The PROBLOC BSG series of over-voltage surge protective devices have been developed to protect against partial direct and indirect lightning discharges and are intended to provide protection in zones 0A - 1, per IEC 62305.
As a protective element the serial connection MOV and GDT is used. Advantage of this kind of connection is absense of leakage current. PROBLOC BSG(R) 25 series: for TNS single phase networks with separate N and PE conductors, TNC three phase networks with combined PEN conductor, TT single phase networks, where N to PE galvanic isolation is required.