A Hydrodynamic Drift-Diffusion Model to Simulate Positive Air Discharges Under Atmospheric Pressure

Even though controlled non-thermal (low-temperature) electrical discharges have a wide range of applications from biomedicine to nanotechnology to environmental science, the electrical breakdown of insulation systems caused by discharges within the dielectrics is one of the most unwelcome events in the operation of high-voltage electrical apparatuses and power system components. A deeper understanding of non-thermal discharges is therefore of paramount relevance with reference to increasing levels of operating voltages and technological advancements. Particularly, the behavior of freely available atmospheric air, as the most commonly used gaseous dielectric, under applied high voltage calls for specific technical and analytical attention. This study set out to mathematically model, simulate, and analyze nonthermal plasma discharges in the insulation systems with air as the dielectric under normal atmospheric conditions. In this paper, a new hydrodynamic drift-diffusion model to simulate positive air discharge under atmospheric pressure is developed. This model contains a set of continuity equations for electron, positive, and negative ions (to include the dynamics and generation/loss of these charged particles and development of space charge) strongly coupled with Poisson's equation (to account for the mutual influence of space charge and interelectrode electric field). The model is validated with experimental results. The spatial and temporal evolution of charged particles and development of space charge, distribution of local electric field, and discharge current in the interelectrode air volume are presented and analyzed. Also, the effects of different parameters are studied. Simulations are carried out using COMSOL Multiphysics software. Comprehensive computer simulations enable it to gain a more profound insight into the behavior of atmospheric air as dielectric and non-thermal plasma discharges through this medium, which was not possible until some years ago. Therefore, this study not only corroborates the existing experimental findings but also facilitates further investigations in this area of study.