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Power cord quiz
2012-02-18 22:00:39

Power cord quiz

Qiaopu Electric Co., Ltd. Technical quiz organized by the professional power cord. Exam and answers are as follows:
1, commonly used in wire, cable, by use what types?
A: The use can be divided into bare wire, insulated wire, heat-resistant wires, shielded wires, power cables, control cables, communication cables, RF cable.
Two insulated wires are there?
A: insulated wires often are the following: PVC insulated wires, PVC insulated flexible wire, a mixture of nitrile PVC insulated cords, rubber insulated wire, farm buried underground aluminum plastic insulated wire, rubber insulation cotton yarn textile cord, PVC insulated and Nylon sheathed wire, electric power and lighting, PVC insulated flexible cord and so on.
3, the cable tray is suitable for what occasion?
A: The cable tray to the general industrial and mining enterprises of indoor and outdoor aerial laying of power cables, control cables, can be used for the erection of telecommunications, radio and television sector in the indoor and outdoor.
4, cable accessories?
A: The common electrical accessories cable terminal box, cable junction box indirectly, connecting pipes and terminals, steel plate and wiring trough cable tray.
5 What is the Cable Joints?
A: The conductor connecting cable and the cable insulation shield and protective layer, so that the power cord to connect the device, known as the Cable Joints.
6, what is the main electrical wiring?
A: The main electrical connection is a major electrical equipment in power plants, substations and bus connections, including the main bus and auxiliary power system connected by a certain functional requirements.
7, in the choice of the cross-section of power cable should comply with the regulations?
A: The choice of power cable should comply with the following principles:
(1) cable rated voltage greater than or equal to the installation point of the rated voltage of the power supply system;
(2) Cable continues to allow the current should be equal to or greater than the maximum continuous power supply load current;
(3) cross-section of wire core to meet the requirements of the stability of short circuit of the power supply system;
(4) According to the cable length checking voltage drop to meet the requirements;
(5) the minimum short-circuit current of the line at the end of the protective device and reliable action.
8, XLPE cables and oil paper cable What are the advantages?
A: (1) easy to install, because it allows the minimum bend radius is small, light weight;
(2) from the line drop limit;
(3) thermal properties, permissible operating temperature is high, the transmission capacity;
(4) cable accessories, are dry-type structure;
(5) operation and maintenance is simple, no leakage problems;
(6) a lower price;
(7) high reliability, low failure rate;
(8) manufacturing process and less, simple process, and significant economic benefits.
9, the clip of the single-core cable of fixed exchange requirements? Why?
A: The fixture should be no pieces of iron constitute a closed magnetic circuit, this is because when the cable core by the current around the magnetic field lines, magnetic field lines is proportional to the size of the current through the wire core, the use of pieces of iron and other magnetic materials, according to electromagnetic induction shows that the iron in the vortex cable heat, and even burn the cable. So we can not use iron for single-core AC cable fixture.
10, the maximum features and benefits of the following heat-shrinkable cable head attachment What is it?
A: heat shrink attachment is characterized by the stress of tube instead of the traditional stress cone, it not only simplifies the construction process, and also reduced the size of the connector terminal, easy installation, saving time workers, superior performance, saving metal. Perfusion of heat-shrinkable cable accessory set and dry-inclusive as a whole, the collection of the advantages of these two attachments.
11, cable laying, which inspections should be carried out?
A: (1) bracket should be complete, complete paint.
(2) cable type, voltage, specifications comply with the design.
(3) cable insulation, oil paper cable seal doubt, damp judgment; buried cable and a small underground cables qualified DC withstand voltage test is difficult; oil-filled cable, oil samples should be passing the test.
(4) hydraulic oil-filled cables should not be less than 1.47MPa.
12, there is doubt on oil paper insulated power cable gland, with a relatively simple way to check the cable insulation paper damp?
A: The cable insulation paper lit or placed in oil of about 150 ° C cable check, "hissing" sound or the white foam, and have not been exposed to moisture.
13, cable and signs should indicate what? Writing What are the requirements?
A: The signs should indicate the number of Power cord design, the cable model, specifications, and a starting point, the parallel use of the cable should be the order number. Requirements for writing clear, easy to fall off.
14, the orientation indicator of the buried cable should be set in which position?
