针对10 kV中压电网谐振接地系统，利用瞬时对称分量法对电源、消弧线圈、对地电容以及接地点建立瞬时正序网络的数学模型，进而建立谐振接地系统的瞬时正序网络的数学模型。基于该模型推导了故障支路和非故障支路瞬时正序电流实部和虚部的数学表达式。理论上得出瞬时正序网络的特性为：故障之后稳态时，故障支路瞬时正序电流实部的相位滞后各非故障支路瞬时正序电流实部的相位一定角度，各非故障支路瞬时正序电流实部的相位几乎相同；故障支路瞬时正序电流实部的幅值较故障之前变大。仿真验证了理论分析的正确性。

In this paper, a mathematical model of instantan eous positive sequence network is built through the instantaneous symmetrical component method. The model built for the 10 kV medium-voltage resonance grounding system, includes the variation of power source, petersen coil, ground capacitance and ground point. Based on this model, the mathematical expression of instantaneous positive sequence current real part and imaginary part in fault branch and unfault branch is derived. The character of the instantaneous positive sequence network is given as follows： in the steady-state after fault, the phase of instantaneous positive sequence current real part in fault branch lags behind unfault branch with a certain angle, while all unfault branches phase is almost equal; the amplitude of instantaneous positive sequence current real part in fault branch is bigger than the one before fault. The simulation finally validates the theoretical analysis.