The Influence of Harmonic Current on The Loss and Temperature Distribution Characteristics of a Converter Transformer Winding
Tan Youbo1, Yu Xiaoling2, Zang Ying3, Wang Haotian4, Li Junhao4
1. School of Energy and Power Engineering Xi’an Jiaotong University Xi’an 710049 China; 2. School of Chemical Engineering and Technology Xi’an Jiaotong University Xi’an 710049 China; 3. Shandong Electric Power Equipment Co. Ltd Jinan 250022 China; 4. State Key Laboratory of Electrical Insulation and Power Equipment Xi’an Jiaotong University Xi’an 710049 China
Abstract：Since the harmonic current aggravated the local overheating and insulation aging of converter transformer windings, studying the influence of harmonic current on the loss and temperature distribution characteristics of windings attributed to improve the stability of transformer operation and prolong its service life. Accurate thermal modeling was critical for this study. However, there were different degrees of simplifications in the existing numerical calculation models of winding temperature. Moreover, most of current research focused on the influence of harmonic current on the loss and hot-spot temperature values, whereas there was a lack of quantitative analysis on the influence of harmonic current on the loss and temperature distribution characteristics of windings. To address these issues, this study improved winding temperature numerical calculation model, and based on this improved model, the influence of harmonic current on the loss and temperature distribution characteristics of windings was investigated. Firstly, a novel simplification method of disc was developed and an electromagnetic-thermo-flow coupling numerical model of a full-scale valve-side winding of a converter transformer practically applied in engineering was established, in which the key factors affecting the calculation accuracy of the winding temperature were comprehensively considered. The model was validated by both measured and literature results. Secondly, the losses and temperature of the winding under the fundamental wave and rated conditions were calculated, respectively. Finally, the influence of harmonic current on the loss and temperature distribution characteristics of the winding was quantitatively analyzed. The results showed that compared with the non-simplified model, the axial heat transfer rate of the simplified model established by the simplification method of disc proposed in this study was almost the same, and the deviation of the radial heat transfer rate was within 2%. Moreover, compared with the fundamental wave condition, under the rated condition, along the axial direction, the losses of the first to fourth disc in winding top increased by 64.86%, 51.29%, 43.06% and 37.45%, respectively, and the losses of the first to fourth disc in winding bottom increased by 65.71%, 53.55%, 45.49% and 40.36%, respectively. And along the radial direction, the total losses of each disc unit column increased by 41.69%, 32.61%, 24.83%, 18.87% and 15.40% from the innermost to the outermost column. Besides, under the fundamental wave condition, the winding hot-spot and mean temperatures were 81.7℃ and 74.3℃, respectively. The difference of winding temperature distribution along the radial direction was not obvious. By contrast, under the rated condition, the winding hot-spot and mean temperatures were 90.3℃ and 77.8℃, respectively. The winding temperature was unevenly distributed along the radial direction, and the hot spot was concentrated on the winding inside. The following conclusions were drawn: ① The simplification method of disc proposed in this study was accurate for calculating the heat transfer of the disc. Compared with the traditional simplification method, i.e. electrothermal analogy, adopting the simplification method proposed in this study, not only the huge workload of establishing thermal resistance network was avoided and the computational hardness was lowered, but also this method was applicable to the special-shaped disc structure. ② The uncertainty caused by partial simplification of existing numerical calculation models was reduced after adopting the multi-physics coupling model established in this work. ③ Compared with the fundamental wave condition, the harmonic current intensified the eddy current effect of the end and radial inside disc unit, which increased the losses of the end and radial inside disc unit. ④ Compared with the fundamental wave condition, the harmonic current made winding temperature unevenly distributed along the radial direction, and the hot spot was concentrated on the winding inside. The hot spot and mean temperatures were increased by 8.6℃ and 3.5℃, respectively.
谭又博, 余小玲, 臧英, 王昊天, 李军浩. 谐波电流对换流变压器绕组损耗及温度分布特性的影响[J]. 电工技术学报, 2023, 38(2): 542-553.
Tan Youbo, Yu Xiaoling, Zang Ying, Wang Haotian, Li Junhao. The Influence of Harmonic Current on The Loss and Temperature Distribution Characteristics of a Converter Transformer Winding. Transactions of China Electrotechnical Society, 2023, 38(2): 542-553.
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