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Ensuring the separation distance of independent lightning protection device plays a significant role in lightning protection activities. In order to make the separation distance calculating suitable for the actual situation and improve the safety, based on the formation mechanisms of lightning counterattack, the separation distance formulas for defending the lightning counterattack damage of the first positive lightning, the first lightning after the first negative lightning, and the first negative lightning are derived, and then develops the common separation distance formula that can defend simultaneously the lightning counterattack damage of all these three typical lightning by solving the common solution of those formulas. Comparing with these formulas, it is found that there are problems in the related design standards of lightning protection for buildings. The analysis indicates that those formulas are more reasonable and safe.