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Analysis of the necessity of replacing conventional cables with photovoltaic cables
2019-04-08
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In recent years, under the support and guidance of relevant national policies, the solar photovoltaic power generation industry has developed rapidly, and the installed capacity of photovoltaic power plants has increased year by year. However, due to the relatively lag in the research and development of domestic photovoltaic cables and their market promotion, in the process of photovoltaic power station construction and operation, photovoltaic power station equipment connection cables still use conventional cables. Due to the fact that conventional cables do not consider the complex and changeable factors such as the use and laying environment of photovoltaic power plants in the design and manufacturing process, they cannot meet the use requirements, resulting in frequent quality problems of photovoltaic power plants. In particular, the quality problem caused by the fact that the performance of the conventional cable itself cannot meet the requirements of the power station operating environment is particularly obvious. The special photovoltaic cable is designed according to the complex and changeable photovoltaic power station operating environment, which can meet the laying and operation requirements of the photovoltaic power station. The use of special photovoltaic cables in photovoltaic power plants, especially the DC side, can effectively reduce the occurrence of quality problems.
Photovoltaic power stations are built all over our country, which requires a wide range of temperature resistance grades of cables. For example, in the western and northern regions of our country, cables are required to withstand lower temperatures, and extreme low temperatures in individual areas can reach -40°C below zero. , even lower temperatures. In the eastern and southern regions of my country, the surface temperature can easily reach above +70°C. Considering that the working temperature of the conductor is higher than the ambient temperature and generates heat volatilization, it is very likely that the extreme temperature in the area where the roof is not ventilated and the heat dissipation effect of the bridge is not good Above +90°C, which requires the material temperature of the cable to meet the requirements of the power station working in extreme temperatures.
Frequent changes in temperature and humidity have a direct impact on the insulation and aging of the material, especially in areas with large daily temperature differences and annual temperature differences and in humid and rainy areas, which have a greater impact on the insulation and aging properties of the material. In my country's fish-light complementary projects, many power stations are directly built on fish ponds or on the water surface, requiring cables to work normally in a humid environment for a long time. The performance of conventional cables does not consider the influence of moisture and heat changes on the aging performance of materials, while the design of photovoltaic special cables takes into account the factors that affect the aging performance of insulation and sheathing materials in the design of photovoltaic special cables. Therefore, qualified photovoltaic cables can meet the requirements of photovoltaic power plants. Requirements for temperature and humidity changes.
Photovoltaic power plants have a long sunshine time, and their intensity of exposure to sunlight is greater, and sunlight contains a variety of rays, especially ultraviolet rays, which can accelerate the aging of cable insulation and sheathing. Most of the cables of photovoltaic power plants are laid bare. In most cases, the cables from solar modules to combiner boxes and even to inverters are directly laid bare. This requires that the cables must be able to withstand sunlight and ultraviolet radiation. It works normally for a long time under the vertical radiation of ultraviolet rays. Therefore, qualified photovoltaic cables can work normally for a long time under the conditions of sunlight and ultraviolet radiation, while the insulation and sheath of conventional cables will accelerate aging under the conditions of sunlight and ultraviolet radiation, resulting in reduced insulation performance or failure, sheath The problem of reduced protection.
Some photovoltaic power plants are built in special areas such as seaside and tidal flats. These areas have high levels of salt spray in the air. Some photovoltaic plants are located in former salt pans, where the soil is high in salinity. Cables used under the above environmental conditions must have strong resistance to salt spray and acid and alkali. Therefore, qualified photovoltaic cables have strong resistance to salt spray and acid and alkali. The ozone content in some areas where photovoltaic power plants are located is relatively high, and ozone has a certain corrosive effect on the cable sheath, that is, it accelerates the aging of the sheath and affects the use of the cable. Conventional cables do not consider -
Why can't the legendary high-voltage cables be buried underground? do you know
2019-04-08
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Ultra-high voltage power transmission refers to the use of 500 kV - 1000 kV voltage level to transmit electrical energy. If the 220 kV transmission index is 100%, the relative investment per kilometer of ultra-high voltage transmission, the relative cost of 100 kilometers per kilowatt-hour transmission, and the consumption of metal materials will be greatly reduced, and the utilization rate of the line corridor will be significantly reduced. improve.
In daily life, we can often see overhead ultra-high voltage power transmission projects. Have you ever thought about such a question: why can't we bury all high-voltage wires underground like urban underground cables?
The current underground cables are generally of low voltage level, and the line transmission with high voltage level is often overhead, which is mainly due to cost and technical factors.
