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大型水轮发电机励磁绕组匝间短路故障不仅会使励磁电流增大、输出无功功率减小,还会导致机组振动加剧,影响系统的安全稳定运行。为对故障特征及其机理进行研究,以三峡左岸VGS发电机为例,首先通过分析故障时励磁磁动势及其作用在不均匀气隙产生的磁场性质,得出定子相绕组内部存在分数次不平衡分支电流的特征。以定子支路为基本分析单元推导出分支电流时间谐波次数与电枢反应磁动势空间谐波次数的对应关系,进而得到电枢反应磁场在转子绕组中产生的附加电流谐波次数的一般性通式。最后利用经过实验验证的多回路方法对故障进行定量计算,验证了理论分析的正确性,并基于计算结果对故障的保护进行了初步探讨。提出分数槽水轮发电机励磁绕组匝间短路故障特征的分析方法,为故障在线检测与保护奠定了理论基础。
Large-scale hydroelectric generator excitation winding turn-to-turn short-circuit fault will not only make the excitation current increases, the output reactive power decreases, but also lead to increased unit vibration, affecting the safe and stable operation of the system. In order to study the fault characteristics and its mechanism, taking the left bank VGS generator of the Three Gorges Project as an example, firstly, by analyzing the field magnetomotive force in the fault and the magnetic field generated by its action in the uneven air gap, Characteristics of unbalanced branch currents. The stator branch is taken as the basic analysis unit to derive the corresponding relationship between the number of times harmonic of armature reaction and the number of spatial harmonics of armature reaction magnetomotive force, and then the number of additional current harmonics generated in armature reaction magnetic field in rotor winding is obtained General formula. Finally, the experimental verification of the multi-loop method for quantitative calculation of the fault, verify the correctness of the theoretical analysis, and based on the calculation results of the fault protection were discussed. The analysis method of fault characteristic of inter-turn short circuit of excitation winding of fractional slot hydrogenerator is proposed, which lays a theoretical foundation for on-line fault detection and protection.