How are transmission lines protected against lightning?

Lightning protection uses multiple strategies: shield wires (ground wires above phase conductors intercept strikes), surge arresters (limit overvoltage by providing low-impedance path to ground), grounding (low tower footing resistance reduces backflashover risk), and insulation coordination (sufficient BIL on insulators). Line design balances protection cost against outage probability. Critical lines may use underbuilt shield wires or line surge arresters. Tower footing resistance below 10 ohms is typically desired.