Due to the unclear value requirements for air striking distance between lightning protection towers and protected equipment in the regulations

there is often excessive margin in the actual power transformation projects. Firstly

based on the analysis of the factors affecting impulse grounding resistance and the lightning diversion effect of lightning protection lines

the probability method based on lighting safe operation years in substation is adopted

and according to the layout of substations

the actual annual lightning stroke probability is compared to determine the critical lightning stroke probability of air striking distance of lightning protection towers. Secondly

the amplitude of the corresponding critical lightning current is obtained through the probability distribution

and

based on the simplified transient potential model of lightning protection towers and breakdown field

a simplified calculation method for determining the air striking distance between lightning protection towers and protected equipment is obtained. Finally

based on actual substation cases

the calculation is carried out

the corresponding simplified calculation formula is proposed and the influence of air clearance on the electrical layout of substations is analyzed.