Effects of adding M-xylene on breakdown strength for propylene carbonate in microsecond range

Liquid dielectric has been widely used as the energy storage medium in Pulse Forming Line (PFL) due to its high density, good self-healing and easy-shaping[1-2]. One of the liquid dielectric breakdown model and mechanism is the bubble discharge theory which successfully providing an explanation of pressure impact on liquid electric breakdown strength. In this paper, based on the bubble discharge theory, m-xylene is added in propylene carbonate (PC) to investigate the influence on the breakdown voltage for PC. As a kind of aromatic hydrocarbon, m-xylene can react with gas and generate saturated hydrocarbon which may cause decrease of the bubbles and improvement of the liquid dielectric breakdown strength. The devices used in this study involve a compact capacitive-energy-storage pulsed power source with charging time varying from 5 to 20 microsecond and a test cell with the needle-plate electrodes. The breakdown voltage is recorded by a digital oscilloscope for each test. The studies on breakdown voltage of pure PC and mixed PC are undertaken in order. The data of the experiments showed that the breakdown voltage of PC mixed with 12.5% m-xylene is 18.9% higher than that of pure PC. In the end, some explanations about the results are given based on the bubble discharge theory and gassing properties of aromatic hydrocarbons in high electric field.