A: The ends of the cable, the cable is a straight line segment 50 to 100m at several cable of the cable connector to change direction at the corners.
15, the production of cable connector with the yellow wax ribbons, black glass paint with non-alkali glass ribbons, pre-construction, how to row tide handle?
A: (1) constant temperature drying method: tape rolled into a diameter of 25 ~ 30mm small volume into the oven temperature of 110 ~ 120 ℃ bake 4 ~ 5h, cooling dry to remove into a dry seal barrel.
(2) oil immersion row influx of France: the insulation with a small volume into the constant temperature of 120 ~ 130 ℃ cable oil, 30mm distance from the bottom of the pot to keep the oil level after a certain period of time is no longer a bubble, remove a receptacle cable oil barrel, oil level should be more than all the objects loaded and sealed.
16 What is the role of the cable outer sheath?
A: The protection from mechanical damage and chemical corrosion protection layer to enhance the mechanical strength.
17 outdoor cable trench shall comply with the requirements?
A: the upper cable trench should be slightly higher than the ground, stamped with the production of concrete cover, cables should be deposited in the bracket, there is good drainage pipes.
18 What is the role of the cable sheath?
A; insulating layer not in contact with water, air or other objects to prevent the insulation from moisture and insulation from mechanical damage.
19, use wire cutters should pay attention to what?
A: Before use, be sure to check the insulating handle insulation is intact and not use wire cutters shear over the metal wire specifications allow, and to prohibit the use of pliers instead of a hammer tool to avoid damage.
20, What is dielectric strength?
A: The insulation material in the electric field breakdown when the electric field strength is increased to a limit, this leads to insulation breakdown electric field strength is called the dielectric strength.
21 cross-linked heat shrinkable cable accessories What are the advantages?
A: This is a new material, with other types of attachments have superior electrical performance, small size, quality, ease of installation, and supporting materials, etc., also has weather resistance, anti-dirty sex, flame-retardant self-extinguishing capacity.
22, the mechanical strength of the cable conductor connection point requirements?
A: The mechanical strength of the connection points are generally lower than the tensile strength of the cable conductor, power cables for fixed laying, the tensile strength of the connection point requires not less than 60% of the tensile strength of the conductor itself.
23, electrical cable insulation material should have What are the main performance?
A; shall have the following main properties:
(1) high breakdown strength;
(2) a low dielectric loss;
(3) very high insulation resistance;
(4) excellent resistance to discharge performance;
(5) has a certain softness and mechanical strength;
(6) insulation performance of long-term stability.
24, mechanical cable laying, traction strength What are the requirements?
A: For copper cable, when pulling the head, allowing the traction strength of 70N/cm; aluminum cable, when pulling the head, allowing the traction strength of 40N/cm; if the use of steel mesh sleeve traction, lead care sheathed cable allows the strength of 10N/cm;
Lead-sheathed cable 40N/cm.
25, any provision of cable protection pipe?
A: (1) cable need to wear protective pipe laying, pipe inside diameter of not less than 1.5 times the cable diameter concrete pipe, clay pipes and asbestos cement pipes internal diameter of not less than 100mm;
(2) The bending radius of cable pipe shall comply with the provisions of the penetration of cable bend radius;
(3) Each pipe should not be up to more than three elbows, the right angle bend should be no more than two.
26, how to measure the outside diameter of the cable sheath?
A: 5 points uniformly distributed in the jacket circumference measurement sheath outer diameter and the average, the average outer diameter of both the sheath outer diameter.
27 different cross-section of copper cable connected?
A: The different sections of copper cable connection can be used to open a weak back copper to take over, connected to the soldering method, can also be used pure copper rods connected into copper taken over by different cross-section requirement, a crimp connection.
28, brief 10KV XLPE cable heat shrinkable production indoor terminal head process?
A; (1) preparation phase: check the heat-shrinkable cable accessories are available, and whether the type of match, check to make sure, check the cable after the cable with or without moisture.
(2) removal of excess cable to determine cable length, according to the situation.
(3) stripping the sheath.
(4) welding ground wire, ground wire is welded to the metal strip.
(5) to fill Sanchakou and wrapped with sealant.
(6) installation of three core branch jacket, the jacket sleeve into the roots began to shrink from the central, first to the roots go down to the finger.
