Research on optimisation of minimum air clearance of 1000 kV UHV AC substation

Based on air clearance discharge characteristic curve and insulation coordination method, it is pointed out that the minimum air clearance of 1000 kV ultra‐high voltage (UHV) AC substation can be further optimised. On the basis of analysis of the merits and demerits of the two insulation coordination methods for air clearances of UHV substation stated in the national standard GB/Z 24842–2009, it is concluded that using statistical method for insulation coordination is more reasonable and feasible. The minimum air clearance of UHV substation is optimised with the statistical method based on 1000 μs switching impulse characteristic test results. According to the study results, the phase‐to‐earth air clearance A1′ can be 1 m less than that specified in standard, the air clearance between conductors 0.5 m less than that specified in standard, and the phase‐to‐phase air clearance of grading ring and tubular bus 0.6 and 1.8 m, respectively, less than that specified in standard.