Please use this identifier to cite or link to this item: http://hdl.handle.net/10397/32608
Title: Observations from measurements of the furfural content of oil samples from transmission transformers
Authors: MacAlpine, JMK
Zhang, CH
Keywords: Ageing
Furfural analysis
Transformer insulation
Issue Date: 2001
Publisher: Elsevier
Source: Electric power systems research, 2001, v. 57, no. 3, p. 173-179 How to cite?
Journal: Electric power systems research 
Abstract: The concentration of the chemical furfural in transformer oil is well known to be an indicator of the extent to which the paper insulation of the windings has deteriorated. However, the majority of publications on this topic are based on small-scale laboratory investigations with very little on field experience with power transformers. This paper reports on the analysis of data on the concentration of furfural in oil samples from 310 transmission transformers. The data showed that while high furfural concentrations (FC's) tended to occur in older transformers, there was no distinct trend. This, together with the lack of an upward tendency for the FC in cases where two readings were taken several months apart, indicated that the deterioration in paper strength and the associated increase in FC, occur in occasional and discrete steps. The model proposed is that these step-changes are due either to internal faults causing extreme local overheating, or to overloading of the transformer causing general overheating. A simulation based on these criteria gave a similar pattern of FC versus service age. Overall the results indicated an upward trend of log(FC) versus length of service but with very large scatter and with clustering by manufacturer. It was clear that the majority of transformers show negligible deterioration even after 20 years in service. This is in agreement with the above scenario. There was reason to believe that transformers located in industrial areas were likely to have been overloaded during the 1980s, so an analysis by locality was done. This showed that the percentage of transformers with high (>4 mg/l) FC's in nominally industrial areas was double that of the rest. This difference, although suggestive, proved not to be statistically significant. The model described indicates that, because of the auto-catalytic nature of the process, oil changes would be beneficial where the FC level exceeds 4 mg/l: less deterioration will occur when the transformer is overloaded.
URI: http://hdl.handle.net/10397/32608
ISSN: 0378-7796
EISSN: 1873-2046
DOI: 10.1016/S0378-7796(01)00099-2
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