Wideband characterisation of a high-voltage test transformer using Pseudo-Random impulse sequence perturbation

Abstract

High-voltage test transformers are commonly operated in step-up mode to generate high voltages for testing power system equipment such as transmission cables, insulation, and transformers. Accurate equivalent circuit models of these transformers can provide insight into the processes that take place within the device, improve the simulation accuracy, and provide an understanding of the transformer interaction with external circuits. This paper explores the use of a Pseudo-Random Impulse Sequence (PRIS) as a perturbation signal for the wideband characterisation and parameter estimation of a high-voltage test transformer, which formed part of a larger master's study [1]. A 7.5kVA, 230V/100kV high-voltage test transformer is perturbed with a PRIS signal using a custom-designed perturbation source, and the frequency responses of the transformer open-circuit and short-circuit input impedances are determined. A wideband six-section lumped parameter equivalent circuit model is proposed for the transformer, and it is shown that the topology can represent the observed resonances in the frequency responses of the input impedances accurately up to 10kHz. A two-step parameter estimation methodology is subsequently implemented to solve for the model parameters that best fit the measured frequency responses.