Influence of tower width and ion current on gap flashover characteristics of EHV/UHV AC and DC hybrid transmission lines during live-working

The EHV AC and UHV DC hybrid transmission lines on one tower differs from the traditional 500kV transmission lines, the tower width which paralleled to the 500kV line was one more time than the single circuit 500kV tower. The ion flow from 800kV transmission line spread to the air gap of the lower 500kV lines and may effect on the air gap insulation performance. In order to provide technical support to live working on the transmission line, according to the factors that influence on the switching impulse flashover performance of live working gaps, the flashover performance of “equipotential person - tower” gaps was researched with different lateral tower width which vary from 1.4m to 11.0m. In addition, the influence of ion current density on switching impulse flashover performance was investigated under the short air gaps. Experimental results show that the width of transmission tower had an impact on switching impulse flashover performance of live-working and the switching impulse flashover voltage of air gaps decreased with tower width increasing. When the tower width is 11m, the switching impulse flashover voltage of the 7.5m live working gap decrease about 14% than that of the 1.4m tower width. And the ion current density which range from 0 to 167nA/m2 had no obvious effect on the switching impulse flashover voltage of 0.80m~1.25m air gap, the live-working on the lower lever lines of hybrid AC and DC transmission system could ignore the impact of ion flow.