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High performance electrical insulation materials and structures must be free from unwanted and unpredictable dielectric breakdown through the insulator as well as surface flashover along the interface between the insulator and the ambient or vacuum. The last decade has witnessed significant developments in the area of nano-particulate and nano-dielectric materials, and significant effects of nano-scale fillers on electrical, thermal, and mechanical properties of polymeric materials have been observed. Surface flashover is one of the major issues in electrical insulation in power systems operating either in space (vacuum or partial vacuum) or atmospheric (earth-bound) environments. Thus, development of new and advanced materials to be used in power systems requires extensive studies on electrical insulation characteristics of these materials before they can be used in commercial systems. Most of the research in characterization of nano-dielectric materials has been for systems operating in atmospheric environment; there are limited or no data for systems using these materials in space environments. In this paper, we present experimental results of surface flashover characteristics of epoxy resin and epoxy resin cast with powdered Al2O3 in partial vacuum. The flashover studies were conducted separately using DC and AC signals. Surface flashover voltage and current waveforms of the samples and light emission waveforms and video images during the breakdown were recorded. Optical data collected by a video camera along with the PMT light emission data are analyzed and the results of the optical emission characteristics of surface flashover are presented along with the electrical data. The samples used in the experiments were produced by using either epoxy resin of known properties or by mixing known quantities of Al2O3 with epoxy. The electrode material placed over the dielectric samples was copper.