【作者】 管春伟；

【导师】 郑萍；

【作者基本信息】 哈尔滨工业大学 ， 电机与电器， 2013， 博士

【摘要】 作为发电站中的重要能源转换装置，汽轮发电机一旦发生故障不仅影响电力系统的可靠性，还会造成巨大的经济损失。电力系统负荷处于低谷时，其过剩无功导致电网电压升高，为了保证供电质量，要求发电机具有进相运行的能力，以便吸收电网中多余的无功。发电机进相运行深度过大，会造成端部磁场过高，电机端部结构件发热严重。此外，水-氢-氢汽轮发电机运行中发生的定子绕组空心股线堵塞以及断水，会造成定子绕组冷却能力下降，局部温度过高。上述问题，都会对发电机的安全稳定运行带来影响。通过研究汽轮发电机不同端部结构和定子冷却结构对电磁和温度分布的影响规律，优化电机结构，对降低发电机损耗，改善电机内温度分布，提高发电机的运行寿命具有重要的意义。本文对水-氢-氢汽轮发电机定子端部采用不同阶梯段铁心结构、不同端部绕组结构尺寸及进相运行深度对端部磁场分布和结构件损耗大小的影响开展了研究，对定子绕组空心股线堵塞及断水运行下绕组温度变化进行了分析，通过实测数据验证了三维电磁场和温度场求解方法和求解结果的正确性。首先，对水-氢-氢汽轮发电机有效段区域二维电磁场进行了计算，采用双收敛迭代方法，确定了发电机额定运行时励磁电流和功角。针对发电机端部复杂结构，建立了包括4段阶梯段铁心的端部电磁场计算模型，采用三维时步有限元方法得到了端部阶梯段铁心的磁场分布和铁耗数值，给出了端部阶梯段铁心区域定转子气隙处磁场沿着轴向的变化规律，对比分析了端部漏磁场对阶梯段铁心损耗的影响程度。建立发电机端部采用不同阶梯段结构与不采用阶梯段结构电磁场数学模型，揭示几种结构下发电机端部铁心段齿部磁密的分布规律，研究几种结构对端部铁心损耗和结构件涡流损耗的影响程度，为汽轮发电机的端部结构优化设计提供重要参考。其次，对发电机定转子端部绕组尺寸变化对端部结构件涡流损耗、阶梯段铁心铁耗及端部区域磁场分布规律的影响进行了研究。计算分析了发电机定转子端部绕组伸长量不变、定子绕组端部直线段伸长和转子绕组端部直线段伸长三种结构下端部结构件涡流损耗的变化情况，确定了定子和转子绕组端部直线段伸长对端部气隙磁密的影响程度，研究了三种结构下压圈合成磁密及其轴向和径向分量的变化规律，揭示了端部绕组结构对阶梯段铁心发热的贡献程度。再次，针对汽轮发电机进相运行端部损耗过大的问题，对发电机端部电磁分布和损耗大小随进相深度的变化规律进行了研究。在计及铁心饱和等因素下，确定了转子励磁电流和功角随进相深度的变化情况；对比分析了发电机进相深度对端部结构件涡流损耗和定子端部铁心损耗的影响程度，综合评估了发电机不同进相深度下的安全运行能力；探讨了发电机进相运行工况下，端部压指、压圈和铜屏蔽磁密在不同位置的分布趋势，为发电机进相运行情况下端部不同区域的磁场和涡流损耗的分布及大小提供运行参考依据。最后，对水-氢-氢汽轮发电机定子绕组空心股线堵塞及断水故障下定子温度分布、绝缘热承受能力及发电机断水运行温度随时间变化规律开展了研究。建立了定子三维共轭传热耦合计算模型，确定了共轭传热的边界条件，计算得到了发电机正常运行下的绕组温度分布，分析了空心绕组冷却能力对绕组股线绝缘温度分布的影响；研究了定子绕组空心股线发生堵塞时，堵塞股线位置和堵塞根数对定子绕组最高温度的影响程度，给出了空心股线堵塞情况下绝缘的热承受能力；提出空心股线交错式冷却新结构，研究了新冷却结构对空实心股线涡流损耗的影响程度，得到了新冷却结构对降低堵塞故障下绕组最高温度的贡献程度；此外，研究了两种冷却结构发电机断水运行时，定子股线和空心绕组内冷却水的温度随时间的变化规律，对发电机断水运行时间进行了评估。更多还原

