Frequency Response Analysis (FRA) Fault Diagram Assessment Method

Frequency response analysis (FRA) is an extended technique for transformer condition assessment. In recent times, its proven sensitivity for detecting different type of faults have generated interest for rotating machine applications. However, at present, the interpretation of FRA results is mostly made by visual inspection of curves and is a hard task for nonexpert maintenance personnel. This article presents a mathematical model to simplify diagnostic tasks from FRA results. The developed model is called "Fault Diagram" and it is conceptualized to be applied to any coil, so it could be extensive to any type of machine. The fault diagram is based on a paradigm which states that a healthy machine is a machine with infinite impedance fault. The model uses a first-order frequency response for the purpose of fitting a linear function SMALL ELEMENT OF R3. The input of the model is the FRA curve of the machine, and the output is a point in a three-dimensional space. This approach can give an accurate diagnosis without ambiguous interpretations about if the machine is healthy or not and can provide an estimation of the fault location in case of damage. For validating the method, it was applied in a pole of a 40 MVA synchronous generator.