Abstract
Corrosive sulfides in transformer oil could react with copper wire to produce cuprous sulfide, causing insulation failure. At present, both the quantitative measurement method and distribution of sulfur components in operating oil are not clear yet. In this paper, the existing types and contents of sulfides in oil samples with different alkyl groups and different voltage levels were investigated. With quantitative testing methods, the distribution of sulfur composition in the operating oil was analyzed. Results showed that the thiophene sulfide in transformer oil existed mainly in the form of benzothiophene with an unsaturation of 6 and dibenzothiophene with an unsaturation of 9. The content of monosulfide sulfide with unsaturation of 3 or 6 was the highest. The disulfide existed basically in the form of Dibenzyl disulfide (DBDS). The influence of sulfides on the oil quality were analyzed on this basis. Results showed that the existence of sulfides would increase the moisture content in oil. The absorbed moisture could cause the decrease of the breakdown voltage and rise of the dielectric loss. The above study could provide some engineering practice for understanding the sulphide distribution in transformer oils and further prevent the sulfur corrosion faults.
Highlights
Transformer oil is mostly mineral oil refined from petroleum
According to current studies by scholars, the source of corrosive sulfurs in insulating oil exist mainly four forms: (1) Corrosive sulfur contained in crude oil, (2) sulfur contained in electrical equipment, (3) corrosive sulfur compounds generated by crude oil pyrolysis reaction, and (4) corrosive sulfur compounds produced by hydrogenation reactions [3,4]
The results showed that the main form of active sulfur in transformer oil is bisulphide and mercaptan sulfur, and the content of elemental sulfur is very low
Summary
Transformer oil is mostly mineral oil refined from petroleum. In addition to carbon and hydrogen, sulfur is the third most abundant element, ranging from a few parts per million to as much as five percent. The corrosion of sulfides in crude oil on petroleum refining equipment and the corresponding detection methods have been studied extensively. With the outbreak of corrosive sulfur problems, the detection of total sulfur content in transformer oil has been taken as an indicator by the power grid company [9,10,11,12]. One sulfide may convert to another under certain conditions, so the study on sulfur corrosion requires further analysis of other sulfide existing in the insulating oil. Contents, and sources of sulfides in the transformer oil samples with different alkyl and voltage levels, the quantitative test methods for various sulfide in transformer oil were established. The distribution of sulfur in oil was detected by these methods, and the influence of sulfide on oil quality was analyzed
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