The PROTEC B2S 12.5 series of over-voltage surge protective devices has been developed to protect against partial direct and indirect lightning discharges and is intended to provide protection in zones 0A - 1, per IEC 62305.  PROTEC B2S 25 (2+0) series combines two PROTEC B2S 12.5 modules to provide protection for single phase TNS network.  PROTEC B2S 50 (4+0) combines four PROTEC B2S 12.5 units, to provide protection for TNC three phase networks with a separate N and PE conductor.