No abstract

In EHV and UHV power transmission lines, corona could occur even on well designed transmission line hardware and insulators especially under wet conditions. Corona if allowed to occur continuously can significantly damage the polymeric insulators used in such lines in the long run. This paper presents the experimental results of corona aging studies conducted on unfilled silicone rubber as well as filled silicone rubber nanocomposites. Corona aging studies were conducted on silicone rubber samples with filler concentrations of 0, 1, 2 and 3 % by wt of nanosilica for 25 h and 50 h. Needleplane electrode geometry has been used to create the corona on the samples. Different characterization techniques such as Scanning Electron Microscopy, Energy Dispersive X-ray analysis, Hydrophobicity, Fourier Transform Infrared Spectroscopy, and Optical Profilometry have been used to assess the relative performance of the samples with respect to corona aging. Results indicate that at 3 wt %, the performance of the nanocomposite is much better than the unfilled silicon rubber which can be attributed to the modifications in the material caused by the size factor of the filler.

No abstract

No abstract

Dielectric breakdown strength of poly (ethylene-co-butyl acrylate) (EBA)nanocomposites filled with spherical alumina particles was studied as a function of particle coating, moisture content and the effective specific surface area. Two kinds of alumina nanoparticles were used: NA (25 nm in diameter) or ND (45 nm in diameter). The particles were either unmodified or surface-treated with aminopropyltriethoxy silane or octyltriethoxy silane. Two different relative humidities of air were used for conditioning the samples prior to testing: 0 % RH (dry case) and 86 % RH (samples were saturated with moisture). The dielectric breakdown strength measurements were performed with a DC ramp of 1.2 kV/s. Twenty samples were tested for each material formulation -ten of which were tested in dry conditions and ten were tested after conditioning in humid environment. Results were compared to the reference unfilled EBA samples. Applying Weibull analysis to the measured breakdown voltages indicated that the material filled with amino-coated ND particles exhibited the highest breakdown strength under dry conditions. As expected, conditioning materials in a humid environment had a negative impact on breakdown strength. This effect was more pronounced for nanocomposite materials, compared to the unfilled reference material.