Investigating the Capacitive Inter-Winding Response of Power Transformer

This paper presents an investigation on the occurrence of oscillation in the frequency response of transformer due to aging process. The frequency response was obtained using frequency response analysis (FRA) test and capacitive inter-winding test configuration. It has been reported that, there is abnormal occurrence to the frequency response after some period of operating time. The response shows a small oscillation at the mid-frequency region. Although, this oscillation was not there at first measured response. Therefore, three case studies are presented to investigate this occurrence, the measurement, the transfer function mathematical equation and the developed circuit. The case studies of the transfer function and the developed circuit are simulated using MATLAB and being compared with the actual measured response. The parameters that control the mid-frequency oscillation are also studied. The oscillation occurred at mid-frequency region is related with the actual condition of the transformer experiencing aging process. The new finding provides an understanding on the factors that affecting transformer aging. It is believed that, thermal, moisture and oil degradation are the main contributors of transformer aging process. Therefore, the significance of this study is to present the relationship between occurrence of mid-frequency oscillation and transformer aging condition.