Suitable of AC50Hz,Ue 400V and hereinafter,TT,IT,TN-S,TN-C-S grounding system,using for equipotential bonding, protect the circiut and equipment avoid to over-voltage caused by either lightning strike or operation,suitable for installing in front of the distribution box or electric equipment,like front-end of terminal power distribution box,information,electronic,control equipment or latest plugging box.