Investigations on the transformer high frequency transfer function to interpretation of FRA measurements

Frequency Response Analysis (FRA) is a powerful technique for condition monitoring and fault diagnosing of power transformers. The challenge in this regard is the analysis of the transformer transfer functions due to different existing faults. In another word, the correlation between different faults and transfer functions is not fully yet known. The main idea in this study is that the transformer physical and insulating construction during manufacturing stages are changed. As the result, investigating on the variations of winding transfer function in these stages can be very helpful. In this contribution the transformer winding is simulated in different manufacturing stages. All simulations performed for a 63/20 kV, 30 MVA power transformer based on availability designed information. After that, some measurements are performed that confirm the simulations. The obtained results will be useful to understand the winding high frequency characteristics and also to interpret the changes in transfer function due to different common faults.