A DC Grid Protection Method Based on Differentiation of Transient Abrupt Magnetic Flux Variation of Current‐Limiting Reactor

ABSTRACT To address the challenges in traditional DC grid protection, including difficulties in detecting high‐resistance faults, insufficient setting criteria, and the susceptibility of fault characteristics to inter‐pole coupling effects, this paper proposes a fast protection method based on the differentiation of transient abrupt magnetic flux variation (DTAMFV) of the current‐limiting reactor (CLR). Considering the impact of the dedicated metallic return (DMR) on inter‐pole coupling in the DC grid with DMR, an analytical model of the traveling wave (TW) characteristics is developed using the generalized Clarke transformation and Bergeron line model, enabling fault characteristic decoupling. Based on this, the analytical expression for the initial TW of the CLR transient modal voltage under both internal and external fault conditions is derived, and its high‐frequency attenuation characteristics are quantitatively analyzed. Furthermore, a fault section identification criterion based on DTAMFV is developed, enabling both fault section localization and direction discrimination. Additionally, the phase plane of the two‐mode and zero‐mode DTAMFV is utilized for fault polarity and type determination. Finally, the effectiveness of the proposed method is validated through PSCAD/EMTDC simulations. The results show that the protection method can operate within 2 ms after fault occurrence, demonstrating high tolerance to transition resistance and strong anti‐interference capability.