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A polymeric nanocomposite system (nanodielectric) was fabricated, and its mechanical properties were determined. The fabricated nanocomposite was composed of low concentrations of monodispersed titanium dioxide ([TiO.sub.2]) nanoparticles and an epoxy resin specially designed for cryogenic applications. The monodispersed [TiO.sub.2] nanoparticles were synthesized in an aqueous solution of titanium chloride and polyethylene glycol and subsequently dispersed in a commercial-grade epoxy resin (Araldite® 5808). Nanocomposite thin sheets were prepared at several weight fractions of [TiO.sub.2]. The morphology of the composites, determined by transmission electron microscopy, showed that the nanoparticles aggregated to form particle clusters. The influence of thermal processing and the effect of filler dispersion on the structure-property relationships were identified by differential scanning calorimetry and dynamic mechanical analysis at a broad range of temperatures. The effect of the aggregates on the electrical insulation properties was determined by dielectric breakdown measurements. The optical properties of the nanocomposites and their potential use as filters in the ultraviolet-visible (UV-vis) range were determined by UV-vis Spectroscopy. POLYM. ENG. SCI., 51:87-93, 2011. [C]2010 Society of Plastics Engineers, INTRODUCTION In the last decade, the field of nanodielectrics has had a significant impact on the voltage endurance characteristics and the miniaturization (thickness and volume reduction) of electrical insulation systems [...]

In the current study we focus on dielectric properties (as a function of frequency and temperature) of a polymeric composite system composed of polyvinyl alcohol and barium titanate nano powder. In the investigations, the temperature range is between 50-295 K, and the frequency range is between 20 Hz--1 MHz. Polarization and conduction processes are investigated in the linear regime. Dielectric breakdown strengths of samples are also reported. The materials presented have potential to be implemented in cryogenic capacitor or field grading applications. Index Terms--Dielectric relaxation, composites, dielectric breakdown, nanodielectric.

High voltage testing of a three-phase 5-meter prototype high temperature superconducting (HTS) cable is discussed. Findings reveal an inception voltage in excess of the required 15.6 kVrms.

The electrical properties of semiconducting tapes used for field grading applications in high voltage technology are examined. Findings reveal that the tapes have U-shaped temperature dependence of resistivity corresponding to metallic and insulator type character for temperatures over and below 170 K.

In this study, we report fabrication and characterisation of a nanocomposite system composed of a commercial resin and extremely small (several nanometres in diameter) titanium dioxide particles. Nanoparticles were synthesised in situ with particle nucleation occurring inside the resin matrix. In this nanodielectric fabrication method, the nanoparticle precursor was mixed to the resin solution, and the nanoparticles were in situ precipitated. Note that no high shear mixing equipment was needed to improve particle dispersion – nanoparticles were distributed in the polymer matrix uniformly since particle nucleation occurs uniformly throughout the matrix. The properties of in situ nanodielectrics are compared to the unfilled resin and an ex situ nanocomposite. We anticipate that the presented in situ nanocomposite would be employed in high-temperature superconductivity applications. In additions, the improvement shown in the dielectric breakdown indicates that conventional high-voltage components and systems can be reduced in size with novel nanodielectrics. [ABSTRACT FROM PUBLISHER]

Non-metallic structural materials that act as an electrical insulation are needed for cryogenic power applications. One of the extensively utilized materials is glass fiber reinforced resins (GFRR) and may also be known as GFRP and FRP. They are created from glass fiber cloth that are impregnated with an epoxy resin under pressure and heat. Although the materials based on GFRR have been employed extensively, reports about their dielectric properties at cryogenic temperatures and larger thicknesses are generally lacking in the literature. Therefore to guide electrical apparatus designers for cryogenic applications, GFRR samples with different thicknesses are tested in a liquid nitrogen bath. Scaling relation between the dielectric breakdown strength and the GFFR thickness is established. Their loss tangents are also reported at various frequencies. [ABSTRACT FROM AUTHOR]

In this paper we report the recent advances in nanodielectrics that were developed and tested for cryogenic dielectric applications. The systems studied are composed of nanometer size particles. Particles were produced using either an ex-situ or in-situ technique. It is observed that there are clear differences in the structural properties of materials produced using these two approaches. Either no significant degradation or improvement in the electrical insulation properties were observed for ex-situ nano-partide samples processed with an ultrasonic processor and in-situ nano-particle samples. Nanodielectrics have the potential to be tailored with better thermal and mechanical properties without losing their electrical insulation characteristics. [ABSTRACT FROM AUTHOR]

In order to qualify the electrical insulation design of future HTS cables installed in the electric grid, a number of high voltage qualification tests are generally performed in the laboratory on either single-phase model cables and/or actual three-phase cable samples. Prior to installation of the 200-rn Triax HTS cable at the American Electric Power Bixby substation near Columbus, Ohio, in September, 2006, such tests were conducted on both singlephase model cables made at ORNL and tri-axial cable sections cut off from cable made on a production run. The three-phase tri-axial design provides some specific testing challenges since the ground shield and three phases are concentric about a central former with each phase separated by dielectric tape insulation immersed in liquid nitrogen. The samples were successfully tested and qualified for partial discharge inception, ac withstand, and lightning impulse where voltage is applied to one phase with the other phases grounded. In addition one of the phase pairs was tested for dc withstand as a "worst case" scenario to simulate the effect of VLF (Very Low Frequency) tests on the actual cable installed at the Bixby site. The model and prototype cables will be described and the high voltage test results summarized. [ABSTRACT FROM AUTHOR]

High temperature superconducting (HTS) cable technology is rapidly developing for use in the areas of power generation and distribution. While significant progress has been made thus far in developing this technology, further effort is needed to improve the efficiency and cost of dielectric materials for use in these systems. These materials must be compatible with cryogenic operation, exhibit excellent dielectric properties at cryogenic temperatures, and provide a high level of reliability when in service. Moreover, the dielectric materials must be able to be produced into complex forms using cost-effective, industrially scalable processes. To improve upon current fiber-reinforced-polymer composite dielectric materials, the present study investigates the advantages of including nanomaterial reinforcement within the polymer resins. It was found that the nanomaterial additions did not greatly impact the polymer viscosity or increase the cure rate, which enables the nanomaterial-enhanced polymer to be used in fabricating fiber-reinforced composite dielectric materials. The nanomaterial-enhanced composite dielectric materials demonstrated greater than 60% higher AC dielectric breakdown strengths and improved consistency of performance compared to the current standard, G10. Similarly, shear and compression strengths of nanomaterial-enhanced composite dielectric materials compared well with those of G10. [ABSTRACT FROM AUTHOR]

In this paper, we report the dielectric properties of composite systems (nanodielectrics) made of small amounts of mono dispersed magnetic nanoparticles embedded in a polymer matrix. It is observed from the transmission electron microscope images that the matrix polymeric material is confined in approximately 100 nm size cages between particle clusters. The particle clusters are composed of separated spherical particles which comprise unconnected networks in the matrix. The dielectric relaxation and breakdown characteristics of the matrix polymeric material are altered with the addition of nanometer size cobalt iron-oxide particles. The dielectric breakdown measurements performed at 77 K showed that these nanodielectrics are potentially useful as an electrical insulation material for cryogenic high voltage applications. Finally, structural and dielectric properties of nanocomposite dielectrics are discussed to present plausible reasons for the observed low effective dielectric permittivity values in the present and similar nanodielectric systems. It is concluded that polymeric nanoparticle composites would have low dielectric permittivity regardless of the permittivity of nanoparticles are when the particles are coordinated with a low dielectric permittivity surfactant. [ABSTRACT FROM AUTHOR]