Study On Harmonic Loss And Superposition Of Loss Of Distribution Transformer

Distribution transformers is an important electrical equipment for distribution system.Not only has it a large number,its’ capacity is growing biger and biger.The widespread application of a large number of power electronics and other nonlinear components in the power distribution network leads to the increasing harmonics of the power grid.When these harmonics flow through the transformer,a large amount of harmonic loss will be caused,resulting in huge economic losses.Precise quantification of harmonic losses can provide the basis for energy-saving retrofit and energy efficiency evaluation.The methods used at present are simply superposing harmonic losses,however,due to the skin effect and the proximity effect,how the current density is distributed and whether the total current loss can be regarded as a linear superposition of the losses when the individual harmonics exist alone are still issues that deserve further study.Basing on the basic principle of electromagnetic field,this paper deduces the expression of the current density distribution and power loss of the transformer windings under multiple harmonics background.The superposition of the harmonic loss under different harmonic conditions is obtained.The experimental results show that the correctness of the theoretical derivation.And the research can provide the basic theoretical basis for the calculation and analysis of the harmonic loss of the power grid.On this basis,the generation mechanism of hysteresis loss,eddy current loss and winding loss of distribution transformers under harmonic environment are analyzed.The three-dimensional model of distribution transformer is established by ANSYS Maxwell to analyze the transient leakage magnetic field of distribution transformers.The magnetic field distribution and harmonic loss of distribution transformer windings are calculated and analyzed,and the distribution of leakage magnetic field of distribution transformer is obtained.The distribution laws of the horizontal leakage flux and longitudinal leakage flux of inner and outer windings of high and low voltage windings are respectively analyzed in the winding axial direction,which lays the foundation for the analysis of the hot spot temperature rise of the transformer winding.