Answer: the introduction of grounding technology was originally a protective measure taken to prevent power or electronic equipment from being struck by lightning. The purpose is to introduce the lightning current generated by lightning to the ground through the lightning rod, thus playing the role of protecting buildings. At the same time, grounding is also an effective means to protect personal safety. When the phase line (such as poor insulation of the wire, aging of the line, etc.) caused by some reason touches the equipment shell, dangerous voltage will be generated in the equipment shell, and the resulting fault current will flow through the PE line to the ground, thus playing a protective role. With the development of electronic communication and other digital fields, only considering lightning protection and safety in the grounding system is far from meeting the requirements. For example, in the communication system, the interconnection of signals between a large number of devices requires each device to have a reference ‘ground‘ as the reference ground of the signal. Moreover, with the complexity of electronic equipment, the signal frequency is getting higher and higher. Therefore, in the grounding design, special attention must be paid to electromagnetic compatibility problems such as mutual interference between signals. Otherwise, improper grounding will seriously affect the reliability and stability of system operation. Recently, the concept of "ground" has also been introduced into the signal return technology of high-speed signals.