... boxes of different floors, computer center, telecommunication room, etc. LYD1-C Surge suppression :SPD have only one side terminal, able to ... ,3P+N SPD consist of 1P,2P,3P SPD and NPE neutral and earthing protection modules, used in the power supply system ... of TN-S,TN-C-S and etc.Technical parameter Model and specificationLYD1-CNo. of poles1P2P3P4PNetwork service voltage Un ...