Nonlinear evolution of space synthetic electric field in positive DC corona mode transition

Abstract

Positive corona discharge in the air exists under several distinctive forms depending on DC voltage amplitude, including pulses or pulseless glow. Previous studies obtained the current and optical image characteristics of corona discharge through experiments. However, the synthesized electric field characteristics of the different corona modes have not been deeply studied by experiments, and lack of sufficient understanding of the effect of space charges. In this paper, electro-optical modulation technology is used to investigate the characteristics of the space synthetic electric field (SSE) for positive DC corona modes transition. The experimental results show the significant nonlinear evolution characteristics of the SSE and discharge modes transition with the increase of applied voltage. In the pulsed mode, the SSE first changes slowly and then increases sharply. As the applied voltage increases, the discharge mode transition from pulse mode to pulseless glow mode, while the SSE changes slowly. The electric field change rate in the sharp increase is 2–3 times that in the slow change. Dynamic accumulation behavior of space charges is the main reason for the nonlinear evolution of the SSE. When the pulse current starts, the discharge amplitude and frequency are low, and the ions are far away from the ionization region, which has little effect on the migration process of the high field strength region and subsequent ions. With the increase of the applied voltage, the continuous accumulation of positive ions enhances the migration of subsequent positive ions, thereby rapidly increasing the SSE. During the glow discharge mode, the generation and dissipation of space charges are close to dynamic equilibrium, and the fusion of multiple positive ion clouds will increase the SSE.