Accurate Self-Synchronization Strategy for Pilot Differential Protection

Accurate time synchronization is a prerequisite for pilot differential protection in power systems. Existing synchronization methods either rely on external references such as global positioning system (GPS), which are vulnerable to signal loss and cyber attacks, or require additional communication channels, which increase system cost and complexity. To address these limitations, this paper proposes a two-stage self-synchronization scheme that achieves high accuracy using only electrical measurements. The method first exploits the initial traveling waves generated by a fault and then refines the result with steady-state phasor information, thereby ensuring robustness against various non-ideal conditions. Theoretical derivation proves its validity, and extensive PSCAD/EMTDC simulations, hardware experiments, and a field fault record confirm its effectiveness under different fault scenarios, parameter uncertainties, frequency deviations, and noise disturbances. The results demonstrate that the proposed approach can achieve synchronization errors well within acceptable limits, making it a promising solution for practical deployment in power system protection.