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.

Increasing arc pressure by tens of times with fine pouring tube, a positive shock wave by the pouring arc entering the closed space of the thin tube (electric arc recoil wave). The pressure of electric arc recoil wave is 8 to 23 times than that of the arc tube pouring wave. Since the recoil wave has more pressure than the arc tube pouring wave, and their directions are opposite, the tube poring arc is driven away from the tube channel by the recoil wave. The arc completely emptying and a large scale truncation to the electric arc are formed. Therefore, the truncation arc interrupts the lightning current, and recombusts to form a new tube pouring wave and backwash wave. The arc truncation and recombustion are caused by arc tube pouring and electric arc recoil alternately, and forming the intermittent lightning discharge, a large decrease in the amplitude of lightning current, steepness and discharge time. The results show that the amplitude of lightning current can reduce from 67.14 kA to 35.1 kA, and the lightning current steepness can decrease 77.3%. This attenuation method of lightning current amplitude could significantly reduce the lightning current flowing into the ground, the induced overvoltage and the ohm potential difference. Additionally, the problem of lightning strike step voltage in high soil specific resistivity areas and electromagnetic induced overvoltage can be solved by the method in this paper. The probability of original fault is reduced, and the operation reliability is enhanced. The method can lower the cost of ground network and improve the lightning protection performance.INDEX TERMS Electric arc recoil, arc fine tube pouring, grounding, lightning current, lightning protection.