变压器是电力系统中的重要设备之一其作用是将高压电能转换为低压电能以满足电力系统各个级别的用电需求。在变压器的实际运行中由于高电压和高局部场强的存在会引起变压器油中流注的分叉现象从而导致绝缘失效。因此研究变压器中流注分叉特性的动态演化机理对于提高变压器的运行可靠性和延长其使用寿命具有重要意义。流注是指在液体绝缘介质中由于电场作用下的电荷运动导致沿着电场方向形成的细长通道。流注的形成和发展过程是一个复

"Transformer is one of the important equipment in the power system, which converts high voltage electrical energy into low voltage electrical energy to meet the power demand at various levels of the power system. During the actual operation of the transformer, the presence of high voltage and high local electric field can cause the phenomenon of streamer branching in the transformer oil, leading to insulation failure. Therefore, studying the dynamic evolution mechanism of streamer branching characteristics in transformers is of great significance for improving the operational reliability and extending the service life of transformers.

Streamer branching refers to the formation of a slender channel along the electric field direction in a liquid insulation medium due to the movement of charges under the action of an electric field. The formation and development process of streamer branching is a complex physical process, involving the comprehensive effects of electric field, medium properties, fluid mechanics, and other factors. Streamer branching in different propagation modes has different geometric shapes. The commonly used streamer development model can only describe the change in the average development speed when the streamer propagation mode changes, and cannot quantitatively describe the changes in the geometric shape of the streamer. Therefore, quantitative analysis of the geometric features of streamer branching can provide a deeper understanding of the evolution laws and mechanisms of streamer branching.

In this paper, common mineral oil and gas oil in transformers are studied. The streamer images in the 25mm gap needle-plate electrode under standard lightning impulse voltage are pre-processed, and the streamer skeleton is extracted and fractal analysis is performed to calculate the quantitative changes in geometric parameters such as fractal dimension and branching number during the development of streamer. Fractal analysis is an emerging mathematical tool that can be used to study the geometric features of complex systems. By analyzing the fractal dimension of streamer, the fractal characteristics and geometric shape changes of streamer can be understood. At the same time, by statistically analyzing the branching number of streamer, the branching characteristics and branching shape changes of streamer can be understood.

The research results show that the streamer in transformers has obvious fractal characteristics, and its fractal dimension gradually increases with time, indicating that the geometric shape of the streamer becomes more complex. At the same time, the branching number of streamer also gradually increases with time, indicating that the branching characteristics of streamer gradually strengthen. These research results provide important support for further exploring the dynamic evolution mechanism of streamer branching characteristics.

In conclusion, this paper studies the dynamic evolution mechanism of streamer branching characteristics in transformers and proposes a quantitative analysis method based on fractal analysis, which can provide a deeper understanding of the evolution laws and mechanisms of streamer. These research results are of great significance for improving the operational reliability and extending the service life of transformers."