Identification of high frequency transformer equivalent circuit using Matlab from frequency domain data

High frequency modelling is essential in the design of power transformers, to study impulse voltage distribution, winding integrity and insulation diagnosis. In this paper, a PC based, fully automated technique for identifying parameters of a high frequency transformer equivalent circuit is proposed. At each discrete measurement point, voltage ratio and phase between input and output is calculated to obtain the frequency response. A parametric system identification technique is utilised to determine the coefficients of an appropriate transfer function to model the measured frequency response from 50 Hz to 1 MHz, divided into low, medium and high frequency ranges. The proposed technique is simple to implement, fully computerised and avoids time consuming measurements reported earlier. Test results on several transformers indicate that the method is highly reliable, consistent and is sensitive to transformer winding faults