Mf. Lachman et Yn. Shafir, INFLUENCE OF SINGLE-PHASE EXCITATION AND MAGNETIZING REACTANCE ON TRANSFORMER LEAKAGE REACTANCE MEASUREMENT, IEEE transactions on power delivery, 12(4), 1997, pp. 1538-1546
Low voltage and single-phase excitation are often used to measure leak
age reactance or short-circuit impedance of transformers. Winding dist
ortion may be detected by comparing field results with factory namepla
te values measured at 25-100% of the rated current using three-phase e
xcitation. The results of single-and three-phase excitation will not a
lways correlate. If the voltage applied in the field is not properly s
elected then the data may be influenced by the magnetizing reactance.
The resulting difference between the nameplate value and the field dat
a might then lead to erroneous analysis of test results and could be i
nterpreted as an indication of winding distortion. The intent of this
paper is to analyze the physics of the process and gain insight on tes
t circuit selection and analysis of the results. Methods for avoiding
erroneous test results are suggested.