本文提出了零序直流小电流接地选线系统的一种新的选线原理,并依据该原理,设 计出以MSP430 为核心的选线装置,该装置具有性能高,价位低,运行可靠,易于 维护等特点。 关键词: MSP430单片机;自然直流; 选择性 Abstract This article illustrates a new fault-line-selection principle in the Zero-sequence DC grounding system. According to the principle, it also introduces a fault-line-selection device based on MSP430. This device has sound quality, and is in the lower price . It can work smoothly, and is easy for maintenance. Key words MSP430 Microcontroller; natural directive current; selectivity;