; the processing technology is mainly pressure processing, such as smelting, rolling, pulling System, stranding/pressing and stranding, etc.; products are mainly used in suburban areas, rural areas, user main lines, switch cabinets, etc.

(2) Power cable

The main features of this type of product are: Extruding (wrapping) the insulation around the conductor, such as overhead insulated cables, or strands of cores (corresponding to the phase, neutral and ground of the power system), such as over two core overhead insulated cables , Or increase the jacket layer, such as plastic / rubber sheathed wire and cable

The products are mainly used for transmission of strong electric energy in the transmission, distribution, transmission, transformation, and power supply lines, with large currents (tens of amps to several thousand amps) and high voltages (220V to 500kV and above).

(3) Wire and cable for electrical equipment The main features of this type of product are: variety of specifications, wide range of applications, use voltages of 1kV or less, and continuous development of new products such as fire-resistant cables and flame retardant cables for special occasions. Cables, low-smoke halogen-free/low-smoke low-halogen cables, termite-proof, rat-proof cables, oil/cold/temperature/wear resistant cables, medical/agricultural/mineral cables, thin-walled wires, etc.

(4) Communication cables and optical fibers (brief introduction)

With the rapid development of the communications industry over the past two decades, the products have also been developing at an alarming rate. From the simple telephone telegraph cable in the past to the development of thousands of pairs of voice cables, coaxial cables, optical cables, data cables, and even composite communication cables.

The size of such products is usually small and uniform, and the manufacturing precision is high.

(5) Magnet wire (winding wire)

Mainly used for various motors, instruments and meters.

Wire and Cable

Wire and Cable

Use different materials such as flame-retardant cables, low-smoke and halogen-free/low-smoke and low-halogen cables, termite-proof cables, mouse-proof cables, oil/cold/heat-resistant cables, etc.;

Change product structure such as: fire-resistant cables;

Improve process requirements such as: medical cables, etc.; combination products such as: OPGW; easy to install and reduce equipment costs such as: prefabricated branch cables.

35, wire and cable

1. Power system: wire and cable used in power system

2. Information transmission system: wire and cable used for information transmission system

3, machinery and equipment, instrumentation systems: This section except for overhead bare wires, there are applications for almost all other products, but mainly power cables, electromagnetic wires, data cables, instrumentation cables and so on.

36. In 35kv and below power cable joints, there are several ways to improve the distribution of the electric field at the break of the jacket (please list five types), and briefly describe the method.

Answer: (1) Swelling flare: The edge of the lead package should be picked up at the cutting point of the lead package and it should be horn-shaped. Its edge should be smooth, round and symmetrical.

(2) Retained package insulation: There is a piece of turn-up insulating paper between the lead-bag cuts and the separation point of the cable core.

(3) Cut off the semiconductive paper: Cut the semiconductive paper below the bell mouth.

(4) Enveloping the stress cone: Tapering the tape with an insulating tape and a conductive metal material artificially expands the shielding layer to improve the electric field distribution.

(5) Equipotential method: For dry-type or cross-linked polyethylene cable heads, a metal band is wrapped around the insulation surface of each core and connected together.

(6) Install the stress control tube: For the 35kv and the heat-shrinkable tube cable heads, firstly surround the two layers of the semiconductor tape from the end of the copper shield layer of the core through the semiconductor tape to the insulation of the core, and then bend the corresponding specifications. The tube, sleeved at the end of the copper shield, is heat-shrink molded.

49, before the torch ignition should pay attention to what inspection?

Answer: The following items should be checked:

(1) Whether the pump is leaking oil or leaking oil, leaking oil or gas at the oil barrel or nozzle;

(2) Whether the amount of oil in the drum exceeds 3/4 of the capacity of the drum, and if the screw plug for refueling is tightened.

3, using the torch should pay attention to what matters?

