中文摘要：

分布式电源（DG）接入配电网后，配电网结构变为多电源网络，解决多电源网络保护问题最有效的方法是差动保护方案。传统差动保护方案需要使用被保护线路两端同步数据，但当前配电网通信自动化水平无法满足同步采样要求。文中提出了故障同步识别技术，测量线路工频基波电流故障时刻前后两相邻的相同趋势过零点的时间间隔，通过该时间间隔可计算故障后两端基波电流相位差并识别故障，有效克服保护无法同步采样的困难。基于故障同步识别技术，提出了充分式差动保护复合判据：仅由基波电流幅值和故障同步识别技术测得的时间量构成，包含改进标积制动判据和充分式比幅判据两部分。新复合判据解决了传统差动保护判据无法同时提高相移制动能力和灵敏性的矛盾。仿真验证了故障同步识别技术的准确性，充分式复合判据具有良好的动作特性。

英文摘要：

The distribution network becomes a multi-source network after distributed generators （DGs） are connected to it. The differential protection scheme is the most effective way to solve the problem about protections of the multi-source network. Limited by the level of distribution network communication automation, the double side synchronous sampling requirement is hard to meet, which means the traditional differential protection scheme cannot be applied in the distribution network with DGs. To solve the problem above, this paper presents a fault synchronous identification technique. Before and after the fault moment, the time interval between two adjacent zero crossing points of fundamental current with the same trend is measured. The time interval can be used to calculate the fundamental current phase difference and identify the fault, while effectively overcoming the difficulty of high precision synchronous sampling. Based on the fault synchronous identification technique, the compound criterion for sufficient differential protection is proposed. Only fundamental current amplitude and time information obtained by the fault synchronous identification technology are used to structure the compound criterion which consists of the improved scalar product restraining criterion and the sufficient current amplitude comparison criterion. The new criterion has solved the contradiction between improving the phase shift restraining capacity and sensitivity. Simulation has verified the accuracy of the fault synchronous identification technique and the action features of the compound criterion.