Reproducing Transformers’ Frequency Response from Finite Element Method (FEM) Simulation and Parameters Optimization

Abstract

Frequency response analysis (FRA) is being employed worldwide as one of the main methods for the internal condition assessment of transformers due to its capability of detecting mechanical changes. Nonetheless, the objective interpretation of FRA measurements is still a challenge for the industry. This is mainly attributable to the lack of complete data from the same or similar units. A large database of FRA measurements can contribute to improving classification algorithms and lead to a more objective interpretation. Due to their destructive nature, mechanical deformations cannot be performed on real transformers to collect data from different scenarios. The use of simulation and laboratory transformer models is necessary. This research contribution is based on a new method using Finite Element Method simulation and a lumped element circuit to obtain FRA traces from a laboratory model at healthy and faulty states, along with an optimization method to improve capacitive parameters from estimated values. The results show that measured and simulated FRA traces are in good agreement. Furthermore, the faulty FRA traces were analyzed to obtain the characterization of faults based on the variation of the lumped element’s parameters. This supports the use of the proposed method in the generation of faulty frequency response traces and its further use in classifying and localizing faults in the transformer windings. The proposed approach is therefore tailored for generating a larger and unique database of FRA traces with industrial importance and academic significance.

Measurement Based Linear and Nonlinear Time Invariant Representations for High Voltage Inductive Transformer Frequency Response up to 10 kHz

“…However, this model representation assumes that the IVT behaviour is linear and hence the model validation is carried out at lower voltage levels in comparison to the nominal voltage rating of the IVT. In addition to the above, a parametric model that uses a finite element method (FEM) to estimate the internal impedance parameters of an IVT is presented in [24] . This frequency response analysis (FRA) method is widely used to identify the internal winding defects and damages in power transformers.…”

“…However, the approximate solution of H red (m) can be evaluated by calculating the Moore-Penrose pseudoinverse matrix of 𝑋 𝑖𝑑 𝑟𝑒𝑑 (𝑚) , denoted by (𝑋 𝑖𝑑 𝑟𝑒𝑑 (𝑚)) * [37]. Based on this calculation, H red (m) can be expressed according to (24).…”

Derivation of transformer winding equivalent circuit by employing the transfer function obtained from frequency response analysis data

“…Several TW EC models, encompassing two or 3 TW models, were investigated in Refs. [33][34][35][36][37]. In these configurations, high voltage (HV), medium voltage (MV), and low voltage (LV) windings are depicted using the EC model shown in Figure 1.…”