High-Frequency Modeling of a Surge Isolation Transformer Based on Time-Domain Parameter Extraction

Abstract:
This paper is dedicated to the determination of a linear black-box model of a surge isolation transformer, aiming at the analysis of differential-mode voltage surges, based on time-domain parameter extraction. Measurements were performed by applying a voltage step in the time domain and the time-domain vector fitting (TDVF) was the mathematical method used to obtain the admittance matrix representation in the form of rational functions. After the fitting of all the transfer functions, an equivalent RLCG circuit was extracted. The rational functions obtained via TDVF were validated through comparisons with measured frequency responses and time-domain simulations. In addition, the equivalent circuit proposed to represent the transformer was validated by comparing time-domain simulations with measurements. It is shown that approximations performed by the TDVF and the computational model satisfactorily represented the transient performance of the isolation transformer under analysis.