The thermal stability of the insulation material is the main factor affecting the life and overload capacity of the oil-immersed transformer. By explaining the preparation process, physical and chemical properties, electrical performance and anti-aging ability of high-temperature insulation materials used in oil-immersed transformers, the issues that need attention in their application are proposed.

The oil-immersed transformer has the characteristics of good heat dissipation, low loss, large capacity and low cost. It has become the most widely used power transformer in the power grid, and its reliability directly relates to the safety and stability of the power grid. 

The oil-immersed transformer uses a solid-liquid composite insulation structure. Currently, a conventional oil-paper insulation system composed of cellulose insulation paper and mineral insulation oil is often used. The safety and reliability of the insulation system are the basic conditions for the normal operation of the transformer. 

During its operation, the insulation system will gradually age due to the influence of temperature, oxygen, moisture and many other factors. Among them, thermal aging is the main reason. The thermal stability of the insulating material has become the main factor affecting the lifespan, load capacity and volume of the oil-immersed transformer. According to the provisions of GB / Z1094.14-2011, the heat-resistant ultra-cellulose insulating paper / mineral insulating oil solid or liquid insulating material belong to high-temperature insulating materials. Different insulating materials can be combined into an insulating system with different heat resistance levels. Different heat resistance levels should be selected according to different temperature requirements, taking into account their heat resistance and economy.

In short, insulation materials used in transformers mainly play the role of insulation and mechanical support.The quality of insulating material determines the service life of transformer.Insulating materials are gaseous insulating materials, such as air, nitrogen, sulfur hexafluoride, and so on.At present, gas transformers insulated with sulfur hexafluoride are widely used.Liquid insulation material, also known as insulation oil, such as transformer oil, switch oil, capacitor oil, etc.Solid insulating materials, such as insulating paper, insulating board, wood, electrical laminated wood, phenolic board, phenolic cloth board, glass cloth board, etc.