Analysis of Transformer Protection Performance and New Method Research in Renewable Energy HVDC Transmission Systems (CICED 2024)

The focus of this study is on transformers in large-scale renewable energy HVDC transmission scenarios. It highlights that when faults occur in transformers at the renewable energy sending end, the differential current exhibits high harmonic characteristics. Research indicates that the traditional second harmonic restraint criterion in transformer protection may block protection during internal faults in step-up transformers, thereby prolonging the protection response time. To address this issue, the paper proposes a transformer time-domain equivalent inductance method based on fitting weights. This method, combined with parameter identification, calculates the equivalent inductance to intuitively reflect the transformer's state and uses the fitting error to construct cumulative weights. This approach overcomes the significant fluctuations associated with traditional time-domain calculations, thereby enhancing the stability and reliability of the protection. Finally, simulation tests validate the effectiveness of this method.