Residual Flux Density Measurement Method of the Single-Phase Transformer Based on Phase Difference

When the power transformer is energized under no-load conditions, the residual flux will accelerate the saturation of the core, and generated magnetizing inrush current will cause many harms to the power grid. To determine the residual flux in the transformer core with a closed magnetic circuit structure, this paper proposes a method for measuring the residual flux of the transformer based on the phase difference between the test voltage and the transient current. The finite element method is used to model and analyze the core to be tested and obtain an empirical formula for calculating the based on the simulation results. Finally, an experimental measurement platform was built, and the measurement results verified the feasibility and accuracy of the proposed method.