What is the difference between overhead cables and ordinary power cables?
What is the overhead cable?
Many people are confused as to what is the difference between what is commonly referred to as an overhead cable and an ordinary power cable. When is an overhead cable used?
The following is with ZMS cable editor to understand it.
Definition of overhead cable
Overhead cable, known as overhead insulated cable, is equipped with insulation and a protective sheath of the overhead wire, similar to the production process of cross-linked cable manufacturing a special cable, which is between the overhead wire and underground cable between the new transmission method.
The overhead cable is a cable construction method in which the cable is hung on a pole at a certain height from the ground.
Compared with underground cables, although more susceptible to external influences, not safe enough, but also not beautiful, but easy to erect, low construction costs, so far from the Bureau, the number of users and change in the larger, laying underground cables are still widely used in places with difficulties.
Overhead cables are single-core and can be divided into hard aluminum wire structure, hard drawn copper wire structure, aluminum alloy wire structure, steel core or aluminum alloy core support structure, and self-supporting three-core stripe structure, etc. The core can be hard aluminum or hard copper wire, etc.
It has the main features of high reliability of power supply, good safety of power supply, convenient erection and maintenance, and reasonable economy. Its main technical parameters include weather resistance, insulation level, and internal and external semi-conductive shielding layer.
There are 3 differences between overhead lines and cable lines:
The meanings of the two are different
The meaning of overhead lines
Overhead lines mainly refer to overhead bright lines, erected above the ground, which use insulators to fix the transmission conductors and the upright on-the-ground tower to transmit power transmission lines.
The meaning of cable lines
The electrical signal transmission system is composed of communication cables and their ancillary equipment. A communication cable is a bundle of multiple mutually insulated cores or conductors stranded in a certain way, which is covered with a sealed sheath, and some are also covered with an outer sheath. Cable lines can be used to transmit telegrams, telephones, images, data, and TV programs.
The characteristics of the two are different
The characteristics of overhead lines
Erection and maintenance are more convenient, and lower cost, but easily affected by the weather and environment (such as high winds, lightning, dirt, ice, and snow, etc.) and cause failure, while the entire transmission corridor occupies more land area, easy to cause electromagnetic interference to the surrounding environment.
Characteristics of the cable line
Cable lines have the advantages of long service life, large communication capacity, stable transmission quality, less interference from the outside world, good confidentiality performance, etc., and thus occupy a major position in the cable electric communication lines.
The basic requirements of the two are different
The basic requirements of overhead lines
(1) Cable specifications should be in line with the provisions, the arrangement should be neat, with no damage, and complete, correct, and clear labeling.
(2) The fixed bending radius of the cable, the distance and the wiring of the metal sheath of the single-core power cable should meet the requirements.
(3) Cable terminal, the intermediate head does not leak oil, firmly installed, oil-filled cable oil pressure and meter calibration value should meet the requirements.
(4) Good grounding.
(5) The cable terminal phase color is correct, and the metal parts of the bracket and other paint integrity.
(6) Cable trench and tunnel, the bridge should be free of debris, complete cover.
The basic requirements of the cable line
(1) Overhead lines should be widely used steel-core aluminum stranded wire or aluminum stranded wire. High-voltage overhead lines of aluminum stranded wire cross-section shall not be less than 50 square millimeters, core aluminum stranded wire cross-section is not less than 35 square millimeters, air line cross-section is not 16 square millimeters.
(2) Wire cross-section should meet the needs of the maximum load.
(3) The choice of cross-section should also meet the voltage loss of not more than 5% of the rated voltage (high-voltage overhead lines), or 2% to 3% (for the higher visual requirements of the lighting line), and should meet a certain mechanical strength.
As we all know, overhead cable has the main characteristics of high reliability of power supply, safe power supply, easy erection and maintenance, and reasonable economy.
Therefore, it can be used in many places.
But, do you know how to choose overhead cable? What kind of conditions need to be met for the laying of overhead cables? In the following, I will take the overhead cable produced by the ZMS cable manufacturer as an example to help you understand how to choose the right overhead cable.
As overhead cables are vulnerable to natural disasters such as typhoons, ice, and floods, as well as the influence of external forces and the weakening of their mechanical strength.
Therefore, the failure rate of overhead cables is higher than that of direct buried cables and pipe cables, so the selection and laying of overhead cables should be careful.
Since overhead cables are hung on poles, overhead cables can adapt to various natural environments.
Selection of overhead cable
WDZ-YJY low smoke halogen-free flame retardant compound cross-linked polyethylene insulated polyethylene sheathed cable can be laid overhead without an additional protective sheath.
The laying requirements of overhead cable
(1) When the overhead cable is laid on flat ground, use hooks to hang it.
When laying cables on mountains or steep slopes, lay cables by tethering, cable joints should be selected for easy maintenance of straight pole locations, and reserved cables should be fixed on reserved brackets.
(2) The cable of the overhead pole needs U-shaped telescopic bending every 3–5 files, about 15 meters per kilometer.
3) Overhead (wall) cables are protected by galvanized steel pipes, and the mouths of the pipes should be plugged with fireproof mud.
(4) Every 4 stalls pole laying overhead cable, across the road, across the river, across the bridge, and other special locations should be suspended cable warning signs.
(5) The intersection of the empty hanging line and power lines should be protected by a trident protection tube, each end of the extension shall not be less than 1 meter.
(6) The highway near the power pole pulling line should be wrapped luminous rod, a length of 2 meters.
7) To prevent the induction current from causing harm to people, each electric pole pulling wire requires an electrical connection with the hanging wire, each pulling wire bit should be installed with a pulling wire type ground, requiring the hanging wire to be connected directly with a liner ring and grounded directly at the terminal.
The above is about the overhead cable laying requirements, I hope it can give you a reference when using the overhead cable.
