Fault Detection of Stator Non-Roundness in Hydro-Generator Based on Branch Circulation
Wu Yucai1, Zhang Guangxiang1, Yue Jianfeng2, Yang Guangyong2, Dao Yajuan2
1. Hebei Key Laboratory of Green and Efficient New Electrical Materials and Equipment Department of Electrical Engineering North China Electric Power University Baoding 071003 China; 2. Huaneng Lancang River Hydropower Co. Ltd Maintenance Branch Kunming 650051 China
Abstract：Problems such as manufacturing tolerances in the stator of large hydro-generators and uneven seams during lamination assembly are complex to avoid, making it impossible to guarantee an ideal roundness of the stator bore. During operation, mechanical and electromagnetic vibrations, as well as thermal expansion due to temperature variations, can readily cause loosening and deformation of the stator core. The induced unbalanced magnetic pull will continuously worsen the stator non-roundness, ultimately causing severe stator core deformation. Accurate early warning of stator non-roundness faults can effectively enhance the safe operation level of hydro-generator units. Therefore, this paper proposes a circulating-current comparison detection method for stator branches, which can be employed for online detection of stator non-roundness faults. First, using the mesh current method and Kirchhoff's second law, the paper derives an expression for the circulating currents in multiple in-phase branches of the generator. Considering the irregular distribution of the air-gap magnetic field caused by stator non-roundness, it is deduced that differences in the magnetic permeability harmonics in the regions of each in-phase branch due to stator non-roundness result in discrepancies in the amplitude and phase of the branch electromotive forces (EMFs). Thus, a correlation between the characteristic harmonics of the circulating currents and the severity of the stator non-roundness fault is established. Subsequently, a finite-element electromagnetic simulation model was constructed, using a 334 MV·A hydro-generator as an example. The stator non-roundness was simulated at the spatial locations of single-, dual-, and multi-branch windings. Odd-order characteristic harmonic circulating currents consistent with the predicted frequencies were extracted. The relationships between the time/frequency domain characteristics of circulating currents and the stator deformation range, radial displacement, and concave-convex points were analyzed, revealing a connection between the circulating currents and stator core deformation in the spatial regions where the branches are located. Finally, an experimental platform was used for a salient-pole synchronous generator, and an outwardly convex stator non-roundness fault was simulated. The circulating-current comparison method for stator branches was used to compare circulating currents across branches of each phase, determine the relative deformation magnitude in branch regions, and detect the overall non-roundness of the stator. The results indicate that after a stator non-roundness fault occurs, odd-order harmonic circulating currents appear between the in-phase branches of the stator. The greater the differences in the deformation range and magnitude of stator non-roundness in each branch region, the higher the harmonic circulating currents between the branches. Therefore, by real-time online monitoring, comparison, and analysis of the relative magnitudes and trends of these circulating current signals, the relative severity of non-roundness at different spatial locations along the stator circumference can be determined. Online assessment and monitoring of the overall roundness condition of the generator stator can be achieved by integrating the relative non-roundness information from all compared branch circulating currents.
武玉才, 张广翔, 岳建锋, 杨光勇, 刀亚娟. 基于支路环流的水轮发电机定子不圆度故障检测[J]. 电工技术学报, 2026, 41(6): 1986-2000.
Wu Yucai, Zhang Guangxiang, Yue Jianfeng, Yang Guangyong, Dao Yajuan. Fault Detection of Stator Non-Roundness in Hydro-Generator Based on Branch Circulation. Transactions of China Electrotechnical Society, 2026, 41(6): 1986-2000.
