Protection of apparatus against lightning surge in an extended earthing arrangement

The influence of grounding conditions on apparatus to be protected and subjected to surges due to resistive coupling for an extended earth arrangement is investigated. This paper deals with the case of apparatus to be protected supplied by a Secondary Board (SB) connected well distant from the Main Distribution Board (MB), where an SPD1 is installed for the protection of distant apparatus. Flowing of the lightning current to earth gives rise to a common-mode voltage that can stress the apparatus to be protected in spite of the installed SPD1. The SB grounding intentionally or de facto increases the stress on the apparatus. Possible measures for the protection of the apparatus are identified. The analysis has been performed by several simulations obtained by means of the transient software EMTP-RV.