Investigation on the Relationship between Failure Rates and Health Index of Distribution Transformer Population

Abstract

In this paper, a study is carried out to investigate the relationship between failure rate and Health Index (HI) of the transformer population based on condition monitoring information. In total, 3192 oil samples from 370 transformers with age ranging from 1 to 25 years were analysed in this study. First, the HI and failure rate of transformer was computed based on yearly individual condition monitoring data of the oil samples. Several parameters were measured such as oil quality, dissolved gases, furanic compounds and age. The HI of transformers was determined based on scoring and weighting method while the failure rate of transformer was determined based on relative risk method. Next, the average HI and failure rate for each age was computed and the relationship between the HI and failure rate were obtained based on two-parameter exponential function model. Based on the study, it is found that there is a relationship between failure rate and HI of the transformer population. The failure rate increases almost exponentially as the HI decreases to around 55%.