The reliability of busbar protection adopting electronic transformer relies on the synchronization of sampling values. The sampling value synchronization method used for smart substation busbar protection currently is discussed. An optimized busbar protection theory, that is adaptive switch over synchronization between normal and abnormal and adjustment sampling differential value key parameter method is established to analyze the influence caused by maximum synchronization error in conditions of using electronic transfers, in order to assure selectiveness and reliability. A non-accurate synchronization for sampling in merging unit method is analyzed and simulated in abnormal synchronization conditions. Floating threshold is carried to avoid unbalance current threshold-crossing block and enhance adaptiveness of busbar protection.% 采用电子式互感器母线保护的可靠性依赖于采样值同步，论述了目前智能变电站中母线保护采用的采样值同步方案。在同步标异常时，研究了合并单元自由采样的非精确同步方法及母线保护可以实现的最大同步误差，针对电子式互感器的应用，提出了优化母线保护原理和调整采样值差动关键参数的思路，分析最大同步误差对采样值差动原理母线保护的影响。在同步标正常和异常之间自适应切换同步方法和调整采样值差动保护原理及关键参数，保证母线保护采样值差动的选择性和可靠性要求，通过仿真分析了非精确同步时的动作行为。采用浮动门槛的方法，避免最大同步误差引起的不平衡电流越限闭锁，最终达到在同步标异常时母线差动保护不退出运行，提高了母线保护在智能变电站中应用的适应能力。
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