Disturbing energies (e.g. voltages, currents, fields) can infiltrate into the building by ways of different couplings whereas cabling and its layout represent an important part here. Following, there are three most important mechanisms of coupling described.
During near and direct lightning strokes into the lightning conductors of buildings, the overvoltage shows in consequencesof a galvanic coupling. The galvanic coupling is given by a different size of ground potentials along the building. By arrangements for equipotential bonding (earth electrodes, protective connection etc.) it is possible to achieve certain flattening of potential funnel. This flattening results in reducing the difference of potentials in regard of its center – place of stroke. However, the difference of potentials can never be fully eliminated in consequence consequence of impedances of conductive lines of LV power system and indispensable impedance of earth.
There is always a capacitive coupling (parasitic capacity) between the source of interference and the receiver.The higher the front rate of rise of the disturbing voltage impulse (du/dt) is, the stronger its interference effect is.
There is always an inductive coupling (magnetic field) between the source of interference and the receiver. The higher the front rate of rise of the disturbing current impulse (di/dt) activating the magnetic field is, the higher the interference effect is.