An Adaptive Pilot Protection for Wind Farm Transmission Line Employing Multiscale Morphological Gradient

Abstract

The complex fault-currents and prominent harmonic components of doubly-fed induction generators (DFIGs) pose significant sensitivity and mal-operation risks for traditional pilot protection on long-distance transmission lines. To address these issues, this article proposes a novel adaptive time-domain pilot protection scheme based on multiscale morphological gradients. This method uses morphological gradient with multiscale structural elements for robust fault-current characterization, extracting transient fault current features at both ends of the line, balancing computational efficiency with detailed waveform preservation. Fault detection is achieved through kurtosis of morphological gradients within a sliding window, complemented by an adaptive weighted sum of energy differences criterion to distinguish internal from external faults. The proposed method was validated using a wind farm transmission line model in power systems computer aided design (PSCAD)/electromagnetic transients, including DC (EMTDC). Extensive PSCAD/EMTDC simulations demonstrate that the proposed scheme achieves ultrafast fault detection within 1.5 ms and requires a minimal computational load of only 11 core operations (COps) per data point. Furthermore, by extracting and transmitting only scalar feature values via an adaptive alignment mechanism, it completely eliminates the reliance on strict time synchronization. The energy index maintains a distinct selective margin even under extreme boundary conditions, proving its superior practical reliability for wind farm export lines.