Materials Literature
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The effect of air density on the flashover voltage of polluted high-voltage insulators has been analyzed for AC, DC, and lightning-wave energizations. The findings, based on the physics of the flashover process and test data from representative models and actual insulators, are presented as an altitude scaling factor.…
An online partial discharge test for large steam turbine generators has been developed whereby partial discharges and noise are distinguished on the basis of pulse width. The pulse signals are detected by stator slot couplers (SSCs) which are permanently installed within the generator. Experiments have shown that part…
A series of experiments was conducted on polymeric insulators to examine the role of molecular bond motion in the recovery of hydrophobicity. The samples were also analyzed with characterization techniques which provided important information concerning surface topography, surface hydrophobicity level, and surface che…
Results are presented from analyses of pulses from partial discharges (PDs) in single spherical voids in filled and unfilled epoxy plastic and related to the observed surface deterioration. The filler types used were dolomite, alumina, and silica. Long-time aging tests including pulse phase/height analyses were perfor…
Zinc oxide (ZnO) thin films were accurately and reliably delineated by wet chemical etching in 5% NH/sub 4/Cl in water and by reactive ion etching in a SiCl/sub 4/ plasma. With the etch solution at 55 degrees C, the ZnO etch rate was approximately 300 nm/min. Aluminum, silicon and silicon dioxide were not attacked by…
Sol‐gel processes allow for the synthesis of powders with a more elaborate structure from the point view of composition, purity, size, and size distribution. In the powder case, sol‐gel refers to processing in a liquid medium to obtain a solid, which does not settle under gravity due to the formation of a diffuse netw…
The authors discuss the characterization, evaluation and performance of polymer weathershed materials and insulators used for high-voltage outdoor applications. Ethylene propylene diene monomer (EPDM), ethylene propylene monomer (EPM), silicone rubber (SR), and an EPDM/silicone rubber alloy were tested. The tests cons…
The authors describe experiments which have been designed to study the effect of mechanical strain on the short-term AC breakdown strength of cross-linked polyethylene (XLPE) cable insulation. Laboratory experiments were performed on mechanically stressed Rogowski-type test objects and on sharply bent samples of 12-kV…
The phenomenon of interfacial AC breakdown is considered. Two pieces of EPDM (ethylene-propylene diene monomer) rubber were pressed together and a special jig was conceived to provoke arcing along the interface. The voltage at which breakdown occurred was measured and its dependence on interfacial length and pressure…
An investigation of the pulse propagation characteristics of motor stator windings is reported. The results indicate the effects of electrical and physical length and pulse risetime on the propagation characteristics. They explain the observed phenomena and place them in the context of partial discharge measurement te…
Apical, Upilex, Kapton, Teflon AF, and PEEK polymers are characterized for AC and DC dielectric breakdown in air and in silicone oil at temperatures up to 250 degrees C. The materials are also tested in terms of their dielectric constant and dissipation factor at high temperatures with an electrical stress of 60 Hz, 2…
To elucidate the chemical changes due to dry band arcing, under wet and contaminated conditions, of room temperature vulcanized (RTV) silicone rubber used for coating HV outdoor insulators, the thermal impact of the arcing on the rubber surface was investigated. A loss of hydrophobicity, resulting in a reduction of th…
A series of the bis(octaalkoxyphthalocyaninato)lutetium(III) complexes [(CnO)8Pc]2Lu (n = 10, 12, 14, 16, 18) were synthesized. The mesomorphic behaviour was revealed by using polarization microscopy and DSC. The detailed mesophase structures were clarified by using temperature-dependent X-ray diffraction and temperat…
In this paper, we report the results of the high field magnetization and the high field/high frequency ESR measurements on [Mn III ( taa )], which is a spin-crossover complex. The observed ESR signals will be discussed in connection with the results of our high field magnetization which exhibits the first observation…
Polypropylene, a low-loss, high-dielectric-strength film was characterized for its dielectric properties under high-voltage, high-frequency conditions. The properties that were measured included the breakdown voltages and the high-voltage aging characteristics at frequencies up to 30 kHz. The exponential law is used i…
The time dependence of PZT (lead zirconate titanate) (Navy I and III) was investigated in the case of a high stress applied parallel to the poling axis. The time dependence was found to be linear in ln(t), with slope activated in temperature with an activation energy of 0.29-0.32 eV for the Navy I material and 0.62-0.…
This review is the first one in a planned series on the systems potentially suitable for high-magnetic-field and high-frequency electron magnetic resonance (HMF-EMR) studies. Such systems must best exhibit large or very large zero-field splitting (ZFS). The transition metal 3d 4 and 3d 6 ions with an orbital singlet g…
The authors present experimental results on space charge distribution at the metal-polymer interface and the polymer-polymer interface by a pulsed electroacoustic method. In order to determine how much influence impurity diffusion has on the original material, two kinds of molding LDPE (low-density polyethylene) sampl…
Even 33 years after the discovery of electrical switching in chalcogenide glasses, a complete understanding of the mechanisms responsible for this phenomenon is lacking. It is believed that threshold switching in chalcogenide glasses is electronic in origin whereas memory switching is of thermal origin. According to t…
Two new poly(ethylene glycol) supported manganese porphyrins have been prepared and their catalytic activity and recyclability were investigated for the epoxidation of alkenes using H2O2 and PhIO as stoichiometric oxidants.