Numerical study on partial discharge in a dry air cavity with a two-dimensional fluid model considering practical reactions

Abstract

Partial discharge (PD) is an important factor leading to insulation degradation of electrical equipment. Understanding the PD mechanism is of great significance for maintaining the safety of power systems. Compared with the previously reported PD models, this work develops a well-validated plasma fluid model considering more practical particles and reactions in order to explain the PD behaviour from the physicochemical point of view. The simulation results reveal that, under the power frequency voltage (50 Hz), the PD in a small dry air cavity operates at the weak Townsend mode. Besides, since the electric field nearby the perpendicular wall is significantly distorted by the void geometry, the local intense discharge presents a radial migration. Such a migration route of the local intense discharge can enlarge the discharge area per radial distance and is believed to be capable of inducing the oscillation of the current pulses. Furthermore, the main reaction pathways of ions production/destruction are elaborately analyzed, as well as the contribution of different ions to the surface charge accumulation. Finally, the generation law of the main oxidative product of the dry air discharge-O3 is obtained. It is revealed that the O3 concentration elevates with a fixed increment during each voltage half-cycle in the steady-state, and such an increment basically increases linearly as the voltage amplitude rises. The corresponding discussions in this work would be helpful both to achieve a better understanding of plasma dynamics in PD and to predict the PD intensity or position in the practical application scenarios.