【Abstract】 As the important energy conversion device in power station, the abnormaloperation of the turbo-generator not only have a serious effect to the power plantand power system security, but also bring huge economic losses. When the powersystem load is low, the surplus of reactive power in power grid will cause voltagerise. In order to ensure the power quality, it requires the generator to have the abilityof leading phase operation to absorb the excess reactive power in power grid. Theend magnetic field will increase with the increasing of the phase depth, which willcause the serious fever end in the end metal parts. Besides, the blocking failure andrun off the water occurred in the water cooled generator will cause the coolingability in the stator decreased, which will cause the high local temperature. All ofthe above problems will impact the safe and stable operation of the generator.Therefore, it is important to research the electromagnetic and temperaturedistribution of turbo-generator which will reduce the generator loss, improve thetemperature distribution, and extend working life of the generator.In this thesis, the influences of different end stator step packets, end windingdimensions and the phase depth on end magnetic field distribution and eddy-crrentlosses are studied using three dimensional transient electromagnetic field and theeffect of the blocking and water break failures of hollow strands on the stator localtemperature variation are investigated. The calculated results of the3Delectromagnetic field and temperature field were verified by the test values, whichverify the correctness of the computational method.First of all, for a water-hydrogen-hydrogen cooled turbo-generator endstructure, the end electromagnetic field calculation model including four stator steppackets was established. By using the3D time-stepping finite element method(FEM), the magnetic field distribution and iron losses of the stator step packets wereobtained. The air gap magnetic flux density for various axial positions in end regionwas analyzed and the effect of the end leakage magnetic field on the iron losses inend stator step packets was comparatively studied. The influences of the end statorpackets with ladder structure and without step packes on the magnetic flux densityin the teeth were studied. The magnetic field distribution and end losses withdifferent step angles were comparativly analyzed. The obtained conclusion willprovide important reference for the structure optimization design in the end part.Sencondly, the influences of stator and rotor end winding dimensions on endlosses and electromagnetic distributions were studied. A2D iterative calculation wasdone with the power factor and the phase voltage as the target of convergence, and the field current and angle were obtained. The effect of the length of stator endwinding and rotor end winding in the line segment parts on the end losses wascomparativly analyzed, and the influence of different end winding dimensions onend air gap magnetic was studied. The changes of magnetic flux density, also theaxial and radial component were investigeted, and the influence degree of the endwinding to stator step packes on iron core losses were analyzed, and also the eddycurrent loss distribution in the end metal parts was obtained.Thirdly, for the increasing losses of the end parts, the changing rules of endmagnetic field and electromagnetic loss with generator running under differentphase depth were studied. Excitation current and power angle under different phasedepth were calculated and analyzed considering the saturation characteristic ofstator and rotor cores. The eddy-current losses and iron losses under different phasedepth were obtained, and radial and axial component of the magnetic flux density inthe press plate, press finger and copper field are analyzed.Lastly, the temperature distribution and thermal aging property with theblocking and water break failures in the water cooled stator windings are researched.Temperature variation law with time under water break fault were analyzed.Considering the complex cooling structure, a three-dimentional conjugate heattransfer coupling analysis modle was established, and the series solid-fluid heattransfer conditions are determined. The cooling capacity of hollow strands wasanalyzed and the influences of hollow strands on strand insulation temperature wasinvestigated. The effects of blocking hollow strands numbers and locations on themain insulation were investigated. A new cooling structure of stator windings wasproposed, and the effects of the new cooling structure on the strand eddy-currentlosses and the impact of new cooling structure on reducing the highest temperaturewith blocking failure were investigated. Meanwhile, the running ability of thegenerator with water break failure were evaluated. Temperature variation law withtime of the cooling water and stator winding were obtained.更多还原