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.

Static charge accumulated by epoxy post insulation stressed at high DC voltages

Abstract: Solid insulators are used for support in many types of high voltage apparatus. Because these supports are often composed of high resistivity materials, static charges may be accumulated and held by them for extended periods of time. The electric field distribution in the vicinity of the insulator is then altered so that electrical breakdown in the surrounding gas may result.

Insulation characteristics of GIS insulators under lightning impulse with DC voltage superimposed

Abstract: To study the dc insulation design of gas insulated switchgear (GIS), the insulation characteristics under lightning impulse (LI) voltage with a superimposed dc voltage (superimposed voltage) must be clarified. The paper experimentally examined the GIS breakdown characteristics under this superimposed voltage. The test models simulating an insulator creepage surface were used for which consideration of the influence of dc voltage among various other GIS insulating elements is particularly important. To be specific, a cylindrical model made of epoxy resin or fiber-reinforced plastic (FRP) as the material and a conical epoxy spacer model were tested. For the cylindrical model, a cap-shaped electrode was placed on the insulator and a small gap was established between the end of the electrode and the insulator. When the dc breakdown voltages were measured using these samples, they were higher for the applied voltage of positive polarity than that of negative polarity for all samples. The post-test observation of the electrification condition revealed greater electrification on the insulator surface for the applied voltage of positive polarity. The electrification charges are considered to have relaxed the electric field and increased the breakdown voltage. Subsequently, the breakdown test was conducted using a superimposed voltage, whereby a foregoing dc voltage was applied to samples for a certain period, whereupon a LI voltage was applied with the dc voltage continually applied. The breakdown voltage when the LI voltage and dc voltage had equivalent polarity was approximately same to the LI alone breakdown voltage. Conversely, when they were opposite in polarity, the breakdown voltage under the superimposed voltage obviously tended to decrease from the LI alone breakdown voltage. It is considered attributable to the fact that the insulator surface was electrified by the foregoing dc voltage and applying LI voltage opposite in polarity to this electrification intensified the electric field where the breakdown started to occur. Accordingly, it emerged that the GIS breakdown characteristics changed significantly depending on the polarity combinations of LI and dc voltages. The influence of these polarities must be taken into consideration when studying the GIS dc insulation design.

Analog circuit and semiconductor device

Abstract: An object is to obtain a semiconductor device having a high sensitivity in detecting signals and a wide dynamic range, using a thin film transistor in which an oxide semiconductor layer is used. An analog circuit is formed with the use of a thin film transistor including an oxide semiconductor which has a function as a channel formation layer, has a hydrogen concentration of 5×10 19 atoms/cm 3 or lower, and substantially functions as an insulator in the state where no electric field is generated. Thus, a semiconductor device having a high sensitivity in detecting signals and a wide dynamic range can be obtained.

Fluorinated epoxy insulator with interfacial conductivity graded material for HVDC gaseous insulated pipeline

Abstract: In this paper, a novel procedure is put forward to fabricate epoxy insulators with surface functionally graded material (SFGM) with optimized surface conductivity as obtained from the field non-uniformity and the leakage current. For fabrication, a temperature control system is employed to form a spatial temperature gradient, thus regulating fluorination from top to bottom of the insulator surface. Flashover tests are reported under DC voltage, and with DC voltage with polarity reversal; the results show the effectiveness of the SFGM to improve the performance of the insulator. A trap distribution and carrier transport model are utilized to analyze the improved flashover characteristics.