Statistical models in engineering , Statistical models in engineering , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Statistical Models in Engineering

The consequence of the coupling of a charged particle with a polarization field is the formation of a quasi-particle called the 'polaron'. The degree of 'localization' of such charge depends on the nature of this coupling. In this way, trapping at an atomic scale is described as resulting from the evolution of a coupling involving successively: the electronic polarization field, the infrared polarization field, and the quasi-static ionic polarization field. The internal energy stored in the surrounding medium polarized by the charge is high because the charge is so well localized. The maximum of this energy is obtained for the quasi-static polarization field; its magnitude is of the order of 5 to 10 eV per trapped charge. This work addresses the physics of aging and of the breakdown process on the basis of an unsustainable increase in local internal energy within the material, due to charge trapping-the polarization around a trapped charge increases the local energy; the relaxation of the material lattice then follows a rapid detrapping of charges from their sites, releasing the local excess site region energy into the material. Such a release executes transient virtual work on the material, producing macroscopic dielectric damage, and when critical, unstable conditions are achieved in the time domain, this is followed by electrical breakdown. This interpretation of electrical material breakdown is related to bulk breakdown as observed in thin film laminate structures (/spl sim//spl mu/m) and surface flashover as seen in large structures (/spl sim/mm to cm).

Space charge in dielectrics. Energy storage and transfer dynamics from atomistic to macroscopic scale

Fundamentals of dielectric capacitor technology and multifactor stress aging of all classes of insulating media that form elements of this technology are addressed. The goal is the delineation of failure processes in highly stressed compact capacitors. Factors affecting the complex aging processes such as thermal, electromechanical, and partial discharges are discussed. Diagnostic measurement techniques available and those being developed to determine material degradation affecting available life and failure probability of capacitors are presented. >

Energy-storage pulsed-power capacitor technology

Over the last decade, significant increases in capacitor reliability have been achieved through a combination of advanced manufacturing techniques, new materials, and diagnostic methodologies to provide requisite life-cycle reliability for high energy pulse applications. Recent innovations in analysis of aging, including dimensional analysis, are introduced for predicting component performance and fault tolerance. In addition, voltage scaling issues that may drive bank fault-tolerance performance are described.

Energy storage capacitors: aging, and diagnostic approaches for life validation

This is the first time that energy discharge capacitor technology capable of graceful ageing has been demonstrated at these energy levels.

Energy storage in polymer laminate structures-ageing and diagnostic approaches for life validation

Publisher Summary This chapter reviews the measured characteristics of polymer laminate structures. With the advent of expanding applications at high voltages and temperatures in airplanes and spacecraft systems such as lasers, a compilation of high-voltage laminate data is of some utility. Experiments have shown that long lifetime operation to date has generally required impregnation of the laminate structure with an insulating liquid dielectric of specific properties. For the purposes of describing progress in this difficult and demanding area, the content of this chapter discusses the characteristics of liquid-impregnated polymer laminate structures. The chapter emphasizes that the trapping/detrapping process of a charge must be considered as a phase transition involving a participation of the material through atomic-scale motion. The consequence is that the internal energy concentrated around a trapped charge is released during the detrapping process, producing either local damage (aging) or a catastrophic event (such as electric breakdown and fracture) according to the circumstances, as is supported in the partial discharge and related electrothermal-chemical damage observed in other parts of this work. The effects of space-charge on prebreakdown and breakdown mechanisms are far from simple, and need further investigation and modeling via a collaboration of theoretical and practical considerations and analysis.

Polymer Laminate Structures

Evolving power conditioning system requirements in many technological areas will place severe demands upon long-lived, repetitive, pulse-power components. A major pacing system component in this high reliability, repetitive pulse-power technology is the energy storage capacitor [1]. Recently, increasing availabilities of quality plastic films, especially polypropylene, and the discovery of the excellent properties of perfluorocarbon liquids for impregnation fluids, make spirally-wound, plastic film/liquid impregnated capacitors a leading candidate for high energy density, repetitively operated, pulse discharge energy storage devices. The dominant lifetime-limiting mechanism in this type of high energy density capacitor is a direct result of partial discharge activity at the buried foil edges, where the electric field is maximum. Objectives of ongoing research programs include the characterization and understanding of the mechanisms of this and related partial discharge phenomena.

T.E. Springer

Papers

Polymer Laminate Structures

Partial discharges in polymer insulation