Evaluation of the Lightning Performance of Transmission Lines Partially Protected by Surge Arresters Considering the Frequency-Dependent Behavior of Grounding

This work evaluates the efficiency of installing surge arresters in only one or two phases concerning the lightning performance of transmission lines. The simulations were performed in the ATP software, taking as reference a Brazilian 138 kV transmission line, and considering the rigorous representation of the frequency-dependent behavior of the tower footing impedance. The electrical parameters of the soil were considered as either constants or frequency-dependent, in order to analyze the influence of this effect in partially protected lines. The results obtained have shown that the partial protection technique is highly efficient. Although it does not guarantee the protection of the unprotected phase(s), the probability of insulation breakdown is strongly decreased. It was also verified that the inclusion of the frequency-dependent effect in the soil parameters significantly reduces the backflashover rate estimates of the studied line when compared to the constant values situation.