FREQUENCY-ANALYSIS OF THE INDUCED EFFECTS DUE TO THE LIGHTNING-STROKE RADIATED ELECTROMAGNETIC-FIELD

A lightning stroke to the protection system of the control building of an industrial plant can produce various effects such as transient voltages induced in feed cables, in measuring, protection and control cables, and in components of electrical equipment within the building, as well as transient voltages between down conductors and metal bodies often characterized by high peak values. These effects can give rise to operating anomalies in the equipment which may sometimes be damaged, and can also constitute a hazard to human life. This paper reports the results of a frequency-analysis study of effects connected with point values of the electromagnetic field generated within the building (e.g., the impact on field-effect transistor, etc.) or due to the presence of radiation fields, namely fields whose harmonic components, characterized by small wavelengths compared to the dimensions of the ''victim'' circuit, assume not negligible values. The best way of calculating these effects is through a procedure based on a field approach [1]-[3]. Characterization of the electromagnetic field is therefore ensured by a numerical procedure that permits simultaneous simulation of the protection system and analysis of the electromagnetic field by means of the Method of Moments used by various authors [5]-[8] for the study of direct lightning strokes into thin-wire structures. Two distinct points of impact of the lightning stroke to the protection system are considered and the ensuing results are compared.