(7) stripping copper strip and the outer semi-conductive layer, peel cut three core branch above the mouth 20mm copper strip is strictly prohibited damage to the main insulation, clear clean, semi-conductive layer.
(8) to install the stress control tube, nozzle heat shrinkable terminal part of the support sets of docking.
(9) to install the terminal block.
(10) to install the insulation tube.
(11) installation gland.
(12) nuclear installation phase colorimetric tube.
29, indoor and outdoor prefabricated terminal installation steps?
A: (1) of the cable in place a predetermined position, fixed, clean the surface, refer to the manual stripping except the jacket, if the special needs of the outer sheath stripping cut length adjustable from the Copperbelt, the outer sheath armor fitted leads two groups of ground.
(2) to take up the amount of the outer sheath mouth need to size, removal of excess cable into plus heat shrink heat-shrinkable three finger to Sanchakou of roots from the middle finger catchy up the amount of take the required size (35kv to 350 ~ 380mm ). Get rid of excess copper strip (reservations 20mm), to retain the semiconductor predetermined position, crimp the outlet terminals sealed.
30, under what circumstances, the motor on-site installation should be carried out pumping core examination?
A: The motor has one of the following conditions should be pumping core examination:
(1) the date of manufacture more than the factory warranty period;
(2) by visual inspection or electrical testing, quality, suspicious;
(3) open the motor end of the inspection and suspicious;
(4) anomalies in the commissioning.
31, the generator manually Juxtaposition should have what conditions?
A: The three conditions of the generator in parallel until the generator voltage, frequency, phase, and run the system voltage, frequency, phase difference is less than the specified value.
32, finished construction of the bus devices should be what to check?
A: The following checks should be carried out:
(1) metal structures, processing, preparing, welding screw collusion compliance;
(2) ministries bolts, washers, cotter pins and other components should be complete and reliable;
(3) buses preparation and mounting bracket should be consistent with the provisions of the white and ground electrical distance to meet the requirements;
(4) pieces of porcelain, iron and glued at should be complete, oil-filled casing should be no oil leakage, oil level is normal;
(5) paint a complete, relative to color correct, and well grounded.
Improve their jacket disconnect the electric field distribution at the 33, 35kv and below power cable connector, there are several (Please list five), and outlined its approach.
A: (1) inflation Bell: cut off in the lead pack to lead package edge to pry into the trumpet-shaped, their edges should be smooth, round, symmetrical.
(2) reserved turnkey insulation: left some turnkey insulation paper between the separate lead package incision to the cable core.
(3) removal of semi-conductive paper: a semi-conductive paper removal following the bell.
(4) surrounding the stress cone: package with insulation package with a conductive metal material into a cone, shield artificially expanded to improve the electric field distribution.
(5) potential method: dry package type or cross-linked polyethylene cable head in the line core profiles on the insulating surface of the package for some metal band, and are connected together.
(6) the installation of the stress control tube: 35kV and made under the heat shrink tube cable head first from the line core copper shield the end of the direction of the semiconductor band to the wire core insulation profiles surrounding the two-layer semiconductor band, and then the corresponding specifications of folding stress tube, set at the end of the copper shield, thermal forming.
34, the processing of the cable holder shall comply with the requirements?
A: (1) The steel should be straight, no obvious distortions, cutting error should be within 5mm incision should be no curling, hair assassination;
(2) The bracket should be welded solid, no significant Achillea deformation, each cross brace between the vertical spacing and design deviation should not exceed 5mm;
(3) metal stents must be embalmed, in hot and humid, salt, fog and chemical corrosion region should be based on a design for a special anti-corrosion treatment.
35, lists you are familiar with the cable rack.
A: The tailor-welded-type E-type frame fabricated E-type frame, the bridge cable racks, cable trays, hook type bracket, a single cable such as a stent.
36, laying of cable shall meet the requirements?
Answer: should meet the following requirements:
(1) safe operation, as far as possible to avoid external damage, improve the supply reliability of the power cord;
(2) the economic front, the investment in the most economical aspects into account;
(3) the construction side, the path of the power cord must be easy to spin the workers and put into operation after maintenance.
37, the production of the cable termination head or middle joints of insulating material?
A: insulation, insulation tape, insulating pipes, insulating gloves, insulating resin.
38 brief cable head general operating procedures.
