1. What kind of power cables and cables are used?
Answer: the use can be divided into naked wire, insulated wire, heat-resistant wire, shielded wire, power cable, control cable, communication cable, radio frequency cable, etc.
What kinds of insulated wires are there?
Answer: often the insulated wire has the following kinds: PVC insulated wire, PVC insulated flexible wire, nitrile soft PVC compounds insulation wire, rubber insulated wire, agricultural underground buried plastic insulation aluminum core wire, rubber insulation cotton textile soft wire, PVC insulated nylon sheathed wire, electric power and lighting soft PVC insulated wire and so on.
3. What kind of place is the cable bridge?
Answer: the cable bridge is suitable for the installation of power cable and control cable in the indoor and outdoor space of general industrial and mining enterprises, and it can also be used in the setting up of the departments such as telecommunication and broadcast television.
What are the cable accessories?
Answer: the commonly used electrical accessories have cable terminal terminal box, cable intermediate junction box, connecting pipe and wiring terminal, steel plate connection slot, cable bridge, etc.
5. What is the middle connection of cable?
Answer: the conductor, insulation shielding layer and protective layer connecting cable and cable, to make cable line connection device, called the cable intermediate joint.
6. What is the electrical main wiring?
Answer: electrical main wiring is the connection mode of main electrical equipment and bus line in power plant and substation, including the main bus and plant power system according to certain function requirements.
7. What rules should be followed when selecting the section of power cable?
Answer: the choice of power cable should comply with the following principles:
(1) the rated voltage of the cable shall be greater than or equal to the rated voltage of the installation point power supply system;
(2) the continuous permissible current of the cable shall be equal to or greater than the maximum continuous current of the power supply;
(3) the linear core section shall meet the requirement of the stability of the short circuit of the power supply system;
(4) whether the voltage drop of the cable length is met the requirement;
(5) the minimum short circuit current at the end of the line should enable the protection device to act reliably.
8. What are the advantages of crosslinked polyethylene cable and oilpaper cable?
Answer: (1) easy installation, because it allows the minimum bending radius to be small and lightweight;
(2) it is not limited by the line gap;
(3) good thermal performance, allowing high working temperature and high transmission capacity;
(4) the cable accessories are simple and are all dry structure;
(5) operation and maintenance is simple, no oil leakage problem;
(6) lower prices;
(7) low reliability and low failure rate;
(8) small manufacturing process, simple process and remarkable economic benefits.
9. What are the requirements for fixed ac single-core cable? Why is that?
A: fixture should be no iron constitute a closed magnetic circuit, this is because when the cable core by current, produced in the surrounding magnetic field lines, the lines of magnetic force and core through the line current is proportional to the size, if the use of magnetic material such as iron, according to electromagnetic induction, will produce eddy current in iron making cable fever, even burning cables. Do not use the iron piece as a single core ac cable fixed fixture.
10. What are the characteristics and advantages of the attachment to the heat-shrinkable cable head below?
Answer: the biggest characteristic of the heat-shrinkable attachment is to replace the traditional stress cone with the stress tube. It not only simplifies the construction process, but also reduces the size of the terminal of the connector, convenient installation, and time saving labor and sex
Be superior and save metal. The heat-shrinkable cable accessories and dry package are integrated, and the advantages of these two accessories are set.
11. What inspections should be conducted before the cable is laid?
Answer: (1) the bracket should be complete, the paint is complete.
(2) the cable model, voltage and specification are in conformity with the design.
(3) the cable is well insulated and should be judged when there is doubt about the sealing of oil-paper cable; The direct buried cable and the small cable shall be qualified through the dc withstand test. Oil - filled cable should be tested.
(4) oil pressure of oil filling cable should not be less than 1.47 MPa.
12. When there is doubt about the sealing of oil-paper insulated power cable, how to check the cable insulation paper in a simpler way?
A: put the cable insulation paper light or in the cable oil check of around 150 ℃, no "hiss" sound or white bubble, not be affected with damp be affected with damp.
13. What should be indicated in the cable sign? What are the requirements for writing?
A: the cable line design number, cable type, specification and starting point should be indicated on the sign. The cable shall be in serial number. Require clear handwriting, easy to fall off.
14. Where should the directional marks of the direct buried cable be located?
Answer: at the end of the cable, the cable in line segment 50~100m cable joint several cables to change the direction of the corner.
15. How to arrange the discharge treatment before construction, such as the yellow ribbon, the black glass paint belt and the non-alkali glass ribbon?
Answer: (1) constant temperature and drying method: the insulation tape is rolled into a diameter of 25~ 30mm, and put it in
Within 110 ~ 120 ℃ constant temperature drying oven drying 4 ~ 5 h, cooling dry out and placed in dry sealed chamber.
