Design approaches for EHV OHL 'compact' tower grounding systems

The lightning performance of an EHV overhead transmission line (OHL) largely depends on tower grounding behavior; when high ground flash density values are expected, a proper design of grounding arrangements, focused on their high frequency behavior instead of the conventional power frequency analysis, can significantly reduce the backflashover rate (BFR) of the OHL. A technical optimization is reported, aiming at improving the BFR of an EHV OHL in Brazil, which crosses a region with widely different soil resistivity values, resulting in a compact tower grounding system design. Although exhibiting a larger resistance at power frequency value, the proposed compact grounding system offers better impulse responses than conventional buried counterpoises.