A Two‐Stage Transient Current Differential Protection Method Considering Fault Inception Angle

ABSTRACT

In power systems with high penetration of renewable energy, fault currents exhibit limited amplitude and controlled phase, which degrades the performance of conventional power‐frequency protection for outgoing lines. To address this issue, this paper proposes a two‐stage transient current differential protection method that accounts for the influence of the fault inception angle. First, an analytical model of the fault transient current is established based on the distributed parameter line model and the compositional differences between the high‐ and low‐frequency components of the differential current under internal and external faults are theoretically analysed. Then, the impact of the fault inception angle on the transient high‐ and low‐frequency currents is examined, revealing the physical mechanism responsible for the distortion of low‐frequency feature extraction under specific time windows and certain inception angles. On this basis, the complete ensemble empirical mode decomposition (CEEMD) algorithm is employed to decompose the differential current into high‐ and low‐frequency modes and the fault inception angle is identified in real time using the steady‐state voltage zero‐crossing information. A two‐stage time‐window protection scheme utilizing fault inception angle identification is thus developed. PSCAD/EMTDC simulation results demonstrate that the proposed scheme effectively avoids the adverse effect of varying fault inception angles on the frequency‐band feature extraction of transient currents, thereby significantly improving the reliability of transient current differential protection. The scheme remains sensitive and reliable under high‐resistance grounding faults and strong electromagnetic noise interference. RTDS simulation results verify the effectiveness and practical applicability of the proposed protection method.