overhead line

How many rumors do you know about wires and cables?

by

The rapid development of the Internet age has not only brought convenience to everyone’s life, but also brought new challenges to our social management. In particular, we have seen the rapid spread of rumors. I believe you can distinguish many rumors, but how many rumors about wires and AAAC Cables have you heard? Can you identify it in time?


If the square of the wire is not enough, it will not be qualified?
not always! For many people, this is already a “common sense” existence, but is this really the case? With the improvement of conductor material production process and scientific and technological progress, the advanced production process of oxygen free copper has been widely used. The resistivity of copper conductor material is enough to ensure that the copper wire less than the nominal diameter can meet the requirements of DC resistance of corresponding specifications, while the conductor of wire and cable has strict requirements on the resistivity of conductor, for example, The DC resistance of 25 mm2 copper core conductor specified in the standard at 20 ° is not greater than 0.727 Ω / km (the second stranded conductor), so the conductor is qualified as long as it is not greater than this value.
Flame retardant ABC Cables will not burn?
wrong! Flame retardant of flame-retardant wire and cable refers to that when a wire and cable fire accident occurs, it can block and delay the diffusion and spread of flame along the wire and cable, and minimize the expansion of fire range of wire and cable. This type of cable has the characteristics of self extinguishing after fire. Fire resistant wire and cable refers to that in the case of wire and cable fire accident, the wire and cable product can adhere to the normal operation for a certain time under the condition that the external flame is still burning, maintain the integrity of wire and cable lines and maintain the normal operation of line equipment.
Will wires and cables have radiation?
Wires and cables do have radiation. However, the fact is that all live things have radiation. For example, 220V wires also have radiation, but the radiation is very small and basically negligible. Moreover, the radiation of wires is much lower than that of mobile phones. If you are really afraid of wire radiation, it is recommended to throw away the mobile phones first. If you are afraid of the magnetic field generated by wires and cables and think that the magnetic field will cause any harm to the human body, the geomagnetic field is even more terrible. Therefore, I think that “radiation from wires will damage health” is just groundless, and I think too much.


The thicker the cable insulation, the better?
No, too thick cable insulation will increase the difficulty of AAC Cable laying. At present, cable laying is mainly bridge or through pipe. Now many enterprises are implementing cable requirements, with tight cable requirements and small outer diameter. There can be gaps in the laying process to emit heat energy to ensure that the outer sheath of the cable is not damaged. Otherwise, it will bring some difficulties to the construction unit and cable laying. In summer, the working temperature will rise, and these temperatures will be emitted through the outer protective layer. The thickness of the sheath increases, and the heat energy is difficult to be emitted, which will affect the service life of the cable. Due to the thermal action of PVC, a series of physical and chemical changes will occur in the insulating layer, losing the original excellent performance, resulting in obvious decline in the insulating performance and even short circuit, Therefore, when selecting the cable, the thickness of the cable must be moderate.
The laying of water and electricity shall be horizontal and vertical
unnecessary! Although the water and electricity wires laid horizontally and vertically look very good, there are really many hidden dangers! Firstly, the material cost of the wire pipe is much higher than that of other laying methods. Secondly, because it is 90 degrees horizontally and vertically, it is easy to get stuck when threading the wire in the later stage! So as long as it complies with the specifications, how convenient it is to lay it!


In addition to the above, there are numerous rumors about wires and cables: wires and cables are cheap, so selling cables makes a lot of money; Wires of the same quality can certainly be bought at a cheaper price; The copper conductor used in wires and cables is not so high; Wires and cables will leak electricity in rainy days, which is unsafe.
Although some are rumors, it’s not too much to say that wires and cables are lifelines. We should be more careful when buying. Only by selecting manufacturers, products and national standard products can we use them at ease.

Analyze the development opportunities of cable accessories industry

by

1. Market demand
China’s power grid construction investment will continue to grow steadily, including smart grid construction, new energy construction and distribution network transformation, which will bring a new round of development opportunities for the cable accessories industry.


The “long-distance, large-scale, high-capacity and high-voltage” pattern of power grid construction will further stimulate the demand for high-voltage and EHV cables and ABC Cable accessories. At the same time, with the development of new energy such as photovoltaic, wind power and nuclear power, the demand for high-voltage and ultra-high voltage DC cable accessories will also increase significantly. Among them, offshore wind power has become a research hotspot of global wind power development. All countries in the world regard offshore wind power as an important direction of renewable energy development, and China has also classified it as an important part of strategic emerging industries. China’s offshore wind power development has entered the stage of large-scale and commercial development. Therefore, it also brings opportunities for the development of submarine cable accessories (submarine cable terminals, intermediate joints and repair joints).
At present, China’s cable accessories industry is still dominated by the domestic market to meet domestic demand. Because Chinese products are competitive with imported products in cost and price. Along with one belt, one road construction will promote the rapid development of the regional economy along the line, and the demand for power construction will be sustained. One belt, one road, China’s home appliances network is relatively backward. In addition, China’s local equipment companies are backward in technology, limited in supply capacity and high in import dependence. This brings considerable business opportunities to China’s cable accessories enterprises with superior price performance.
In the next five years, the average growth of medium and low voltage power cables for power grid construction will still be 7% – 10%. High voltage ACAR Cable accessories of 66kV and above will also become the growth highlight of the industry.


