中文摘要：

为实现换流变压器故障诊断，研究交流与直流电压比例对油纸绝缘放电特性的影响对换流变压器的故障诊断判据选取具有实际工程意义。因此该文搭建了一套交直流复合电压作用下油纸绝缘气隙缺陷局部放电测量平台，通过多次试验得到了局部放电特征与交直流复合比例的试验关系；另外建立了油纸绝缘气隙缺陷的物理模型，从理论上分析了比例与放电特征关系的仿真结果。试验测量和理论仿真结果相同：随着交流和直流叠加电压中直流成分的增大，脉冲重复率和放电量不断减小；交流时的放电起始电压低于交直流复合电压作用时的起始电压，而且直流比例越高，起始电压越高；随着交流中直流成分的增加，放电起始相位从交流正负半周过零点附近向负半周期峰值附近移动，换流变压器不同位置的绝缘问题应该采用不同的诊断依据。

英文摘要：

In order to realize the fault diagnosis for converter transformer, to study the influence of ratios of AC and DC voltages on partial discharge （PD） characteristics has practical engineering significance for diagnosis of converter transformer. A set of platform was built for PD detection under AC and DC voltage. The relationship between ratios of AC and DC voltage and PD characteristics was obtained by several tests and simulated by building physical model. The experimental measurement and theoretical simulation results are the same： the pulse repetition frequency and PD amount decrease with the DC voltage increasing. But the PD inception voltage increases when DC voltage becomes larger. In addition, the PD phase moves form two locations to just one part in negative half cycle. So for converter transformer, the diagnosis basis should distinguish with the insulation problem at different location.