This study investigates the relationship between void size and insulation lifetime due to partial discharges (PDs) in internal voids. Experimental results clearly show that the larger the void size, the shorter the insulation lifetime, which decreases the lifetime nvalue index of the voltage-time characteristics. The results also show a clear relationship between the insulation lifetime of a solid insulator having void defects and the PD energy generated in the void, which is related to the cumulative PD energy density per cycle. Therefore, we propose estimating the insulation lifetime of an insulator with voids by calculating the cumulative PD energy density per cycle.
Partial discharge (PD) monitoring system for cubicle type gas-insulated switchgear (C-GIS) filled with compressed dry air as an insulation gas was developed. The shield electrodes embedded in the solid insulator of bushings are used as PD sensors. For verification of the sensitivity of the sensors and propagation characteristics of PD pulse, artificial defects such as fixed particle on high voltage conductor and defect on creepage surface of insulator in C-GIS were used. It is clarified that the sensors had good sensitivity to PD pulse propagating along high voltage conductor in the range from VHF to UHF and that the amplitude of the sensor output had good correlation with apparent charge, pC, detected by conventional PD detector. The PD monitoring system is connected with our condition based maintenance (CBM) controller, which also monitors the abnormality of circuit breaker, disconnecting switch, gas pressure and so on, as a total diagnosis tool for our C-GIS.
SUMMARY
To understand the properties of composite insulating materials, dc breakdown testing and the thermal conductivity measurement of polymethylmethacrylate (PMMA)/aluminum oxide (alumina) composite material created using the electrostatic adsorption method were performed. In the PMMA/alumina sample, which has an alumina as a main particle and a PMMA as an adsorption particle, the dc breakdown strength decreased as the alumina content was increased. It is thought that the increase of the interface between an alumina particle and a PMMA particle leads to a lower dc breakdown strength. The thermal conductivity in PMMA/alumina composite material increased with an increase in the alumina content. From these results, it is suggested that the electrostatic adsorption method can produce the various structures in the material and the insulating materials with various properties such as a higher thermal conductivity and greater tolerable breakdown strength by using a combination of the particle size of the main particle and the adsorption particles.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.