SIMPLIFIED MODELS FOR SIMULATING TRANSFORMER WINDINGS SUBJECT TO IMPULSE VOLTAGE.

Voltage frequency response of a transformer winding, is identified in a wide bandwidth by means of a gain function that presents a single or a double resonance and an asymptotic value at high frequency. The synthesis of the identified gain function is carried out by means of simplified R-L-C models. An algorithm is proposed to compute transient responses of the equivalent circuits to any input waveform. Experimental tests were carried out on a three-phase, core-type, ehv auto-transformer with load tap changers, in the frequency and time domain. Part-winding measured spectra were used to define the simplified equivalent circuits. Comparison between the computed and measured pulse responses, proves that the proposed simplified models can be utilized with satisfactory results.