为节约输电线路走廊，我国建设的中短距离（800～1 300 km）范围内的直流输电工程常常采用双回±500 kV直流同塔并架输电方式，并且单回输电容量从3 000 MW提高到了3 200 MW，相应带来了损耗增加、换流阀的设计难度提高等问题。基于溪洛渡右岸送电广东直流工程实例，对3 200 MW容量直流输电工程的电压等级从±500 kV提高到±535或±550 kV进行研究，分析了3个电压等级的设置分别对直流主回路参数、绝缘配合、主设备、直流线路设计、损耗以及投资带来的影响。最后通过技术经济的综合比较，提出了优化的电压等级。

Considering that the space for line installation is not enough,DC transmission projects for mid-and short-distance (800~1 300 km) in China recently are designed to be contrusted by±500 kV double circuits on the same tower,and the transmission capacity of single circuit is rasied from 3 000 MW to 3 200 MW,which lead to the increased loss,and more difficulty in the converter valve design etc.Aiming at the DC transmission project from Xiluodu to Guangdong,the feasiblity of the voltage raised from ±500 kV to ±535 kV or ±550 kV is studied,and the effects of three voltages are analyized on main circuit parameters,insulation coordination,main equipments,DC line design,loss and investment.As a result,the optimized operating voltage is given by a comprehensively technological and economic comparison.