EMI study on down-conductors spacing

The arrangement of down-conductors is essential in the lightning protection system design. However, requirements for down-conductors spacing is different between NFPA 780 and IEC 62305. This paper reviews what NFPA 780 and IEC 62305 require for their spacing, simulates EMI for the two codes cases by the software CDEGS, discusses the relationship between EMI and down-conductors interval, and shows that distance of the down-conductors on structures should be determined through EMI analysis for the exact evaluation of the impact on electronic devices.