Polarity reversal discharge on polypropylene surface applied with nanosecond pulses

In this paper, a needle-plane electrode system and non woven polypropylene filters were used to study the space charge formation on the surface of dielectrics by nanosecond pulse discharge. Ordinarily, the charging of polymers shows the same polarity as the voltage applied. A novel discovery of polarity reversal discharge was found that the accumulated space charges on the surface of polymers show a different polarity against the applied pulse. It was found that a higher positive pulse peak leads to easier polarity reversal charge accumulation in polymers. It was also found that a negative pulse causes a positive charge accumulation when the peak is sufficient high and the pulse width is sufficient small. In addition, a negative pulse will produce the same polarity of charges on the surface of polymers when the width of pulse is larger than 200 ns. A novel mechanism of two charging processes of high fluid injection and return stroke injection has been put forward here to fit the polarity reversal charging phenomena. We concluded that the polarity reversal charging of polymers can be inherently related to the discharge in gases and the needle-plane electrode system.