This paper proposes a novel technique to fabricate epoxy/alumina nanocomposites with nanoparticle composite process by combination of ultrasonic wave and centrifugal force. The particle dispersion effect of the nanoparticle composite process and its influence on dielectric permittivity were discussed quantitatively. Experimental results clarified that the combination of ultrasonic wave and centrifugal force was effective to increase dispersed nanoparticles and as well as to separate residual agglomerates. We verified that the improvement of particle dispersibility in the nanoparticle composite process by combination of ultrasonic wave and centrifugal force could bring about lower permittivity of the nanocomposites, especially than that of unfilled epoxy material.
Adopting CO 2 as an alternative gas of SF 6 in a gas circuit breaker from the environmental viewpoint, a 72 kV-31.5 kA class CO 2 gas circuit breaker (CO 2-GCB) model, which does not contain SF 6 gas at all, was designed, and produced. In the CO 2-GCB model, some effective technologies for current interruption by CO 2 gas were adopted; namely, puffer pressure enhancing techniques utilizing arc energy during a current interruption and ablation phenomena of a polymer element located in the puffer cylinder. As a result of current interruption and electric insulation tests, the CO 2-GCB model achieved practical levels of performance. Furthermore, it was found by carrying out a life cycle assessment (LCA) that the CO 2-GCB model could reduce the global warming impact by about 40% compared to the latest SF 6 gas circuit breaker in the same rating for 20 years operation including one maintenance opportunity.
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