电力变压器绕组中电磁、热和力的耦合作用机理及其累积效应研究

The damage of transformer caused by insufficient short-circuit strength has become the leading cause of transformer faults. The damage of winding result from the cumulative effect produced by external multiple short-circuit impact is the principal form. It is significant to solve the problem for the safety operation of the transformer and the power grid. In this project, the key research problems include: a three-dimensional (3-D) transient magnetic field-electric circuit-temperature field coupling mathematical model will be established to accurately compute magnetic field distribution, current and dynamic force under short-circuit condition; the laminated cylindrical shell with stiffeners.mathematical model will be proposed to compute and analyze the winding cumulative deformation due to the material plastic deformation repeatedly under multiple short-circuit condition, on this basis, the effect of transformer breakdown characteristics due to the change of insulation distance will be studied; the Palmgren-Miner cumulative damage model will be proposed to evaluate the cumulative damage of material, the thermal effect during the extended service and multiple short-circuit impact are comprehensive considered in the model, and lead the effect of material mechanical properties due to cumulative damage into the calculation of winding cumulative deformation; some experiments, e.g., the magnetic field property, the mechanical properties of wire and insulation material, the winding vibration displacement and damage under multiple short-circuit condition, will be designed, and combined with theoretical analysis to present the winding strength and instability criterions. Then the short-circuit damage problem of transformer under multiple short-circuit condition can be solved.

因短路强度不够引起的变压器损坏事故已成为我国变压器事故的首要原因，由外部多次短路冲击而产生累积效应造成绕组损坏是其主要形式。解决这个问题对于变压器和电网安全运行具有重要意义。本项目重点研究：建立磁场-电路-温度场耦合的三维瞬态数学模型，准确计算短路下的磁场、电流和动态力；提出层合加筋圆柱壳数学模型计算分析多次短路冲击下由于材料反复进入塑性变形而引起的绕组累积形变，在此基础上研究由于绝缘距离改变对变压器击穿特性的影响；引入Palmgren-Miner累积损伤模型评估绝缘等材料的累积损伤，在模型中综合考虑长期运行热效应和多次短路冲击的双重作用，并将由于累积损伤对材料力学特性的影响引入绕组累积形变计算中；设计短路试验模型并测试多次短路的磁场特性，导线、绝缘材料力学特性，绕组动态振动位移以及累积损伤，与理论分析相结合，提出多次短路冲击下绕组强度和失稳判据，解决多次短路冲击下变压器短路损坏问题。

因短路强度不够引起的变压器损坏事故已成为我国变压器事故的首要原因，由外部多次短路冲击而产生累积效应造成绕组损坏是其主要形式。解决这个问题对于变压器和电网安全运行具有重要意义。本项目重点研究内容：建立了磁场-电路-温度场耦合的三维瞬态数学模型，准确计算短路下的磁场、电流和动态力；提出层合加筋圆柱壳数学模型计算分析多次短路冲击下由于材料反复进入塑性变形而引起的绕组累积形变，在此基础上研究由于绝缘距离改变对变压器短路特性的影响；引入累积损伤模型评估绝缘等材料的累积损伤，在模型中综合考虑长期运行热效应和多次短路冲击的双重作用，并将由于累积损伤对材料力学特性的影响引入绕组累积形变计算中；设计了短路试验模型并测试多次短路的磁场特性，导线、绝缘材料力学特性，绕组动态振动位移以及累积损伤，与理论分析相结合，提出了多次短路冲击下绕组强度和失稳判据，解决多次短路冲击下变压器短路损坏问题。