This paper describes the influence of AC harmonics in HVDC systems on one of the main indicators of high voltage insulation deterioration, partial discharge. HVDC systems may be subject to various disturbances including harmonics and ripples in the form of pulsating voltages. Experiments, performed on model void specimen at DC voltage with selected superimposed harmonics, are described. A novel approach for recording partial discharges at DC, based on synchronization with selected superimposed harmonics, is proposed. In this way individual partial discharge pulses, occurring during a given measurement time, are accumulated with respect to the phase angles of certain harmonics. The partial discharge inception threshold is analyzed for cases where the DC level is held constant and the AC magnitude and harmonic frequency are varied and for cases where the DC level is varied and the AC magnitude is held constant. In addition, a long term aging test where insulating paper and resin impregnated paper was subjected to pure DC voltage and DC containing 12th harmonic 600 Hz, is described. The aging test shows that the superimposed harmonic content resulted in an amplification of partial discharge presence. By mapping the discharge spots occurring on the void surface, it is possible to quantify the level of erosion in both cases. It was observed that in case of harmonic crest voltage being below partial discharge PD inception level the DC component is crucial, however when harmonics magnitude is above the inception voltage the role of AC is dominant relative to DC. Thus, the presence of harmonics may result in a strong acceleration of the deterioration of insulating materials subjected to DC voltage.

中文翻译：

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具有叠加交流谐波的 HVDC 绝缘中的局部放电

本文介绍了高压直流系统中交流谐波对高压绝缘劣化、局部放电的主要指标之一的影响。HVDC 系统可能会受到各种干扰，包括谐波和脉动电压形式的纹波。描述了在具有选定叠加谐波的直流电压下对模型空隙试样进行的实验。提出了一种基于与选定叠加谐波同步的直流局部放电记录新方法。这样，在给定测量时间内出现的各个局部放电脉冲相对于某些谐波的相位角进行累加。针对直流电平保持恒定且交流幅度和谐波频率变化的情况以及直流电平变化且交流幅度保持恒定的情况分析局部放电起始阈值。此外，还描述了绝缘纸和树脂浸渍纸经受纯直流电压和含有 12 次谐波 600 Hz 的直流的长期老化试验。老化测试表明，叠加的谐波含量导致局部放电存在的放大。通过绘制空隙表面上出现的放电点，可以量化两种情况下的侵蚀水平。据观察，在谐波峰值电压低于局部放电 PD 起始电平的情况下，直流分量至关重要，然而，当谐波幅度高于起始电压时，交流相对于直流的作用占主导地位。因此，谐波的存在可能导致承受直流电压的绝缘材料的劣化的强烈加速。