Pulsed breakdown characterization of two dielectric oils with a BST nanoparticle suspension and varying filtration pore size

As more applications require high power and rep-rate capabilities, the University of Missouri-Columbia is investigating the design of liquid dielectric switches. In particular, the design and characterization of oil dielectrics is critical for optimum switch performance. Previous improvements, such as tuning of the oil pressure and flow rate, have dramatically reduced the rep-rate self-break jitter by eliminating breakdown byproducts. By introducing a suspension of Barium Strontium Titanate (BST) nanoparticles in the oil dielectric we hope to further reduce the breakdown jitter. Electrostatic simulations show that a nanoparticle suspension within the oil dielectric generates non-linear electric fields on both the electrode surfaces and in the bulk of the oil dielectric with a uniform applied electric field. These electric fields may help reduce jitter by enhancing cathode electron emission and streamer propagation across the gap. The two oils utilized in the experimental study were Hexadecene C₁₆H₃₂ and a synthetic oil dielectric developed by NYCO called NYCODIEL. A pulse generator, specifically designed for the characterization of oil dielectric strength, is implemented for this study. The pulse generator produces a voltage rise of 160-kV/μs across an adjustable electrode gap. Fifty voltage pulses are applied to each of the two oils at two oil pressures, totaling 100 breakdown measurements per oil. Before each test cycle, the oil is sparged with dry nitrogen to reduce the water content, and the switch electrodes are polished. The water content was measured by a K-F coulometric titrator. The oils are filtered between shots with three different filter pore sizes: 5-μm, 1-μm, and 0.45-μm. This was done to determine the optimum size filter for the system as the buildup of carbon byproducts reduces switch performance. A description of the pulse generator is provided, and the experimental procedure is described. Data - - for the dielectric oils is presented and analyzed, including the mean and percent standard deviation of the voltage breakdown data.