Directly to the power distribution network distribution Power line Conditioner applications at home and abroad belong to large wide range of products. In China, annual production of distribution transformers KVA up to about 50 million, accounting for all the transformers annual l / 3 or so. Therefore, the distribution transformer reliability, technical performance and economic indicators will directly affect the country's economic construction and urban and rural residents and enterprises security of electricity supply.

In recent years, to meet national needs in urban and rural power grids, the development of a number of new, high quality distribution transformers, power distribution network to more advanced equipment, transformers, power supply more reliable, more low-cost electricity in rural areas. Recent development of distribution transformers in the declining value of the loss, especially in no-load loss values ??decreased more, mainly due to magnetic permeability performance improvement, followed by the core type magnetic structure diversification. Such as thin high permeability silicon steel or amorphous alloys application, the whole helical structure of the ladder core joints, wound core (planar, three-dimensional), the annealing process applications. And also in reducing the loss of attention to reduce the noise level. In the dry type distribution transformers in turn as a routine test partial discharge test, the user has a requirement for partial discharge, dry-type distribution transformers as a reliability evaluation index, more than the current provisions of the International Electrotechnical Commission required to strictly. Therefore, our prediction based on the existing trends in various types of distribution transformers, distribution transformers and to promote further development should be a more important work.

Requirements of fire, explosion-proof place, such as commercial centers, airports, subway, high-rise buildings, hydropower, etc., are often used in dry-type distribution transformers. At present, there are dozens of factories to produce the traditional cast resin dry-type distribution transformers. Both the non-excitation voltage, load tap there. Normal operation, but for the way from cold, when the device is equipped with hair to provide first aid conditions (other start-up transformer is faulty fan) as the ultra-running nameplate capacity. In China, the largest single-phase capacity of up to 20000kVA (35kV level), the maximum voltage rating of up to 110KV (single-phase 10500kVA). Dry-type transformer distribution transformer annual accounts for the entire annual output of 20%. In view of epoxy cast dry-type distribution transformers, there are still some of the following questions:

(1) the design freedom is not, each winding to be used for injection mold in order to scratch.

(2) Once in the heat of combustion will produce a lot of smoke.

(3) The epoxy resin and wire are not the same coefficient of thermal expansion, if the buffer layer set properly, easily in hot and cold temperature impact, pouring layer cracking, partial discharge increased, some companies have such a quality individual products exposed in operation.

(4) environmental issues, once the epoxy cast dry-type distribution transformer life expectancy has reached, or a fault condition due to a variety of Transformer Manufacturer  winding damage, to destroy the winding-casting is difficult, now we can not make the ring epoxy resin degradation. From an environmental point of view, this will be an increasingly serious problem.

(5) epoxy cast dry-type distribution transformers are mostly Class F temperature rating, individual companies can produce only Class H temperature rating of the cast dry-type distribution transformers. For these reasons, there are some enterprises in the development of open ventilated dry-type distribution transformers and Class H