Study on the lightning shielding characteristics of the crossover area of UHV/HV transmission lines

Due to space limitations of transmission corridors, ultrahigh voltage (UHV) lines inevitably cross over other lines. UHV lines in a crossover section have a lightning shielding effect similar to that of a lightning conductor of lower lines. While, whether a 500-kV line below a crossover section meets the lightning protection requirements is unknown. Therefore, a calculation method for the shielding failure trip rate of transmission lines in a crossover section in a three-dimensional space is proposed. The calculation of the shielding failure trip rate of the 500-kV line without a ground wire below the UHV line was performed. The results revealed that the shielding failure rate of the lower line was positively correlated with the length of the lower line and was negatively correlated with the crossing angle and length of the upper line. The maximum traversal lengths for a 500-kV line without a ground wire below a UHV AC or DC line were 200 m and 150 m, respectively. These findings provide a scientific basis for lightning protection design of ultra-UHV line crossing areas.