Since oil-immersed power transformers cannot be arranged in the main body of high-rise buildings, this speeds up the process of popularization and application of dry-type transformers. Especially 10 kV dry-type transformer.
However, due to the rapid development of dry-type transformer technology, it is necessary to correctly select the dry-type transformer.
At the same time, we must do a good job in the operation and maintenance of dry-type transformers to ensure the economy and safety of dry-type transformer operations.
The immersion type is one of the earliest structural forms used in dry-type transformers, and the coils need to be impregnated with insulating varnish after winding.
The impregnated dry-type transformer has a good heat dissipation effect, and can be recycled well after the expiration, and has a very good environmental performance. However, the damp-proof and dust-proof ability of the immersed dry-type transformer is weak.
The coil structure of the immersed dry-type transformer is very similar to that of the oil-immersed transformer, and mainly consists of two types of insulation: Class B and Class H.
Class B insulated coil is a coil shape commonly used when dry-type transformers are first used. When the coil is immersed, a layer of moisture-resistant covering paint will be applied. Because of its simple production, the product has poor moisture resistance. As a result, its insulation level cannot be effectively guaranteed.
For H-class insulation products, the coil winding method is usually the encapsulated type for cylindrical coils, while the open type used for pie-type coils uses NOMEX paper for turn insulation and layer insulation.
Effectively improve the electrical performance of the coil.
At present, these two representative products are represented by the products of DuPont in the United States and the products of MORA in Germany.
Moreover, Class H insulating dry-type transformers will be impregnated with excellent solvent-free resin paint, which effectively improves the moisture-proof performance of the product.
The cast coil uses a mold to insert the wound coil into it, and then uses epoxy resin to pour it in a vacuum state and cure it at a high temperature, thereby effectively ensuring the improvement of the product’s moisture resistance and corrosion resistance. People call it: cast resin dry-type transformer.
However, this kind of coil process is more complicated, and the molds of the required equipment are more expensive.
At present, the pouring structure usually takes two forms: with filler and without filler.
Non-filler casting materials are mainly based on resin, curing agent, toughening agent and accelerator color paste.
The material with filler is the addition of quartz powder on the basis of the material without filler. Due to the addition of filler, the component ratio of other materials changes greatly. This effectively reduces the material cost, improves the thermal conductivity inside the coil, and has a better heat dissipation effect, but it is difficult to ensure the filling effect during the pouring process.
In the initial use of 10kV dry-type transformers, due to the thicker insulation structure of the product cast with filler, the resin thickness of the outer layer of the coil is usually more than 6mm, and there is a certain difference between the thermal expansion coefficient of the resin and the thermal expansion coefficient of the wire. It is an inevitable phenomenon that the transformer generates heat during operation, which can easily lead to cracks in the epoxy resin casting layer, which can lead to accidents.
To solve this problem, you can choose a material with a thermal expansion coefficient similar to that of the epoxy resin layer as the wire as much as possible. In the actual casting process of the cast dry-type transformer coil with filler, aluminum wire is selected to effectively prevent the occurrence of cracking. The use of aluminum wire cannot completely avoid the occurrence of cracking. In the concrete casting process, it is also necessary to embed reinforced glass fiber mesh cloth in the coil to truly solve the problem of epoxy resin cracking.
Wrapped dry-type transformer This is a type of winding that needs to be wound simultaneously with the glass fiber when the coil is wound.
Before the glass fiber is wound on the coil, it needs to pass through a resin tank, so that the glass fiber will be wound onto the coil together with the resin.
After the coil is wound, it needs to be heated and cured in an oven, and proper rotation is required during the heating of the solid, so as to ensure that the surface of the coil has better flatness.
At the same time, variable pressure degassing is required.
The wound dry-type transformer does not require special equipment and molds during the coil winding process, but it is not performed in a real state during the tree finger injection process.
Therefore, it is difficult to avoid the presence of air bubbles inside the coil, and the product has a large volume, which requires a long time and the cost is relatively high.
Through the analysis of the immersed, cast and wound dry-type transformers, it can be found that each dry-type transformer has its own advantages and disadvantages. However, they are all feasible in the actual application process.
Therefore, when modeling, users need to choose the appropriate form according to their own operating environment. At the same time, when selecting dry-type transformers, they also need to comprehensively consider factors such as the rationality and quality of the manufacturer’s design process.
Ensure the correctness of the shape, so as to ensure the safe and reliable operation of the dry-type transformer.
Currently cast resin dry type transformer is the most widely used dry type transformer.
In actual operation, cast resin dry type transformer has strict requirements on operating conditions and is easily affected by external environmental factors.
Therefore, it is necessary to strengthen its maintenance to ensure the standardization of maintenance, so that it can meet the operating conditions stipulated by the standard.
Putting large-capacity equipment into operation caused long-term overload of the transformer, and the heat could not be dissipated in time, and the user did not take appropriate measures.
Although the fan speeds up the heat dissipation of the transformer after turning on, and can increase its load capacity, the increased overload capacity can theoretically increase by up to 40%, but if it is operated for a long time, safety and economy will be affected.
Detailed explanation of the difference between dry-type transformers and oil-immersed transformers
As an air insulation product, dry-type transformers will affect their insulation performance and easily lead to accidents once their surface is dusty.
In addition, the dry-type transformer itself is not strong against moisture, especially when the dry-type transformer is out of service for a period of time, it will be damp, and there will be dust and debris on the performance, which makes it difficult for its coils to achieve natural air drying. It is bound to have a greater impact on its insulation performance.
Therefore, it is necessary to ensure the cleanliness of the dry-type transformer operation site, avoid dust and debris on the surface of the dry-type transformer, and take corresponding moisture-proof measures.
The accurate selection of dry-type transformers is an important guarantee to ensure the safe and economical operation of dry-type transformers. Therefore, it is necessary to have a detailed understanding of the characteristics of dry-type transformers of various structures and make reasonable choices.
At the same time, as a manufacturer of dry-type transformers, Daelim will take effective preventive measures according to the specific conditions of customers. And provide you with a manual. We also provide a professional installation team to help you install and maintain dry-type transformers. Ensure the safety and economy of dry-type transformer operation.
When you need to find more than just existing transformers, Daelim’s Transformer Service Center can help you design and produce distribution transformers that meet your unique needs.
We have our own factory and a professional team of engineers, which can design and modify application requirements that meet all your conditions.
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