Abstract
This paper describes the approach to the frequency response modelling of transformer windings consisting of coils connected in parallel. At present, computer models are intensively developed with the aim of simulating the influence of faults on the frequency response of the active part of power transformers. Frequency response analysis (FRA) is one of the standard methods used for the assessment of the mechanical condition of a transformer’s windings and core. The interpretation of the FRA results is crucial in the diagnostics of the active part of the transformer. Proper simulations of the FRA results allow the improvement and simplification of the interpretation process of the windings’ faults. Usually only serial winding wires are simulated in computer modelling and parallel wires are simplified, leading to simulation inaccuracies. In this work, a combined electromagnetic field/network method, which includes parallel connections of the coils, is proposed. The method is based on lumped RLC elements. The results of the analysis conducted by the computer model are referred to as the real transformer measurement. The modelling was also performed for the case of a winding with a fault. The results of modelling were assessed with four numerical indices used for FRA interpretation.
Highlights
Frequency response analysis (FRA) is one of the methods used for transformer diagnostics
FRA measurement was proposed made on field-network model is compared to the measurement was the tested winding with an Omicron FRAnalyzer
The research presented in this paper provides a model for the simulation of the frequency response of the active part of a transformer
Summary
Frequency response analysis (FRA) is one of the methods used for transformer diagnostics. Assuming that the prepared model has a response similar to the real object, simulated faults can be introduced to provide information on their influence on the shape of the FR curve. Models based on lumped RLC parameters, together with electromagnetic field studies using Finite Element Method (FEM), allow for the most exact reproduction of the frequency response in comparison to the results obtained from tested unit. Simulation of the influence of the transformer winding faults on its frequency response will lead to the establishment of a standard procedures for FRA results identification [21]. The authors present an algorithm in which the presence of parallel wires in a winding is taken into consideration Such a construction of windings is typical, especially in low voltage windings, and it is usually simplified in computer models. Characterized by different capacitances’ distributions, which need to be considered in the model
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