Technical economic analysis of design methods of subtransmission line grounding systems

This paper presents a study of the lightning performance of subtransmission lines located in high ground flash density areas according to the design of the grounding systems. Analysis of the behavior of 69 kV and 138 kV lines under direct lightning strokes is performed for grounding systems dimensioned based on a fixed value of the low frequency resistance established by Brazilian regulations, and considering the effective length. A technical and economic analysis of both a hypothetical and a real line profile located in a high ground flash density area showed that designing the grounding configuration according to the effective length is more effective to guarantee a minimum line outage rate due to lightning strokes considering the difference between the installation and the faults costs.