DC Bias Content Extraction of Power Transformer Under AC and DC Environment and its Suppression Measures

The phenomenon of transformer dc bias (TDB) will saturate the transformer core, resulting in the local overheating, accelerating the ageing of insulating material, and even affecting the transformer safe operation. Therefore, it is of great significance to carry out the TDB detection and suppression. In this article, first, according to the distortion characteristics of the transformer excitation current under TDB. This article presents a method for measuring the bias voltage content of the transformer in the ac/dc environment to detect TDB. Second, the value of TDB is calculated by measuring the voltage difference before and after the dc bias, so as to obtain the degree of TDB. The feasibility of this scheme is verified by multigroup simulations of single-phase transformer (SPT) and three-phase transformer (TPT). Finally, the SPT and TPT simulated experiments of TDB are designed, and one kind of TDB suppression is carried out based on a hybrid transformer model. The experimental results are in good agreement with the simulation results, which can provide certain reference for TDB control in the dc transmission and ac/dc distribution networks.