The thermal stability of insulating materials is the main factor affecting the life and overload capacity of oil immersed transformers. The high-temperature solid insulating materials that can be used for oil immersed transformers are described from the aspects of preparation process, physical and chemical properties, electrical performance and anti-aging capability.
Oil immersed transformers have the characteristics of good heat dissipation, low losses, large capacity, and low cost, and have become the most widely used power transformer in the power grid. Their reliability is directly related to the safety and stability of the power grid. The oil-immersed transformer adopts a solid-liquid composite insulation structure, and currently a conventional oil-paper insulation system composed of cellulose insulation paper and mineral insulation oil is commonly used. The safety and reliability of the insulation system are the basic conditions for the normal operation of transformers. During the operation of oil-immersed transformers, the insulation system will gradually age due to various factors such as temperature, oxygen, moisture, etc. Among them, thermal aging is the most important factor among many aging factors. The thermal stability of insulation materials has become the main factor affecting the lifespan, load capacity, and volume of oil immersed transformers. According to the regulations of GB/Z 1094.14-2011, the solid or liquid insulation materials of heat-resistant cellulose insulating paper mineral insulating oil are high-temperature insulation materials. Different insulation materials can be combined to form insulation systems with different heat resistance registrations, and insulation materials with different heat resistance levels can be selected according to different temperature requirements, taking into account the heat resistance and economy of the insulation materials.
Domestic and foreign scholars have conducted extensive research on high-temperature insulation materials that can be used for oil-immersed transformers. In the field of solid insulation materials, on the one hand, aromatic polyamide paper and polyamide material adhesive paper have been applied in oil-immersed transformers. On the other hand, the application of polymer materials in oil-immersed transformers has received official attention, such as polyester, polycarbonate, etc. Improving the aging resistance and heat resistance of insulating materials for oil immersed transformers is still an important part of the development of insulating materials.