Influence of secondary winding terminal conditions on impulse distribution in transformer windings

A simple computational method for the calculation of natural frequencies and transient voltage distribution in both primary and secondary transformer windings was developed. The equivalent circuits developed for different test conditions for transient analysis account for various inductive and capacitive couplings between various sections of the windings. The validity of the computational method was verified by comparison between the measurements and calculations on a model transformer. The influence of secondary winding termination on the measured natural frequencies in the case of a three phase winding model was studied. The natural frequencies measured for similar excitation of the primary and different terminal conditions of the secondary were significantly different, and the differences were as high as 300%.>