A: (1) pre-production preparation: ○ 1 Read the installation instructions; ○ look at the scene; ○ 3 preparation; the 4 cable test tide; ○ 5 pre-production testing.
(2) the joint production process: including ○ cut off excess cable; cable protective layer of peel cut ○ 2; ○ 3 conductor connection; ○ surrounding the insulation (or shrink tubing); ○ 5 to install the connector shell; ○ 6 perfusion insulation to agent; ○ sealing treatment.
(3) Production of electrical test.
39, the processing of cable protection tube should meet the requirements?
A: (1) The nozzle should be hairless assassination and sharp flute angle, the nozzle should be made of the trumpet.
(2) cable tube bending, there should be no cracks and significantly dented phenomenon, its extent should not be bent flat 10% greater than the pipe outside diameter; cable pipe bending radius of not less than the penetration of cable minimum allowed bending radius.
(3) metal pipe should be coated with anticorrosive paint or bitumen table, galvanized pipe, zinc spalling Department should also be coated with anti-corrosion paint.
40, the cable arrangement meet the requirements?
A: (1) power cables and control cables should not be configured on the same floor stand.
(2) high and low voltage cable, strong, weak control cables shall be required to sequence the hierarchical configuration, in general, should be top-down, but it contains more than 35kv high voltage cable to the introduction of cabinet plate, in order to meet the bend radius by the following configuration .
41, the cable trench laying cable What is it?
A: The cable trench laying cables is similar to the buried cable laying method, generally pulley on the trench, the cast is completed, the cable is put in the ditch or bracket, and cable lashing cable signs.
42, cable laying equipment commonly used?
A: (1) air compressor is mainly used to destroy the road to prepare for the future of cable laying;
(2) electric winch or cable traction machine is mainly used to drag the cable;
(3) cable conveyor, with the tractor to use to overcome the enormous friction, reduce damage to the cable;
(4) cable tray Actinobacillus bracket;
(5) The roller device;
(6) anti-twist, minus rope distortions;
(7) brake cable tray;
(8) tonometer.
43, the cable channel bracket installation distance requirements.?
A: The cable is fixed in the wall of the cable trenches and tunnels, the level of device, the cable when the cable outer diameter equal to or less than 50mm should be at intervals of 1m-plus-one support; outside diameter greater than 50mm every 0.6m plus a support; arranged in a triangle of a single cable, every 1m applications strap fastened, vertical device, every 1 ~ 1.5m to be fixed.
44, how to handle the installation of power cables and control cables in the same bracket?
A: The power cables and control cables should not normally be laid in the same bracket, but when the cable is less control cable, power cable laid in the same bracket, the application separated by partitions.
How to install the ground wire 45, the cable tunnel?
A: The total length of the tunnel and the trench shall be equipped with a continuous ground wire, ground wire should be connected and all the bracket, two and grounding connectivity. The ground wire must also comply with the design requirements. Cable lead covered and armored in addition to insulation requirements should be fully interconnected and connected to the grounding wire, cable racks and grounding wire should be coated with anti-rust paint or galvanized.
46, What are the requirements for cable holes in the fire blocking?
A: For larger cables run through holes, such as the cable runs through the floor at, blocking a fire blocking material should be based on the actual situation, the cable surface and painted four to six fire-resistant coating of about 1.5m, length of the hole below, and then refractory material processed into a certain intensity Bracket fire blocking material, to ensure that the block after a solid and easy to replace the cable when disassembly block dense pore blocking to effectively block the smoke fire.
47, the torch ignition should be noted that check?
A: The following checks should be carried:
(1) pump oil leaks or oil leakage, the drums and the nozzle spill, leak;
(2) within the barrel of oil is more than 3/4 of the barrel capacity fuel Lo Si Se are tightened.
48, use the torch should be noted that what matters?
A: (a) blowtorch maximum injection fuel oil cylinder volume 3/4;
(2) boost the morale of the pressure is not too big, lit the flame from yellow to blue can be used;
(3) around may not have the combustible air to circulate;
Close the adjustment switch (4) disabled, the fire put out, slowly rotating the pine oil hole cover the deflated air release after Loosen adjustment switch, cool completely and then unscrew manhole covers;
(5) kerosene blowtorch with the gasoline torch to be used separately.
49, manual hydraulic clamp used? How does it work?
