Investigation of SF6 decomposition under partial discharge induced by protrusion defect

Abstract

The aim of this paper is to compare the decomposition characteristics of sulfur hexafluoride, using the study of decomposition by-products, under AC partial discharge of three protrusion defect configurations. This comparison can reveal the influence of quantity, size, and material of the protrusion defect on the insulation status of GIS and demonstrate the most severe configuration by analyzing the by-products. In literature, previous researchers have shown that there is a direct relationship between the generated products and the amount of PD. In this analysis, the effect of each configuration was achieved by using the important relationship between the concentration of decomposition products and the concentration ratio of SOF/SOF with the level of PD along with the stress duration. Using a coaxial gas chamber, an experimental platform was set up using various artificial protrusion defects to simulate partial discharge initiation in GIS. The applied voltage was gradually increased from the initial discharge until the breakdown over the aging cycle. Gas samples were obtained every 18 hours and byproduct gases were detected using Fourier transform infrared spectroscopy. Results show that the amount and concentration of products and the SOF/SOF ratio have shown interesting trends. It is concluded that the severity of the defect increases with the increase of the quantity and size of the defect. The study of the impact of protrusion, as the common form of defect in GIS, reveals the partial discharge severity in terms of produced by-product gases, and their concentrations are directly related to the configuration of the protrusion defect.