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Lightning strikes on aircraft are mainly due to self-triggered bidirectional leader discharges. Understanding the physical processes of lightning strikes is the basis for designing appropriate lightning protection measures. For this purpose, the development processes of bidirectional leaders triggered by a floating conductor were studied in a laboratory. In this paper, an experimental platform for the observation of bidirectional leader discharges is established through a reasonable gap arrangement. The discharge processes were recorded by a high-speed camera with up to 504 000 f/s. The effects of negative streamer discharges on the positive leader propagation speed as well as brightness during the bidirectional leader discharge at different electric field rise rates were mainly studied and quantitatively analyzed by introducing incremental coefficients. The experimental results show that the discharge development at the negative end of the floating conductor lags behind that at the positive end, and there is a coupling phenomenon between the positive and the negative discharge. At low electric field rise rates, when a negative streamer discharge occurs, it causes a positive corona burst, resulting in a sharp increase in brightness, while on the contrary the leader speed change is not as pronounced as the brightness change. As the rate of rise of the electric field increases, the effect of the discharge at the negative end on the positive end gradually decreases. This work could provide a theoretical basis for understanding the physical process of lightning strikes on aircraft. [ABSTRACT FROM AUTHOR]

A three-stage-five-coil inductive power transfer (IPT) system which is based on cylindrical solenoid coupler (CSC) is proposed in this article. The shape and parameters of the CSC are optimized. The five litz coils compensated by series capacitors are considered to form an IPT system based on equivalent CLC/S/CLC compensation topology with constant voltage characteristics. The mutual inductance between compensation auxiliary coil (CAC) and power transfer coil could be changed by moving the position of CAC, and the freedom of parameter design is enhanced. Mathematical model and loss model of the system are established, and power transfer characteristics of the system are analyzed. The system is considered to be used as a power source for state detection equipment of high-voltage (HV) device to achieve long-distance IPT, the effect of the coupler on the HV electric field is verified. Finally, a prototype with a length of 1.54 m was built. Based on the platform, output voltage and dc–dc power transfer efficiency curves with changed input voltage and load are obtained. The maximum efficiency of the dc–dc system can reach about 60%. [ABSTRACT FROM AUTHOR]

Knowledge of leader corona is the basis for long spark discharge modelling, which is critical to understand the underlying physics of lightning flashes and dielectric breakdown of long air gap widely utilized in power systems. This paper presents an accurate observation of the leader corona. The morphology of the leader corona region during the discharge was obtained using a high-speed camera and an image-enhanced charge-coupled device camera. Statistical results showed that the morphology of the streamer region varied at different discharge sub-phases. The first corona was a conical region with the average apex angle of 118.91°; the leader corona region behaved as a cone with an average vertex angle of 75.87° during the leader propagation process; the streamer area in the final jump was a combination of a cylinder and a cone with the average vertex angle of 82.61°. Noting that the obtained cone apex angle of the leader corona during the leader propagation phase was significantly smaller than that in photographical reports, and the observation results were related to the selected temporal resolution of the optical image apparatus. The discussion on the effect of the single-frame exposure time on observation results found that the average vertex angle of the conical streamer region gradually decreased with the decrease of the single-frame exposure time, and eventually tended to a stable value of about 75.96°. For comparison purposes, discharge experiments under two gap-distances demonstrated that on the premise of stable leader, the statistical distribution characteristics of the leader corona vertex angle were consistent, indicating the universal applicability to the simulation researches. Finally, it is found that the distortion of the electric field caused by the space charge explained the variation of the streamer area during the discharge process. [ABSTRACT FROM AUTHOR]