... surge protective devie (in short :SPD, alias:surge protector , surge arrester ) is suitable for TN-S,TN-C-S,TT,TI ... protects the electric network not shocked by the thunder and lightning ,its designed according to GB18802.1,IEC61643-1,it adopts ... low residual voltage.Installation B grade lightning current SPD is used for equipotential connection when lightning ,Install to the juncture of LPZOA ...