Impact of corrosive sulfur in transformer insulation paper

Abstract

In recent years a significant volume of research has been undertaken in order to understand the latest failures in oil insulated power apparatus due to deposition of copper sulfide on the conductors and in the insulation paper. Dibenzyl Disulfide (DBDS) has been found to be the leading corrosive sulfur compound in the insulation oil. As there are currently no nondestructive techniques available to analyze the degree of damage from sulfur corrosion, electrical plant operators are faced with a choice of either replacing an asset which might still have several years of operational life or keeping a transformer operational with an increased risk of failure. This paper investigates permittivity and loss factor curves of transformer oil impregnated insulation paper, at different corrosive sulfur degradation stages. Three types of transformer conductors are investigated; new, artificially aged and service aged. To increase the understanding of the electrical behavior of Cu 2 S this paper demonstrates how the electrical properties change with moisture content. Dielectric spectroscopy is used to demonstrate some of the electrical changes across a wide frequency range, from 1mHz to 1MHz.

Reviews on sulphur corrosion phenomenon of the oil–paper insulating system in mineral oil transformer

“…In order to further realise the quantitative characterisation of sulphur corrosion degree, some scholars tested the total sulphur concentration in oil to evaluate the corrosivity of insulating oil and the corrosivity of various sulphides in oil [76]. The copper sulfide deposition could influence the frequency dielectric spectrum curve of insulating paper, therefore this method can be used to evaluate the corrosivity of insulating paper [77]. Other scholars have proposed using the adhesion amount of Cu 2 S and the Cu 2+ concentration to characterise the corrosion degree of copper sheet, as well as the mass fraction change of copper ion in nitrogen, air and oxygen environments in experiments [78].…”

A review: Research on corrosive sulphur in electrical power equipment

“…The permittivity of the paper with Cu 2 S deposition dropped a lot more than that of the paper without deposition, and the rate of change reached up to 28.47% [15]. A heavy Cu 2 S deposition on the inner layer of the insulation papers can be found on the samples with DBDS [88]. Moisture has a similar effect.…”

Copper Release Kinetics and Ageing of Insulation Paper in Oil-Immersed Transformers

“…Another common additive is a copper corrosion inhibitor, such as 5-methyl-1,2,3-benzotriazole or tolutriazole (TTA). According to Maina et al [41] and Amaro et al [42], some commercial products might have contained DBPC in combination with another undeclared additive, dibenzyldisulphide (DBDS). DBDS is an effective antioxidant of peroxide decomposer type, acting synergistically with DBPC and significantly improving the oxidation stability of the oil.…”