Novel procedure for low frequency FRA traces interpretation

This paper describes a new procedure to estimate separately the magnetization inductance Lm and winding shunt capacitance Cm for each power transformers phase, using and R-L-C electrical equivalent circuit developed to simulate the impedance measured in the Frequency Response Test. The Lm and Cm parameters can be used to analyze the traces obtained in the test. It is also shown experimental results that demonstrate the procedure ability to interpret the FRA traces providing an added value to the graphical comparison. This procedure has a direct application in the FRA based diagnosis because allows failure detection using reliable parameters when the magnetic field of the core is involved.