Interaction of lightning and other high power surges with intrinsically safe installations

It is demonstrated that heavy current surges from faults in power electrical equipment and lightning can theoretically create a transient problem in intrinsically safe circuits. It is argued that in a well bonded plant with adequate power and lightning earths then in Zone 1 and 2 this slight transient risk is acceptable as existing installations demonstrate. In the particular case of Zone 0, acceptance of the German requirement for galvanic isolation is advocated for the usual risk, and where there is a high potential risk of severe transient potential voltages then a more elaborate configuration similar to Dutch practice is commended. It is believed that these proposals are a practical compromise and might remove one major obstacle to creating a uniform European Code of Practice