A Study Of Electric Power System Time Synchronization Technology Based On Bei-dou And GPS Dual-mode Timing Service

With comprehensive application of modern electrical power system, a strict clock synchronization is required various systems and automation devices, such as dispatching automation systems, microcomputer relay protection devices, sequence of events recording devices, remote devices, computer data exchanging network. Currently, the time synchronization technology used in electrical power system of China is mainly based on the satellite timing of the American Global Positioning System (GPS). The electrical power system using GPS timing reference, which a distributed network relates to people's livelihood, is a potential safety hazard. Considering the security and stability of the electrical power system, we studies the electrical power system clock synchronization technology which is based on the Bei-dou and GPS dual-mode timing, accord with the electrical Power systems time synchronization of the technical specification in the paper.At first, the principle of the satellite dual-mode timing service technology is explained, and the precision of time service of Bei-dou and GPS system has been tested. By analyzing the test data, we verify the feasibility that the clock of GPS and Bei-dou system is used as time synchronization source of the electrical power system and automation devices. Then, Bei-dou receiver, GPS receiver and external IRIG-B code use as the external sync signal, hot spare of each other. The adaptation technologies of Multi-Sync Source is adopt the system, to ensure the reliability and stability of Bei-dou and GPS dual-mode synchronous system. The system adopts a measurement method of the time interval based on digital phase-shifting technique and PI control algorithm for adjustment, completing the frequency calibration of local oscillator. By a study of the IRIG-B code encoding, the system implements the IRIG-B code decoding and encoding. With the modular design, it realizes the IRIG-B (DC) Code, the time packet information (RS-232), SNTP network time service, fiber and alarm information and other output interfaces, to satisfy the IEEE STD 1344-1995 standard.Bei-dou and GPS dual-mode synchronization system has been tested by the "Automation Equipment EMC Lab. of State Grid Co." and "The Quality Inspection & Test Center of Power Industry for Automation Equipment". The time synchronization accuracy of the system is improved up to±0.1μs and punctual accuracy is better than 1μs/min. The device satisfies the technical requirements for electrical power system time synchronization, which has practical application value.