[1] 潘郑楠, 邓长虹, 徐慧慧, 等. 考虑灵活性补偿的高比例风电与多元灵活性资源博弈优化调度[J]. 电工技术学报, 2023, 38(增刊1): 56-69. Pan Zhengnan, Deng Changhong, Xu Huihui, et al.Game optimization scheduling of high proportion wind power and multiple flexible resources considering flexibility compensation[J]. Transactions of China Electrotechnical Society, 2023, 38(S1): 56-69. [2] 鲜于虎成, 黄显峰, 张艳青, 等. 考虑短期波动与弃电风险的水光互补系统中长期双层嵌套优化调度[J]. 电工技术学报, 2023, 38(21): 5781-5793. Xianyu Hucheng, Huang Xianfeng, Zhang Yanqing, et al.Medium-and long-term double-layer nested optimal scheduling of hydro-PV complementary system considering short-term power fluctuation and curtailment risk[J]. Transactions of China Electrotechnical Society, 2023, 38(21): 5781-5793. [3] 王海伦, 丁一凡, 李杨, 等. 计及混合式抽水蓄能改造的清洁微网分布鲁棒容量优化配置[J]. 电工技术学报, 2025, 40(7): 2112-2126. Wang Hailun, Ding Yifan, Li Yang, et al.Distributionally robust capacity optimization for clean energy microgrid considering pumped-storage retrofitting[J]. Transactions of China Electrotechnical Society, 2025, 40(7): 2112-2126. [4] 樊世英. 大中型水力发电机组的安全稳定运行分析[J]. 中国电机工程学报, 2012, 32(9): 140-148. Fan Shiying.Analysis of stability for large and medium-sized hydro-generating unit[J]. Proceedings of the CSEE, 2012, 32(9): 140-148. [5] Li Z G, Yang F Y, Chen J H, et al.Analysis on the roundness of bulb turbine generator based on the unbalanced magnetic[J]. IOP Conference Series: Earth and Environmental Science, 2012, 15(4): 042005. [6] 陆宏江, 王连庆, 秦钊林. 发电机定子变形原因分析及改造方案[J]. 电工技术, 2015(9): 46-47, 73. Lu Hongjiang, Wang Lianqing, Qin Zhaolin.Cause analysis and reconstruction scheme of generator stator deformation[J]. Electric Engineering, 2015(9): 46-47, 73. [7] 钏毅民, 杨迪, 蔡武卫, 等. 漫湾电厂发电机定子铁芯变形故障分析[J]. 云南电力技术, 2000, 28(3): 6-7. Chuan Yimin, Yang Di, Cai Wuwei, et al.Fault analysis of generator stator core deformation in Manwan Power Plant[J]. Yunnan Electric Power, 2000, 28(3): 6-7. [8] Zhou Jianzhong, Peng Xuanlin, Li Ruhai, et al.Experimental and finite element analysis to investigate the vibration of oblique-stud stator frame in a large hydropower generator unit[J]. Energies, 2017, 10(12): 2175. [9] Nandi S, Toliyat H A, Li X.Condition monitoring and fault diagnosis of electrical motors: a review[J]. IEEE Transactions on Energy Conversion, 2005, 20(4): 719-729. [10] 舒均盛. 水轮发电机铁心松动引发定子接地故障的分析及处理[J]. 大电机技术, 2006(5): 6-8. Shu Junsheng.Cause analysis and treatment of a hydrogenerator stator grounding fault due to loosening of stator core[J]. Large Electric Machine and Hydraulic Turbine, 2006(5): 6-8. [11] 江贤义. 浅析水轮发电机定子铁心松动的原因及技改措施[J]. 福建水力发电, 2021(1): 47-50. [12] 李兴邦. 青海某电站4#水轮发电机定子低频振动原因剖析及处理[J]. 上海大中型电机, 2024(1): 45-48. Li Xingbang.Analysis and treatment of low frequency vibration of stator of 4# hydrogenerator in a power station in Qinghai[J]. Shanghai Medium and Large Electrical Machines, 2024(1): 45-48. [13] 赵晓嘉, 郭耀先, 龚登位. 小湾水电厂发电机定子振动原因及改进措施[J]. 水力发电, 2015, 41(10): 47-50. Zhao Xiaojia, Guo Yaoxian, Gong Dengwei.Stator vibration reason analyses and improvements of generators in Xiaowan hydropower station[J]. Water Power, 2015, 41(10): 47-50. [14] Pollock G B, Lyles J F.Vertical hydraulic generators experience with dynamic air gap monitoring[J]. IEEE Transactions on Energy Conversion, 1992, 7(4): 660-668. [15] Xuan M T, Simond J J, Wetter R, et al.A novel air-gap monitoring system for large low speed hydro-generators[C]//2006 IEEE Power Engineering Society General Meeting, Montreal, QC, Canada, 2006: 8. [16] Adamowski J C, Souza A T, Pérez N, et al.Ultrasonic dynamic air-gap monitoring system for large hydrogenerators[C]//2013 IEEE International Ultrasonics Symposium (IUS), Prague, Czech Republic, 2013: 1311-1314. [17] 齐鹏, 李永刚, 马明晗. 