Investigation Into the Axial Vibration Behaviour of Helical Windings With a Transposition Structure Under External Short‐Circuit Faults

Low‐voltage helical windings, typically constructed with multiple parallel continuous transposed cables (CTCs), often include transposition structures. These transpositions alter the axial short‐circuit electromagnetic force distribution within the winding, consequently influencing its axial vibration behaviour. Although previous studies have modelled winding axial vibration using ‘mass‐spring‐damper’ systems and examined the effect of spacers' nonlinear characteristics, the impact of transposition‐induced changes in electromagnetic force distribution on axial vibration remains unexplored. This paper addressed this gap by analysing the axial short‐circuit electromagnetic force distribution in two 110 kV transformer low‐voltage helical windings considering the existence of transposition structures. Subsequently, axial vibration calculations were conducted using a ‘mass‐spring‐damper’ model. Comparison with calculation results that neglecting the transposition structure reveals that the transposition structure alters the low‐voltage helical winding’s vibration mode. Specifically, it reduces both the vibration displacement and the axial stress experienced by individual disks. The results indicate that it is necessary to consider the transposition structure when analysing the axial stability of helical windings under external short‐circuit faults.