A time-domain fault location scheme using voltage gradient and traveling wave analysis in MMC-based HVDC lines

• Efficient fault location for MMC-HVDC lines using time-domain analysis. • Utilizes 2nd-order voltage gradient for precise wavefront detection. • Lowers costs with moderate sampling (33.3 kHz), no complex transforms. • PSCAD simulations show high accuracy in diverse fault cases. • Offers robust and fast fault distance estimation for modern HVDC grids. −This paper introduces a computationally efficient and robust time-domain fault location estimation scheme for Modular Multilevel Converter (MMC)-based High-Voltage Direct Current (HVDC) transmission lines. The proposed method leverages the novel application of the second-order voltage gradient of traveling wave signals to detect and calculate wavefront arrival times at line terminals, enabling precise and fast fault distance estimation. Operating at a moderate sampling rate of 33.3 kHz, the scheme circumvents the need for computationally intensive signal transformations, high-frequency measurements, and stringent reliance on exact wave velocity data. The fault distances are calculated by analyzing the time difference between wavefront arrivals at each terminal, combined with known wave propagation speeds, using straightforward time-domain computations. Extensive PSCAD simulations on a 400 km HVDC line under various fault scenarios, including different fault resistances and fault types (pole-to-ground, pole-to-pole), validate the approach. The results demonstrate consistently high accuracy, with fault location errors remaining below 0.953 km across all tested conditions. Moreover, the scheme proves robust against changes in fault parameters, underscoring its practicality for real-time applications. This method offers a reliable, cost-effective solution for fault location in modern HVDC grids, making it a compelling choice for use in next-generation power grids.