中文摘要：

提出一种基于零模复合导纳的小电流接地故障暂态方向保护新方法。在特征频段内（SFB），利用单一频率零模无功功率与整个频段内同频率零模电压与零模电流产生的无功功率代数和的比值作为该频率下零模导纳的加权系数，对整个频段内的单一频率零模导纳进行加权积分作为零模复合导纳。通过计算零模复合导纳的相角确定故障方向，实现接地保护。根据故障方向的不同可进一步实现故障选线与定位。最后利用仿真和现场数据验证了所提方法的正确性。

英文摘要：

A new transient direction protection principle using zero-module combination admittance is presented for non-solidly earth fault. In selected frequency band （SFB）, ratio of algebraic addition of single frequency zero-module reactive power to that of the reactive power caused by zero-module voltage and zero-module current of same frequency in the whole frequency band is taken as weighted coefficient of zero-module addimitance, and the weighted integral of single frequency zero module admittance in the whole frequency band is considered as transient combination admittance. The fault direction is determined by calculating zero-module combination admittance angle. According to the different fault directions, the fault line selection and earth fault location can be realized. In the end, simulation results and field data demonstrate the feasibility of the approach. This work is supported by National Natural Science Foundation of China（No. 51077090）.