Dynamic model of impulse characteristics of concentrated earths

A dynamic model to describe the nonlinear surge-current characteristics of several concentrated earths has been developed. The model accurately accounts for the surge behaviour of these earths on a time-to-time basis, in soils with resistivities ranging from 5000 ¿ cm to 31 000 ¿ cm. This results in a significant improvement over the previous methods used to describe them. The use of the new model for studies of concentrated earths at high lightning currents reveals that greater surge reduction factors than was previously assumed can be expected. This study serves to overcome previous difficulties in having to extrapolate values from meagre experimental results.