In view of the digital relay protection device configuration is complex and plug-in replacement difficult phenomenon, design the digital relay protection device plug and play system, developed a PNP handheld terminal deployment, in detail elaborated the system structure and working principle of the plug and play system, describes the key technologies used in the system, including the establishment of the PNP file directory library methods, data check, system communication process control connection and information processing. Finally, test the system can achieve good digital relay protection device of the plug-in plug and play, greatly improving the efficiency of intelligent substation operations.