(2) in oil moisture removal method: will be insulated with small volume in a constant temperature in the cable oil of 120 ~ 130 ℃, keep a 30 mm distance from the bottom of the pot, after a certain period of time the oil level no longer produces bubbles out, in a cable of barrels of oil storage and oil level should be more than all the loaded object and seal it.
16. What is the role of the outer layer of the cable?
Answer: protect inner protecting layer from mechanical damage and chemical corrosion, enhance mechanical strength.
What are the requirements for outdoor cable trench?
A: the upper part of the cable trench should be slightly higher than the ground, with the cover made of concrete, the cable should be applied to the bracket, and there are good drainage pipes.
18. What is the role of the inner layer of the cable?
A; The insulation layer will not contact with water, air or other objects to prevent insulation and insulation from mechanical damage.
What should you pay attention to when using wire pliers?
Answer: before use, be sure to check whether the insulation of the insulated handle intact, is not available when using cutters cut more than allowed by the specification of metal wire, and prohibited from use combination pliers instead of a hammer tools, so as to avoid damage.
20. What is the insulation strength?
A: in the electric field, the electric field strength of the electric field will be penetrated when the strength of the electric field increases to a certain limit. The electric field strength which leads to insulation breakdown is called the insulation strength.
21. What are the advantages of cross-linking thermal contraction cable accessories?
A: this is a new type of material, which is more electrical than any other type of attachment
It has the advantages of small volume, small quality, simple installation and supporting materials. Besides, it also has the ability of weatherproof, anti-pollution and self-extinguishing.
22. What are the mechanical strength requirements for cable conductor connection points?
Answer: join mechanical strength, generally lower than the tensile strength of cable conductor itself, for fixed installation of power cable, the tensile strength of the connection requirements of less than 60% of the tensile strength of conductor itself.
23. What are the main properties of insulating layer materials for power cables?
A; The following main properties should be met:
(1) high breakdown strength;
(2) low dielectric losses;
(3) high insulation resistance;
(4) excellent discharge resistance;
(5) having certain softness and mechanical strength;
(6) long-term stability of insulation performance.
24. What are the requirements for traction strength when laying a cable?
Answer: for the copper core cable, when pulling the head, the allowable traction strength is 70N/cm; For aluminum core cable, when the head is pulled, the traction strength is 40N/cm; If the steel wire mesh is used, the strength of the lead sheath cable is 10N/cm. Lead sheathed cable is 40N/cm.
What are the regulations on cable protection?
Answer: (1) the pipe should not be less than the outer diameter of the cable when the cable needs to be put on the protective pipe
1.5 times, the inner diameter of concrete pipe, clay pipe, asbestos and cement pipe shall not be less than 100mm;
(2) the bending radius of the cable tube shall conform to the rules of the bending radius of the cable in which it is inserted;
(3) each pipe should not exceed three corners, and no more than two corners.
26. How to measure the outer diameter of the cable sheath?
Answer: at five points evenly distributed on the circumference of the sheath, the outer diameter of the sheath and its average value are measured. The average outer diameter of the sheath is the outer diameter of the sheath.
27. How to connect the copper core cables of different sections?
Answer: the copper core cable connection of different sections can be taken over by the open and weak back copper, with solder joint, and the copper rod can be connected to the copper receiver according to the different sections.
28. Describe the process of the end head of 10KV crosslinked cable heating system?
A; (1) preparation phase: check whether the attachment of the heat-shrinkable cable is in place, the model is matched, check and confirm that the cable is out of moisture and check the cable.
(2) remove redundant cable and determine cable length according to the scene.
(3) stripping the armor.
(4) weld the grounding wire and weld the ground wire to the steel belt.
(5) fill the three forklift and wrap the sealant.
(6) install the three-core branch sheath, cover the sheath into the root, and start to shrink from the middle, first to the root and then to the finger.
(7) stripping the copper strip and the outer half conductive layer, stripping the copper belt of the core of the three-core branch by 20mm, the damage of the main insulation shall be strictly forbidden, and the clean and semi-conductive layer shall be removed.
(8) install the stress tube, and the butt end of the pipe ends after butt joint.
(9) install the terminal.
(10) install insulating tubes.
(11) install the sealing pipe.
(12) after the nuclear phase, the phase color tube shall be installed.
29. What are the installation steps of indoor and outdoor pre-made terminal?
Answer: (1) to a predetermined position in place, the cable fixed, clean surface, reference manual peel except sheath, if there are any special needs, outer sheath, cutting length can be adjusted respectively by copper belt, outer sheath armoured ground leads to two groups.
(2) it is required to take the size of the outer sheath, remove the redundant cable, and set the three finger sleeve to the base of the three forklift to be contracted by heating in the middle, and the specified size (35kv is 350~380mm) from the upper mouth of the sleeve. Remove the excess copper (20mm) and retain the semi-conductor position and press the outlet terminal seal.
