用外加电源式定子接地保护提高保护灵敏度的研究

定子绕组单相接地故障是发电机最常见的故障之一，且其他故障大多由定子单相接地引发。传统大型机组基于纵向零序电压三次谐波的100%定子接地保护存在灵敏度较低的缺点。外加电源式定子接地保护灵敏度较高，但随着单机容量越来越大，其灵敏度还是不能满足要求。借助现代的电气控制技术，对其进行改进，在原有的外加电源式定子接地保护中引入反馈量，从而提出了一种新的保护模式，仿真计算表明它可以有很高的灵敏度并具有很高的可靠性，能够满足现代大型机组对接地保护的要求。

Study of improving sensitivity of stator ground fault protection by injecting external voltage

In electric power system it is always significant to improve the performance and credibility of large generator. Protection is an important equipment to achieve those purpose. Stator single phase ground fault is one of the most vulgar faults. Further it is the occasion of other generator faults. Traditional protection for large-scale generator third hamoniclO0% stator ground fault is with low sensitivity. Injecting external voltage stator ground fault protection relatively has a high sensitivity. With the large-scale generators coming, the sensitivity of protection is expected to be higher and higher. With the development of modern electronic controls, adding a feedback heft to the original injecting extern voltage stator ground fault protection, this paper introduces a new scheme to improve sensitivity. The analysis and experiment result proves that these protections are with high sensitivity and reliability. It can satisfy the protection requirement of large modern generators.