Lightning current in the process of discharge can cause the potential differences between insulators to rise, hindering the normal operation of the equipment. To reduce the potential difference between insulators during a lightning strike, this study proposes a semi-enclosed structure to limit the rise of potential between insulators. Lightning-induced overvoltage causes the semi-enclosed structure to discharge, forming an arc channel. Because the arc is compressed by the structure, an overpressure-induced shock wave is generated. Positive reflection occurs when the shock wave hits the wall that damages the development of the arc through superposition. By using the theory of positive reflection of shock waves, the overpressure due to a positively reflected wave, generated by an impulse current of 8/20 µs with a peak value of 10 kA, was as high as 4.8 MPa, 48 times the initial pressure. Moreover, a 3D high-current impulse discharge model was established in COMSOL to simulate the process of shock discharge of the structure in the case of a large current. Finally, current-induced shock tests were carried out in the semi-enclosed structure. The results show that the maximum pressure in the semi-enclosed structure was 4.38 MPa at 10 µs and conductivity dropped to zero at 80 µs. In experiments, the amplitude of the impulse current decreased from 9.54 to 5.72 kA, and the current dropped to zero at about 65 µs. The results show that the semi-enclosed structure can extinguish the arc and limit the rise of potential between insulators.
The problem of resistance reduction has always been the key and difficult point of lightning protection. However, the problem of reducing the grounding resistance efficiently has not been solved. A method is introduced in this paper to solve this problem from the lightning current attenuation. The lightning discharge shock wave mechanism, shock overpressure reflection mechanism, and arc truncation mechanism are included to theoretically analyze the lightning current attenuation mechanism. The overpressure of the lightning discharge is much higher than the cut-off arc radial tolerance pressure, which contributes to the temporarily closing of discharge channel. Moreover, a lightning discharge model is established in COMSOL to simulate the process of discharge in lightning current. The results show that the pressure in the tube reaches up to 4×10 8 Pa rapidly, and the velocity in the mouth of the tube could reach as high as 4200 m/s. Finally, the current attenuation experiments are designed to validate the lightning current attenuation effect. The results show that the current is attenuated by the action of the prototype, the amplitude of the impulse current decreased from 66.95 kA to 35.10 kA, and the steepness of the impulse current decreased from 18.49 kA/µs to 4.14 kA/µs. All of the results show that this method could efficiently attenuate lightning currents. INDEX TERMSGrounding resistance, lightning current, lightning protection, current attenuation. YANG LU received the B.S. degree in electrical engineering and its automation from Jiangsu University, China, in 2020. He is currently pursuing the master's degree with Guangxi University, Nanning, China. His research interests include high voltage technology and modern lightning protection technology. JUFENG WANG received the M.Sc. and Ph.D. degrees in high voltage engineering from Wuhan
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