Abstract: According to the same site construction of the sending ends of the two Belo Monte HVDC Projects in Brazil, this paper puts forward the connection form of two electrodes as mutual standby, and designs the sequence control logic and the strategies for monitoring and controlling the grounding current in order to realize the safe and reliable mutual standby of electrodes. Taking the Bipole Neutral Bus Differential Protection as an example, this paper analyzes the impact of the connection form of two electrodes as mutual standby on the bipolar zone protection, and on this basis, the protection optimization strategy is proposed. The control and protection strategy of mutual standby of two electrodes has been verified by detailed tests and simulations, and has been successfully used in the actual construction and operation of Belo Monte HVDC Projects in Brazil. These strategies are able to greatly reduce the DC outage rate and improve the reliability and economy of the HVDC project.