The structure of underground cables is more complex than that of overhead lines, the technical requirements are higher, and the manufacturing and construction are difficult. In addition, the cables are buried underground, so it is not easy to find faults, and it is also difficult to repair and maintain. In terms of cost, the cost of underground cables of the same voltage level is generally 3 to 5 times higher than that of overhead lines.
Especially our common high-voltage lines are often used for long-distance transmission. If underground cables are used, especially long-distance transmission often has to pass through complex terrain, the cost and technical requirements will increase linearly.
On the other hand, it is also a congenital "hard injury" of the underground cable itself. Overhead lines have good heat dissipation conditions in the air, while the air around underground cables does not flow and it is difficult to dissipate heat, which limits the power level that can be transmitted by underground cables to a large extent.
The important thing is
For ultra-high voltage transmission, an effective insulating material has not been found to be the outer insulation layer of the wire. Therefore, the ultra-high voltage wires are exposed and cannot be buried underground. There are distributed capacitances around the wires, and current can leak out through these capacitances, which increases consumption on the one hand; on the other hand, if any animal approaches, there is also a danger of electric shock.
Air is an insulator, but the earth is a conductor. In the air, as long as the wire is directly placed there, it is fine, but in the ground, a layer of insulating casing should be added to the wire, otherwise the electricity in the wire does not go far, and there will be little leakage left.
The structure of underground cables is more complex than that of overhead lines, the technical requirements are higher, and the manufacturing and construction are difficult. In addition, the cables are buried underground, so it is not easy to find faults, and it is also difficult to repair and maintain. Generally speaking, the cost of underground cables of the same voltage level will be several times or even dozens of times that of high-voltage lines in the air.
Burying ultra-high voltage cables into the ground has both safety and economic problems. If there is a fault, the inspection and repair of the cables is very huge and cannot stand the toss. Therefore, the current ultra-high voltage cables should be hung high. air.
The insulation layer and protective layer of the underground cable conductor are very strict, and there will be no danger for the human body to touch the outer skin of the cable normally. The laying of cables is also very particular. Most of the cables are buried in special cable trenches, cable pipes or cable tunnels, which are well isolated and protected. The depth is generally less than half a meter. deep.
Moreover, every tens of meters on the ground where the cables are buried, there will be a cable work well or a cable marker pile as a sign to remind people to pay attention to safety. Therefore, underground cables generally do not pose a danger to residents. -
"Photovoltaic + energy storage" has become the key to breaking the situation in the era of affordable Internet access
2019-04-08
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In 2019, the development of my country's photovoltaic industry has come to a critical adjustment period. Not only does the development of the entire industry tend to be orderly from "barbaric growth", but the entire industry chain needs to complete an all-round transformation of quality, technology and efficiency. At present, my country's photovoltaic industry has achieved great progress in technology, technology, efficiency and other aspects in recent years, and policies have also begun to focus on reducing the non-technical costs of the industry. It is reasonable to say that the development of the photovoltaic industry should be bright.
But in the long run, as photovoltaic power generation gets closer to grid parity, and as photovoltaic power generation becomes more and more deeply embedded in the national power market, there is a problem that will increasingly become a bottleneck for the development of photovoltaic power generation.
Photovoltaic power generation faces bottlenecks
According to data released by the National Energy Administration, the national photovoltaic power generation in 2018 was 177.5 billion kWh, a year-on-year increase of 50%. In the future, as photovoltaic power generation achieves grid parity, the scale and power generation of photovoltaics will further explode and begin to gradually replace traditional energy sources.
It can be said that with the advent of the era of grid parity, photovoltaic power generation will face the competition of traditional coal power. In addition to price and cost, photovoltaic power generation has a huge disadvantage compared to traditional coal power, that is, stability. Since the intensity of sunlight is changing at any time, the voltage and current output of photovoltaic power stations are fluctuating. Even with the modulation of photovoltaic inverters, this fluctuation can only be smoothed out as much as possible, but cannot be eliminated. The most important thing is that in the dark night without the sun, the photovoltaic power station cannot generate electricity at all, and this instability will make the power grid connected to the power station suffer greatly.
At present, with the continuous development of photovoltaic technology, the cost of photovoltaic power generation is lower than that of traditional coal power is just around the corner. In this way, stability may become the primary factor that undermines the competitiveness of photovoltaic power generation.
However, as far as the mode of photovoltaic power generation is concerned, there is basically no way to solve its instability through ordinary photovoltaic systems. What can solve the stability of photovoltaic power generation is energy storage.
