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This article provides a perspective on the development of polymer nanodielectrics for electrical insulation applications. It includes a short history of the development of the field, barriers to implementation, a chemical toolbox available for optimizing properties, some examples of potential commercial development, and the latest advances. It offers opinions on critical research needed to fully develop the models needed to predict the behavior and to develop design tools. Key findings include the need for quantification of nanofiller dispersion, investment in long term aging data research, better scale-up methods, a data resource that brings the broad data together in a format that enables faster scientific discovery, and a commercial entity willing to take the risk in implementing these promising materials. [ABSTRACT FROM AUTHOR]

Research on the vacuum surface flashover mechanisms of insulating material under nanosecond pulses is important for the design and manufacture of high-power pulse generators. Here, the vacuum surface flashover characteristic of epoxy composites filled with different microfillers [Al.sub.2][O.sub.3]x3[H.sub.2][O, [Al.sub.2][O.sub.3], BaTi[O.sub.3], and Ti[O.sub.2] is investigated using a unipolar pulse generator (50-ns rise time and 600-ns full-width at half-maximum). In addition, their thermally stimulated depolarization current and secondary electron emission (SEE) coefficients are measured. The results show that the flashover performance does not depend just on the SEE coefficient, but that the different effects of shallow and deep traps must also to be taken into account. Index Terms--Epoxy composites, microscale inorganic oxide particles, pulsed vacuum flashover, secondary electron emission (SEE), thermally stimulated current.

Electron Paramagnetic Resonance (EPR) has been used to study the properties of trapped electrons or holes in XLPE and in 12.5% vinylsilane-treated Si[O.sub.2] nanoparticles in XLPE specimens. Both electrically unstressed and electrically stressed (up to 25 kV/mm) specimens were used. The EPR spectra of both materials indicated that the acceptors/donors were oxygen radicals in the polymer, probably originating during the cross-linking. It was found that the anisotropic oxygen environments were not randomly oriented, but were textured, presumably during the fabrication of the sheet specimens. It was found that under the action of an applied electric field, the population of an additional number of oxygen radicals occurred. This result is discussed in relation to the implied polymer structure and conductivity mechanisms. Index Terms--Electron paramagnetic resonance, nanocomposite, interface, polyethylene.

The formulation and computation of an optimal load shedding time algorithm is presented. This new concept was developed as an enhancement to the application of optimal load shedding for corrective control to support future islanded power systems with anticipated, enhanced communications infrastructure. The methodology combines nonlinear mathematical programming and discretized differential-algebraic power systems equations to estimate the optimal amount of load to be shed as well as the best time to shed it. Several simulated scenarios are studied and results presented. Index Terms--Distributed generation (DG), load shedding, optimization.

The utility of condition monitoring of the stator insulation structure of large machines has been enhanced substantially by the use of computer-based analysis of partial discharge signatures. A number of indices are examined through tests in a multi-stress aging facility to assess their promise in describing insulation degradation in machine insulation. In transitioning such tests to the field environment, an operational test is also described which offers some promise in identifying degradation without prior baseline data for a machine. On the basis that most electrical failures have mechanical precursors, acoustic methods are described for assessing stator bar mechanical integrity. This includes both using the conductors as waveguides and also employing acoustic emission for the location of large discharges. Index Terms--Acoustic probes, electrical machines, fractal dimension, insulation aging, life extension, on-line monitoring, partial discharge.

The incidence of streaming electrification in large transformers (and other industrial equipment) has generated the need for both an understanding of the underlying physics and a mathematical description of the phenomenon. Modeling is needed since the mechanisms do not readily scale and small-scale laboratory experiments are limited in predicting performance. The development of both steady-state and transient descriptions of the streaming electrification process is described for a rectangular duct structure. The nature of the phenomenon is such that appropriate assumptions and approximations need to be made. As a consequence, some experimental verification of the outcomes, at least in qualitative form, is also included. The entrainment of charge from the interface charge layers also intimately involves the flow of the liquid. A description of the flow regimes and a transient solution of the charge development through a duct are thus an integral part of the modeling effort. The utility of the steady-state model developed is demonstrated by application to an oil-cellulose system typical of a large core-form transformer. The method advocated takes advantage of the repeat duct arrangement in such units. The results presented allow the internal behavior of such a unit to be studied in considerable depth, and provide insight into the complex interplay between generation and relaxation in circumstances when flow rates, temperature, external fields and influent charge are changed. Index Terms--Streaming electrification, electrostatic charging, transformers, flow, modeling.

Based on the physical mechanisms believed to underlie the ac electrical breakdown of liquid/solid structures, a volume theory of failure is used to justify the application of a semi-empirical cumulative stress criteria for the assessment of dielectric integrity. The method advocated is extended through th use of a complex Laplace equation to permit the analysis of structures having simultaneous capacitive and resistive stress distributions. Computer algorithms are described for automating dielectric design on this basis and case studies provided to illustrate the utility of the techniques advanced.

Discusses the simulation and measurement of corona for electrostatic pulse powered precipitators. Formulation of model; Ion and electron advection; Evolution of a Trichel pulse.

Presents a study that investigated the effect of a collected flyash layer on electrostatic precipitator behavior. Background on the experimental apparatus and procedures used in the study; Examination of the modeling effect of precipitated dust layer; Assessment of the high-resistivity dust layer parameters used by the corona simulation.

Presents a study that examined an electrostatic precipitator to determine its salient electrical behavior, particle charging and collection characteristics for pulse powering under clean plate conditions. Background on pulse energization; Analysis of the impact and interplay of particle diffusivity and electron charging; Results and implications.

