一次典型的定子接地故障分析与优化保护原理

通过对一次典型的定子接地故障情况和保护录波数据分析，证明了保护动作行为的正确性。在分析过程中发现定子接地故障点离机端近，接地电阻在燃弧过程中很快减小，故障零序电压很快升高，保护也及时切除了故障。文中对基波零序电压和外加电源定子接地保护的原理进行了比较分析，提出了测量式定子接地保护的概念，以及定子接地保护的灵敏性、可靠性、速动性，同时可对发电机定子绕组做出安全、健康的评估。

Typical Analysis of Stator Ground Fault and Principle of Optimal Protection

Based on the analysis of a typical stator ground fault and its recording data, the protection action is proved to be correct. From the data it can be found that when the fault locates far from the start point, the earth impedance decreases quickly during arc-burning and the zero sequence voltage increases rapidly at the same time, and the relays switch off the fault in time. This paper analyzes and compares the principles of stator ground fault protection with voltage injection and the 90% ground fault protection with zero sequence voltage. The concept of measuring ground fault relay is proposed to improve the sensitivity, speediness and reliability of protection. In addition, the health of the stator can be evaluated.