Abstract:The large - scale grid - connected wind farm should avoid taking off the grid when minor faults occur on one hand, on the other it needs to isolate promptly as soon as the own outgoing line faults of boost station of wind farm occurs. A protective action resistance for fault disconnection of wind farm after the typical ground fault of outgoing line in booster station is analyzed,and following the low - voltage ride - through characteristics of wind farm,the under - voltage isolation protection is improved by adding outgoing line protections as auxiliary criterion. After the improvement,the protections ensure the wind farm in continuous operation will not be taken off the grid when minor faults occur,which maintains the economic benefits of wind farm. Meanwhile it ensures the prompt isolation when the faults of own outgoing line in boost station occur,which improves the safety and stability of power grid.