中文摘要：

提出一种基于故障分量能量函数的Powerformer定子单相接地保护新原理。不同于传统保护方案需要测量发电机中性点和机端的基波零序电压和3次谐波电压，文中提出的方法利用Powerformer机端处的零序电流和母线处的零序电压，通过分析能量方向检测接地故障，对于发电机区内故障和区外故障具有很好的区分性。MATLAB仿真结果证明，在不同的故障情况下，该方案具有较高的灵敏性和可靠性，能够满足Powerformer的保护要求。

英文摘要：

A new principle of stator single phase to ground fault protection for Powerformer is proposed based on the energy function of the fault components. Different from the traditional protection schemes, which needs the measurements of the zero-sequence fundamental frequency voltage and the zero-sequence third-harmonic voltage at both the neutral and the terminals, the proposed approach detects the ground fault by analyzing the energy direction. Zero-sequence current from the terminal of Powerformer and zero-sequence voltage from the busbar are used in this scheme, which can distinguish the internal faults from external faults. Simulation results using MATLAB have shown that, under different fault conditions, the new scheme can obtain high sensitivity and reliability that a large generator Powerformer requires.