An Early Degradation Phenomenon Identified through Transformer Oil Database Analysis

S.J. Tee, Q. Liu, Z.D. Wang, G. Wilson, P. Jarman, R. Hooton, D. Walker, P. Dyer

Research output: Contribution to journalArticlepeer-review


Ageing of large transformer fleets is a challenge for utilities. To assess the condition of existing transformer fleets, transformer oil is commonly tested for multiple parameters and the data are recorded in large databases for subsequent interpretation. Through analysing multiple databases including oil test results and individual transformer details pertaining to UK in-service transformers operating at primary voltage levels of 33 kV, 132 kV, 275 kV and 400 kV, population analyses revealed a generic early degradation phenomenon as indicated by an early peak in acidity and 2-FAL trends with in-service age. By exploring the phenomenon from manufacturer, loading and oil chemistry change perspectives, results suggested that the early degradation was most likely due to an oil chemistry change resulting from hydrotreatment oil refining method introduced in the late 1980s. Judging from the faster degradation trend of the affected transformers, a separate asset management strategy may be needed.
Original languageEnglish
JournalI E E E Transactions on Dielectrics and Electrical Insulation
Publication statusPublished - 13 Dec 2015


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