Abstract: In order to meet the resolution requirement of hundreds of microseconds，microsecond global clock synchronization must be achieved in Sequence of Event (SOE) system. By means of assessing the existing clock synchronization methods and analyzing the cause of the error in the clock synchronization process, a new method based on the combination of improved Network Time Protocol (NTP) server synchronization and 1PPS synchronization was proposed. That is: advanced NTP server was used to eliminate the clock error between the control stations, "cross-second" phenomenon was avoided in this situation; 1 PPS was used to synchronize the millisecond counters in order to eliminate the crystal accumulated error of Field Programmable Gate Array (FPGA). This method is simple, precise and stable. The resolution of SOE system by using this technique can be up to 0.5 ms, and it has been applied to the turbine protection system in a power plant successfully.

Key words: Sequence of Event (SOE), Global Positioning System (GPS), Network Time Protocol (NTP), synchronous clock, Field Programmable Gate Array (FPGA)

摘要： 为了满足事件顺序记录（SOE）系统数百微秒级分辨率的要求，系统必须实现精确到微秒级的全局时钟同步。通过对现有同步方法的评估并对时钟同步过程误差产生原因的着重分析，利用全球定位系统（GPS）信号为时间源的网络时钟协议（NTP）校时服务器，提出了一种基于改进NTP服务器同步法和1PPS秒脉冲同步法相结合的新方法。新方法利用先进的NTP服务器同步全局秒时钟，消除控制站间时钟误差，并解决同步过程中出现的“跨秒”问题；用1PPS秒脉冲同步毫秒计数器时钟，消除现场可编程门阵列（FPGA）晶振累积误差。该方法实现简单，同步精度高，系统稳定性好。使用该同步方法实现的SOE系统分辨率达0.5ms，并成功应用于某火电厂汽轮机保护装置。

关键词: 事件顺序记录, 全球定位系统, 网络时钟协议, 同步时钟, 现场可编程门阵列