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Wire and cable a little common sense

Information Source:Henan Huadong Cable Co., Ltd  Release date:2014-03-19

1, the single core cable sheath is grounded way why must be installed along a cable lay back line?
The cable line grounding metal sheath end, in order to ensure the induction voltage protection sleeve does not exceed the permissible standard, must be installed along a cable lines laid parallel conductor, and the conductor grounded at both ends, the conductor called return line. When single-phase earth fault occurs, the short-circuit current can flow back into the system through the return line center point, because the return wire grounding current produces a magnetic flux offset magnetic flux a portion of the cable conductor earthing current generated, thus reducing the short-circuit fault induced voltage.

2, cable engineering can be divided into several projects?
(1) site transportation: including engineering material from the warehouse to the construction of loading and unloading, transport and empty backhaul.
(2) the local engineering: including road excavation, tunneling, channel construction etc..
(3) laying project: including the laying head, middle production, cover lifting plate, pipe, school tide, traction head production.
(4): including the production team, two engineering bridge frame and the basic installation, terminal manufacturing, oil pressure and signal devices, a kind of electrical performance test etc..
(5) stop project: including oil filled cable stopper head production, automatic water supply tank, and a signal device installation etc..
(6) the ground project: including the insulating joint, transposition box, protector, grounding box installation.

3, Acceptance of cable line what checks should be carried out?
(1) cable specifications should be consistent with the provisions, shall be arranged orderly, no damage, a full plate, correct, clear;
(2) connecting the metal shield cable fixed bending radius, relative distance and single core cables shall conform to the requirements;
(3) the cable terminal head, middle and no oil leakage, installation is firm, oil filled cable oil and meter setting value shall comply with the requirements;
(4) good grounding;
(5) the cable terminal phase color correct, metal parts such as paint complete bracket;
(6) the cable trench and tunnel, bridge should be no debris, the cover is complete.

4, What are the requirements of cable positive sequence impedance measurement process?
Phase conductor AC resistance and inductance of the cable three identical and known as positive sequence impedance.
The positive sequence impedance of the cable can be directly measured in cable tray, the general use of voltage, low measurement therefore, need to buck with a step-down transformer, converter adopts star connection, capacity is more than 10kVA, voltage, wide adjustment range, measuring the AC power should be relatively stable, to ensure that the current reach the required standard measurement, reading the actual voltage tables must be voltage cable end, close to the cable test current best long-term allowable ampacity, reading the meter value, close the current read at the same time three values.

5, according to the "electric power production safety regulations", what is electrical personnel must have the conditions?
(1) the doctors to identify the health of the body, not hinder the work conditions;
(2) basic knowledge of electrical necessary, according to the position and the nature of the work to master relevant rules, professional technology and safety operation technology, and pass the examination;
(3) Master shock first aid method.

6, cable what should be paid attention to in the transport loading and unloading?
(1) in the transportation, loading and unloading process, should not make the cables and cable trays are damaged, it is strictly prohibited to cable tray directly from the car down, cable like should not flat transport, horizontal storage.
(2) the transport or rolling cable tray, must ensure that the cable firm, an electric cable winding, oil filled cable to the pressure oil tank should be fixed, not damage, pressure tank should be firm, the pressure indication shall conform to the requirements.

7, cable fire what measures?
(1) the fire retardant cable;
(2) adopts the fireproof cable bracket;
(3) the use of fire retardant paint;
(4) cable tunnel, interlayer exit setting fire wall, fire damper;
(5) the overhead cable should avoid the oil pipe, explosion-proof doors, or else should have to take local wear tube or fire insulation measures.

8, Section choose the power cables from which a few respects?
(1) cable to allow long-term work through the current;
(2) once the thermal stability of short circuit;
(3) the voltage drop on the line can not exceed the permitted scope of work.

9, power cables and overhead lines are what are the advantages?
(1) reliability, as installed in the underground shelter, damage by external forces, safety and less chance of failure, power supply, will not cause harm to the person;
(2) maintenance workload is small, do not need frequent inspection;
(3) do not need to set up the tower;
(4) helps to improve the power factor.

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