It is well known that the hot spot temperature represents the most critical parameter identifying the power rating of a transformer. This paper investigates the effect of the degradation of core magnetic properties on...It is well known that the hot spot temperature represents the most critical parameter identifying the power rating of a transformer. This paper investigates the effect of the degradation of core magnetic properties on temperature variation of aged oil-cooled transformers. Within this work, 2D accurate assessment of time average flux density distribution in an oil insulated-cooled 25 MVA transformer has been computed using finite-element analysis taking into account ageing and stress-induced non-uniform core permeability values. Knowing the core material specific loss and winding details, local core and winding losses are converted into heat. Based upon the ambient temperature outside the transformer tank and thermal heat transfer related factors, the detailed thermal modeling and analysis have then been carried out to determine temperature distribution everywhere. Analytical details and simulation results demonstrating effects of core magnetic properties degradation on hot spot temperatures of the transformer’s components are given in the paper.展开更多
The stochastic finite element equations for random temperature are obtained using the first-order per-turbation technique taking into account the random thermal properties and boundary condition, based on heat transfe...The stochastic finite element equations for random temperature are obtained using the first-order per-turbation technique taking into account the random thermal properties and boundary condition, based on heat transfer variational principle. The local average method for 2-D is used to discretize random fields. Then, the random temperature fields of embankment in cold regions are investigated on condi-tion that the thermal properties and boundary condition are taken as random fields, respectively, by using the program, which is written by the methods. The expected value of temperature field and the standard deviation of the temperature field of embankment in cold regions are obtained and analyzed.展开更多
提出了一种基于有限元法和有限体积法的变压器三维电磁-流体-温度场耦合分析方法。通过建立变压器三维模型,采用有限元法分析变压器内磁通密度分布,并求得变压器及绕组损耗。将变压器铁芯及绕组损耗作为热源,采用有限体积法求解变压器流...提出了一种基于有限元法和有限体积法的变压器三维电磁-流体-温度场耦合分析方法。通过建立变压器三维模型,采用有限元法分析变压器内磁通密度分布,并求得变压器及绕组损耗。将变压器铁芯及绕组损耗作为热源,采用有限体积法求解变压器流体-温度场,分析变压器内部油流及温度分布,同时根据温度场结果对变压器损耗进行修正,通过迭代求解变压器流体-温度场获取变压器内部最终温度分布结果,提高求解精度。采用所提方法对35 k V油浸式变压器进行三维电磁-流体-温度场分析,将结果与经验公式的热点温度计算结果进行对比,验证了所提方法的有效性和正确性。展开更多
文摘It is well known that the hot spot temperature represents the most critical parameter identifying the power rating of a transformer. This paper investigates the effect of the degradation of core magnetic properties on temperature variation of aged oil-cooled transformers. Within this work, 2D accurate assessment of time average flux density distribution in an oil insulated-cooled 25 MVA transformer has been computed using finite-element analysis taking into account ageing and stress-induced non-uniform core permeability values. Knowing the core material specific loss and winding details, local core and winding losses are converted into heat. Based upon the ambient temperature outside the transformer tank and thermal heat transfer related factors, the detailed thermal modeling and analysis have then been carried out to determine temperature distribution everywhere. Analytical details and simulation results demonstrating effects of core magnetic properties degradation on hot spot temperatures of the transformer’s components are given in the paper.
基金the "National Science Fund of Distinguished Young Scholars of China" (Grant No. 40225001)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX3-SW-351)+3 种基金the CAS Special Fund for the National Excellent PhD Dissertation Author (to Dr. Lai, Y.M.)the Foundation of "Hundred People Plan" of Chinese Academy of Sciences (to Dr. Lai Y M)the Knowledge Innovation Program of the Chinese Academy of Sciences (Grant No. KZCX1-SW-04)the National Natural Science Foundation of China (Grant No. 40640420072)
文摘The stochastic finite element equations for random temperature are obtained using the first-order per-turbation technique taking into account the random thermal properties and boundary condition, based on heat transfer variational principle. The local average method for 2-D is used to discretize random fields. Then, the random temperature fields of embankment in cold regions are investigated on condi-tion that the thermal properties and boundary condition are taken as random fields, respectively, by using the program, which is written by the methods. The expected value of temperature field and the standard deviation of the temperature field of embankment in cold regions are obtained and analyzed.
文摘提出了一种基于有限元法和有限体积法的变压器三维电磁-流体-温度场耦合分析方法。通过建立变压器三维模型,采用有限元法分析变压器内磁通密度分布,并求得变压器及绕组损耗。将变压器铁芯及绕组损耗作为热源,采用有限体积法求解变压器流体-温度场,分析变压器内部油流及温度分布,同时根据温度场结果对变压器损耗进行修正,通过迭代求解变压器流体-温度场获取变压器内部最终温度分布结果,提高求解精度。采用所提方法对35 k V油浸式变压器进行三维电磁-流体-温度场分析,将结果与经验公式的热点温度计算结果进行对比,验证了所提方法的有效性和正确性。