A: The two wire connection is usually two-wire side through the pressure tubes in the same material, using the crimping tool to squeeze a few pit, so that the wires are connected together, crimp, the handle is lifted up when, piston moves outward, the inlet valve of the inferior vena creates a vacuum, the oil tank into the plunger cavity. Handle under pressure, the plunger moved inward, oil pressure, so that the inlet valve off, open the outlet valve, hydraulic into the hydraulic cylinder, to promote between the piston and the male mold, Yang, Yin mold release pressure to take over crimp squeeze the pit depth to a certain value, open the oil return valve piston automatically returns to the pressure of a pit, mobile pressure clamp, and then pressing a.
50, commonly used in low voltage power cable insulation and protection layer different, can mainly be divided into several categories?
A: (1) of the oil impregnated paper insulated lead covered (or aluminum clad) power cable;
(2) does not trickle oil impregnated paper insulated power cables;
(3) PVC insulated PVC sheathed power cable;
(4) XLPE insulated and PE sheathed power cable;
(5) cross-linked PVC insulated PVC sheathed power cable;
(6), rubber insulated power cables.
51 categories of commonly used insulating materials which? Example?
A: (1) inorganic insulating materials: mica, asbestos, marble, porcelain, glass, etc.;
(2) of the organic insulating material: resin, rubber, paper, linen, cotton yarn;
(3) hybrid insulation material: processing while forming species insulation materials, insulating materials.
52 In either case, the laying of pipe? What are the advantages?
A: The pipe laying is generally used in the cross and other buildings, road or rail, and sometimes also building up areas with The main advantage is the small footprint, can withstand a large load cables to each other independently of each other, safer.
53, what is meant by cable to allow long-term carrying capacity?
A: The cable allows the long-term carrying capacity of the cable through the provisions of current, thermal stability, the cable conductor to achieve long-term to allow the current value when the operating temperature.
54, decided to cable to allow long-term the factors of carrying capacity?
A: The following three factors:
(1) the cable is long-term allowable working temperature;
(2) the thermal performance of the cable itself;
(3) the thermal conditions of the cable installation and the surrounding environment.
55, cable laying There are several ways?
A: There are the following:
(1) directly buried in the ground;
(2) installed in the cable trench;
(3) installed in the underground tunnel;
(4) is installed inside the building wall or ceiling;
(5) installed on the bridge;
(6) laying in the row of tubes;
(7) laying at the bottom.
56, cable pipe connection work?
A: must buckle and fittings to connect the cable pipe connection, such as the use of welding, can not be direct butt connections to put on a thick pipe welding, so as not to fall into the pipe welding slag.
57, produced the first cable in place, up and down bending the cable core requirements?
A: bending the wire core, not damage paper insulated wire bending radius not less than 10 times the cable core. To be especially careful when making the curved part of the wire core should be made even by force, or vulnerable to damage the insulation paper.
58 brief the plastic cable heat shrink seal.
A: The heat-shrinkable method applies to medium and low voltage rubber, plastic cable joints and terminations, the first seal, also apply to a trickle and adhesive impregnated insulated cables. The cross-linked polyethylene and silicon rubber two categories evenly when exposed to heat shrink the heat shrinkable tube. This pipe set in pre-adhesive sealing parts, and glue the parts coated with hot melt adhesive, heat-shrinkable tube to shrink when heated to a temperature, and hot melt adhesive to melt, to be the natural cooling after the formation of a good sealing of the sealing layer.
59, with the electric bending machine bending cable protection tube should pay attention to what?
A: (1) bending machine should understand its performance and familiar with the operational knowledge of the personnel to operate;
(2) prior to use must be checked, buttons, operating handle, the trip switch should be in good condition, bending machine must be grounded;
(3) selected in line with the requirements of the mold to determine the bending radius;
(4) around the construction site, there should be plenty of scope of activities;
(5) used to be idle to normal before with a load operation, is strictly prohibited contact with hands and feet to turn the part;
(6) the work is completed should be power outages, the release of oil pressure.
60, cable inventory of the contents and meaning of the cable No. What is it?
A: The cable inventory cast the basis of the cable and guide the construction, operation and maintenance of archives. Should be included in the number of cables, the starting point, models, specifications, length, and separate statistics on the total length of the control cable should be listed in the spare cores of each cable.
The cable number identify the sign of the cable, and called the whole plant number does not repeat, and have some meaning and laws of the expression of the characteristics of the cable.
