长距离数字化管输系统中精确时钟同步的设计方案

针对各个站场内单独装设GPS接收器或其他精确时钟源的独立对时同步方式不能达到微秒级精度，成本较高的问题，提出通过长距离全线网络进行精确时钟同步的设计方案．从常用的多种网络对时方式中选择资源消耗最少且精确度最高的IEEE1588网络精确时钟同步协议（IEEE1588协议），实现从时钟偏移量的修正以及传输时延的修正，并通过一个精确的首端主时钟源周期性的对全线网络内所有从时钟进行校正．结合工程实际设计了时钟设备、交换设备和控制设备的具体架构、基本配置及其功能实现．通过德国赫斯曼公司的三层交换机MACHll40和美国罗克韦尔公司ControlLogix可编程逻辑控制器等行业内主流成熟设备的系统配置，完成整体架构对IEEE1588协议的支持．在全线局域网络缓存负荷率不超过50％的前提下，使长距离数字化管输系统全线的自动化设备能够作为从时钟，与首端的主时钟源在100ns范围内实现精确时钟同步．

Design of precise clock synchronization in long distance digital pipeline system

To solve the problem of difficult synchronization of all sample data under the condition that independent time tick synchronization method of global position system receivers or other accurate clock source can＇t reach microsecond precision and result in the high general cost, IEEE 1588 network precise clock synchronization protocol（IEEE 1588）was chosen to realize revision of clock offset as well as transmission delay, and to revise all clocks within the whole network by an accurate master clock source periodically. Combined with the clock equipment in the practical project, the concrete framework of switching equipment and control equipment and the realization of basic configuration functions were designed. Main trend mature equipments of system configuration in this field, such as MACHll40 of the three layer switches of Hirschmann and ControlLogix PLC of American Rockwell, were used to implement the support for IEEE 1588 protocol from the overall frame. Under the condition that cache load of the whole line LAN is less than 50%, the whole line automation equipment of long distance digital pipeline transportation system is taken as the slave clocks to realize accurate clock synchronization with the master clock source within the scope of 100 nanosecond.