It’s a article about China Transformer Technology Present Situation & Development Trend.
1. Overview of China Transformer Industry
Product process is the process of product manufacturing, and it is an indispensable basic technology throughout the whole manufacturing process.
Advanced technology is the fundamental guarantee to achieve the design goal, ensure product quality, improve operational reliability, save energy and reduce consumption. It is also the technical basis to improve and strengthen the internal management of enterprises.
Transformer plays an important role in power transmission and transformation system. The requirement for safe and reliable operation of transformer is particularly prominent.
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The reliability of transformer operation depends largely on the level of manufacturing technology, besides the reasonable structure design.
In addition to the generality of general product process, transformer manufacturing process has its particularity, which can be summarized as follows:
Firstly, there are many kinds of transformer products.
The range of voltage and capacity varies greatly. Voltage varies from several kilovolts to several hundred kilovolts (the highest voltage level in our country is currently 1000 kilovolts), capacity varies from several kilovolts to hundreds of thousands of kilovolt-amperes.
In addition, there are many kinds of special transformers with different applications. Transformers are not only used in AC transmission system, but also in HVDC transmission system. According to incomplete statistics, there are more than 2000 kinds of transformer products.
Secondly, the level of production automation is not high.
Except for some small-scale products which can be produced in small batches, most of them can be produced repeatedly. And transformer manufacturing mainly depends on manual operation, which is an important factor of low labor productivity and unstable product quality.
Thirdly, there are many professional fields and disciplines involved in transformer manufacturing. The performance of conductive, magnetic conductive and insulating materials used are different and difficult to control.
Finally, once the transformer product has an accident, its hazards will spread widely.
A small factory, a small district, a large province or even several provinces will suffer from its hazards. The economic losses are huge, so the responsibility is great.
In a word, the manufacturing technology of transformer is rich in content and involves a wide range, so it is difficult to accurately summarize the complicated interlocking. The following is just for your reference.
2.Current situation of Transformer Industry
With the rapid development of China’s national economy, the demand for electric power is increasing day by day. As the main equipment in power transmission and transformation system, transformer has also been greatly developed.
In order to meet the market demand, many manufacturers have made unremitting efforts in the exploration of new technology and materials in order to continuously improve product structure and improve product performance by introducing advanced production technology and equipment from abroad.
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At present, transformers are mainly developed in two directions.
First, it will develop to super-large and ultra-high voltage.
The voltage level is 220 kV, 330 kV and 500 kV will develop to 750,1000 KV in the future. The Northwest has decided to adopt 750 KV. The capacity of a single transformer is getting larger and larger.
At present, the largest single transformer in China is a three-phase 720,000 kVA/500 kV transformer manufactured by Shenyang Transformer Plant, and the single transformer used in the Three Gorges Project is a three-phase 840,000 kVA/500 kV transformer.
These transformers are generally used in large power plants or power transmission. So the reliability of operation is very important, so the manufacturer has taken many measures to improve the performance and rationality of distribution of electricity, magnetism, heat and force.
The process and equipment involved in core manufacturing should reduce the additional process coefficient of transformer’s no-load loss as much as possible.
At present, the silicon steel sheets used are cold-rolled lattice oriented high-quality silicon steel sheets. The sheet shape is getting thinner and thinner. 0.35 mm has been eliminated. Generally, 0.3 mm or even 0.27 mm or 0.23 mm thick silicon steel sheets are used.
In order to make the flux flow more reasonable and reduce the loss, multi-step joints are gradually adopted, which requires a matching step-by-step shear line.
In order to reduce unnecessary working hours and wastage, some manufacturers have adopted non-overlapping yoke technology, which requires accurate positioning of non-overlapping yoke overlapping platform.
Core binding is usually tied artificially with weft-free glass tape, so the binding strength is not enough and uneven. At present, the effect of core binding is good in individual manufacturers, and should be gradually promoted.
The process and tooling involved in the manufacturing of_coil should ensure lower load loss, higher ability to withstand short-circuit mechanical force and better heat dissipation performance.
At present, electromagnetic wires are seldom pulled by electrolytic copper rods, which basically use low resistivity and better surface quality anaerobic copper rods.
However, some small factories still use electrolytic copper, which can be used for large-scale products to improve mechanical strength. Semi-hard wire.
When transposed conductors are used to reduce load loss, there are also manufacturers that use self-sticking transposed conductors, which are very beneficial to short-circuit resistance.
In order to ensure the coil winding tightly, the coil width and direction dimension should be zero tolerance as far as possible, especially the impedance error of the converter transformer is very strict.
This requires the use of vertical winding machine or horizontal winding machine with tension, amplitude and axial compression device. When the coil is dried, the use of pressure drying or constant pressure drying as far as possible, so that the coil can withstand short-circuit mechanical force. Great improvement.
Insulation processing, many manufacturers do not attach importance to insulation processing workshop environment is not good, so it is difficult to ensure the insulation strength of coils.
Even some small enterprises share the same equipment for insulating parts processing and metal parts processing. We should keep constant temperature and humidity. It is better to use high density cardboard for insulation cardboard or densification treatment.
Most manufacturers can do this. In this way, the performance of insulation, heat dissipation and mechanical resistance can be ensured. The brace cushion must be depilated and chamfered. Conditions should be added to the insulation processing center equipment.
