Bundle conductor minimum ground clearance of 1 000 kV AC UHV transmission lines

The minimum ground clearance of bundle conductors for 1 000 kV AC UHV transmission lines is one of the key factors in UHV transmission line design.Based on the foreign research results and combined with the domestic design experience of UHV transmission lines,it is suggested that the maximum threshold value of ground electric field strength is taken as the principle for selecting the minimum bundle conductor ground clearance of AC UHV transmission lines.The mathematical model of the power frequency electric field under UHV overhead line is established based on the successive images method.The minimum bundle conductor ground clearances of 1 000 kV AC UHV single-circuit and double-circuit lines on same tower are calculated according to the control indices of ground electric field for different regions.The influences of operating voltage,phase spacing,bundle conductor structure,phase conductor configuration,phase order arrangement on the minimum ground clearance are studied.