The electrical insulation between the air-termination or the down-conductor and the structural metal parts, the metal installations and the internal systems can be achieved by providing a distance d between the parts greater than the separation distance S
ki :depends on the selected class of LPS (see Table 10);
kc :depends on the lightning current flowing on the down conductors
km :depends on the electrical insulation material
l:is the length, in metres, along the air-termination or the down-conductor, from the point where the separation distance is to be considered, to the nearest equipotential bonding point
Insulation of the external LPS Values of coefficients ki and km
h :Total number of down conductors
c :Distance of a down conductor to the next down conductor
h :Spacing (or height) between ring conductors
If we don’t create S protection distance we have to use Isolated Lightning Down Conductor