Energy storage is the key to breaking the game
In fact, the use of energy storage to solve the instability problem of photovoltaic power generation has long been reflected. In order to solve the fluctuation caused by a large number of photovoltaic power generation, the power grid generally needs to use the energy storage system to cut peaks and fill valleys, so as to achieve the purpose of stabilizing the large power grid system. This is the help that energy storage provides to photovoltaic power generation on the grid side, and this is only one aspect of it.
In the off-grid mode, energy storage can help the photovoltaic system to stabilize the output power and realize the self-sufficient power consumption mode of users. At present, our photovoltaic projects are all grid-connected projects, that is, they are directly integrated into the large power grid system after completion, and then used after the deployment of the large power grid. There is no doubt that users cannot directly use photovoltaic power in the grid-connected mode. This is the reason for the fluctuation of power generation, and it is also to solve the problem that the power station cannot generate electricity at night. In the off-grid mode, the photovoltaic system is loaded with the energy storage system, and its power does not need to be integrated into the grid, but can be used directly. At the same time, the excess electricity generated by the photovoltaic system can be stored by the energy storage system, so that there is no power outage at night.
At present, there are relatively few off-grid projects, mainly because the cost of energy storage systems is still high, and the current policy subsidies are more inclined to grid-connected projects. So off-grid models are often not as economical as grid-connected models. However, in some special scenarios, such as mountainous areas and rural areas where the power grid cannot reach, off-grid photovoltaic projects are also used. In the future, with the reduction of energy storage costs and the disappearance of photovoltaic subsidies, off-grid photovoltaic projects are expected to be promoted on a large scale.
The above is the help that energy storage brings to photovoltaic power generation in grid-connected mode and off-g -
How to distinguish the "national standard" and "non-standard" of wire and cable?
2019-04-08
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When choosing cables, you should choose cables according to your own site usage, and don't be greedy for cheap. Thinking that the cable is cheap and can be guaranteed to be the national standard, in all likelihood, it is a rubbish. Fudge unprofessional users who do not understand the industry. In order to enable the majority of users to have a clearer understanding of the quality standards of cables and wires and the difference between national standard and non-standard self-judgment. So, how to distinguish "national standard" and "non-standard" of wire and cable?
It is recommended that you take a look, try the second, weigh the third, compare the price fourth, look at the copper quality fifth, test the quality six, and see the difference in the sixth.
A look: Check whether the wire and cable products have quality system certification, whether the certificate of conformity is standardized, whether there is a factory name, factory address, inspection stamp, production date, and whether there are trademarks, specifications, voltages, etc. printed on the wires. It also depends on the cross-section of the copper core of the wire. The superior-quality copper has a bright color and a soft color, otherwise it is a defective product.
Second test: It is advisable to take a wire end and bend it repeatedly by hand. Any product with soft feel, good fatigue resistance, high elasticity of plastic or rubber, and no cracks on the wire insulator is an excellent product.
Three weighing: good quality wire and cable, generally the weight per 100m is within the specified weight range. For example, the commonly used plastic insulated single-strand copper core wire with a cross-sectional area of 1.5mm2 has a weight of 1.8-1.9kg per 100m; the plastic insulated single-strand copper core wire of 2.5mm2 has a weight of 3-3.1kg per 100m; Insulated single-strand copper core wire, the weight per 100m is 4.4-4.6kg, etc. Poor quality wire is underweight, either not long enough, or has too much impurities in the copper core of the wire. If it is a cable, especially a large-sized cable, the soil method of weighing is the easiest method to best reflect whether the copper content of the cable meets the standard and whether the conductor cross-section meets the standard. Generally, there is a small cross-section cable made of copper. After weighing, the copper content can not reach the weight range of the allowable error stipulated by the state, and it can basically be regarded as non-standard.
Four price ratios: Because the production cost of counterfeit and shoddy wires is low, traders often sell them at low prices under the guise of low prices and high quality, which makes people fooled. Therefore, when buying, be careful, don't get carried away by the "good quality and low price" advertised by the merchant, and end up being deceived. Five look at copper. Qualified copper core wire copper core should be purple, shiny and soft to the touch.
5. Look at the copper material: The copper core of the fake and inferior copper core wire is purple-black, yellowish or white, with many impurities, poor mechanical strength and poor toughness. When checking, you only need to peel off one end of the wire, and then rub a piece of white paper on the copper core. If there is black material on the white paper, it means that there are more impurities in the copper core, and it can be identified as "non-standard" "Wire and Cable.
Six quality inspection: in the case of differences in cable quality, it can be sent to a third-party inspection agency for inspection. It is based on whether the authoritative test report is qualified.
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Anhui Weiguang Cable Co., Ltd.
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