Online monitoring of winding deformation and error analysis based on transformer impedence circle character

This paper introduced the main point of three winding transformer impedance circle characters that is constructing the 3D locus between the voltage differences in the high- and low-(or middle-) sides of a particular phase against the cur rents of this two windings. In additional, error terms caused by exciting current of both two winding and three-winding trans former have been analyzed. Current compensation was employed to reduce error. A Matlab code was developed to calculate the feature parameter of the impedance circle character. Winding deformation can be diagnosed by comparing the index with the fingerprint. PSCAD simulation and fault recorder analysis results show that the technique is free from load, does not call for any special equipment and enable on-line monitoring.