Lightning current distribution to ground at a power line tower carrying a radio base station

Radio base stations are often mounted on towers of power transmission lines. They are usually powered from the low-voltage network through an isolating transformer, to separate the high- and low-voltage networks. The isolating transformer ensures security at customers´ premises in the case of nearby power faults and particularly in case of lightning striking, which is a frequent cause of flashover of the high-voltage insulators and a subsequent phase-to-ground fault. To optimize such protection, a better understanding of the current distribution to the ground in the initial phase of the lightning striking is required. This work presents a computer simulation method and its results for the lightning current distribution between the sky wires, grounding systems, and power cable network. What is of special concern is the part of the lightning current that might be led into the metal-shielded distribution cable network. A rigorous electromagnetic modeling approach was applied for the analysis of the grounding effects in a network of coated and uncoated low- and medium-voltage cables. The analysis was then applied to a practical case.