It is also known as surge arrester, it can release lightning and power system operating over-voltage energy to protect electrical equipment from transient over-voltage hazards, it also can cut off freewheeling to interrupt the short-circuit caused by grounding . Arrester is usually connected between the live wire and the earth, and connect with the protective devices in parallel. When the over-voltage reach the required actions voltage, the arrester immediately begin working, flows through the electric charge to limit over-voltage amplitude, and protect the equipment insulation; when the voltage is normal, the arrester will reinstate to ensure the system work normally. There are a variety of components can be used as lightning arrester, such as voltage dependent resistor, discharge lamp and so on. Note: The lightning voltage is the high voltage discharge between the earth and atmospheric, therefore, the lightning arrester should have a good grounding to work.