中文摘要：

针对变压器的直流偏磁问题，分析了特高压变压器直流偏磁时无功损耗的响应机理。给出无功损耗计算方法，进行无功损耗特性分析。采用增加串联电阻的方法，提高计算电流中直流分量的计算精度。结合电压补偿，消除增加串联电阻后导致的电压下降问题。根据特高压变压器的实际参数．建立变压器的场路耦合模型，进行特高压变压器不同直流偏磁电流下的仿真计算。研究表明，变压器直流偏磁时，励磁电流波形严重畸变。随着直流偏磁电流的增加，特高压变压器的空载无功功率逐渐增加，直流偏磁电流超过一定范围后，无功功率随着直流偏磁电流的增加近似呈线性增加。相同直流偏磁电流时．负载下的无功功率明显大于空载下的无功功率。相比于无直流偏磁时的无功功率，相同直流偏磁电流时，空栽与负载下的无功增额大体相同。

英文摘要：

For the DC bias problem of transformer, the response mechanism of reactive power loss of UHV trans- former under DC bias is analyzed and the method of reactive power loss is indicated. On the basis of this,when given no power loss calculation method, the characteristics of reactive power loss is analyzed. The efficiency about the calculated current can be enhanced by increasing the series resistance. The problem of voltage drop can be solved effectively resulting in the series resistance by the method of voltage compensation. The magnetic field model is established according to the product level of UHV transformer parameters. The time domain simulations of different direct current can be carried out based on the field-circuit coupled model, established according to the product level of UHV transformer parameters.The study shows that the exciting current is distorted wave severely. The reactive power loss in no-load increase linearly with DC current grows. Compared to the no-load, the reactive power loss with load increases more with the same DC bias current. In addition, with the same DC bias current, the increase of reactive power loss is nearly the same in no-load and load.