Broadband Port Circuit Model for Distribution Transformers Based on Frequency Impedance Analysis

Building a broadband equivalent circuit model of a transformer is highly significant for studying the characteristics of high-altitude electromagnetic pulse conduction environments in real scenarios and guiding the high-altitude electromagnetic pulse effect tests of power equipment. This paper utilized an impedance analyzer to obtain the port impedance characteristics of distribution transformers with two insulation forms and five capacities within the range of 20Hz to 30MHz, based on the concept of passive system circuit modelling. By analysing the impedance characteristics of passive circuit components and observing the trend of changes in the port impedance curve, broadband port circuit models were constructed for both the high-voltage and low-voltage sides of transformers. Model parameter acquisition methods using a combination of function fitting and resonance point characteristics were provided. A high-altitude electromagnetic pulse injection test platform was constructed to verify the accuracy of the transformer model through comparison. Finally, the influence of transformer capacity and insulation form on the parameters of the transformer broadband port model was summarized. The results demonstrate that the proposed broadband port equivalent circuit model is suitable for different types and capacities of distribution transformers and can be employed to investigate the characteristics of high-altitude electromagnetic pulse conduction environments in transmission and distribution lines.