The lightning stroke discharging between the cloud layer and earth is constituted by one or several individual lightning. Every lightning carries several currents with very high amplitudes and short duration. One typical lightning discharging shall include two or three lightning. There is about an interval of 1/20 second between two lightnings. Most lightning currents drop in the scope of 10, 000~100, 000 Amp, and its duration is generally lower than 100ms.
Because of the operation of high-capacity equipment and frequency conversion equipment in the power supply system, an increasingly serious interior surge problems have been generated. We conclude it into the influence of transient overvoltage (TVS). Any power equipment has the allowed scope of power supply voltage. Sometimes, even very narrow overvoltage impact might damage the equipment power supply or entire equipment. The destructive effect of transient overvoltage (TVS) is just like this. In particularly, as to some sensitive microelectronics devices, some very low surge impacts will probably case fatal damage.