In places where lightning explosion probability is high in Bai area, surge protective devices should be installed on the incoming cabinet and its cabinets. The maximum discharge current should be greater than 60kA for surge protection device of incoming line cabinet, and 20-40KA for other cabinets. If it is not the area with high lightning probability, it is OK to set surge protection device in the incoming cabinet or special equipment. The maximum discharge current of SPD for special equipment is generally 5-10kaChina High Voltage Switchgear website:http://www.chmahalalel.com/high-voltage-switchgear/