The lightning down conductor is one of the most important components of external lightning protection systems. The lightning captured by the external lightning protection system is discharged to the ground via the down conductor. However, there are factors we need to pay attention to in the design of the lightning down conductor. The first of these is ensuring the “S separation distance” between the down conductor and the surface it descends. Otherwise, the burning effect of the lightning will affect the system. If this S distance cannot be calculated, an insulated down conductor should be used.
HOW TO CALCULATE THE S SEPARATION DISTANCE?
S Separation Distance formula
kc: Depends on the design of down conductors.
ki: Depends on the protection class.
km: Depends on the system materials (insulation material).
l: Distance to the nearest equipotential bonding point.
PROTECTION CLASS CHART
Furthermore, if the surface where the down conductor descends is conductive, an insulated down conductor should be used. Another important situation is the magnetic field effect created by the lightning down conductor. This magnetic field causes sensitive devices to break down. The insulated conductor also eliminates magnetic field effects.
