Dry-type transformer is mainly composed of iron core and winding two parts. The iron core is composed of an iron core column and an iron yoke. The iron core is generally made of a silicon steel sheet coated with insulating paint on both sides. The iron yoke is usually made of a silicon steel sheet with a high silicon content and coated with insulating paint on the surface. This structure can not only reduce the hysteresis inside the core, but also reduce the eddy current loss of the core.
Winding is the main circuit channel of dry-type transformer. Most of them are made of paper-wrapped insulated flat wire or round wire. At present, the winding of most dry-type transformers gradually uses foil structure. Because this structure can not only improve the cooling performance and mechanical strength of the dry transformer, but also can greatly improve the pressure resistance of the dry transformer.
In addition to the windings and core, the dry transformer has an insulating structure. The insulation structure of the dry type transformer is composed of internal insulation and external insulation. Understanding the structure of dry-type transformers is helpful to deepen the understanding of the characteristics of dry-type transformers.
2, the characteristics of dry type transformer
Dry transformer is a transformer that uses air as the cooling medium. It is different from the cooling method of oil-immersed transformer. It mainly uses the cooling method of natural air cooling and forced air cooling. Natural cold air is mainly used in transformers with small capacity and long time operation, while forced air cooling is mainly used in transformers with large capacity and high temperature requirements. And in the process of operation allows an appropriate amount of temperature rise, which is of vital significance to improve the safety and stability of the dry type transformer applied in the power system. The following is a summary of the characteristics of the dry-type transformer:
(1) At present, most dry transformers are cast with epoxy resin. This new type of material not only has a strong ability to prevent combustion, but also is very environmentally friendly and safe.
(2) the insulation performance of the dry transformer is good and the reliability is strong. The allowable temperature rise of the dry-type transformer greatly improves the moisture-proof function of the dry-type transformer compared with the traditional oil-immersed transformer.
(3) the perfect temperature protection monitoring system of dry transformer not only ensures the safe operation of the power system, but also reduces various costs and expenses to a certain extent. And because there is no need for oil immersion, there is no need to accumulate oil pits and other ancillary buildings, thus greatly reducing the cost of civil construction.
(4) compared with the oil-immersed transformer, the dry transformer does not need to be immersed in oil in operation, which makes its operation will not bring toxic air pollution because of oil leakage, thus playing a role in protecting the environment. At the same time, the dry transformer operation process is more stable, and without increasing the environmental impact, can be maintained for a long time, so it will not bring serious noise pollution.
(5) dry transformer because of its good safety performance, low energy consumption, moisture-proof, simple operation, easy maintenance and other advantages are more and more used in a variety of power engineering, in 6-35KV city buildings, rail transit facilities and other public places, dry transformer is particularly widely used. Dry-type transformers are widely used in the construction of the western power input network and the construction of the Three Gorges of the Yangtze River. It is a rare opportunity for the dry-type transformers.
3, the choice of dry type transformer
The correct choice of dry type transformer plays an important role in improving the safe and stable operation of power system. In the above paper, we have understood the structure and characteristics of dry type transformer. This part of us will describe how to choose dry type transformer according to the load nature and use environment of dry type transformer.
(1) Choose according to the load nature of power. There are many kinds of power load, different power load to choose different dry type transformer. If the baseline impact level of the power load is less than 150kV, it is best to use a Class H dry-type transformer; If the base impact level of the power load is greater than 150kV, epoxy cast dry-type transformers shall be used.
(2) according to the use of dry type transformer environment to choose. For very harsh environment, the best choice of epoxy resin casting dry type transformer, because this environment does not need to preheat the dry type transformer, can run immediately; But for general use environment, H class dry type transformer can be applied.
The author according to the dry type transformer load nature and the use of the environment of these two aspects are briefly described, but in the specific power system application process, according to the actual situation, to other factors should also be considered, such as loss, noise and protection system.
4, the development direction of dry type transformer
With the acceleration of China's urbanization and industrialization development process, China's demand for dry-type transformers increases at the same time, the function of dry-type transformers and other aspects also put forward new requirements, the following is the new direction of the development of dry-type transformers in China.
(1) Portable. With the increasing number of urban buildings and density of residents, in order to facilitate the installation and handling of dry-type transformers, it is required that dry-type transformers are small in size and light in weight. Therefore, in the production of dry-type transformers not only to use high-quality electromagnetic and insulating materials, but also continue to optimize the structure and design of dry-type transformers.
(2) reliable operation and easy maintenance. The safe operation and maintenance of dry-type transformers are related to the safe and reliable operation of power system, so it is particularly important to ensure the long-term reliable operation of dry-type transformers. In the production of dry-type transformer, we should not only choose good materials and reasonable design, but also improve the use function of dry-type transformer and do a good job in maintenance.
(3) environmental performance. With the improvement of people's living standards and the gradual improvement of the awareness of environmental protection, it is self-evident to improve the environmental performance of dry transformers. Therefore, in the production of dry-type transformers, it is not only necessary to continuously improve the moisture-proof and waterproof performance of dry-type transformers, but also to do a good job in the treatment of discarded dry-type transformers.
(4) low noise type. With the development of society, the requirement of improving the low noise performance of dry-type transformer is higher and higher. Therefore, in the design, material and structure of the dry transformer, attention should be paid to reducing the noise produced in the operation of the dry transformer.
5. Conclusion
Dry-type transformers play an important role in the development of power system. With the increase of national input on dry-type transformers, different types of dry-type transformers have also entered the practical application scope of engineering. But each transformer has its own advantages and disadvantages, and is not absolutely good and bad, so consumers should according to the functions and characteristics of these transformers, and combined with their own needs, such as conditions, comprehensive consideration, and then choose suitable for their own dry transformer. As the research and development enterprises and manufacturers of dry transformers, should be based on the needs of social development direction, constantly strengthen the research and development of various new technologies conducive to improving the function of dry transformers and improve the function of dry transformers, so as to produce more suitable for the market demand of high quality dry transformers.
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