In transformer quality accidents, there are more insulation and mechanical accidents caused by lead problems, so we should pay more attention to lead processing.
At present, flame brazing or resistance brazing of copper brazing machine are widely used in the welding of lead wire, and cold-press brazing is used in some large enterprises.
At present, cold-press brazing or high-frequency brazing are mostly used in foreign countries. At present, high-frequency brazing is still blank in China. Lead length must be moderate, that is, not too tight to cause vibration force, and not too long to avoid vibration, short-circuit discharge.
For large enterprises, especially for the production of products above 220 kV, the most advanced kerosene vapor-coherent drying process is basically adopted to ensure reliable operation.
Some 110_kV manufacturers are also using vapor-coherent drying process, but there are still quite a number of 110_kV manufacturers using variable pressure or hot air circulation process.
In the past, people generally believed that the vapor-related drying of 110 products is equal to the loss of a big horse trolley, so the pressure-changing method or hot air circulation method is generally used, but now it is different.
110 also requires the measurement of local discharge in the electrical performance, while the user requirements are more stringent, requiring about 100-300 pC.
There are many factors affecting the local discharge, but the body is clean. Cleanliness is a very important link. Only kerosene vapor coherent drying can wash the body thoroughly in the drying process, and the drying effect is very good and can shorten the drying cycle.
The fully automatic vapor coherent drying equipment developed by Shenyang is the most advanced first-class equipment which can guarantee the performance at present.
At present, the leakage of oil-immersed transformer is more serious in domestic oil tank processing. Mainly the sealing surface, flange threaded holes and corner parts of the welding wire, sealing materials are unsatisfactory, the recent production of acrylate sealing performance is better, some manufacturers have steel plate pre-treatment and shot blasting treatment technology tank.
Production environment, cleanliness of electrical products, especially high-voltage products, directly affects electrical performance. At least, dust-proof rooms are required for coil winding and body assembly areas.
Large enterprises in our country basically have such conditions to ensure electrical performance, but their management is not strict, and some of them even fail to meet the requirements.
They should meet the daily dust reduction of less than 20 mg/m2. Large foreign companies Dust-proof has basically been achieved in the whole plant, and there is a big gap between China and foreign countries in this respect.
The second is to develop towards energy-saving, miniaturization, low noise, high impedance, explosion-proof, intelligent and other aspects.
These products are mainly small and medium-sized products, such as the new S9 distribution transformer recommended for urban and rural power network transformation, which is the seventh generation of energy-saving products, as well as coil core transformer, amorphous alloy transformer, fully sealed transformer, combined transformer, dry transformer, high ignition point oil transformer, SF6 gas insulated transformer and so on.
The production process of these transformers can basically borrow the production process of the large transformers mentioned above and have different process characteristics according to different products.
For example, coil core transformer, the current production of coil core transformers are closed core multi-stage and R-core, which requires equipped with coil core machine, special winding machine, core annealing furnace, otherwise it is difficult to produce coil core transformer.
For example, the corrugated tank type fully sealed transformer, which is developed to achieve less maintenance of products, should be equipped with corrugated tank production line.
At present, the simple corrugated tank production line in our country can also meet the production requirements. Amorphous alloy transformer, because the amorphous tape is very thin 0.03mm and very brittle, it is difficult for ordinary manufacturers to process into cores, so they usually buy ready-made cores, such as those produced by United Credit Corporation of the United States or China Steel Research Institute.
With the development of national economy, cities are becoming larger and more prosperous, densely populated, and high-rise buildings are clustered. It is stipulated in the urban network transformation that 110_kV lines should be transferred to urban substation so that 110_kV transformers should be distributed.
Taking Beijing as an example, a substation within the Third Ring Road has a power supply radius of 1.5 km and a power station is usually equipped with three transformers from 50,000 kVA to 6.3 kVA.
So many large transformers are like time bombs in the center of the city, especially in the politically charged city of Beijing. Therefore, people begin to attach importance to high ignition point oil transformer and SF6 gas insulated transformer.
There are many kinds of high ignition point oil, such as silicone oil Midel-7131 oil, alpha oil, beta oil, etc., but the combination of various factors is the most suitable beta oil.
Beta oil is non-toxic and compatible with all materials used in transformers. Its ignition point is 308 C and the price is about 20 RMB per kg. Only the viscosity is slightly higher than that of transformer oil.
Therefore, enough attention should be paid to oil passage and heat dissipation. There is no special equipment needed for producing beta oil transformer.
SF6 gas insulated transformer, SF6 gas colorless, non-toxic, odorless below 600 C is a stable inert gas, non-combustion, non-explosion, good insulation thermal capacity than transformer oil slightly worse, but above 0.14 Mpa heat dissipation performance is good to meet the heat dissipation requirements of transformer.
The production of SF6 gas insulated transformer should be equipped with SF6 gas charging recovery device, gas pressure gauge, densitometer, on-load switch for SF6 gas insulated transformer and other special components.
Polyester materials such as PPS or PET are used for insulation and bracing of turn insulation layer. Because SF6 is a greenhouse gas, it is necessary to ensure a low annual leakage rate of less than 1%/year.