Towards online ageing detection in transformer oil: a review

Ugochukwu Elele, Azam Nekahi*, Arshad, Issouf Fofana

*Corresponding author for this work

Research output: Contribution to journalReview articlepeer-review

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Transformers play an essential role in power networks, ensuring that generated power gets to consumers at the safest voltage level. However, they are prone to insulation failure from ageing, which has fatal and economic consequences if left undetected or unattended. Traditional detection methods are based on scheduled maintenance practices that often involve taking samples from in situ transformers and analysing them in laboratories using several techniques. This conventional method exposes the engineer performing the test to hazards, requires specialised training, and does not guarantee reliable results because samples can be contaminated during collection and transportation. This paper reviews the transformer oil types and some traditional ageing detection methods, including breakdown voltage (BDV), spectroscopy, dissolved gas analysis, total acid number, interfacial tension, and corresponding regulating standards. In addition, a review of sensors, technologies to improve the reliability of online ageing detection, and related online transformer ageing systems is covered in this work. A non-destructive online ageing detection method for in situ transformer oil is a better alternative to the traditional offline detection method. Moreover, when combined with the Internet of Things (IoT) and artificial intelligence, a prescriptive maintenance solution emerges, offering more advantages and robustness than offline preventive maintenance approaches.
Original languageEnglish
Article number7923
Number of pages25
Issue number20
Publication statusPublished - 18 Oct 2022


  • ageing
  • high voltage
  • insulator
  • Internet of Things
  • sensor
  • superhydrophobicity
  • transformer oil
  • electric power supplies
  • reproducibility of results
  • artificial intelligence
  • maintenance

ASJC Scopus subject areas

  • Analytical Chemistry
  • Information Systems
  • Instrumentation
  • Atomic and Molecular Physics, and Optics
  • Electrical and Electronic Engineering
  • Biochemistry


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