Alexander Riedel, Senior Researcher of the Scientific and Educational Center "Physical and Mathematical Foundations of Electromagnetic Safety and Electric Power Transport" of the Novosibirsk State Technical University (NETI), with the financial support of the Russian Science Foundation, is working on the project "Mechanisms for Initiating Discharge Processes in Insulating Fluids Containing Inclusions". The main goal is to develop a physical model of the electrical breakdown of transformer oil at alternating voltage. The work carried out in this direction allows to reduce the number of accidents of the equipment of the power grid complex. NSTU-NETI is actively developing a scientific school founded and headed by Prof. Sergey M. Korobeinikov, Doctor of Physical and Mathematical Sciences. One of the areas of scientific activity is the study of electro physical processes in transformer oil at alternating voltage.
"In 2022, as the head of the research team, I applied for a grant from the Russian Science Foundation as part of the competition "Conducting research by scientific groups under the leadership of young scientists of the Presidential Program of research projects implemented by leading scientists, including young scientists." After three years of work, I can confidently say that a research team with the highest competencies has been formed on the basis of our university, as evidenced by the scientific results. It is worth noting that we actively involve students in the implementation of scientific works, "says Alexander Riedel.
According to what he told, the key element in the transport of electricity is high-voltage oil-filled electrical equipment. Its service life is mainly due to the quality and condition of electrical insulation. This is the most problematic and emergency part of transformers. Electrical insulation consists of two components: paper and oil, electrical and thermos physical processes in which cause its degradation, which leads to emergencies at energy facilities. In the field of electrical insulation, the most fundamental and controversial issue is the ignition of the discharge, which occurs in the liquid and, in turn, is provoked by inclusions in it. The efficient and safe operation of high voltage power equipment is based on physical processes. However, not all of them have been fully studied. Currently, the team is studying the fundamental processes that lead to the appearance of partial discharges and electrical breakdown of insulation at operating values of the electric field strength. Thus, as a result of work carried out in 2024—2025, a three-dimensional model of the development of an electric discharge in a helium bubble in a condensed dielectric was developed. The calculations allow us to talk about four stages of the development of the discharge in the bubble: the explosive growth of charge concentrations, the propagation of the electron wave to the bubble wall with a slow increase in the electron concentration, the propagation of the wave of positive ions to the bubble wall, the residual relaxation of the charge to the bubble wall.
"Members of the research team under the leadership of the main executor of the project, Denis Karpov, obtained the distributions of charge concentrations on the surface of the bubble, which allows us to investigate the processes that precede the breakdown of the gap. In addition, an end-to-end model for calculating the partial discharge in the bubble and the subsequent formation of the discharge structure in the dielectric from the bubble surface is implemented. The model allows you to monitor the change in charges in the channels of the structure and the electric fields in them, "notes Alexander Riedel.
The funds allocated by the Russian Science Foundation were used for the purchase of modern equipment, the presentation of research results at various scientific events, as well as the involvement of young specialists in the research environment. At the next stage, the team, based on experimental and theoretical studies, will develop and describe a single physical model of the discharge in the bubble — from the appearance of the primary electron initiating the partial discharge to the development of the instability of the bubble boundary, leading to the formation of discharge channels in the liquid phase. Such a task is set for the first time and is relevant, as it will increase the level of predictability of breakdown of liquid dielectrics in the presence of bubbles in them. Its solution will significantly increase the awareness of electro physical processes in condensed dielectrics.
In the photo: Distribution of the horizontal component of the electric field strength in the central section of the bubble. Time since seed appearance: $t = $0.3 ns (a), 0.9 ns (b), 1.2 ns (c), 1.7 ns (d).