Following continuous development of science and technology, human beings have made great achievement in surge protection. Gradually, the serious damages to human beings caused by surge are getting into control and alleviation. The modern surge protection technique has developed the protection object from construction to electronic information system inside the construction.
From the lightning strike cases, most were caused by surge overvoltage entering from power supply wirings and caused damages directly to computers, communication ,medical equipment, precision instruments and elevators control system. However, the surge overvoltage is unable to be eliminated by transformer and UPS etc. Equipped surge protection device (SPD) to the system such as computers, communication and other control system will be able to reduce the overvoltage to a endurable level.
The main function of power system surge protection is to control the lightning surge and lightning overvoltage on the input wires. The electric magnet will become stronger when lightning strikes due to most constructions are built on the relatively open land. The power and communication cables can be attacked easily by interference lightning, and the interference overvoltage will flow into equipment through the wires and circuits to cause the damage. Therefore, the surge protection devices are installed at the main distribution boards and every distribution boards discharge the overvoltage into the earth to protect equipment inside building.