Papers by Keyword: Surface Flashover

Abstract: The applicability of functionally graded materials (FGM) for solid insulator of gas insulated switchgear (GIS) was investigated. First, a new fabrication method based on layer-by-layer casting technique was demonstrated to prepare FGM insulator possessing spatial distribution of dielectric constants. Then, electric field strength in the FGM spacer model was calculated and optimized by using finite element method (FEM). Three types of truncated cone spacers were fabricated according to the optimization results. Finally, surface flashover tests were performed under AC voltage and lightning impulse voltage applications. Results in both circumstances indicated an evident improvement of flashover voltage when FGM insulator was employed. As a result, we verified the fabrication technique and the applicability of FGM insulator for enhancement of insulation performance in GIS device.

Abstract: Based on the platform of laser-triggered surface flashover in pulsed voltage, experiment of laser-triggered surface flashover is carried out in air and vacuum condition with pulsed voltage. A single/double harmonic, with wavelength of 1064/532 nm, Q-switched Nd:YAG laser is applied to trigger the surface flashover. The test system consists of flat electrodes and columned insulator. The material of electrode is copper and the material of insulator is Al₂O₃. Laser pulse’s wavelengths are 532nm and 1064nm, and laser is focused with rectangle. The results of experiment show that flashover delay time and jitter time decrease with increase of pulsed voltage or laser energy density, the delay time of 1064nm laser trigger is larger than that of 532nm laser trigger, and the delay time and jitter time in vacuum condition are less than the delay time and jitter time in air condition.

Abstract: Under the high electric field, discharge sometimes occurs along the surface of solid in vacuum, gas or liquid dielectrics, which is called surface flashover.SiO2-B2O3-K2O-Li2O-Al2O3-ZnO-MgO-F system glass ceramics has great machinability and excellent dielectronic property.This paper tries to study different time of ion-exchanged samples and their microstructures，which affect surface flashover performance of this novel material under the systerm of high voltage in vacuum. Compared to traditional coating method on alumina ceramic, the ion exchange treatment on glass ceramic can produce a tremendous improvement of flashover characteristics. The results show that the 10 hours ion-exchanged glass ceramic enjoys the most prominent insulation strength.Based on the theory of SEEA (Secondary Electron Emission Avalanche), these phenomena can be reasonably explained by the charge carrier injection and transport behaviors.