Experimental investigations of water breakdown.

摘要

The Water Breakdown System was designed to investigate various techniques for increasing the high voltage breakdown strength of water and increase the time before breakdown. The interest in water for high voltage applications is because of water's unusually high dielectric constant {dollar}(varepsilonsb {lcub}rm r{rcub}){dollar} which is typically 80. This is about 30 to 40 times higher than most other insulator materials. If the insulating ability of water could be mastered, then high energy capacitors could be made 30 to 40 times smaller than they presently are.; Several techniques were tried during this investigation which included magnetic fields, SF{dollar}sb6{dollar} gas, and HCl. The electrodes were also coated with two different polymers and black wax to see if there would be an improvement in voltage holdoff.; For the magnetic field experiments, neodymium iron boron magnets were placed inside hollowed out copper tungsten electrodes. The magnetic fields showed a small, though, statistically significant effect on the maximum voltage and the effective time-width of the pulse. The level of effect depended on the orientation of the magnetic field and whether the magnets were used in both electrodes or only one electrode.; Initial use of SF{dollar}sb6{dollar} gas with the water appeared promising but the results could not be reproduced. The lack of effect may have been due to an insufficient amount of the gas mixing with the water.; The HCl experiments were similar to work done by Russian scientists except that the voltage level was measured rather than the prebreakdown current measured by the Russians. Adding HCl caused the voltage holdoff capability of the water to decrease with increasing amounts of HCl.; Copper tungsten and stainless steel electrodes were coated with either a thin layer of poly(ethersulfone) or polycarbonate. No noticeable effects were seen with either of these coatings. Also, black wax did not appear to work with large area electrodes. The initial breakdown mechanism is believed to be an electrode surface effect and the use of a coating to grade the field effects at the electrode surface has the greatest chance for improvement in the voltage holdoff capability of water.