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A new class of insulating materials is the class of polymer nanocomposites. In the past twenty-five years, a lot of attention was paid to the various electrical, thermal and mechanical properties of polymer nanocomposite materials. In the present work, epoxy resin samples without and with nanoparticles (0 wt%, 1 wt%, 3 wt%, 5 wt%, and 10 wt%) are investigated regarding the surface discharges and the flashover voltages. Four different water droplet arrangements were used, with eight different water conductivities in order to see the effect of the nanoparticle content on the surface discharges and the flashover voltages. [ABSTRACT FROM AUTHOR]

This study focuses on characterization of silicon carbide (SiC)‐epoxy nanocomposites with different mass loading of SiC using different techniques to evaluate the physicochemical, thermo‐physical and surface discharge activity of the insulating materials. A marginal increase in surface discharge inception voltage (SDIV) was observed with increase in wt% loading of SiC in the epoxy but not much variation is observed with increase in supply frequency. Surface discharge process radiates electromagnetic waves in the UHF signal frequency range of 0.5–1.5 GHz. The dielectric properties of the material get altered with the percentage of SiC material in epoxy resin. TEM analysis indicates uniformity of dispersion of nano particle in epoxy resin. Charge retention capability of the material is high when the deposited charges are unipolar. Optical emission studies indicate the presence of silicon peaks with SiC‐epoxy nanocomposites in wavelength range of 350‐400 nm. Oxygen peaks were observed for all samples. Using the spectral peak positions and intensities of the peaks obtained, the plasma temperature for SiC‐epoxy nanocomposites was estimated to be c.a. 2240 K low when compared to that for pure epoxy. LIBS spectra clearly indicate an increase in carbon intensity with corona damaged specimen. Also for the same level of fluency, the amount of damage is less with higher percentage of SiC included epoxy nanocomposites. Pyrolysis GC/MS study indicates that the presence of SiC in the epoxy matrix enhances the timescale of primary pyrolysis vapors such as bisphenol components to form more monomeric phenols via secondary cracking reactions. POLYM. COMPOS., 39:3268–3279, 2018. © 2017 Society of Plastics Engineers [ABSTRACT FROM AUTHOR]

In the present study, the partial-discharge activity under nonstandard voltage formed by ac and dc voltages was studied. It is identified that the ac superposed with positive dc enhances the discharge activity in the medium and if the ac voltage is superposed with the negative dc, it can mitigate the discharge activity. The acoustic emission signal generated due to the partial discharges in gas-insulated systems under the composite voltage formed by ac superposed with dc voltage/ac/dc voltages, has a dominant frequency content at around 250 kHz. Index Terms--Acoustic emission, composite voltage, gas-insulated system (GIS), partial discharge, SF6 gas.