61, cable laying method can be divided into several categories?
A: (1) manual laying, that is, the human sea tactics, under the command of one or more co-ordination required for laying;
(2) mechanized laying, that is, using the scroll wheel, traction control, conveyor control through a synchronous power, relatively safe;
(3) manual and mechanical combination of some site due to turn more difficult construction, the whole machinery is more difficult, so using this method.
62, control of the secondary circuit wiring shall comply with the requirements?
A: (1) according to the drawings wiring correctly;
(2) wire electrical connection should be solid and reliable;
(3) The conductor of the disk cabinet should not have connectors, wire core wire should be no damage;
(4) cable core end shall be marked with its loop ID number should be correct, legible and easy bleaching;
(5) Ensure that all wiring is neat, clear, beautiful, wire insulation should be a good, non-destructive;
(6) on each side of each terminal wiring should be a maximum limit of more than two. 63, cable pipe requirements?
A: (1) row tube top to the ground distance in the plant is 0.2m sidewalk 0.5m, the general area of ​​0.7m;
(2) change the direction and branch office should be housed row of the tubewell pit, more than 30mm in length, should be added the pits;
(3) the depth of pits is not less than 0.8m, the diameter of the manhole is not less than 0.7mm;
(4) The pipe should be the tendency of pits 0.5% to 1% drainage slope.
64, for the resistance of the cable conductor connection point requirements?
A: for the connection point of the resistance is small and stable, the resistance of the connection point with the same length, the ratio of the same cross-section of conductor for the newly installed terminal head and middle head, should not be greater than 1; for the operation of the terminal head and middle The head of this ratio should not exceed 1.2.
65, cable connectors and the middle of the head should be designed to meet the requirements?
A: The requirements to be met:
(1) high strength conductor connection;
(2) mechanical strength, dielectric loss is small;
(3) simple structure, strong sealing.
66, What is a cable fault? There are several common types?
A: The cable fault refers to the cable insulation breakdown in the operation, due to insulation breakdown, wires blown such as forcing the Power cord blackout failure occurs when preventive tests. Common fault ground fault, short circuit failure, break failure, flashover failure and mixed failure, etc..
67, how to handle the power cord of the single-phase ground fault?
A: Generally speaking, single-phase ground fault of the power cord, the cable conductor damage is only partial, if they are mechanical damage near the point of failure of the soil is drier, generally a local repair with the addition of a false joint, ie saw off the cable core, only to strengthen the point of failure insulation and sealing it.
68, the power cables before laying should be carried out which tests and inspections?
A: laying should be checked before the cable type, size and length to meet the requirements, whether there is external damage, the low voltage cable with 1000V megger telemetry insulation resistance, resistance is generally not lower than 10MΩ, high voltage cable shake test with 2500V megger resistance is generally not arrived at 400MΩ.
69, laying of cables inside the main plant in general should pay attention to what?
A: The laying of cables in the main plant generally should be noted that:
(1) Where control cables to the central control room should be overhead installation;
(2) the 6KV cable to use the tunnel or exhaust pipe laying, the groundwater table height can also be aerial or pipe laying;
(3) 380V cable when both ends of the cable at zero meters to use the tunnel, trench or row of tubes, when the end of the device, one end of the next can be part of the overhead laying, when the high water table should be overhead.
70, the power cable inside the shield and outer shield layer in what parts? What material? What is the role?
A: The insulation and the cable conductor has a good contact, eliminating the conductor surface is not smooth due to the conductor surface electric field intensity increases, the general surface of a conductor package metallized paper or the inside of the semiconductor tape shield. In order to make insulation and metal jacket good contact, and general appearance of bread in the insulating layer have the outer layer of shielding. The same screen on the outside layer and the internal display layer of material, sometimes outside bar copper tape or braided copper wire with.
71, outlined the composition and properties of the epoxy compound.
A: epoxy compound is joined by the epoxy resin hardener, filler toughening agent and diluent. With the following properties:
(1) have sufficient mechanical strength;
(2) excellent electrical properties;
(3) The electrical properties and stability;
(4) there is sufficient adhesion force and the nonferrous metals;
(5), good corrosion resistance;
(6) when used outdoors, resistant to rain, light, resistance to heat.
