基于相角差的发电机定子接地保护方向元件

分析了发电机发生内外部单相接地故障后，机端和中性点侧3次谐波电压、基波零序电压和零序电流之间相角的变化关系。在此基础上，提出基于相角判别的新型发电机定子接地保护方向元件。该方向元件由2部分组成:对距中性点50%以内的定子绕组故障，利用机端和中性点两侧故障分量3次谐波电压的相角值相等且为负值的特点构成;对50%以上范围的定子绕组故障，由于零序故障电压和电流均相对较大，采用零序电压和零序电流相位的关系来识别故障方向。该方向元件构成原理简单，可以与目前现场应用的各种单相接地保护方案配合使用，具有较强的工程应用前景。

Directional Element Based on Phase-angle Difference for Generator Stator Grounding Protection

The third-harmonic voltages at the generator neutral and the terminals,and the phase angle relationship between fundamental frequency zero-sequence voltage and zero-sequence current under different single-phase grounding faults are analyzed.According to that,a phase-angle difference direction element for generator stator grounding fault protection is presented.It consists of two parts:for fault location less than 50% of stator winding from neutral point,the direction function is based on the phase compariso...