* System according to the earth connection (according to IEC 60364-1)
Over-voltages in common mode concern all neutral point connections. They occur between the live conductors and earth (e.g. phase/earth or neutral/earth). The neutral conductor is a live cable, as well as the phase conductors.
This overvoltage mode destroys not only earthed equipment (Class I), but also non-earthed equipment (Class II) with insufficient electrical insulation (a few kilovolts). Class II equipment that is not situated close to an earthed mass is theoretically protected from this type of attack.
Over-voltages in differential mode circulate between the live phase/phase or phase/neutral conductors. They can causeconsiderable damage to any equipment connected to the electrical network, particularly “sensitive” equipment.
These over-voltages concern TT systems. They also affect TN-S systems if there is a significant difference in length between the neutral cable and the protective earth cable.
The Common mode protection or differential mode of protection are required depending on the grounding configuration of the system (IT, TNC, TNS, TT). According to the system configuration you can select appropriate Otowa products to protect (single pole, 2L, 3L, 1P2W, 3P4W).
