Partial discharge of the dielectric is an important problem in fault detection of transmission line systems. It has gained gigantic attention to understand the breakdown characteristics of partial discharge. In this paper, the needle–plate discharge experiment is carried out by using the needle–plate defect discharge device and high voltage pulse power supply under atmospheric pressure. The breakdown characteristics are measured and analyzed by changing the needle plate clearance distance and using the step-up method. Finally, a simulation model of the needle plate was established to calculate the electric field intensity when the needle plate gap with different spacing was broken down, and the relationship between the maximum electric field intensity and the needle plate spacing was obtained. It is found that the breakdown voltage increases with the increase in the spacing between the needle and plate. The measured value is only slightly larger than the theoretical value of the breakdown voltage without the influence of harmonics. The simulation found that the larger the spacing between the needle and plate was, the smaller the maximum electric field intensity was during the breakdown, which was different from the theory.

Three-dimensional (3D) reconstruction of high-dynamic-range (HDR) surfaces plays an important role in the fields of computer vision and image processing. Traditional 3D measurement methods often face the risk of information loss when dealing with surfaces that have HDR characteristics. To address this issue, this paper proposes a simple 3D reconstruction method, which combines the features of non-overexposed regions in polarized and unpolarized images to improve the reconstruction quality of HDR surface objects. The optimum fringe regions are extracted from images with different polarization angles, and the non-overexposed regions in normally captured unpolarized images typically contain complete fringe information and are less affected by specular highlights. The optimal fringe information from different polarized image groups is gradually used to replace the incorrect fringe information in the unpolarized image, resulting in a complete set of fringe data. Experimental results show that the proposed method requires only 24~36 images and simple phase fusion to achieve successful 3D reconstruction. It can effectively mitigate the negative impact of overexposed regions on absolute phase calculation and 3D reconstruction when reconstructing objects with strongly reflective surfaces.

The streamer that is driven by the specific pulse DC discharge parameters can stably form a three-dimensional helical plasma channel in a long dielectric tube in the low-temperature plasma experiment, in cases when there were neither external background magnetic field or other factors that destroyed the poloidal symmetry of the tube. The formation mechanism and chirality of helical streamers are discussed according to the surface electromagnetic standing wave theory. The shape of the helical streamers and the characteristics of helical branches are quantitatively analyzed to further expand the application of plasma and streamer theory in the helix problem and chiral catalytic synthesis.

This paper describes the design of a new type of pantograph-catenary arc simulation test device and simulation of the arc generated by the pantograph during operation under laboratory conditions. The influence of the burning position of the pantograph-catenary arc on the overvoltage of the traction system is studied. Corresponding suppression measures for the arcs are proposed, and the dynamics of the arc processes are carried out by theoretical simulation. The characteristics of the pantograph-catenary arc and the discharge process are analyzed, and the relationship between the characteristics of the pantograph and the arc is explored.

Helical and chiral plasma structures are ubiquitous, especially in nuclear fusion devices and space plasmas. However, the spontaneous formation of helical structures has rarely been noticed in non-equilibrium cold plasma jets that have wide applications in biomedicine and material science. Recently the chiral plasma plume without any notable asymmetry has been discovered. Under the specific parameters of pulsed discharges, the plasma bullets that at the beginning propagated in the straight lines spontaneously turn into 3-D helical discharge trajectories. Here, the electromagnetic mechanism for the chiral plasma plumes is clarified by the numerical investigation of the 3-D electromagnetic field. According to the specific standing-wave mode with the periodic poloidal component in simulation, a type of plasma plume which shows the apparent poloidal rotation only at the periodic position of the tube and moves nearly in a straight line at other positions is revealed. These findings are relevant to the development of high-voltage active electromagnetic media for artificial 3-D optical meta-material devices and precise 3-D materials processing involving helical and chiral patterns in diverse fields.