Time-domain distance protection shows superior performance for transmission lines integrated with renewable energy sources (RESs). However, in 35–110 kV renewable power transmission systems, the inhomogeneity of the mixed overhead lines (OHLs) and underground cables (UGCs) negatively affects the feasibility of distance protection. This paper proposes a robust algorithm of time-domain distance protection for renewable power transmission system with the mixed OHLs and UGCs. First, based on the time-domain mathematical model, the accuracy and robustness of the conventional algorithm under inhomogeneous line parameters are evaluated. To solve the “0/0” problem caused by weak signals, the singular value decomposition-based least squares method (SVD-LSM) is adopted to avoid calculation outliers and improve the protection reliability. Meanwhile, a weighting method based on Euclidean norm is designed to overcome the problem of computational non-convergence. It also ensures the protection operation speed by using a short time window. In addition, a distance correction method is designed for mixed lines to improve the accuracy of fault location. On the basis, a prototype of the protection device is developed, and extensive hardware-in-the-loop (HIL) tests are performed to verify its feasibility and superiority. In addition, the prototype of the protection device has been applied to actual renewable power transmission systems.
Bin et al. (Thu,) studied this question.