Answer: (1) The maximum fuel injection volume of the torch is 3/4 of the volume of the oil cylinder; (2) The starting pressure should not be too high, and the flame can be used after ignition from yellow to blue; (3) There must be no flammable substances around the air. To be circulated; (4) Turn off the adjustment switch when it is deactivated. After the fire is extinguished, slowly loosen the oil hole cover and let go of air. After the air is released, it is necessary to loosen the adjustment switch, and then completely cool and loosen the hole cover. ( 5) Kerosene burners and petrol burners should be used separately.

4. What is the use of manual hydraulic clamp? How to operate?

A: The connection of two wires is usually done by inserting two wire ends into a pressure tube made of the same material. Several pits are pressed with crimping pliers to connect the wires together. When the handle is lifted up during crimping, The plunger moves outwards, creating a vacuum in the lower chamber of the oil valve, and the oil in the fuel tank enters the plunger chamber. When the handle is pressed down, the plunger moves inward. After the oil is pressurized, the oil inlet valve is closed, the oil outlet valve is opened, the oil pressure enters the hydraulic cylinder, the piston and the male mold are pushed, and a pressure pipe is placed between the male and female molds. When the crimped crater is deep enough to reach a certain value, the oil return valve is opened and the piston automatically returns. After pressing a pit, the pressure pliers are moved and then pressed down. There are mainly local telephone cables, television cables, electronic cables, radio frequency cables, Optical Fiber cables, data cables, magnet wires, power communication or other composite cables. The main products include bare overhead wires, busbars (bus bars), power cables (plastic cables, oil-paper cables (replaced by plastic power cables), rubber cables, overhead insulated cables), and branch cables (in place of some buses). Electrical wires and cables for electrical equipment and electrical equipment. The applications are mainly divided into three major categories: Derivatives/new products are mainly due to the requirements of different applications, different application requirements, and convenience of equipment and lower equipment costs. New materials, special materials, or changes in product structure, or Improve process requirements, or combine different varieties of products to produce. Derivatives/new products

. The main process technologies include drawing, stranding, insulation extrusion (wrapping), cabling, armoring, sheath extrusion, etc. There are certain differences in the different process combinations of various products.

70, cable engineering can be divided into several projects?

A: (1) Site transportation: including the loading, unloading and transportation of engineering materials from the warehouse to the construction site and return of empty vehicles.

(2) Local projects: including road excavation, tunnels, and trench construction.

(3) Laying project: including laying, intermediate head making, flipping cover plate, buried pipe, school tide, traction head making and so on.

(4) Both ends of the project: including the production and installation of supports, suspension bridges and their foundations, the production of terminal heads, the installation of oil pressure and signal devices, and the testing of electrical properties. (5) Plug and stop project: including the production of oil-filled cable plugs and heads, installation of fuel tanks, automatic drainage and signal devices, etc.

（6）接地工程：包括绝缘接头、换位箱、保护器、接地箱安装等。

5、根据《电业生产安全规定》，电气工作人员必须具备的条件是什么？

答：必须具备下列条件：

（1）经医生鉴定身体健康，无妨碍工作的病症；

（2）具备必要的电气知识，按其职务和工作性质掌握相关的规程、专业技术及安全操作技术，并经考试合格；

（3）熟练掌握触电急救方法。

33、简述10KV 交联电缆热缩式制作户内终端头的过程？

答；（1）准备阶段：检查热缩电缆附件是否齐备，型号是否相配，检查并确认电缆有无潮气后，检查电缆。

（2）切除多余电缆，根据现场情况决定电缆长度。（3）剥除护层。（4）焊接接地线，将接地线焊接在钢带上。（5）填充三叉口及绕包密封胶。（6）安装三芯分支护套，将护套套入根部，从中部开始收缩，先往根部，再往指部。（7）剥铜带和外半导电层，剥切三芯分支套口20mm 以上的铜带，严禁损伤主绝缘，清除干净半导电层。（8）安装应力管，管口端部分支套对接后热缩。（9）安装接线端子。（10）安装绝缘管。（11）安装密封管。（12）核相后安装相色管。