Development of the hottest dry-type transformer in

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Development of dry-type transformers in China

Abstract: at present, various types of dry-type transformers in the world have basically appeared in China's market, and users of dry-type transformers have more choices, which is a good thing. This paper makes a preliminary introduction to various types of dry-type transformers on the market, which is convenient for users to choose reasonably. This paper also makes some suggestions on the varieties that can be developed in the future for the reference of manufacturers and users

key words: dry-type transformer Untitled Document 1. Preface:

since Faraday discovered the phenomenon of electromagnetic induction, the earliest transformer that appeared a century ago is dry-type transformer. Because the capacity and voltage of this transformer cannot be increased, it is technically limited. The appearance of transformer oil has made indelible contributions to the development of transformer technology. This kind of cheap oil medium with good insulation and thermal conductivity makes the application range of transformer very wide. At the same time, some accidents, such as combustion and explosion, also occurred in the transformer. It seriously threatens the safety of people's lives and property. All this is attributed to the burning transformer oil. Especially after the rapid growth of power consumption, the distribution center is getting closer and closer to people's activity center. At this time, safety is the first priority, and this kind of distribution transformer does not need to be large in capacity, and the voltage will not be high. It is best to use dry-type transformer. In the 1950s and 1960s, an open, ventilated and cooled dry-type transformer with class B insulation called "OVDT" abroad appeared in China. Due to the high price of insulating materials, poor performance and simple manufacturing process, this dry-type transformer has low reliability and high failure rate. Not recognized by everyone. In fact, at that time, epoxy resin and Nomex Paper had appeared abroad. In this way, the epoxy resin cast dry-type transformer was developed in Europe, while the OVDT open type, ventilated and cooled dry-type transformer with Nomex Paper Insulation was developed in the United States. Then France adopted the UL certified Nomex insulation specification of DuPont company of the United States to develop a secure VDT encapsulated, ventilated and cooled dry-type transformer (secure is a trademark registered by DuPont company of the United States in the world, and Yunnan Transformer Factory translates it as "segmai" -- the author's note)

II. Classification of dry-type transformers:

there are many methods to classify dry-type transformers, such as SC (epoxy resin casting encapsulated type), SCR (non epoxy resin casting solid insulation encapsulated type), SG (open type). It can also be divided according to insulation grade, including grade B, F, h and C. in some foreign countries, there is also a grade n between H and C. Their temperature limits are shown in Table 1

Table 1 temperature limit values of each insulation heat-resistant grade insulation temperature grade a e grade B grade F grade H grade n at present, the total amount of China's traditional petrochemical industry has been very large grade C maximum allowable temperature (℃) winding temperature rise limit (k) performance reference temperature (℃)

here we classify according to the insulation materials selected by the voltage transformer, See Table 2

Table 2 dry type transformer classification

classification SF6 gas epoxy resin Nomex other types of vacuum pouring process winding process open type


impregnation process encapsulated type


coating process thick insulation

thin insulation with filler without filler

let's make a brief introduction to these transformers respectively

1. SF6 gas insulated dry-type transformer:

SF6 transformer is widely used in Japan, but rarely in China. Compared with other dry-type transformers, its most prominent advantage is that it has a wide range of application fields. This kind of transformer can achieve three-phase 300mva capacity and single-phase 500kV voltage (all made in Japan). It can also manufacture 10kV distribution transformers (as early as 1988, Guangzhou high voltage electrical appliance factory, Beijing No. 2 transformer factory and Changzhou transformer factory in China have all developed it, and Beijing No. 2 transformer factory once produced it in small quantities). Moreover, its structural design and manufacturing process have many similarities with the traditional oil immersed transformer. Transformer manufacturers can research and develop it without a lot of equipment investment. Of course, its defects are also obvious. SF6 gas will be decomposed into a highly toxic substance of SF4 when the metal is overheated. Coupled with the poor manufacturing process, the consequences of leakage to the atmosphere and people are unimaginable. Therefore, many domestic experts believe that the development of such transformers in China should not be advocated when the manufacturing process cannot reach a certain level

2. Ring compatible PS photosensitive layer wear resistance experiment oxygen resin vacuum cast transformer:

(1) as early as the 1970s, Shanghai and Beijing transformer factories successively developed epoxy resin encapsulated dry-type transformers with thick insulation and quartz powder filler cast in the vacuum state. According to conservative estimates, since then, dry-type transformers have officially become a new generation of products supplied in batches in China, although because of its material, There are some problems in the manufacturing process, which was replaced by the later thin insulation technology of pure epoxy resin, but it has created a good start for dry-type transformers after all, and promoted the development of dry-type transformer technology in China

(2) because the thick insulation (6mm) is difficult to solve the cracking problem, when people have doubts about the pressure regulator technology of the protection mechanism for the automatic return of the tested product to normal temperature to avoid frost and condensation at the end of the experiment, Shunde transformer factory successfully introduced the pure epoxy thin insulation (mm) technology without quartz filler from Germany. Its emergence has made the technology of dry-type transformers in China develop rapidly. Because the product quality of this technology is relatively stable (using imported pouring equipment and imported resin), users are relatively satisfied. In addition, at that time, the manufacturing plant had better economic benefits, so everyone started one after another. At first, more than 10, then 30, 70, and now more than 100 have adopted this technology. At present, it has accounted for% of the dry transformation market, and the production capacity has exceeded 30million KVA every year. Supply has exceeded demand much better. We are all familiar with this kind of transformer, so we won't talk more about it

(3) at the beginning of this century, Shanghai GE company used American technology to research and develop a class H insulation thin insulation epoxy resin vacuum cast dry-type transformer with filler, and some insulation materials inside the transformer are Nomex insulation paper. He successfully solved the technical problems of insulation coordination, process formula and uniform pouring among various insulating components inside the transformer. Its appearance changed the insulation heat resistance grade of epoxy resin encapsulated dry-type transformer from grade B

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