An Analysis of the Characteristics of Oil-Paper Insulated Bushing with Moisture and X-wax Defects Through Oil Chromatographic and Frequency Domain Spectroscopy

Abstract

This paper presents an investigation on the characteristics of damping and X-wax defects of oil-paper insulated bushing, with a combination of oil chromatograph and Frequency Domain Spectroscopy (FDS) and disintegration analysis. Firstly, based on the disintegration analysis and oil chromatography analysis of five 500 kV bushings with different service periods, the difference of dissolved gas component content in the bushing oil were obtained and were related to damping and X-wax defects. The results show that in the bushing suffering X-wax defect the oil contains a large amount of hydrogen (over $10000\ \mu\mathrm{L}/\mathrm{L}$) and methane, and that shall be acted as a significant characteristic of the X-wax defect. Nevertheless, the content of carbon dioxide (CO2), acetylene (C2H2), ethylene (C2H4) and moisture in the oil of the bushing suffering damping defect is clearly higher than that in the defective bushings with X-wax. Secondly, the frequency domain dielectric spectrum (FDS) analysis of 5 bushings in service and 1 new bushing was conducted. It shows that the FDS is sensitive to moisture and x-wax defects of the bushings. In addition, the moisture mainly affects the dielectric loss of low frequency band (1mHz∼10mHz) of FDS curves. The X-wax defect has little effect on the low frequency band (1mHz∼10mHz) of FDS curves, but mainly affects the dielectric loss of 0.1Hz∼10Hz frequency band of FDS curves.