(1)根据系统中发生单相接地故障时接地电流的大小划分。

(1) the size of grounding current is divided according to the single phase grounding fault in the system.

1)小电流接地系统：中性点不接地中性点经消弧线圈接地。

1) small current grounding system: neutral point neutral point is grounded by arc suppression coil.

2)大电流接地系统：中性点直接接地。

2) large current grounding system: neutral point directly grounding.

(2)小电流接地系统的接地电流。

(2) the grounding current of the small current grounding system.

1)中性点不接地系统单相接地故障时的接地电流特征：当电网发生单相接地故障后，非故障电路电容电流就是该线路的零序电流，故障线路首段的零序电流数值上等于系统非故障线路全部电容电流的总和，其方向为线路指向母线，与非故障线路中零序电流的方向相反，系统中性点电压发生较大的位移。实现方法：基于基波零序电流方向的自动接地选线原理。

1) system when the single-phase grounding fault of grounding current of neutral: when single-phase grounding fault, zero sequence current of capacitor current circuit is the non fault line, the fault line zero sequence current is equal to the sum of the first section of the system of non fault line all capacitance current, whose direction is the line pointing to the bus, instead of zero sequence current and non fault line in the direction of the system neutral point voltage large displacement. Realization method: the principle of automatic grounding selection based on the direction of the fundamental zero sequence current.

2)中性点经消弧线圈接地系统单相接地故障时的接地电流特征：在单相接地时，故障线路首端的5次谐波电流在数值上等于系统非故障线路5次谐波电流的总和，其方向与非故障线路中5次谐波零序电流方向相反，由线路指向母线。实现方法：基于5次谐波零序电流方向的自动接地选线原理。

2) Petersen coil grounding system fault grounding current in single-phase grounding characteristics: when the 5 harmonic current at the head end of the fault line is equal in value to the system of non fault line 5 harmonic current sum of zero sequence current direction 5 harmonic direction and non fault line by line on the contrary, pointing to the bus. The realization method: the principle of automatic grounding selection based on the direction of the 5 harmonic zero sequence current.