72, one end of the single-core cable sheath grounding in the way Why must install one along the cable laid parallel to the return line?
A: In one end of the metal sheath grounded power cord, to ensure that the induced voltage in the sheath does not exceed the allowable standard, you must install one along the Power cord parallel to the laying of conductor, and the ground at both ends of the conductor, the conductor called reflux line. Single-phase ground fault occurs, the ground short-circuit current to flow back into the system the center of the return line, offset part of the cable wire grounding current generated by the magnetic flux due to magnetic flux through the return line of the ground current, which can reduce the short-circuit fault sheath of the induced voltage.
73, the cable works can be divided into to several projects?
A: (1) site transportation: including engineering materials from the warehouse to the construction point of loading and unloading, transport and empty backhaul.
(2) Local projects include: road excavation, tunnel, channel construction.
(3) laying works: laying the middle of the first production of the flip cover, pipe, school boom, traction of the first production.
(4) both ends of the project: including support, bridge frame and based on the production installation, the terminal head production, oil pressure and the installation of signaling devices, types of electrical performance testing.
Plug only works (5): including oil-filled cable plug only the first production for the fuel tank, automatic drainage and installation of signaling devices.
(6) grounding: insulated joint, empathy box, protective devices, ground tank installation.
74, the acceptance of the power cord should check?
A: (1) The cable specifications should be consistent with the provisions of the arrangement should be neat, no damage, signs complete, correct and clear;
(2) a fixed bending radius of the cable distance and single electric power cable connection of the metal sheath shall meet the requirements;
(3) cable terminal, the middle of the head does not leak oil, securely installed, the oil-filled cable oil pressure and the setting value of the meter should meet the requirements;
(4) well-grounded;
(5) cable terminal phase color is correct, brackets and other metal parts, paint and complete;
(6) cable trenches and tunnels, on the bridge should be no debris, complete cover.
75, Power cord positive sequence impedance measurement process What are the requirements?
A: The AC resistance of the cable conductors and cables of the same inductance volume and known as the positive sequence impedance.
Positive sequence impedance of the power cord on the cable tray is generally direct measurement of the measurements generally use a lower voltage, therefore, need to step-down transformer step-down buck is a star connection, the capacity more than 10kVA, a wider range of voltage regulator, and measuring the AC power should be relatively stable, to ensure that the requirements of the current to achieve the required measurements, the actual reading of the voltmeter is the voltage of the cable end, the test current is best close to the cable to allow long-term carrying capacity, measured read the value of each meter, after closing the current read the value of the three tables.
76, according to the electrical production safety requirements, electrical staff must have the condition?
A: You must meet the following conditions:
(1) identification of physical health by a doctor, without prejudice to the work of the illness;
(2) have the necessary electrical knowledge, their duties and the nature of the work to master the relevant procedures, technical and safe operation, and pass the examination;
(3) proficiency in electric shock first aid methods.
77, cable transport loading and unloading process should pay attention to what?
A: (1) in the transport loading and unloading process, should not damage cables and cable tray, is strictly prohibited cable tray directly pushed by the car, not flat transport cable, flat storage.
Before (2) transportation or rolling cable trays, must ensure that a solid cable tray, cable wound tight, the oil pipeline between the oil-filled cables to the pressure tank should be fixed, shall not damage the pressure tank should be firmly, the pressure indicator should meet the requirements.
78, the cable fire which measures?
A: (1) using a flame retardant cable;
(2), fire-resistant cable trays;
(3) fire-resistant coating;
(4) cable tunnel, mezzanine export, etc. set the fire wall, fire dampers;
(5) overhead Power cords should avoid the oil pipeline blast doors, otherwise should have to take the local wear tube or insulation fire protection measures.
79, select the cross-section of power cables where several aspects to consider?
A: It should consider the following aspects:
(1) cable to allow long-term through the work of current;
(2) Once the short circuit, thermal stability;
(3) the voltage drop on the line can not exceed the allowable working range.
80, power cables and overhead lines What are the advantages?
A: (1) reliable operation, as installed in the underground such as shelter, subject to external damage is small, fewer opportunities for failure, security of supply will not cause harm to the personal;
(2) to maintain the workload is small, and do not need frequent inspection;
(3) without the erection of the tower;
(4) help to improve the power factor.

The quiz will be held in Qiaopu Limited Chamber.

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