抽水蓄能电机转子匝间短路无传感器检测方法[J]. 电工技术学报, 2024, 39(20): 6431-6443. Qi Peng, Li Yonggang, Ma Minghan.Sensorless detection method of rotor inter-turn short circuit in pumped storage motors[J]. Transactions of China Electrotechnical Society, 2024, 39(20): 6431-6443. [18] Pöyhönen S, Negrea M, Jover P, et al.Numerical magnetic field analysis and signal processing for fault diagnostics of electrical machines[J]. COMPEL-the International Journal for Computation and Mathematics in Electrical and Electronic Engineering, 2003, 22(4): 969-981. [19] DeBortoli M J, Salon S J, Burow D W, et al. Effects of rotor eccentricity and parallel windings on induction machine behavior: a study using finite element analysis[J]//IEEE Transactions on Magnetics, 1993, 39(3): 1676-1682. [20] Hao Liangliang, Sun Yuguang, Qiu Arui, et al.Steady-state calculation and online monitoring of interturn short circuit of field windings in synchronous machines[J]. IEEE Transactions on Energy Conversion, 2012, 27(1): 128-138. [21] Wan Shuting, He Yuling, Tang Guiji, et al.Investigation on stator circulating current characteristics of turbogenerators under air gap eccentricity and rotor short-circuit composite faults[J]. Electric Power Components and Systems, 2010, 38(8): 900-917. [22] 李和明, 万书亭, 李永刚. 基于定子绕组并联支路环流特性的发电机故障识别方法[J]. 电力系统自动化, 2005, 29(6): 75-78, 107. Li Heming, Wan Shuting, Li Yonggang.Generator fault diagnosis based on the circulating current in stator winding parallel branches[J]. Automation of Electric Power Systems, 2005, 29(6): 75-78, 107. [23] Tu Xiaoping, Dessaint L A, Fallati N, et al.Modeling and real-time simulation of internal faults in synchronous generators with parallel-connected windings[J]. IEEE Transactions on Industrial Electronics, 2007, 54(3): 1400-1409. [24] Yoshida J, Hino N, Takahashi K, et al.Calculation method of circulating current in parallel armature windings in consideration of magnetic circuit[C]// 2013 IEEE Power & Energy Society General Meeting, Vancouver, BC, Canada, 2013: 1-5. [25] 齐鹏, 李永刚, 马明晗, 等. 基于环流时频图谱的抽水蓄能机组励磁绕组匝间短路故障诊断[J]. 电工技术学报, 2023, 38(22): 6104-6120. Qi Peng, Li Yonggang, Ma Minghan, et al.Diagnosis of inter-turn short circuit in excitation winding of pumped storage units based on time-frequency map of circulating current[J]. Transactions of China Electrotechnical Society, 2023, 38(22): 6104-6120. [26] 辛鹏, 戈宝军, 陶大军, 等. 多极隐极发电机励磁绕组匝间短路时的定子分支环流谐波特性[J]. 电工技术学报, 2017, 32(7): 67-76. Xin Peng, Ge Baojun, Tao Dajun, et al.Stator branch circulating current harmonic characteristics of multipole non-salient-pole generator with field winding inter-turn short circuits[J]. Transactions of China Electrotechnical Society, 2017, 32(7): 67-76. [27] 董开松. 基于气隙动态测量技术的定转子变形评价方法研究[D]. 西安: 西安理工大学, 2007. Dong Kaisong.Study on the assessment methods of stator-rotor distortion based on air gap dynamic measurement[D]. Xi’an: Xi’an University of Technology, 2007. [28] 肖孝锋. 水轮发电机组气隙监测与转轮应力测试研究[D]. 武汉: 华中科技大学, 2006. Xiao Xiaofeng.Study on air gap monitoring and runner stress measurement of hydrogenerator unit[D]. Wuhan: Huazhong University of Science and Technology, 2006. [29] 肖鸿杰, 宋金煜, 王如玫, 等. 电机学[M]. 2版. 北京: 中国电力出版社, 2015. [30] 高景德, 王祥珩, 李发海. 交流电机及其系统的分析[M]. 2版. 北京: 清华大学出版社, 2005. [31] 武玉才, 范轩杰, 纪璇, 等. 水轮发电机转子不圆度诱发的定子铁心振动特性研究[J]. 中国电机工程学报, 2025, 45(1): 342-352. Wu Yucai, Fan Xuanjie, Ji Xuan, et al.Study on vibration characteristics of stator core induced by rotor non-roundness in hydro-generator[J]. Proceedings of the CSEE, 2025, 45(1): 342-352.
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