Partial Discharge Characteristics on Pressboard Surface Under Different DC Polarities

摘要

The interphase pressboard barriers sustain ac and dc composite voltage in the converter transformer, and might degenerate after the long terms' operation under composite voltage. The typical needle-plane electrodes model was established under the laboratory condition. This paper researches the partial discharge (PD) characteristics on oil-pressboard interface under different DC polarities. The surface change of pressboard was caught by the high-speed camera, the characteristics of PD were sampled by the commercial PD detector. The results found the PDs were much higher under the negative DC polarity, and the energy of breakdown moment of the negative polarity was much higher the positive polarity. Therefore, the negative DC polarity could make more damaging effects on pressboard surface layers.