The earliest transformers that appeared a century ago were dry-type transformers. Because the capacity of such a transformer cannot be increased and the voltage cannot be increased, it is technically greatly restricted. In the 1950s and 1960s, China appeared B-class insulated open-air ventilation and cooling dry-type transformers. Such dry-type transformers have not been further developed due to high material prices, poor performance, low reliability, and high failure rates.
As early as the early 1970s, Shanghai and Beijing successively developed thick epoxy resin-filled dry-type transformers with quartz powder filler, which were cast under vacuum. Since then, dry-type transformers have officially become a new generation of batch supply in China. product. Although it was replaced by pure epoxy resin thin insulation technology due to some problems in materials and manufacturing technology at that time, it created a good start for the development of China's electroslag furnace transformer .
Arc furnace transformers are widely used, but few in China. Compared with other transformers, the most outstanding advantage lies in the wide range of applications. The capacity of this transformer can be three-phase 300MVA and the voltage can be single-phase 500kV. It can also be used to manufacture 10kV-level distribution transformers. Its structural design and manufacturing process have many similarities with traditional oil-immersed transformers. Manufacturers can develop it without investing a lot of equipment. However, its shortcomings are also obvious. When the metal is overheated, SF6 gas will decompose a very toxic substance called SF4. If the manufacturing process is not good and leakage occurs, it will have unthinkable consequences for the atmosphere and human beings.
The main insulation products of epoxy resin are already common in China. However, many experts have recently pointed out that the final degradation of arc furnace transformers and environmental protection issues should attract everyone's attention. The field strength of the main longitudinal insulation should be selected according to no partial discharge, so the volume of the transformer may be a little larger, and the relative manufacturing cost is not low. In addition, the appearance of the coil is not as smooth as a product cast with a mold. This product is rare in China or abroad.
Since thick insulation is difficult to solve the cracking problem, some accidents have also occurred. When people were skeptical of epoxy dry-type transformer technology, Shunde Transformer Factory successfully introduced pure epoxy thin insulation technology without quartz filler from Germany, which promoted the rapid development of various transformer technologies in China.