Analysis of response of a guyed FM radio broadcasting tower subjected to a lightning strike

This paper reports the results of computer simulations of a telecommunication tower located in a high flash density region and subjected to lightning strikes. This study is a response to lightning incidents which occurred within a few erected guyed towers in several locations in the region, and which resulted in severe damage to the low-voltage (LV) communication equipment connected to the tower. The aim is to elucidate the possible reasons that led to such damage and recommend protection measures to improve lightning performance. Using a realistic geometric representation of the tower, frequency-domain computations are carried out using frequencies representative of the typical lightning current, taking into account the propagation phenomena along the tower. A partial element equivalent circuit (PEEC) approach is used to compute the ground potential rise (GPR) at the surface of conductors and inductively-induced potentials and currents on adjacent LV communication cable. The results show that, depending on the shape of the lightning current, large potential differences in excess of the maximum withstand level of the insulation may occur between the cable core and cable sheath. Mitigating measures to reduce both the induced overvoltages and to improve grounding are suggested.