DC Bias Impact Analysis on Hydropower Plant Excitation Transformer

When the excitation transformer in a hydropower plant is influenced by dc bias, the performance of the transformer suffers from nonlinearly inferior operation, resulting in compromised transformer health and a reduced life span. This paper emphasizes a simple yet powerful modeling and electromagnetic analysis of a dc-biased excitation transformer used in a hydropower plant. The three-dimensional modeling of the excitation transformer was carried out using the transformer constructional details and analyzed using Ansys Maxwell. The finite element method was used to analyze a three-phase 500 KVA excitation transformer. The impact on the excitation transformer was investigated for varying levels of dc bias with different excitations. The simulation results include various plots of variables and the loss characteristics. This research provides new insight on the importance of accurately calculating the losses of an excitation transformer under dc bias during the design stage. The main contribution of this research is a simple approach for performing the electrical and magnetic analysis of a dc-biased excitation transformer, which could be helpful for designers in determining the effects of various variables and can be adequately addressed during the designing stage.