High-impedance fault location method using guessed fault resistance

Electromagnetic time reversal fault location method requires the placement of observation points at a single location and is effective for searching fault location. Among the various existing metrics, the transfer function correlation metric emerged as the most robust. However, its application to high-impedance faults also presents challenges. This difficulty can be attributed to the unknown real fault resistance in the direct-time process, where the guessed fault resistance is typically set to 0 during the reversed-time process of the electromagnetic time reversal fault location method. Consequently, this practice yields comparable direct-time and reversed-time transfer functions for low-impedance faults. Conversely, high-impedance faults exhibit significant discrepancies between direct-time and reversed-time transfer functions, leading to errors in fault location. To overcome this challenge, this paper proposes a location method based on specific guessed fault resistance preset during the reversed-time process. First, the direct-time voltage and reversed-time current transfer functions under high-impedance faults were derived in the frequency domain. Subsequently, by comparing transfer function differences when fault resistances in the direct-time and reversed-time processes did not align, a principle for selecting the guessed fault resistance was established. Additionally, the similarity of the two transfer functions under specific guessed fault resistances was investigated. Furthermore, the symmetry of the fault current was leveraged to reflect the correlation between the two transfer functions, and the differential fault current symmetry coefficient metric was introduced. A fault location time-domain algorithm based on guessed fault resistance was proposed, and its effectiveness was demonstrated through both reduced-scale and simulation experiments. The results indicate that the proposed method is not only applicable to complex lines but also offers a straightforward calculation approach, facilitating fault location under high-impedance faults.