Lightning discharges may occur between clouds or within clouds, or between clouds and the ground; in addition, the use of many large-capacity electrical equipment brings internal surges to the power supply system (China low-voltage power supply system standard: AC 50Hz 220/380V) and The impact of electrical equipment and protection against lightning and surges have become the focus of attention.
The lightning discharge between the clouds and the ground consists of one or several separate lightning strikes. Each lightning strike carries several high-amplitude, short-duration currents. A typical lightning discharge will consist of two or three lightning strikes, each about one-twentieth of a second apart. Most lightning currents fall in the range of 10,000 to 100,000 amps and their duration is generally less than 100 microseconds.
Due to the use of large-capacity equipment and frequency conversion equipment within the power supply system, internal surge problems have become increasingly serious. We attribute this to the effect of transient overvoltage (TVS). Any electrical equipment has an allowable range of power supply voltage. Sometimes even a narrow overvoltage surge can cause power supply or complete damage to the equipment. This is the damaging effect of transient overvoltage (TVS). Especially for some sensitive microelectronic equipment, sometimes a small surge impact may cause fatal damage.