特高压换流变压器拉板损耗的频率特性分析

Frequency Characteristic Analysis of Flitch Plate Losses in UHV Converter Transformer

以三维准静态电磁场方程为基础,结合换流变压器拉板表面磁场强度分布的特点,推导得到拉板损耗的近似数学表达式。通过对该公式进行分析,得到了不同电流频率下,拉板开全槽和不开槽时各自损耗的变化规律及彼此之间损耗频率指数的差别。为了验证理论分析的正确性并进一步确定实际拉板损耗计算的频率指数数值,针对一台800kV单相四柱式特高压换流变压器的拉板损耗进行了八分之一有限元仿真计算。结果表明,不论拉板开槽与否,其损耗的频率指数都随着电流频率数值的增大而减小。但拉板开槽在大幅减小基波损耗的同时也增加了高次谐波损耗,因此其损耗频率指数将远大于不开槽时的数值,实际换流变压器负载损耗计算中损耗频率指数可取1.5。拉板不开槽时取值为0.6,该值与理论推导给出的数值0.5基本吻合。

Based on the three-dimensional quasi-static electromagnetic field equation and the characteristics of magnetic field intensity distribution on the flitch plate surface of converter transformer,the approximate mathematical expression of flitch plate loss is derived.Through the analysis of the formula,the variation law of the loss and the difference of the frequency index of the loss are obtained under different current frequencies when the flitch plate is fully slotted and without slotted.In order to verify the correctness of the theoretical analysis and further determine the actual frequency index value of the flitch plate loss calculation,the one-eighth finite element simulation calculation of the flitch plate loss of an 800kV single-phase four-column UHV converter transformer was carried out.The results show that the frequency index of the flitch plate loss decreases with the increase of current frequency,whether the flitch plate is slotted or not.However,the slotting of the flitch plate significantly reduces the fundamental loss and also increases the high-order harmonic loss,so the frequency index of the loss will be far greater than the value of the non-slotted,and 1.5 is advisable in the calculation of the actual load loss of the converter transformer.When the flitch plate is not slotted,the value is 0.6,which is basically consistent with the value 0.5 given by theoretical derivation.