| Time is the foundation of many key applications in substation automation system (SAS), or the uncertainty of time will bring much matter. Therefore, it is important to synchronize all computer clocks in SAS.In the first part of this paper, the substation automation system is introduced. Then the author summarizes the most familiar synchronization precept in SAS currently and points out the developing trend of network synchronization by comparing existent method of time synchronization and analyzing the characteristic of time synchronization in SAS.In the second part, the background of IEC61850 and its characteristic is introduced briefly. Furthermore, the author constructs the layered model of time synchronization, aimed at different precision request of various settings and according to the system structure based on IEC61850. At the same time, the conjoint project of GPS and network synchronization is put forward, so the partly network synchronization is realized notwithstanding the fact that the existing precision of network synchronization can not satisfy all equipments in SAS.After the explain of work principle of network time protocol (NTP), the optimized arithmetic is advanced, which using statistic methods in a sheer software way .Concrete application in a SAS in three gorges shows that the accuracy requirement of time synchronization for substation level can be satisfied, at the same time, the access frequency of time server can be effectively reduced, and the clock curve becomes more smooth.At last, the author summarizes the whole work in this paper, and point out the future forecast which will work to.
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