30. Under what circumstances, the on-site installation of the motor should carry out the core inspection?
Answer: when the motor has one of the following conditions, the core should be checked:
(1) the factory date exceeds the manufacturer's guarantee period;
(2) if the quality is suspicious after appearance inspection or electrical test;
(3) when the open motor is inspected by the end of the motor for suspicious;
(4) abnormal situation of test operation.
31. What are the conditions for the manual operation of the generator?
A: the voltage, frequency, and phase difference between the voltage, frequency and phase of the generator is less than the specified value.
32. After the completion of the busbar installation, what should be done?
A: the following inspections shall be conducted:
(1) the processing, preparation and welding of metal components shall meet the requirements;
(2) the parts such as bolts, washers and cotter pins should be fully reliable;
(3) the wiring and installation of the bus shall comply with the requirements;
(4) the porcelain parts, the iron parts and the gluing shall be complete, the oil filling sleeve shall be free of oil and the oil level is normal;
(5) the paint is complete, the color is correct and the ground is good.
33. There are several ways to improve the distribution of electric fields in the power cables of 35kv and below (please list the five types) and describe the methods.
Answer: (1) bulge flare mouth: the lead bag is cut at the edge of the lead bag to lift, the horn shape, its edges should be smooth, round, symmetrical.
(2) reserved traditional insulation: a piece of unwrapped insulation paper is left between the cut of lead and the parting of the cable core.
(3) remove half conductive paper: remove the semi-conductive paper to the mouth of the horn.
(4) wrap around the stress cone: it is conical with insulation and conductive metal material, and the shielding layer is artificially expanded to improve the distribution of electric field.
(5) equipotential method: for dry packet type or crosslinked polyethylene cable head, a metal strip is wrapped in the insulation surface of the core profile of each line, and it is connected together.
(6) furnish the stress control tube: for hair heat shrinkable tube under 35 kv cable head, first of all, from the end of the wire core copper shield direction through semiconductor to wire core insulation situation surrounding the 2 layers of semiconductor band, then the corresponding specification folding stress pipe, set at the end of the copper shield, hot forming.
What are the requirements for the processing of cable supports?
Answer: (1) the steel should be straight, without obvious distortion, the lower material error should be within 5mm, and the incision should be no crimping side, and the burr;
(2) the brackets shall be welded firmly, without any deviation of the yarrow, and the vertical spacing and design deviation of each transverse support
Should not be greater than 5mm;
(3) metal scaffolds must be embalmed, and should be treated with special antisepsis according to the design, in the areas of hot, humid, salt, fog and chemical corrosion.
List your familiar cable racks.
Answer: welding type E frame, assembly type E frame, bridge cable holder, cable bracket, hook type bracket, single cable bracket, etc.
What are the requirements for laying a cable?
A: the following requirements should be met:
(1) to avoid all kinds of external damages and improve the reliability of power supply of cable lines.
(2) economic aspects, from the perspective of the most important province;
(3) in terms of construction, the route of the cable must be easy to rotate and repair after operation.
37. What are the insulating materials for making cable end head or intermediate joint?
A: there are insulating rubber, insulating tape, insulating tube, insulating gloves, insulating resin and so on.
Explain the general operating procedure of the cable head.
Answer: (1) preparation before production: include reading installation instructions; View the scene; A. 3 material; Cable test tide; Pre-production test, etc.
(2) the production process of the joint: including 1. The peeling of cable protective layer; Conductor connection; Wrap around insulation (or shrink tube); Install joint shell; Perfusion agent; Seal processing and so on.
(3) electrical test after production.
What are the requirements for the processing of cable protective tubes?
Answer: (1) the nozzle should have no burr and sharp Angle, the tube mouth should make a horn shape.
(2) after the bending system, the cable pipe should not have cracks and significant concave, which should be less than 10% of the diameter of the tube. The bending radius of the cable tube should not be less than the minimum allowable bending radius of the cable.
(3) the metal tube shall be coated with anti-corrosion paint or drain meter, and the flaking area of galvanized pipe shall be coated with anti-corrosion paint.
What are the requirements for cable alignment?
Answer: (1) power cable and control cable should not be configured on the same floor bracket.
(2) the high and low voltage cable, strong, weak current control cable should press must be layered configurations, general appropriate top-down, but in introducing ark contains 35 kv high-voltage cable set, to meet the bending radius, can be made of the following configuration.
41. What is the method of laying cable in cable trench?
Answer: laying cable in the cable trench method and buried cable laying method, can generally be put pulley groove, casting, put on bottom or the cable bracket, and sign on the cable tie cable.
42. What are the common equipment for cable laying?
Answer: (1) air compressor, mainly used to destroy the road surface, to prepare the cable for the future;
(2) electric hoist or cable tractor, mainly used to tow cables;
(3) cable conveyor, combined with tractor use to overcome