Insulator (electricity)

About: Insulator (electricity) is a research topic. Over the lifetime, 15941 publications have been published within this topic receiving 108950 citations. The topic is also known as: electrical insulator.

Surface structural changes of naturally aged silicone and EPDM composite insulators

Abstract: In a long-term outdoor test with high direct and alternating voltages, silicone and ethylene propylene diene monomer (EPDM) rubber composite insulators have, at the beginning, shown a performance superior to that of glass and porcelain insulators. In the long-term test, however, the silicone rubber composite insulator has, in spite of the aging of both insulator types, kept its good performance, while the performance of the EPDM rubber composite insulator was drastically deteriorated. In order to get a better insight into the results obtained, the wettability and the surface structural changes of the insulators were studied by the drop deposition method using a goniometer and by advanced techniques such as scanning electron microscopy, electron spectroscopy for chemical analysis, Fourier-transform infrared spectroscopy, and secondary ion mass spectrometry. The results show that the differences in performance are related to the differences in the surface structural changes and in the dynamic ability of the surface to compensate the aging. Silicone rubber insulators have higher repellency than the EPDM insulators, especially when aged. The reason seems to be low silicone polymer diffusion from the bulk which covers the insulator surface, embeds the pollutants, and keeps the surface hydrophobic. Porcelain insulators with silicone elastomer coatings show lower water repellency than insulators with massive silicone rubber sheds. When aged, EPDM insulators do not, however, seen to possess the same dynamic recovery of their surface, thus becoming hydrophilic. >

DC flashover characteristics of a polymeric insulator in presence of surface charges

Abstract: Effect of surface charges on dc flashover characteristics of a composite polymeric insulator is studied by means of experiments and theoretical calculations The considered insulator consisted of a glass fiber reinforced epoxy core covered with a layer of silicone rubber and terminated by metallic electrodes with rounded smooth edges In the experiments, the insulator surface was charged by external corona while keeping the electrodes grounded and different charging levels were realized by varying its intensity A series of disruptive discharge tests were carried out on the charged insulator under negative dc voltages It was revealed that negative deposited surface charges led to an enhancement of the flashover performance whereas positive ones reduced the flashover voltage level A theoretical model has been developed and utilized for analyzing the experimental results In the model, surface charge density profiles deduced from measured surface potential distributions were used as boundary conditions for calculations of electric fields The measured and calculated flashover voltages were found to be in agreement indicating that the observed variations in the flashover characteristics could be attributed to the modifications of the electric field produced by the surface charges

Current-induced insulator-metal transition and pattern formation in an organic charge-transfer complex

Abstract: Organic molecular Mott insulators, in which carriers are localized as a result of the electron correlation, showed nonlinear electric conduction upon application of a high electric field along the molecular stacking axis. The current-driven low-resistive state of potassium 7,7,8,8-tetracyanoquinodimethanane was stabilized down to 2 kelvin, where a metallic path was visible with a microscope. The current flow caused a stripe-like periodic phase-segregation into the carrier-rich and carrier-poor regions along the current path.

Ground-state decay rate for the Zener breakdown in band and Mott insulators

Abstract: Nonlinear transport of electrons in strong electric fields, as typified by dielectric breakdown, is reformulated in terms of the ground-state decay rate originally studied by Schwinger in nonlinear QED. We discuss the effect of electron interaction on Zener tunneling by comparing the dielectric breakdown of the band insulator and the Mott insulator, where the latter is studied by the time-dependent density-matrix renormalization group. The relation with the Berry's phase theory of polarization is also established.

\b{eta}-Ga2O3 on Insulator Field-effect Transistors with Drain Currents Exceeding 1.5 A/mm and Their Self-heating Effect

Abstract: We have demonstrated that depletion/enhancement-mode b-Ga2O3 on insulator field-effect transistors can achieve a record high drain current density of 1.5/1.0 A/mm by utilizing a highly doped b-Ga2O3 nano-membrane as the channel. b-Ga2O3 on insulator field-effect transistor (GOOI FET) shows a high on/off ratio of 1010 and low subthreshold slope of 150 mV/dec even with 300 nm thick SiO2. The enhancement-mode GOOI FET is achieved through surface depletion. An ultra-fast, high resolution thermo-reflectance imaging technique is applied to study the self-heating effect by directly measuring the local surface temperature. High drain current, low Rc, and wide bandgap make the b-Ga2O3 on insulator field-effect transistor a promising candidate for future power electronics applications.