Influence of contact layer on the sulphur corrosion of copper conductors in power transformers

Abstract

Owing to the corrosive sulphides in the mineral insulating oil such as dibenzyl disulphide (DBDS), copper windings in oil-immersed transformers may suffer sulphur corrosion. This study investigates the influence of different contact conditions on the corrosion of copper conductors in transformers. Oil-immersed accelerated corrosion experiment was conducted on copper conductors with various contact materials and different layers of insulating paper. The surface micromorphology, deposition component and the potentiodynamic polarization characteristics of copper conductors were explored. The results show that copper with different contact materials suffer sulphur corrosion; conversely, bare copper rarely does. It was also verified that the existence of a particular gap between copper and contact layer is a significant factor in sulphur corrosion by the formation of a concentration cell on the copper surface. The insulating paper wrapped around copper conductors does not increase the corrosion tendency of copper; however, it contributes to the formation of a region concentrated with DBDS, Cu 2+ , H + by adsorption and impediment, which plays a key role in facilitating the sulphur corrosion of copper conductors. Moreover, sulphur corrosion can also occur on other metal parts in transformers when there is a particular gap on surfaces other than copper.This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited.

Effect of the grain boundary character distribution on the sulfur corrosion behaviour and mechanisms of copper windings under different high temperatures

“…will be produced during the ageing of papers and oxidation of oils [43]. The acid values of insulating oil can evaluate and determine the oxidation and ageing degrees of insulating oil [4,19]. In Figure 9d, acid values increase with the increase in temperature, in accordance with the above tests.…”

“…In particular, studies on sulfur corrosion protection from the perspective of internal copper were not thorough. Metal materials [30], bending stress, contact conditions [4] and surface states [31] of copper were reported recently. In particular, further improving the chemical energy of copper windings can reduce and decelerate the formation of corrosion products.…”

“…Our group tends to recognise the mechanism involving DBDS. In our studies, the acid generated by insulating paper and copper in the oil can further promote ageing and lead to insulation failure [3, 4]. As a consequence, many scholars were devoted to preventing the common sulfur corrosion phenomenon [3, 4].…”

Gas production mechanism of Irgamet 39 and its long‐term corrosion resistance

“…The phenomenon of transformer failure caused by the presence of reactive sulphur species in insulating oil has received extensive attention [1][2][3]. CIGRE established WG A2.…”

“…The phenomenon of transformer failure caused by the presence of reactive sulphur species in insulating oil has received extensive attention [1–3]. CIGRE established WG A2.32 and A2.40 in 2005 and 2009, respectively, to solve the problem of copper sulfide formation in transformer insulation [4, 5].…”