【作者】 李洪奎；

【导师】 李岩；

【作者基本信息】 沈阳工业大学 ， 电机与电器， 2011， 博士

【摘要】 本文围绕辽宁省重大科技攻关项目“超高压大型电力变压器集成设计与仿真分析系统”课题,在总结有关文献的基础上,对大型电力变压器的暂态电磁场、涌流电磁力、绕组短路强度和多次短路冲击等问题进行了深入的研究,建立了绕组的模态分析模型及多次短路冲击累积形变的弹塑性模型,给出了轴向及辐向稳定性判据,计算了多次短路冲击的累积形变,为提高绕组短路能力的设计提供了理论依据。全文主要包括四部分内容：第一部分用场路耦合的方法对三维暂态电磁场的磁密分布进行研究。根据大容量变压器的结构特点,在ANSYS有限元软件平台上,应用参数化设计语言进行二次开发,建立了大容量变压器在短路及空载工况下的场路耦合有限元模型。应用此模型对电力变压器的故障工况下的暂态电磁场进行研究,给出了变压器的磁密按单元分布规律。第二部分对变压器空载合闸时,不同磁滞的涌流及绕组涌流应力进行分析和计算。由于变压器铁心磁导率的非线性,变压器空载合闸、次级绕组故障切除重合闸等状态下可能产生与短路电流相比拟的暂态励磁涌流,并由此产生较大的机械力,对变压器绕组的动态稳定性和绕组匝绝缘将造成损坏。所以,建立了空载合闸仿真分析模型,计算了故障工况下绕组的电流,分析了涌流电磁力特点,指出了不同磁滞的涌流和短路电流激励下绕组受力的区别,提出了空载合闸时需要校准稳态载荷的原因及方法。第三部分对电力变压器绕组的轴向短路电磁力及短路强度、辐向稳定性等问题进行研究。建立了用于绕组轴向动力学分析的试验模态模型,分析了绕组的固有频率和预紧力关系,给出了避免共振的预紧力条件,并结合数值计算方法,计算了轴向短路冲击力作用下的线饼位移,提出了轴向稳定性判据。根据绕组的结构特点、垫块及撑条分布规律、辐向振动和工艺缺陷等复杂因素,建立了辐向振动仿真分析模型,并用于试验模型的辐向稳定性仿真分析,提出了保证绕组辐向短路强度的措施。第四部分对在多次短路冲击工况下电力变压器绕组的累积形变进行研究。建立了分析多次短路冲击累积形变的层合加筋圆柱壳模型,用大挠度弹塑性理论计算了变压器绕组在多次短路冲击下的累积形变,给出了绕组单元的变形规律及塑性形变的临界载荷,计算结果表明,该模型能够用于绕组多次短路冲击下的弹塑性累积形变分析及稳定性判断。更多还原

【Abstract】 The dissertation focuses on the study of major scientific and technological project in Liaoning Province "EHV large power transformers Integrated Design and Simulation Analysis System". Based on the summary of relevant literature, the dissertation deals with the transient electromagnetic field in large power transformers, surge electromagnetic force, short-circuit strength of winding and the impact of repeated short-circuit deeply. A winding short-circuit modal analysis model and the impact of the cumulative deformation of the elastic-plastic model is established. A few achievements with values on theory and engineering have been gained, theoretical basis are provided to improve capacity for transformer windings to withstand short-circuit. The full text mainly consists of four parts.In the first part, the field-circuit coupled problem of three-dimensional transient electromagnetic field of flux density distribution is studied. According to the structural characteristics of large capacity transformer, the application parameters design language of ANSYS software are used for the second development, where field-circuit coupled finite element model of three-dimensional transient electromagnetic field for transformers under short-circuit and no-load conditions is established, By using this model, Many accidental conditions of magnetic field distribution in large transformers are studied, and laws of transient magnetic flux density in per unit are given.In the second part ,when transformer is switching-on with no-load, inrush current distribution and electromagnetic force is analyzed and calculated. As non-linear of transformer core magnetic permeability, when transformer is switching-on with no-load, outside the fault of secondary winding is removed again, it may have transient inrush which is compared with the short-circuit current. The resulting mechanical force will cause great harm on the transformer winding, changing turn insulation strength and the dynamic stability, so the no-load of switching simulation model is built, the characteristics of surge electromagnetic force is analyzed, where differences between short-circuit current and inrush current are found, That’s the reason why homeostasis loads need calibrating.In the third part, the power transformer windings axial short-circuit electromagnetic force and strengthand and radial stability issues are studied. Axial dynamic analysis model for experimental modal is established, which is used to analyze relations of natural frequency and pro-compression, the conditions of pre-compression are given to avoid resonance, combined with numerical methods to calculate disk unit displacements by impacting of axial short-circuit. The axial stability criterion is proposed. According to the structural characteristics of windings, distribution of spacer and strip, radial vibration process defects and other complex factors, the radial vibration simulation model is established, which is used to analyze stability of test model, measures are provided to guarantee radial short-circuit strength.In the fourth part, the power transformer winding deformation cumulative impact of multiple short-circuit are carefully dealt with. The cumulative impact of repeated short-circuit deformation of laminated cylindrical shell with stiffeners model is built, the impact of accumulated deformation of repeated short-circuit of transformer winding is calculated with large deformation elastic-plastic theory. Displacement distribution of the impact on repeate short-circuit of the winding and plastic deformation of the load are given, the simulation results show that paper of the model and the theoretical formula have great significance, which is for power transformer windings of the elastic-plastic deformation analysis and the stability judgement of winding.更多还原