Characterization of the Sulfur Corrosion of Paper-Wrapped Windings in the Terahertz Range

Abstract

Dibenzyl disulfide (DBDS) in mineral insulating oil reacts with the copper wires of windings in the oil-immersed power equipment, thereby decreasing oil-paper insulation properties and even transformer faults. Existing methods applied to detect sulfur corrosion depend mainly on visual observation, which is destructive to the windings. A laboratory study on the characterization of sulfur corrosion in paper-wrapped windings based on reflection terahertz (THz) time-domain spectrum (TDS) is introduced. Test results demonstrate that copper sulfide (Cu2S), a typical corrosion product, shows a significant absorption and scattering in the THz range. Neither the thickness nor the status of insulating paper nor the oxides on the surface of copper conductor greatly influence corrosion detection. The 2-D image of the corrosion morphology of the winding is obtained by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${X} - {Y}$ </tex-math></inline-formula> horizontal scanning, and the corrosion degree (CD) of the winding is characterized based on reflection THz-TDS.