Physical propagation and anomaly identification of transformer with HVDC&RTTS stray current invasion

• The stray current is characterized by characteristic factors (DC factor and mutation factor). • The virtual simulation model of transformer is constructed, and the variation law of multi-field parameters is summarized. • The multi-information is obtained through dynamic experiments, and the correctness of the simulation conclusion is verified. • The instability criterion of transformer is established with characteristic factor. Aiming at the operation stability of the transformer with stray current invasion, the evolution and propagation of multiple information is investigated in this paper. Firstly, the morphological characteristics of stray current are comparatively analyzed based on the measured data. The persistence and fluctuation of the stray current are characterized by characteristic factors (DC factor and mutation factor). Then, the characteristic factors are associated with abnormal features by sequential coupling. The virtual simulation model of transformer is constructed to simulate the electromagnetic, force, vibration and noise of components, and the laws are summarized. The results show that the vibration and noise become significant with the increase of the DC factor, and the distortion of the time domain waveform becomes serious with the increase of the mutation factor. Through the dynamic experiment platform, the physical entity of the transformer is constructed, obtaining multiple information in different modes. The correctness of the conclusions is verified by the calibration of virtual-physical consistency. On this basis, the multi-mode-state characteristic information domain is formed. The mapping relationship between stray current and vibration noise is studied with characteristic factors. Meanwhile, the abnormality of multiple information can be effectively characterized with characteristic factors. The instability criterion of transformer is established and the state interval is classified, which provides ideas for life-cycle assessment and information-physical fusion of transformer.