Assessing Transformer Aging Using Dielectric Oil Characteristics: Influence of Operating Voltage Levels and Purification

Dielectric characteristic testing of transformer oil is a routine test. Previous studies have explored the correlation between transformer testing parameters and aging factors; however, few have analyzed the influence of operating voltage levels on transformer parameters. Additionally, some utilities do not account for whether the data collected involves purified or unpurified oil. This study analyzes the correlation between oil quality parameters and transformer aging factors, considering the operating voltage levels of power transformers in Indonesia's electrical grid and the impact of oil purification on parameter analysis. The data used in this research consists of historical dielectric characteristic test results for transformers operating at 500 kV, 150 kV, and 70 kV. The dataset is divided into two categories: historical data without considering purification and mixed data, including purified and unpurified oil samples. Statistical analysis using linear regression was conducted to evaluate the correlation of each parameter. The analysis results indicate that the higher the operating voltage, the faster the dielectric oil degradation occurs. Also from results indicated the parameters such as BDV and water content are significantly influenced by purification, in contrast, the color scale shows minimal changes. It was also found that parameters such as acidity, water content, and IFT are suitable indicators for assessing the aging process only in unpurified oil data. In contrast, color provides a more reliable interpretation of the aging process for the insulation system and can serve as a key indicator in determining maintenance activities for power transformers, prevent the misinformation cause by oil purification.