How to suppress lightning strike induction in I/O modules?

Suppressing lightning-induced overvoltages in I/O modules requires a multi-layered protection system. At the system inlet, a primary surge protector, typically a gap-type or varistor-type, is installed to discharge direct lightning strikes or most induced lightning energy. Inside the equipment cabinet, secondary protection is installed for the power and signal lines of the I/O modules, for example, using a tertiary protection circuit consisting of a gas discharge tube, varistor, and TVS diode. Protectors for signal lines must consider signal frequency and be of low capacitance type. The grounding wires of all protective devices should be short and thick, connected to a separate surge protection grounding busbar, which is connected to the equipment's operating ground at a single point. Cables should be laid in metal conduits or cable trays, with both ends grounded. For long outdoor cables, protectors can be installed at intermediate poles. Inside the module, sensitive circuits should be isolated for power supply and signal transmission. Furthermore, equipotential bonding is crucial; the equipment casing, cable shielding, and surge protector grounding terminals should be connected together at the inlet to reduce potential difference. The design must comply with relevant lightning protection standards and be verified through simulated lightning strike tests.