Based on comprehensive consideration of the reliability and economy, DC protection system commonly uses triplicate configuration in the HVDC transmission project and the output mode adopts “selecting 2 from 3” logic. The “selecting 2 from 3” devices achieve “selecting 2 from 3” logic judgment and output action signals, which is important to the analysis and research of “selecting 2 from 3” logic device and its configuration strategy. This paper analyzes the “selecting 2 from 3” device and its configuration strategy in previous project, and then proposes a new design of “selecting 2 from 3” device. It adopts control bus transfer and FPGA logic processing methods, which improves the reliability of the devices and configures “selecting 2 from 3” logic in redundant “selecting 2 from 3” devices as well as in redundant pole control systems, which greatly improves the reliability and usability of DC protection system. The new device with “selecting 2 from 3” logic and its configuration strategy is applied in Gaoling back-to-back II project for the first time. DC protection system has been operating safely and stably. The new device of “selecting 2 from 3” logic and its configuration strategy has successfully passed the test of complex environment in the field, which verifies its security and reliability. It provides a useful reference for the relevant design of DC protection system in new project.