Influencing Factors of Dielectric Breakdown in the PEF Treatment Chamber

Electrical breakdown of the treatment chambers under repetitive high-intensity pulses impedes the industrial application of pulsed electric field (PEF) technology. In this paper, phenomenon and laws of electric discharges in the PEF treatment chambers were studied. The experimental results indicate that temperature increase and formation of gas bubbles under high electric field strength reduces insulation of water solution. Air dissolved in the samples is only a small part of the bubble and hardly affects the size of bubble formed. The majority part of the gas in the bubble comes from the vaporization of liquid. Fluctuations in the temperature curve may be a direct indication of the beginning of bubble formation. Partial electrical discharges occur inside the gas bubble and are the precursor of dielectric breakdown of PEF treatment chambers. Solution temperature and conductivity have significant effect on electrical discharges. Electric field strength needed for the electrical discharge decreases as the initial temperature increases. As the solution conductivity increases, the lowest electric field strength required for electrical discharge occurrence decreases. Findings in the present investigation reveal that measures that help to reduce the bubble formation are helpful to safe operation of the PEF system.