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DC bias caused by HVDC transmission line is becoming a serious problem to AC transformers near the HVDC grounding system. In this paper, a scheme using neutral series resistor is introduced to solve this problem. The feasibility of the application of the resistor is analyzed. The neutral resistor and its protection device are designed to the effect of Gui-Guang HVDC grounding current to Chuncheng substation in Guangdong, China. The experiments are held in Xi'an High Voltage Apparatus Research Institute to verify the reliability of the whole device. And the results of the experiment in Chuncheng substation show the effectiveness of the application of the resistor in field engineering, the neutral DC current is reduced from 32.07A to 4.63A when Gui-Guang HVDC system operates in monopolar ground return mode with a power of 600 MVA.