The need for models that represent the behaviour of transformers operating in steady state or submitted to
transient events is of great importance in studies involving power systems. In this context, this study presents a model
used to represent the impedance frequency response of transformers at no load and under nominal conditions. In the
model, networks of parameters with RLC cells are employed to reproduce the resonances present in the frequency
responses and also RL network sections are used to represent the frequency-dependent effects in the core, which aid
in the current damping during transient events. The parameter values of these networks are determined with the leastsquares
numerical method. To evaluate the model as well as the methodology to determine the parameter values, data
originating from measurements of the frequency responses with frequency range from 10 Hz to 2 MHz of two singlephase
transformers (16 kVA and 55 MVA) are used. Validations of the model are carried out in the frequency and time
domains. The model can be used to simulate transformer operation under nominal conditions of voltage and
frequency and also for a broad frequency spectrum.