High voltage power transformer condition assessment considering the health index value and its decreasing rate

A health index method is a useful tool for the transformer assessment condition. This method has been used in several previous studies. However, most of them have not observed the health index decreasing rate as an aspect to improve the transformer condition assessment. A health index method with different approaches is proposed, considering the values and decreasing rate to assess the transformer condition. Inspection data from in-service and out-of-service 150 kV power transformers provided by the Indonesian electric company are included. The correlation between operating age and Health Index value and Health Index decreasing rate was also observed. With increasing operation age, the Health Index value tends to decrease with a correlation coefficient R-2 of 0.631. Further analysis was conducted to power transformers with historical data of 3 years or more, which showed that the tendency of the Health Index value decreasing rate is higher with older transformers. This paper also illustrates the Health Index analysis of 35 out-of-service transformers, resulting in a more suitable Health Index value compared to the previous approach. This study proposes the transformer risk assessment based on its health index value and the decreasing rate.

Automated summary

This study explores the health index method for assessing transformer condition, focusing on the decreasing rate as an important factor. Data from 150 kV power transformers provided by an Indonesian electric company were analyzed. The correlation between operating age and health index value as well as the decreasing rate was observed, showing a tendency for the health index value to decrease as transformers age, leading to a proposed risk assessment methodology for transformers.