The protection can be done only in the case of the global approach to lightning, which supposes the control of all the stages, such as :
The lightning protection or the “direct effects” consist in :
– capturing the lightning, which constitutes a preferential impact point capture device, natural or specific (Franklin lightning conductor, meshed cage or tight strand), flowing the lightning current helping its path to earth, running out the current of the lightning to the ground by ensuring its dispersion in the ground, with an “earth electrode lightning conductor”.
The transient overvoltage protection or the ” indirect effects” consist in :
– preventing the lightning current from reaching the equipment, directing it to the earth, with surge protective devices like a barrage which stops and channels the water flow,
– keeping a residual voltage compatible with the protected equipment,
– flowing and discharging the current to earth.
An installation can be protected effectively only if :
– the flow of the current to the earth and its dispersion in the ground is guaranteed, using an earthing system of low impedance (this gives best conductivity),
– All the metallic bodies of the building are connected electrically to the electric earth of the building or “excavation earthing system”,
– “the equipotentiality” of the earth of the building and lightning conductor is done.