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 charge accumulation and pre-flashover characteristics induced by metal particles on the insulator surfaces of 1100 kV GILs under AC voltage

Abstract: With the increase in the voltage and capacitance of gas-insulated transmission lines (GILs), the insulation failure of GIL has attracted more and more attention. Further understanding of the partial discharge (PD) and flashover characteristics of metal particles on the insulator surface, as well as the flashover mechanism, is necessary to reduce the failure rate and improve the reliability of the equipment. In this study, an ultra-high voltage (UHV) AC insulator PD test and measurement system based on the cross-reference pulse current (PC) and ultra-high frequency (UHF) methods were established. The PD development and flashover characteristics of 5 mm-long metal particles at different positions on the surface of a UHV AC insulator, as well as the surface charge accumulation, were studied. The results show that the discharge of millimetre-scale metal particles on the insulator surface under PD test conditions is relatively low (generally lower than 2PC), and it is difficult to be detected by the conventional PC and UHF methods due to their insufficient sensitivity. Moreover, it is found that the weak PDs of the millimetre-scale metal particles will result in a charge accumulation on the insulator surface under AC voltage, which eventually will lead to the insulator flashover. The PDs of the UHV AC insulator before flashover are generally small, which will make it difficult for online monitoring systems to give an effective alarm before flashover.

Electron emission device with specific island-like regions

Abstract: An electron emission device includes an electron-supply layer formed of metal or semiconductor; an insulator layer formed on the electron-supply layer; and a thin-film metal electrode formed on the insulator layer, whereby electrons are emitted when an electric field is applied between the electron-supply layer and the thin-film metal electrode. The insulator layer and the thin-film metal electrode have at least one island-like region where the thicknesses of the insulator layer and the thin-film metal electrode gradually decrease.

Electric field driven quantum phase transition between band insulator and topological insulator

Abstract: We demonstrate theoretically that electric field can drive a quantum phase transition between band insulator to topological insulator in CdTe/HgCdTe/CdTe quantum wells. The numerical results suggest that the electric field could be used as a switch to turn on or off the topological insulator phase, and temperature can affect significantly the phase diagram for different gate voltage and compositions. Our theoretical results provide us an efficient way to manipulate the quantum phase of HgTe quantum wells.

Detection and classification of defects in ceramic insulators using RF antenna

Abstract: Defects in ceramic insulators like broken, cracked and punctured discs give rise to the initiation of partial discharge (PD) activities within the samples which has a detrimental effect on the insulator life. Hence it is important for the utilities to identify such defective samples as early as possible so that appropriate replacement strategies can be devised. The work presented in this paper involves the investigation of a number of cases of insulator defects, with the goal of developing an online RF-based PD technique for monitoring ceramic disc insulators. The three classes examined are a cracked ceramic insulator disc; a disc with a hole through the cap, and a completely broken insulator disc. The defective discs are considered individually and are also incorporated into strings of 2, 3, and 4 insulators. The captured RF pulses are processed by extracting wavelet packet based features. Feature reduction and selection is carried out and classification results are obtained. To classify the discharges arising from different types of defects, an artificial neural network (ANN) algorithm is applied to the extracted features, and recognition rates of more than 95% were reported for each class. The results of preliminary field tests carried out on a 40 feet high test transmission tower are also reported and their analysis showed good discrimination between the different defect types.

Manufacture of thin-film transistor

Abstract: PURPOSE: To improve a thin film transistor remarkably in an electrical property and stability by a method wherein a gate insulator layer is formed in such a process that insulator, or metal or semiconductor constituting insulator is sputtered by an ion beam as the surface of a substrate on which the gate insulator layer is to be formed is irradiated by ultraviolet rays and spouted by gas. CONSTITUTION: A first gate insulator film 3 is formed in such a manner that a beam of Ar + , O + , or mixed these ions is irradiated from an ion beam device 21 onto a sputtering target 2, for example, under such a condition that a beam voltage is 500V and a beam current is 200mA so as to sputter Al or Al oxide from the sputtering target 2. Moreover, the face of a substrate 1 is irradiated and spouted by ultraviolet rays and oxygen gas respectively through an ultraviolet ray source and an oxygen outlet 23. In this process, oxygen can be activated in reaction by irradiating ultraviolet rays whose wavelength is 130nm∼300nm. By these processes, as oxygen is sufficiently supplied, the insulator film 3 whose composition is close to a stoichiometric composition can be obtained, which is dense and very small in oxygen deficiency inside the film. COPYRIGHT: (C)1989,JPO&Japio