Jan 07,2025
As an important part of transformer insulation system, edge paper is widely used in oil-immersed transformers. It has excellent electrical strength, heat resistance and mechanical properties, and can remain stable in high temperature and high voltage environments. In the actual operation process, insulating paper withstands the comprehensive effect of many factors such as electric field, heat, oxidation and humidity, and its performance is directly related to the insulation level and service life of the transformer.
Material classification of insulating paper
Cellulose insulating paper
Cellulose insulating paper is the most common and widely used type of transformer insulating paper, and its main component is cellulose. Cellulose, as a natural polymer, is formed by the glucose unit connected by the β-1, 4-glucoside bond, and the molecular chain presents a highly ordered arrangement, giving the insulating paper good mechanical strength and thermal stability. During the operation of the transformer, the cellulose insulating paper can withstand a certain mechanical stress to ensure the stability of the winding and prevent damage to the insulation structure caused by external force. At the same time, the thermal stability makes the insulating paper not easy to decompose or deform within the normal working temperature range, and maintains a stable insulation performance.
NOMEX isolating paper
NOMEX insulating paper is a synthetic aromatic amide polymer insulating paper with unique and outstanding properties. The high temperature resistance of NOMEX insulating paper is particularly outstanding, with the UL material temperature rating of 220°C, which means that it can maintain effective performance for more than 10 years even after continuous exposure to high temperatures of 220°C. In some power systems with demanding temperature requirements, such as transformers in high energy consumption areas such as large thermal power plants and metallurgical industries, NOMEX insulating paper can easily cope with high temperature challenges to ensure stable transformer operation.
Other new insulating materials
With the continuous development of material science, a series of new insulating paper materials came into being, bringing new breakthroughs to transformer insulation technology. Among them, polymethylpentene (PMP) paperboard, as a potential new material, has been widely concerned. PMP paperboard has a lower dielectric constant, compared with traditional cellulose insulating paper, can more effectively improve the electric field distribution inside the transformer, reduce the phenomenon of local electric field concentration, thereby reducing the risk of insulation breakdown. In some high-voltage and ultra-high-voltage transformers, the uniformity of electric field distribution is very important for the reliability of insulation system. The application of PMP paperboard provides a new way to solve this problem.
Classification of transformer insulating paper
Main isolating paper
As the key material in the transformer insulation system, the main insulation paper is responsible for ensuring the electrical insulation between the winding and the iron core and between the winding and the winding, and its performance directly determines the insulation performance and voltage resistance level of the transformer. In high voltage and ultra-high voltage transformers, the main insulation paper needs to withstand extremely high electric field strength, so the electrical strength of its put forward strict requirements. Insulation paper with high dielectric strength and low dielectric loss is usually selected to effectively block current leakage, reduce energy loss and prevent partial discharge. This kind of insulating paper generally has a tight and uniform fiber structure, and the pores between the fibers are very small, which can effectively prevent the intrusion of impurities and water, so as to ensure the stability of the insulation performance.
Interturn insulating paper
Interturn insulating paper is mainly used to protect the insulation between each turn of the conductor in the transformer winding and prevent the occurrence of interturn short circuit, which plays a vital role in maintaining the normal operation of the transformer. Because the winding will be affected by many factors such as electromagnetic force, thermal stress and mechanical vibration during operation, the interturn insulating paper not only needs to have good electrical insulation performance, but also needs to have excellent flexibility and mechanical strength to adapt to complex working conditions.
Lead insulating paper
Lead insulating paper usually has high tensile strength and wear resistance, smooth and flat surface, easy to wrap tightly on the lead, forming a reliable insulating protective layer. In some large power transformers, the lead wire is longer and withstand larger current, in order to ensure insulation performance, in addition to the selection of high-quality insulating paper, will also add a layer of protective sleeve in the outer layer of insulating paper, such as heat shrink sleeve or rubber sleeve, further enhance the insulation effect, while playing a waterproof, moisture-proof, anti-corrosion role.
In operation, insulating paper is like the "guardian armor" of the transformer, from electrical safety, life extension to operation efficiency optimization, all-round escort. Prevent short circuit breakdown, suppress electromagnetic interference, and lay the foundation for stable power transmission; Slow down aging, reduce failure risk, extend transformer service life; Reduce energy loss, improve heat dissipation, help energy saving and efficiency.
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