Compared are clauses in GB 13955-2005 "Installation and Operation of Residual Current Device" with those in GB 50054- 2011 "Code for Design of Low Voltage Electrical Installations". According to the grounding types of TN ,TT,IT and other low voltage distribution systems, combined with practical engineering design, analyzed is the work principle of Residual Current Device (referred to as RCD) in low voltage power distribution protection, proposed is application scope of the residual current device, summarized is the limitation of the residual current device used for line protection and listed are considerations during type selection in combination with design experience and the relative standard, which is beneficial to reduce personal contact electric shock accidents, supervise line insulation level and prevent electrical fires, also can provide technological guidance for installation, operation and maintenance of the residual current device and has very important significance for strengthening low voltage power distribution management, popularizing safety knowledge of electricity and improving the reliability and security of power supply.