The latest development trend and current status of power transformers
The latest development trend and current status of power transformers
Power Transformer is one of the important equipments in the transmission, transmission, transformation and distribution systems. Its performance and quality are directly related to the reliability and operational efficiency of the operation of the power system.
(I) Distribution Transformers China's small and medium-sized distribution transformers were originally developed with insulating oil as the insulating medium. In the 1990s, dry-type transformers developed rapidly in China.
(1) Oil-immersed distribution transformer S9 series distribution transformer, S11 series distribution transformer, coil core distribution transformer, amorphous alloy core transformer. In order to make the operation of the transformer more complete and reliable, the maintenance is simpler and more widely meet the needs of users, in recent years, the oil-immersed transformer adopts a sealing structure to completely isolate the transformer oil from the surrounding air, thereby improving the reliability of the transformer. At present, the main sealing forms are air-sealed, nitrogen-filled and fully oil-filled. Among them, the market share of fully oil-filled sealed transformers is getting higher and higher, and it compensates for the elastic deformation of the corrugated oil tank wall or the expanded radiator when the volume of the insulating oil changes.
(2) Dry-type transformer Dry-type transformers have been produced since the end of the 1950s due to their simple structure, convenient maintenance, and the characteristics of fire prevention and flame retardance. However, mass production began in the past 10 years. There are many types of dry-type transformers, mainly including impregnated insulated dry-type transformers and epoxy-insulated dry-type transformers.
(2) Box-type transformer box-type transformer has a small footprint, can extend into the load center, reduce line loss, improve power supply quality, flexible location, beautiful appearance, etc. Currently, it is widely used in urban 10Kv and 35kV power grids. The box-type transformers currently used in China are mainly European-style box-changing and American-style box-changing. The former transformer is a separate component, that is, a high-voltage power receiving part, a distribution transformer, and a low-voltage power distribution part. The latter structure is divided into two parts, the front part is the wiring cabinet, the rear part is the transformer oil tank, and the winding, iron core, high voltage load switch, plug-in fuse, backup current limiting fuse and other components are placed in the fuel tank. At present, some manufacturers have moved the core transformer to the box transformer, which has reduced the volume and quality of the box transformer, achieving high efficiency, energy saving and low noise level.
(III) High-voltage and ultra-high-voltage power transformers At present, China has already possessed the production capacity of high-voltage and ultra-high voltage transformers of 110kV, 220kV, 330kV and 500kV. The insulating medium of ultra-high voltage transformers is still dominated by insulating oil. According to the development of power grids, the production technology of transformers is constantly improving. SF6 gas insulated high voltage and ultra high voltage transformers are under research and development.
Overall level of manufacturing, China's power transformer technology is in the international level in the early 1990s, a small amount in the world's level in the late 1990s, compared with foreign advanced countries, there is still a certain gap.
In the 1970s, based on the introduction of digestion and absorption of Japanese cold-rolled silicon steel sheet manufacturing technology to produce cold-rolled silicon steel sheets, in the 1990s, Japanese high-magnetic grains were introduced into cold-rolled silicon steel sheets (HI-B). Technology has produced a power transformer core material with better energy saving effect. However, due to the insufficiency of product quantity and production process, some cold-rolled silicon steel sheets are still imported from Japan, Russia and Western Europe. In the development of amorphous alloy materials for distribution transformer cores, China had specialized work in the early 1990s by the former Ministry of Machinery, the former Ministry of Metallurgy, the former Ministry of Electric Power, the State Planning Commission, the State Economic and Trade Commission, and the former State Science and Technology Commission. In the group, the design and manufacturing process of amorphous alloy core material and amorphous alloy core transformer were deeply studied. The amorphous alloy core material developed basically met the requirements of the original plan index, and in 1994, the voltage was 10kV and the capacity was 160. The distribution transformer of ~500kVA has been tested by power users and has basically reached the practical requirements.
However, the manufacturing process of amorphous alloy materials still needs further improvement to meet the requirements of mass production. In 1998, Shanghai Zhixin Company introduced the manufacturing technology of GE Company of the United States, and produced amorphous alloy core transformers with American amorphous alloy materials. At present, it can produce voltages of 10kV, capacity of 50 to 2500kVA, and no-load loss of between 34 and 700W. The amorphous alloy core transformer with load loss between 870 and 21500W has been applied to epoxy resin dry-type transformers, which further promotes the improvement of the manufacturing level of amorphous alloy core transformers in China. In China, some transformer manufacturers have applied products made of amorphous alloy materials to the grid.
Tooling equipment Before the 1980s, the technical level of special equipment for transformers in China was relatively low. Except for the production of professional equipment in the winding equipment, most of the others were relatively simple equipment made by the company, only a few. Several have simple iron core processing slitting lines. In the 1980s, the transformer industry began to introduce foreign advanced special key equipment, such as iron core slitting line and low frequency electric drying system. In the 1990s, due to the vigorous promotion of dry-type transformers, a number of epoxy casting equipment and foil winding machines were introduced. Several large-scale production plants also introduced insulation processing centers, which made China's transformer production tooling equipment level improve. Some domestic special equipment manufacturers have digested and absorbed, and also developed special equipment such as vertical and horizontal production lines. The functions and main technical parameters of these domestic special equipments have basically reached or are close to the international level, and the technology to ensure the quantity of transformers in China and improve the transformers. Performance and productivity have played a crucial role.