以槽电势为分析单元的大型发电机定子接地故障定位方法

已有的大型发电机定子绕组单相接地故障定位方法一般以线圈匝电势为分析单元，对于短距绕组的机组存在理论误差。为此，提出一种以槽电势为分析单元的大型发电机定子单相接地故障定位方法。首先，基于绕组连接顺序，以槽电势为单元建立定子绕组电势分布的解析表达式。然后，针对发电机是否配备注入式定子接地保护采取不同的故障定位方案。若配备注入式定子接地保护，则基于注入式设备的过渡电阻测量值构造故障评价指标。若未配备注入式定子接地保护，则引入3次谐波测量值构造不含过渡电阻的故障评价指标。最后，在故障相人为设置多个虚拟参考点，结合绕组电势分布计算各虚拟参考点的故障评价指标，将计算值最小的虚拟参考点视为故障位置，进而确定故障所在槽编号。利用在PSCAD中搭建的准分布参数仿真模型验证了所提方法的有效性。

Slot potential based stator grounding fault location method for large generator

The current stator grounding fault location methods for large generators often take the coil potential as the analysis unit, and there are theoretical errors for the short-distance winding generators. Therefore, a slot potential based stator grounding fault location method for large generator is proposed. Firstly, based on the winding connection sequence, the analytical expression of stator winding potential distribution is established with slot potential as unit. Then, different fault location schemes are adopted for whether the generator is equipped with injection stator grounding protection. If the injection stator grounding protection is equipped, the fault evaluation index is constructed based on the measured transition resistance of the injection equipment. If the injection stator grounding protection is not equipped, the third harmonic measurement value is used to construct the fault evaluation index without transition resistance. Finally, multiple virtual reference points are artificially set in the fault phase. Combined with the winding potential distribution, the fault evaluation index of each virtual reference point is calculated. The virtual reference point with the smallest calculation value is regarded as the fault location, and the slot number of the fault is determined. A quasi distributed parameter simulation model is built in PSCAD to verify the effectiveness of the proposed method.