The effect of area on pulsed breakdown in water
Truman, Keith Phillip
The use of water dielectrics in pulsed power systems is of considerable interest due to the favorable physical and electrical properties of water. Numerous researcher activities have explored various mechanisms of water breakdown including breakdown initiation. The consensus is that initiation of breakdown is caused by a localized field enhancement at the surface of an electrode near a microprotrusion. The research conducted here examines the effect increased area has on the breakdown strength of water. Experimental results are presented on the degree to which electrode surface area impacts the dielectric strength of water. A water gap of 4 mm was tested under pulsed conditions with a maximum electric field in excess of 1 MV/cm and pulse widths greater than 1µs. Stainless steel electrodes with a Bruce profile were used to generate a uniform electric field across the water gap. The profile of the electrodes enabled areas ranging from 0.5 cm2 to 75 cm2 while minimizing the change in capacitance of the water gap. The results of the testing are compared to existing area breakdown models. Conclusions are made as to the effect electrode surface area had on the breakdown strength of the water gap.