Distribution Characteristics of Three-Dimensional Leakage Magnetic Field at the Transposition Structure of Transformer Winding

When an external short-circuit fault occurs, the transformer windings will be subjected to short-circuit electromagnetic force, and accidents such as winding tiltiing and buckling will occur, which seriously endangers the operating safety of the power system. At present, a winding in which multiple continuous transposed conductors (CTCs) wound in parallel is widely used in transformers. In order to suppress the circulating current, the transposition structure is generally adopted, and the structure of the winding is changed. This will affect the leakage magnetic field distribution, and then change the distribution of electromagnetic force. In this paper, a type of 110kV transformer adopting transposition structure in the low-voltage (LV) winding is studied, and a parametric modeling method is proposed to describe the transposition process of the wire. The local finite element model (FEM) including the winding transposition structure is constructed by analyzing the superposition change of the magnetic field at the transposition position. The model contains iron core, 16 low-voltage winding disks, 20 medium-voltage (MV) winding disks. The cloud diagram of the leakage magnetic field of the CTCs at the transposition area and the change of the leakage magnetic field along the circumferential were obtained. The research results show that the leakage magnetic field at the transposition changes significantly and the force of the conductor at the transposition is significantly different from that at the non-transposition area.