Views: 0 Author: Site Editor Publish Time: 2022-04-25 Origin: Site
Liquid-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. Its reliability is directly related to the safety and stability of the power grid. The Liquid-immersed Transformer adopts a solid-liquid composite insulation structure. At present, a conventional oil-paper insulation system consisting of cellulose insulating paper and mineral insulating oil is often used. The safety and reliability of the insulation system is the basic condition for the normal operation of the transformer. During the long-term operation of the oil-immersed transformer, the insulation system is gradually aging due to the influence of temperature, oxygen, moisture, and other factors. Among them, thermal aging is the most important aging factor. The thermal stability of insulating materials becomes the main factor affecting the life, load capacity, capacity, and volume of Liquid-immersed Transformers. So what is the research status of Liquid-immersed Transformer high-temperature insulating materials?
This is the content list:
l Conventional insulating material
l High temperature solid insulating material
Cellulose insulating paper is composed of about 90% α-cellulose, 10% hemicellulose, and a small amount of lignin, etc. α-cellulose is a long-chain high polymer composed of about 2000 glucose monomers (C6H10O5) hydrocarbons. Mineral insulating oil is obtained by distillation and refining of petroleum, accounting for more than 80% of naphthenic hydrocarbons, and a small number of alkanes and aromatic hydrocarbons. Under the action of heat, the cellulose paper will undergo a thermal degradation reaction, the molecular chain will be de cyclic or broken, the degree of polymerization will decrease, and the mechanical strength will decrease, resulting in gases such as CO and CO2 and furan compounds such as furfural dissolve in oil. When the temperature rises, the degradation reaction is accelerated, and the aging of cellulose paper is aggravated by the effects of hydrolysis and oxidation. The mechanical properties determine the life of the cellulose insulating paper. As the cellulose paper ages, its mechanical strength decreases, making the ability of the transformer to withstand short-circuit current and overvoltage reduced, and it is easy to cause internal discharge under external triggers, and even cause insulation breakdown and failure. The aging of mineral insulating oil is mainly caused by oxidation. Under the action of moisture and temperature, the aging is accelerated, and the oxidation of alcohol, aldehyde, and ketone is formed. Acid compounds and acid compounds will eventually precipitate sludge, and acid compounds and sludge will accelerate the aging of cellulose paper.
Thermal aging is the most important factor among the many aging factors of Liquid-immersed Transformer, and the thermal aging speed is mainly determined by temperature. The conventional insulation system composed of cellulose insulating paper and mineral insulating oil has a heat resistance grade of A, and it operates continuously at a hot spot temperature of 98 °C, with a relative aging rate of 1. For every 6 K increase in temperature, the relative aging rate doubles, and the service life Halved, is commonly referred to as the "6-degree rule" for the life of oil-immersed transformers. The anti-aging ability of insulating materials not only determines the lifespan but also determines the capacity and load capacity of the Liquid-immersed Transformer. The use of high-temperature insulating materials for oil-immersed transformers can delay insulation aging, prolong life, increase capacity and load capacity, and reduce transformer volume and quality.
To improve the heat resistance of solid insulating materials in Liquid-immersed Transformers, currently, thermally modified cellulose paper, aramid paper and adhesives made of cellulose and polyamide materials have been used in oil-immersed transformers. A new insulating paper with properties between cellulose paper and aramid paper. Some polymer materials have excellent heat resistance and have also received extensive attention. Although they have not been used in Liquid-immersed Transformers, they have good application prospects.
Heat resistance is an important property of solid insulating materials, but the application of insulating materials in Liquid-immersed Transformers should not only consider their heat resistance but also their mechanical and electrical properties. The degree of polymerization is a direct reflection of mechanical properties, and electrical properties mainly include breakdown voltage, dielectric constant, and dielectric loss. The breakdown voltage is a direct parameter to characterize the electrical properties of insulating materials; the change of dielectric constant will cause the change in electric field distribution. In solid-liquid composite insulation, the electric field distribution is inversely proportional to the dielectric constant. close, the electric field distribution in the composite insulation system is more reasonable, and the electric strength is higher; the dielectric loss characterizes the energy loss caused by the conductance and polarization of the insulating material under the action of the electric field thermal breakdown.
The above is the relevant content about the research status of Liquid-immersed Transformer high-temperature insulating materials. If you are interested in a Liquid-immersed Transformer, you can contact us. Our website is www.sntoom.com.