Analysis on Lightning Protection Performance of Shielding Failure for 1000kV AC Transmission Line and ±500kV DC Transmission Line Hybrid-Erected on Same Tower

Expansion of power grid scale and shortage of corridors for transmission lines make the hybrid erection of AC and DC transmission lines on the same tower possible under some special conditions.In view of that the shielding failure is the main reason causing lightning-tripout of UHV transmission lines,based on comprehensive analysis on parameters and structural models of existing towers home and abroad for double circuits of transmission lines on the same tower,bipolar DC transmission lines on the same tower as well as the AC and DC transmission lines hybrid-erected on the same tower,a new tower model for the hybrid erection of 1000kV AC transmission line with ±500 kV DC transmission line on the same tower is proposed.In allusion to double circuits of 1000kV AC transmission lines and bipolar ±500 kV DC transmission line hybrid-erected on the same tower,an improved electro-geometric model,in which the impacts of both long-gap discharge characteristic and operating voltage of the conductors are considered and the mutual shielding between AC phase lines and DC polar lines is also taken into account,is applied and the lightning protection performance of shielding failure of UHVAC and UHVDC transmission lines are analyzed.A simulation model based on ATP-EMTP is built and by use of this model the lightning protection levels of shielding failure of DC polar lines and AC phase lines are obtained.By means of programming by Matlab,the impacts of such parameters as different nominal heights of towers,protection angles of overhead groundwires and ground obliquities on respective shielding failure rates of UHVAC and UHVDC transmission lines are analyzed.Results of this research are available for reference to the improvement of lightning protection performance of shielding failure for the hybrid erection of UHVAC and UHVDC transmission lines on the same tower.