The equivalent circuit for transformer with core laminations fault

Summary

Core lamination coating degradation is one of the main ageing processes within a power transformer. It can cause local decrease of initially high core resistivity and consequent eddy current growth inducing further insulation decay. As the result, a conductive domain appears in the transformer core. Mathematical simulation is the most effective approach to prediction of the described phenomenon impact on transformer relay protection. ODE–based models are preferable among others as they can be embedded into software packages for complex power system analysis and used for extensive studies. The paper introduces the equivalent magnetic circuit for a single-phase power transformer with conductive domain within its core. Taking account of magnetic flux leakage, electrical steel saturation, and ferromagnetic hysteresis (Jiles-Atherton model) allows precise simulation of both steady-state operation and low-frequency transients. The developed circuit describes inhomogeneous eddy current density and magnetic field distribution within the faulty core. Transformer primary winding current computed by equivalent circuit is compared to waveform obtained using finite element analysis. Three-dimensional electromagnetic field distribution calculations are carried out to verify the model numerically. With the help of the developed equivalent circuit, the dependency of fault current and loss on conductive domain parameters (such as conductivity and sizes) is studied in detail.

Additional informations

Authors

LIU

Keywords

transformer, simulation, equivalent circuit, core laminations fault, finite element method, ferromagnetic hysteresis