Abstract: The grounding electrode provides a loop for DC current in ground return operation.With the intensive increase of high voltage direct current（HVDC）transmission lines,the erosion of oil-gas pipelines,DC bias of power transformers and other problems caused by the ground return current increase gradually.In severe cases it will even affect the arrangement of power grid operation mode.In the circumstances,a scheme of HVDC operating with station ground grid instead of grounding electrode is put forward,which should be realized by HVDC control and protection system.Taking the ±800kV PuerQiaoxiang ultra high voltage direct current（UHVDC）project in China Southern Power Grid as an example,this article analyzes the key technical difficulties of HVDC operating without the grounding electrode,designs the realization method by modifying the control and protection logics and then tests the scheme with the real-time digital simulator（RTDS）system.The improved control and protection logics have been implemented in engineering practice.