TITLE:
In-Service Distribution Transformer Health Index: Insights from Field Data
AUTHORS:
Imran Sutan Chairul, Sharin Ab Ghani, Fatin Nurkamilia Kamaruddin, Nur Syahida Akryl Azam
KEYWORDS:
Dissolved Gas Analysis, Oil Quality Analysis, Furfural Analysis, Transformer Health Index, Distribution Transformers
JOURNAL NAME:
Journal of Power and Energy Engineering,
Vol.13 No.9,
September
18,
2025
ABSTRACT: This study introduces the Transformer Health Index (THI), which is derived from the weighted scores of Dissolved Gas Analysis (DGA), Oil Quality Analysis (OQA), and Furan Fraction Analysis (FFA). The assessment methods include the Duval Triangle for DGA, the Chendong model for FFA, and the evaluation of breakdown voltage, acidity, and water content for OQA. The THI was applied to 120 in-service distribution transformers rated at 30 MVA, 33/11 kV. Results indicate that transformers classified as “Good” scored high in both DGA and FFA, while those rated “Fair” exhibited lower FFA scores relative to DGA. Conversely, transformers labeled “Poor” showed lower DGA scores compared to FFA, and those in the “Very Poor” category scored low in both DGA and FFA. The impact of service duration on THI indicates that transformer condition generally worsens with age. However, some newer transformers showed signs of rapid deterioration, while certain older units maintained a satisfactory health status.