Field enhancement simulation study of nanoparticle-infused dielectric oil with roughened electrode surfaces

The Center for Physical and Power Electronics at UMC has been having experimental success in reducing the self-break jitter of a single-shot pulsed oil switch with various high-K nanoparticle-infused oil dielectrics. In support of this effort, electromagnetic simulations have been completed to quantify the observed phenomena. The simulation results presented in this paper focus on modeling the electric fields associated with the spatially random placement of both electrode enhancements and polarized high-K particles in a simulated oil gap. The simulation results show that high-K particles increase the average electric field on the surface of a rough electrode surface which contributes to the lower experimental oil breakdown strength. A field enhancement on the surface of an electrode allows electrons to initiate breakdown closure of an oil switch at lower voltages. The high-K particles further decrease the breakdown voltage of the switch by amplifying the effects of these electrode field enhancements. By performing simulations using CST EM Studio software, we have concluded that the particles create field enhancements on the surface of smooth and rough electrode surfaces. The simulated gap is 8 μm wide and is bracketed by two planar electrodes which are 16 μm in diameter. Hemispherical or conical electrode field enhancements of any size can be inserted on the electrode surfaces in fixed or random locations. Particles can be inserted in only random locations to match actual distributions. These simulations are designed to supplement experimental work being done on oil spark gap switches. Experimental testing has indicated that high-K nanoparticle-infused dielectric oils demonstrate reduced breakdown strength and jitter in a pulsed single-shot switch with planar polished and roughened electrode surfaces. The particles are thought to interact with the field enhancements to reduce the breakdown strength of an oil dielectric. By correlating the experimen- al and simulation data, further insight may be gained into the role of the particle and electrode enhancements in the breakdown process.