Factors impacting distance protection for tie line of wind farm and corresponding countermeasures

Based on operation characteristic of wind farms, the acting characteristic of impedance circle of wind farm tie line is analyzed and the existing defect of traditional distance protection adopted for wind farm tie line is researched. A mathematical model of measured impedance of wind farm tie line is built and the impact of operational parameters on the measured impedance is researched. Frequency spectrum characteristics of post-fault currents and voltages at both sides of the tie line as well as their impacts on distance protection are simulated. A scheme to protect the tie line by adaptive distance protection is proposed. A simulation model of grid-connection of wind farm is constructed by PSCAD and the acting characteristic of traditional distance protection and that of adaptive distance protection during fault are compared, and simulation results show that the defect of traditional distance protection can be avoided by adopting adaptive distance protection to wind farm tie line, besides, the adaptive distance protection can suit to various operational model of wind farms and it can eliminate the impacts of non-power frequency current and voltage on the protection.