An experimental study has been conducted to quantify the voltage endurance of electrical grade epoxy resin insulation when subjected to pulse voltages in a divergent field. Voltage endurance has been quantified as a function of pulse width, repetition rate, and polarity. Supporting measurements of free radical generation have been made by electron paramagnetic resonance (EPR), and the progress of the aging mechanism tracked by sensitive photonic emission measurements. The results suggest (at least for positive polarity) that estimates of endurance under pulse voltage conditions can be made from conventional power frequency data. However, it is shown that a correction is necessary to allow for the effects of waveform, and a theory is advanced for that purpose.

After a brief discussion on possible on-line indicators of aging, this paper presents a concept of dynamic aging theory (DAT). Based on the philosophy of a DAT, a dynamic multistress aging model is proposed. Necessary DAT formulation and software have been developed for testing the model against laboratory aging data. In this study, dynamic stagnation voltage (DSV), a derived partial discharge parameter, and the groundwall insulation response to a traveling acoustic wave have been found to be the most appropriate parameters for assessment of remaining insulation machine life. This approach is shown to be a meaningful and practical solution to a very complex problem. Although this study is in its initial stage, it does show significant promise as an on-line tool for dynamically predicting remaining life based on OAT and other appropriate feedback measures.

Streaming electrification remains a problem for large power transformers which require forced-oil cooling. Oil flowing against cellulose insulation surfaces results in the separation of charges from the electrical double layer at the interface. This process can generate hazardous static potentials and volume charge densities in the transformer dielectric system. While streaming electrification has been studied in great detail using small-scale laboratory models, extension of these results to full-scale transformers is rather difficult. This issue has been addressed through the development of a network-based analytical approach which is calibrated against empirical data at the elemental duct level. The model has been utilized to perform a parametric study of streaming electrification in the full-scale high-voltage winding of a core-form transformer. Volume charge densities exiting from each duct in the structure and the local surface potentials are predicted as a function of influent charge, oil volume flow rate, temperature and applied voltage. Index Terms--Charge density, core-form transformer, oil flow, static electrification, static potential, winding ducts.

ABSTRACT In this article, we report the synthesis of a new bimodal surface ligand morphology on silica nanoparticles. Combining grafting-to and grafting-from approaches, in this study, we demonstrated the efficacy of anthracene surface modification for improving the dielectric breakdown strength (DBS) under alternating-current and direct-current conditions and that of a matrix-compatible polymer brush for controlling the nanofiller (NF) dispersion. Ligand-modified spherical colloidal SiO2 nanoparticles (∼14 nm in diameter) were mixed into polypropylene, and the resulting dispersion was improved over the unmodified particles, as shown with transmission electron microscopy. The results suggest that the electronic structure of the anthracene-modified particle surface was critical to the improvement in DBS. In addition, the DBS of the composite was shown to depend on the dispersion state of the filler and the mode of stress; this indicated that the individually dispersed nanoparticles were not necessarily the optimal morphology for all stress conditions. Additionally, the precise nature of the matrix-compatible brush was less important than the NF dispersion it produced. The bimodal grafted architectural design has provided a promising solution for the control of the dispersion and surface properties, especially for high-molecular-weight polymer matrices. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44347. [ABSTRACT FROM AUTHOR]

Many of the electrical failures of large electric machines have mechanical precursors. This premise has led to the attempts described here to detect mechanical changes, such as ground-wall delamination, by acoustic methods as a means of early detection of incipient failure. By optimally launching an ultrasonic wave into a stator bar and using the conductor as a wave-guide, it has been shown possible to interrogate the groundwall insulation and the critical interface region adjacent to the conductor. Laboratory studies using an epoxy mica stator bar subjected to thermal cycling have demonstrated that the acoustic signatures obtained with this method are mirrored by conventional corona spectroscopy conducted simultaneously, although earlier damage is clearly discernible. Based on the results of this study, the acoustic technique appears to have substantial promise as an advanced detection tool., Two different techniques using acoustic diagnosis for detecting defects in groundwall insulation of electrical machines are presented. One method, called the 'tap test,' evaluates the state of insulation degradation by assessing the changes in tone coming from a bar. The other method employs ultrasonic wave into a stator bar to determine the degree of insulation delamination. The advantage of the latter approach over the former as a diagnostic tool is discussed.

The positive-feedback-based anti-islanding schemes invented by the authors are highly effective in preventing islanding without causing any degradation in power quality. This paper presents the basic principles of these schemes and their design guidelines. Moreover, their performance is investigated for inverter-based distributed generators (DGs). The parametric study reveals the factors significantly influencing the performance of these schemes. The simulation results demonstrate the effectiveness of these schemes. [ABSTRACT FROM PUBLISHER]

Research on the vacuum surface flashover mechanisms of insulating material under nanosecond pulses is important for the design and manufacture of high-power pulse generators. Here, the vacuum surface flashover characteristic of epoxy composites filled with different microfillers Al2O3·3H2O, Al2O3, BaTiO3, and TiO2 is investigated using a unipolar pulse generator (50-ns rise time and 600-ns full-width at half-maximum). In addition, their thermally stimulated depolarization current and secondary electron emission (SEE) coefficients are measured. The results show that the flashover performance does not depend just on the SEE coefficient, but that the different effects of shallow and deep traps must also to be taken into account. [ABSTRACT FROM AUTHOR]

Presents an introduction to the August 1, 2005 issue of the journal "IEEE Transactions on Dielectrics and Electrical Insulation."

An introduction is presented to the articles about nanodielectrics published in the February 2008 issue of the "IEEE Transactions on Dielectrics and Electrical Insulation" periodical.