2. Technological innovation and existing problems
The development of cable accessories is closely related to the development of cables. It has also experienced the process from oil filled insulation to dry insulation, from medium voltage to high voltage and ultra-high voltage. The development and production of cable accessories is not a single professional technology, but requires the use of multi-disciplinary comprehensive technology. The fields involved mainly include electrical, mechanical, chemical, polymer materials, etc.
Chinese enterprises lack the core technology of power cable accessories, especially in the research and development of EHV power cable accessories, which has been restricted by technology. In recent years, the cable accessories independently developed by a few domestic technology leading enterprises have gradually become mature, which not only fill the domestic gap and break the foreign monopoly, but also some products have been exported abroad, and the voltage level has reached 500kV. The quality and reliability of domestic cable accessories have also been greatly improved.
Except for a few leading enterprises, the main products of most domestic cable accessories manufacturers are medium and low voltage cable accessories or fittings. Most of them have small production scale, relatively little R & D investment, weak R & D ability, forward-looking and basic common technology research lags behind foreign competitors, and the development of basic materials, basic processes and key components lags behind. Especially in terms of high-voltage, ultra-high voltage AAAC Cable accessories and special cable accessories, there is still a certain gap with the foreign advanced level. There is a long-term shortage of high-quality talents in the industry, the R & D and test ability is weak, and there are few production enterprises with sustainable innovation ability in the industry.
picture

Main Components of Overhead Lines

by

Overhead lines mainly refer to overhead cable, erected on the ground, and are transmission lines that use insulators to fix transmission wires on poles that stand upright on the ground to transmit electrical energy. Overhead lines have low cost, strong mobility, and easy maintenance. However, overhead lines hinder traffic and construction and are easily polluted by debris in the air; moreover, overhead lines may collide with or get too close to trees and other tall facilities or objects, causing electric shocks, short circuits and other accidents.

The main components of overhead transmission lines are Low-voltage cables, insulators, cross arms, low-voltage poles, high-voltage suspension insulators, clamps, high-voltage cables, high-voltage poles,Lightning line.

1.Pole and Tower
The general term for supporting structures that suspend wires through insulators. Pole and tower are the general term for electric poles and iron towers.
The purpose of the tower is to support wires, lightning protection wires and other accessories. In order to keep a certain safe distance between the wires, the wires and the avoidance, the wires and the ground, and the crossing objects.

2. Overhead Wire and Cables
Classification: It can be divided into four types: single-stranded wire, multi-stranded wire, composite multi-stranded wire and insulated wire.
(1). Single-strand Cable: Due to the manufacturing process, when the cross-section increases, the mechanical strength of the single-strand wire decreases. Therefore, the cross-section of the single-strand wire is generally below 10 square millimeters, and currently it is widely used up to 6 square millimeters.
(2). The multi-stranded cable is twisted by multiple thin wires, and the twisting direction of the adjacent layers of the multi-layered wire is opposite to prevent twisting and twisting when paying off. Its advantages are high mechanical strength, flexibility, and flexibility ; And because the surface oxidation resistivity of the strands increases, the current flows along the strands, the skin effect is small, and the resistance is slightly reduced compared with the single-stranded wire of the same cross section.The common type have all aluminum cable (AAC) and all Aluminum Alloy Cable (AAAC ) etc.


(3). Composite multi-stranded wire refers to the multi-stranded wire of two materials. The common type are steel-cored aluminum stranded wire(ACSR cable) and ACAR Cable ,The core part is twisted by steel wire, and the external stranded aluminum wire is integrated. The mechanical properties of aluminum and the electrical properties of aluminum have become the most widely used overhead cable.
(4). Overhead power lines generally use multiple strands of bare conductors, but in recent years, 10kV overhead power distribution lines in urban areas have gradually switched to overhead insulated conductors. The operation proved that it has many advantages, the line failure is obviously reduced, the contradiction between the line and the tree is solved to a certain extent, the maintenance workload is reduced, and the safety and reliability of the line are obviously improved. 10kv mainly has copper core and aluminum core cross-linked polyethylene insulated wires, and low voltage mainly includes JV and JLV.

3. Lightning wire
The lightning protection wire is installed above the wire and is directly grounded for lightning protection to reduce the chance of lightning strikes to the wire, improve the lightning resistance level of the line, reduce the lightning trip rate, and ensure the safe power transmission of the line. Overhead lines have long distances and are exposed to the wilderness, and there are more chances of being struck by lightning. According to the voltage level of the network, the importance of the load, and the number of lightning days and investment conditions in the area, it can be along the whole line or only in the Install lightning protection wires at the entry and exit lines of the substation.

4. Insulator
Insulators, also called porcelain bottles, are used to fix wires and insulate wires and poles. Therefore, the insulator should have sufficient electrical insulation strength and mechanical strength. There are two types of line insulators: high voltage and low voltage. The insulator is a kind of electrical isolation component, its purpose is to insulate between the wire and the wire and between the wire and the ground, support, suspend the wire, and fix it on the cross arm of the tower. The insulator should have good electrical and mechanical properties. . It should also have strong resistance to rain, snow, fog, wind, ice, sudden changes in temperature and the erosion of harmful substances in the atmosphere.

5. Hardware
The role of the fittings: used for suspension, fixation, protection, connection on overhead lines, connecting overhead lines or insulators, and metal devices used to connect the cables on the cable structure of the cable tower.
Basic requirements Electric power fittings are generally made of cast steel and malleable cast iron. It is required that the circuit fittings should have sufficient mechanical strength, and the part of the fittings connecting the conductors should have good electrical properties.