金属杂质侵蚀下的大型发电机定子线棒绝缘劣化机理  

Mechanism of Insulation Deterioration of Large Generator Stator Bars Eroded by Metal Impurities

作　　者：刘凌 张宇[1,2] 靳东松[1,2] 娄建勇 LIU Ling;ZHANG Yu;JIN Dongsong;LOU Jianyong(State Key Laboratory of Electrical Insulation and Power Equipment,Xi’an Jiaotong University,Xi’an 710049,China;School of Electrical Engineering,Xi’an Jiaotong University,Xi’an 710049,China)

机构地区：[1]西安交通大学电力设备电气绝缘国家重点实验室,西安710049 [2]西安交通大学电气工程学院,西安710049

出　　处：《西安交通大学学报》2022年第6期104-111,194,共9页Journal of Xi'an Jiaotong University

基　　金：国家自然科学基金资助项目(51977173)。

摘　　要：为揭示大型发电机全工况域内金属杂质侵蚀定子线棒环氧云母绝缘层的耦合机理,对金属杂质颗粒与定子绝缘层高应变下的材料介损进行了电磁-机械-温度多场有限元模拟与实验分析。在矢量磁位的有旋场下,构建含球型金属杂质的线棒与铁芯槽电磁-机械参数化模型,赋特征单元类型及空气域奇对称边界条件;利用矩阵等交互顺序耦合法,对该模型的体力密度值和非线性瞬态施力行为进行施力渐变分析;研究定子线棒端部环氧绝缘层相变与微观损耗增量,得出金属杂质研磨绝缘层的形变特征值及应力特征值范围;建立含球型金属杂质的电磁-温度模型,运用单向磁热耦合方式进行热侵蚀计算,得出杂质接触面的温度场范围。采用交变磁场下金属研磨实验对线棒切面绝缘层进行模拟施力验证,并对样本采用扫描电镜观测。实验与仿真结果表明:金属杂质焦耳损耗引起的异常温升不足以对环氧绝缘层造成短时热侵蚀;由杂质研磨侵蚀使环氧分子链发生断裂导致云母片缺陷加剧的机械过程是定子线棒绝缘劣化的主因。本文研究可为发电机定子线棒主绝缘的状态监测与故障诊断提供一定的参考。To reveal the coupling mechanism of metal impurities eroding the epoxy mica insulation layer of the stator bar in the whole working condition of large generators,the dielectric loss of metal impurity particles and stator insulation layer under high strain was subject to electromagnetic-mechanical-temperature multi-field finite element simulation and experimental analysis.Firstly,the electromagnetic-mechanical parametric model of bar and core slot containing spherical metal impurities is constructed under the swirl field of vector magnetic potential,and the characteristic element type and air domain odd symmetry boundary conditions are assigned.Then,the force density value and nonlinear transient force application behavior of the model are analyzed by the interactive sequence coupling method such as the matrix method.By studying the phase transition and microscopic loss increment of the epoxy insulating layer at the end of the stator bar,the characteristic value range of stress and deformation of the metal impurity grinding insulating layer are obtained.Furthermore,an electromagnetic-temperature model containing spherical metal impurities is established and the thermal erosion calculation is carried out by using the unidirectional magneto-thermal coupling method.Based on this model,the temperature field range of the impurity contact surface is rigorously analyzed.Finally,the metal grinding experiment under the alternating magnetic field is conducted on the insulating layer of the bar section for simulated force application verification and the samples were observed by the scanning electron microscope in detail.The experimental and simulation results show that the abnormal temperature rise caused by joule loss of metal impurities is not enough to cause short-term thermal erosion of the epoxy insulation layer,and the mechanical process of sheet mica’s defect being aggravated due to the breakage of the epoxy molecular chain ground and eroded by impurities is the main cause of insulation deterioration of the stator

关 键 词：大型发电机 定子线棒 绝缘劣化 有限元分析 扫描电镜 

分 类 号：TM31[电气工程—电机]