中文摘要：

高压直流输电和地磁风暴均可引发变压器直流偏磁，这一现象会给变压器带来很多影响。而励磁电流的试验和分析是研究变压器直流偏磁特性的关键问题。通过直流偏磁下变压器励磁特性曲线，得出励磁电流表达式。对通过比较三相变压器组和三相铁心式变压器的铁心结构，得出三相变压器组更易受直流偏磁的影响。为了统一衡量变压器的直流偏磁的耐受能力，提出直流比置系数这一概念。并在不同直流比置系数条件下，利用PSCAD／EMTDC软件仿真出两种变压器励磁电流波形以及函一，曲线，通过仿真结果并验证了三相变压器组承受直流偏磁差这一特点。

英文摘要：

High voltage direct current transmission （HVDC） and geomagnetic storms can lead to transtormer DC magnetic bias, which give a lot of impacts on the transformer. The excitation current test and analysis are the key problems in studying of transformer DC magnetic bias characteristics. Through the transformer excitation characteristic curve under DC magnetic bias, the excitation current expression is derived. By comparing the core structure of the three-phase transformer group and the three-phase core-type transformers, the conclusion that the three-phase transformer group is more prone to DC magnetic bias influence is reached, In order to unify the measure of transformer DC bias tolerance, the concept of DC ratio opposed coefficient is put forward. Under different DC ratio opposed coefficient conditions, PSCAD/EMTDC software are used to simulate two types of transformers magnetizing current waveforms and Ф-I curves. Simulation results verify poorer performance of the three-phase transformer group to bear DC magnetic bias.