Abstract:
Geomagnetically induced current (GIC) generated by geomagnetic storm and ground current generated by the monopolar operation of high voltage direct current (HVDC) system invade the grid grounding transformers, resulting in magnetic bias anomaly. To address this issue, the time-domain fluctuation features of ground currents under GIC/HVDC scenarios are comparatively analyzed. A multi-physics coupling model of transformer considering the ground currents intrusion is proposed, and physical feature information such as current, flux, electromagnetic force, vibration, and noise in various fields are extracted. The influences of GIC/HVDC ground current on propagation features are simulated and analyzed under the typical scenes, and the coupling relationships of physical features are summarized. Furthermore, the disturbance differences between GIC and HVDC ground current are compared. The results show that the impact of HVDC ground current on transformers is relatively stable, while GIC induces more complex temporal fluctuations in multi-field feature parameters. A dynamic experimental platform is built to measure the current, vibration, and noise data of transformer under different modes, then the correctness and effectiveness of the proposed model and conclusions are verified by comparing experiments and simulations. Finally, the multimodal feature information domains are constructed based on virtual-real consistency, and the disturbance level is used as the key criterion to divide the operation risk states. When the disturbance level reaches 1.5, the disturbance current leads to instability in the electromagnetic and mechanical environment inside the transformer. This method can be adopted to effectively identify the operational risk states of transformers under GIC/HVDC ground current intrusion scenarios, providing a basis for transformer fault identification and equipment protection.