Modified transformer winding ladder network model to assess non‐dominant frequencies

Abstract

In this study, the challenging problem of computing the frequency-dependent lumped parameter ladder network model for transformer winding based on impedance frequency response is investigated. It is shown that the existing conventional model is not capable of simulating the non-dominant resonances; rather, this phenomenon can be adequately modelled using extra intersection capacitors. As usual, this large-scale non-linear optimisation problem is addressed using properly lined-up genetic algorithm. To accelerate the success of the estimation, the dimension of the problem and the search space is reduced by using logical and real constraints and equations derived from the transformer geometry and its electromagnetic specifications; if this is not done, the optimisation fails. The test results on a 20/0.4 kV, 1600 kVA transformer indicates that the computed model, which is improved and detailed, is superior to the conventional one in terms of simulating the non-dominant resonances of the transformer winding. Therefore, it is more reliable for the transformer transient behaviour analysis.