A Frequency-domain pilot protection method considering instrument transformer characteristics

The sensitivity of traditional current differential protection may decrease or even lead to maloperation due to the frequency deviation and limited amplitude characteristics of fault currents from power electronic-based power supplies. To solve aforementioned challenges, this study presents a fast frequency-domain pilot protection method based on line model consistency identification. This approach distinguishes between internal and external faults through transient voltage and current measurements while comprehensively accounting for the frequency response characteristics of instrument transformers. First, the mathematical relationships governing the secondary voltage and current under internal and external faults are rigorously established. Subsequently, the complex frequency-domain components of the transient voltage and current are extracted by applying of the numerical Laplace transform. Then, a consistency criterion for the line model is established, accompanied by a comprehensive protection scheme. Finally, extensive numerical simulations are conducted to validate the effectiveness of the method. Compared with existing approaches, the proposed method functions independently of the output power level of the power supplies at both ends and demonstrates superior robustness against high fault resistance and strong noise interference. In addition, the proposed method exhibits a light computational burden and requires low sampling rates.