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FAQ
Q
Why are high voltage power lines not insulated?
A
1、The voltage flowing in the high-voltage power line is very high, the current is very large, it is easy to generate heat, it will burn the insulation skin, and even break down the insulation.

2、The high-voltage power line is very long, and the bare conductor can reduce weight.

3、The high-voltage power line are generally erected in air, with erection height requirements, and not easy to reach. As long as they meet the safety distance requirements,bare conductor will not cause danger.

Hope our answer can be helpful to you.
Q
Why use non-magnetic materials for single-core armored cables
A
A When a single-core cable is switched on and off by alternating current or direct current, a corresponding alternating magnetic field will be generated around the cable, and an induced current will be generated in the metal material. This current flows inside the metal material, much like a vortex of water, so it is called a vortex. Electric current, referred to as eddy current. The thermal effect of the eddy current can heat the metal material in a short time. If the heat cannot be dissipated in time, it will cause the cable insulation layer to melt or accelerate the aging, and the insulation performance will weaken and cause the cable to break down.

Armored steel tape has good magnetic permeability and can be magnetized under the action of a very small magnetic field to generate eddy currents. Single-core cables should be armored with non-magnetic materials, such as stainless steel tape, copper tape, aluminum tape or non-magnetic metal wire armor.

In addition, single-core cables are easy to use finished glyphs during construction. Single-core cables try to avoid magnetic materials, such as iron pipes, iron clamps, etc., which can form a closed circuit.

In addition, for a three-core cable, the alternating magnetic field generated by the three-core phase relationship cancels each other out, so that the vector sum of the induced current is 0, and no magnetic field lines pass through the armor. Therefore, steel tape armor can be used.
Q
What are the measures for cable fire prevention?
A
(1) Use flame-retardant cables;

(2) Use fireproof cable tray;

(3) Use fireproof paint;

(4) Fire partition walls and fire baffles are installed at cable tunnels, mezzanine exits, etc.;

(5) Overhead cables should avoid oil pipelines and explosion-proof doors, otherwise local pipes or heat insulation and fire prevention measures should be taken.
Q
What should be paid attention to during the transportation and handling of cables?
A
During transportation, loading and unloading, cables and cable reels should not be damaged. It is strictly forbidden to push the cable reels directly from the vehicle. Generally, cables should not be transported and stored flat.

Before transporting or rolling the cable reel, ensure that the cable reel is firm, the cable is wound tightly, the oil pipe between the oil-filled cable and the pressure oil tank should be fixed without damage, the pressure oil tank should be firm, and the pressure indication should meet the requirements.
Q
What inspections should be carried out for the acceptance of cable lines?
A
A) The cable specifications should meet the regulations, the arrangement should be neat, no damage, and the signs should be complete, correct and clear;

B) The fixed bending radius of the cable, the related distance and the wiring of the metal sheath of the single-core power cable should meet the requirements;

C) The cable terminal and the middle head should not leak oil, and the installation should be firm. The oil pressure of the oil-filled cable and the meter setting should meet the requirements;

D) Good grounding;

E) The color of the cable terminal is correct, and the metal parts such as the bracket are completely painted;

F) There should be no debris in the cable trench, tunnel, and bridge, and the cover should be complete.
Q
How many projects can cable engineering be divided into?
A
(1) Construction site transportation: including the loading and unloading, transportation and empty vehicle return journey of engineering materials from the warehouse to the construction site.

(2)Local engineering: including road excavation, tunnel, trench construction, etc.

(3)Laying engineering: including laying, intermediate head production, lift cover plate, buried pipe, school tide, tractor head production, etc.

(4)Two-end engineering: including the production and installation of support, suspension bridge and its foundation, the production of terminal heads, the installation of oil pressure and signal devices, and the electrical performance testing of various types.

(5)Stopping works: including the production of oil-filled cable stop heads, the installation of fuel supply tanks, automatic drainage and signal devices, etc.

(6) Grounding engineering: including installation of insulation joints, transposition boxes, protectors, and grounding boxes.
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