Surface Potential and Breakdown Characteristics of Epoxy/AlN Nanocomposites Under DC and Pulse Voltages

In dc high-temperature superconducting fault-current-limiter (HTSFCL) operation, epoxy resin used as the current lead insulation withstands dc voltage. In the case of lightning stroke or line fault, HTSFCL needs to withstand the additional pulse voltage, which is several times greater than that of the dc voltage, and the polarity may be different from that of the dc voltage. It intensifies the electric field distortion, induces partial discharge, and causes insulation failure. To improve the insulation properties of the current lead, the epoxy/aluminum nitride (AlN) nanocomposites with the filler content of AIN nanoparticles of 0, 1, 3, and 5 wt% were prepared. The trap distribution of the sample was acquired to clarify the effects of AlN content on the surface potential behaviors. The results show that the amplitude and the polarity of the pulse voltage can affect the surface charge accumulation of the sample under dc voltage. Moreover, the addition of AlN nanoparticles improves the breakdown voltage of the sample in LN
₂
under dc and pulse voltages.