Abstract: It is a basic requirement for grid connected wind turbines to provide reactive power support to the system when the grid voltage drops. The reactive power support of wind turbine has a direct impact on the fault current, which may reduce the sensitivity of the current quick break protection of the collector line, and may also make the protection lose its selectivity. Firstly, based on the mathematical model of DFIG（double feed induction generator） and the principle of reactive current support, we analyzed the influence of DFIG regulating output reactive power on fault current through rotor side converter（RSC） and grid side converter（GSC） respectively under shallow and deep fault operation. Aiming at the problem that DFIG reactive power priority control may reduce the current quick break protection sensitivity of the collector line and lose coordination with the box transformer fuse, we proposed a set value adjustment method based on DFIG reactive power priority control calculation of the initial setting value and additional adaptive compensation according to the collector line voltage sag. The simulation results show that the improved setting value can greatly improve the selection ability of protection on the premise of ensuring the rapid operation of the whole line.