Quantification of the Indirect Lightning Using FIT Analysis Under Soil Nonuniformity

One of the phenomena affecting the insulation coordination of power distribution systems is indirect lightning. This article aims to investigate the impacts of stratification of the soil along with the characteristics of the lightning current, i.e., peak, current time-derivative, striking distance to overhead lines on quantification of the lightning indirect overvoltage (LIOV). Accordingly, comprehensive analyses have been established based on the finite integration technique. The flexibility of the method and the simulation results have been compared with the other finite element method and well-known formula, i.e., Rusck and Darveniza. It is also demonstrated that the Darveniza's formula cannot be relied upon as a precise approach in nonuniform grounds. It is revealed that more resistivity of the lower layer results in the increase of LIOV peak in a two-layer soil. It is comprehended that the increase in the number of layers could highly affect LIOVs. Furthermore, the results indicate that the nonuniformity of the ground increases the sensitivity of LIOV to the characteristics of lightning strokes. Finally, an intelligent package is introduced to assess the characteristics of the indirect lightning-induced overvoltage in the complex situation within acceptable accuracy and computation time based on an equivalent resistivity of the soil.