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<p>In the ultra-high voltage direct current (UHVDC) system, ZnO varistors in converter stations are subjected to complex voltage waveforms comprising superimposed DC voltages and high-order harmonics. Under such conditions, ZnO varistors may endure severe operational condition. This paper conducts aging tests on DC ZnO varistor discs at 135&#xa0;°C using complex waveforms from the high-potential converter valve side (A<sub>2</sub>) under varying DC components, followed by thermal recovery tests on the aged specimens at 135&#xa0;°C, to investigate the impact of DC components on the defect structure and electrical performance of ZnO varistors.During the tests, changes in electrical properties, defect structures, double Schottky barriers are analyzed. The results suggest that the electrical properties do not worsen monotonically with the increase of the DC component of the A<sub>2</sub> waveform and the phenomenon can be explained by combining the processes of filling the interface states by electrons and migration of metastable ions. This paper extension of the operational voltage to the breakdown region, this work provides novel insights into aging mechanisms of ZnO varistors.</p>

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Effect of DC component in complex voltage waveforms from converter stations on defect structure and electrical performance of ZnO varistors

  • 期刊论文

  • 发表日期：

    2025年10月6日

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  • Tao Song,
  • Xia Zhao,
  • Nianwen Xiang,
  • Peng Kang,
  • Ziming He,
  • Chaoqun Wang,
  • Chenglin Xu

摘要

In the ultra-high voltage direct current (UHVDC) system, ZnO varistors in converter stations are subjected to complex voltage waveforms comprising superimposed DC voltages and high-order harmonics. Under such conditions, ZnO varistors may endure severe operational condition. This paper conducts aging tests on DC ZnO varistor discs at 135 °C using complex waveforms from the high-potential converter valve side (A2) under varying DC components, followed by thermal recovery tests on the aged specimens at 135 °C, to investigate the impact of DC components on the defect structure and electrical performance of ZnO varistors.During the tests, changes in electrical properties, defect structures, double Schottky barriers are analyzed. The results suggest that the electrical properties do not worsen monotonically with the increase of the DC component of the A2 waveform and the phenomenon can be explained by combining the processes of filling the interface states by electrons and migration of metastable ions. This paper extension of the operational voltage to the breakdown region, this work provides novel insights into aging mechanisms of ZnO varistors.