The latest development trend and present situation of power transformers in China
Power transformer is one of the important equipment in power generation, transmission, substation and distribution system. Its performance and quality are directly related to the reliability and operation benefit of power system.
First, power transformer varieties
(a) distribution transformers in China's small and medium-sized distribution transformers were originally developed with insulating oil as the insulating medium; Entered the 1990s, the dry transformer in our country had a rapid development.
(1) oil-immersed distribution transformers S9 series, S11 series distribution transformers, coil core distribution transformers, amorphous alloy core distribution transformers. In order to make the operation of the transformer more complete and reliable, more simple maintenance, more widely to meet the needs of users, in recent years, the oil-immersed transformer has adopted a sealed structure, so that the transformer oil and the surrounding air are completely isolated, thus improving the reliability of the transformer. At present, the main sealing forms include air sealing type, nitrogen - filled sealing type and oil - filled sealing type. The market share of fully oil-filled sealed transformers is getting higher and higher. When the volume of insulating oil changes, it is compensated by the elastic deformation of corrugated tank wall or expansion radiator.
(2) <0><0 BBB>e to the simple structure, easy maintenance, and fire prevention, flammability and other characteristics, China has been produced since the end of the 1950s, but in the last 10 years began to mass production. There are many types of dry-type transformers, including dip-insulated dry-type transformers and epoxy resin insulated dry-type transformers.
(2) box-type transformer box-type transformer has the characteristics of less occupation, can be extended into the load center, reduce line loss, improve the quality of power supply, flexible location, beautiful appearance and so on. At present, it is widely used in the urban 10KV and 35KV power grid. At present, the box transformer used in our country is mainly European box transformer and American box transformer. The former transformer as a separate component, namely, the high-voltage receiving part, the distribution transformer and the low-voltage distribution part of the trinity. The latter structure is divided into two parts, the front is divided into wiring cabinet, the back is divided into transformer oil tank, windings, iron core, high voltage load switch, plug-in fuses, backup current limiting fuses and other components are placed in the tank body. At present, some manufacturers have moved the coil core transformer to the box-type transformer, so that the box-type transformer volume and quality are reduced, to achieve high efficiency, energy saving and low noise level.
At present, China has a 110KV, 220KV, 330KV and 500KV high voltage, ultra-high voltage transformer production capacity. The insulating medium of ultra-high voltage transformer is still mainly insulating oil. According to the needs of the development of power grid, the production technology of transformer is constantly improving. SF6 gas insulated high voltage and ultra-high voltage transformer is being researched and developed.
Two, the level of manufacturing in general, China's power transformer technology in the international level of the early 1990s, a small number of in the world at the end of the 1990s level, compared with foreign advanced countries, there is still a certain gap.
1, the core material in the 1970 s, wuhan iron and steel company in the introduction of digestion and absorption of Japanese manufacturing technology on the basis of the production of cold-rolled steel for cold rolled silicon-steel sheet, in the 1990 s and the introduction of Japan's high permeability grain to the cold rolled silicon steel sheet - B (HI) manufacturing technology, to create a better energy saving effect of the power transformer core materials. However, because the quantity of products can not meet the demand and the production process, we still have to import part of cold-rolled silicon steel sheet from Japan, Russia and Western Europe and other countries. In developing power distribution transformer core with amorphous alloy materials, in the early 1990 s in our country has the original machinery, metallurgical department, the ministry and the state planning commission, state economic and trade commission, the former state science and technology commission has formed a special working group, the amorphous alloy iron core materials and amorphous alloy core transformer design and manufacturing technology conducted in-depth research, research of amorphous alloy iron core material to achieve the requirement of the planned index, and in 1994 developed voltage 10 kv and 160 ~ 500 kva capacity of distribution transformer, the power user trial showed that the basic meet practical requirements.
However, the manufacturing process of amorphous alloy materials still needs to be further improved to meet the requirements of mass production. In 1998, Shanghai believe company introduced the United States GE company's manufacturing technology, with the United States of amorphous alloy material production of amorphous alloy iron core transformer, now can produce voltage 10 kv, 50 ~ 2500 kva capacity, no-load loss between 34 ~ 700 w, load loss between 870 ~ 21500 w of amorphous alloy iron core transformer, and have this kind of material is applied to the epoxy resin dry type transformer, amorphous alloy core transformer further promotes our country the improvement of manufacturing. Some transformer manufacturers in China have introduced amorphous alloy core products into the power grid operation.
2, tooling equipment before the 1980s, China's transformer special equipment technology level, on the whole is relatively low, in addition to the winding equipment has a professional production plant production, the rest of the vast majority of enterprises are self-made relatively simple equipment, only a few have a simple core processing longitudinal shear line. In the 1980s, the transformer industry began to introduce foreign advanced special key equipment, such as core shear line, low frequency electric drying system, etc. By the 1990s, due to the promotion of dry transformers, the introduction of a number of epoxy casting equipment and foil winding machine, several large production plants also introduced the insulation processing center, so that China's transformer production tooling equipment level greatly improved. Domestic some special equipment manufacturer after digestion and absorption, also developed between vertical and horizontal line, special equipment, the domestic special equipment, its function and main technical parameters of basic at or near the international level, to ensure the transformer products, improve the technical performance of transformer, improve the efficiency of production has played a vital role.
3, transformer technology design nearly 20 years, the voltage level of 110 kv and below oil-immersed transformer optimization design is a lot, and has gradually replaced the standards such as 64, 73, 79, 86, at present is introduced in the late 1990 s, 99 standards, the formation of a new series of energy-saving transformer, reduce various losses further, replacing the energy-intensive products. In 1998, the state further clarified that the 64-series and 73-series old transformers running in the power grid must be phased out and updated, and the S7 transformers produced according to the 1979 standard must also stop production. The type S9 distribution transformer, which has been vigorously promoted in the construction and transformation of urban and rural power grids from 1998 to 2001, conforms to the national standard in 1999. Since 2000, the coil core transformer has been used in the construction and transformation of the two networks.
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