Lightning transients have three main coupling paths:
- Radio-frequency interference (RFI) with limited impact on anything. It can cause data packet loss or similar.
- Induced voltages through magnetic or capacitive coupling. Use shielded signal cables and twisted pairs that are fairly immune against differential coupling. Still, common mode voltages can cause component damage.
- Surge currents caused by localized shifts in ground potential. They cause relatively low-voltage, long-lasting common mode pulses, which can burn series impedance components in multi-phase surge protection circuits.
Ground potential shifts are a common cause of modem failures in systems connected to both the AC (mains) power and telecommunication networks.