Because the sampled value differential protection has the advantages of fast calculation speed and easy consideration of CT saturation, it is widely used in current busbar protection devices. However, when doubly fed induction generators, which have different transient characteristics from traditional thermal power units, are widely connected into power systems, it will bring serious challenges to the existing relay protection. Taking the doubly-fed wind farm connected to the busar of 220 kV substation as an example, the influence of doubly fed wind field incoming line on busbar sampled value differential protection is studied on the RTDS simulation platform. It is found that the short-circuit current provided by the wind side branch has the characteristics of weak feed, high harmonic and frequency offset when the fault occurs in the busbar area. At the same time, taking into account the CT saturation, doubly-fed unit itself reactive power optimization control strategy and other factors, it makes the complexity of the short-circuit current more prominent and results in the traditional busbar sampled value differential protection action being delayed. For this reason, a criterion for sampled value differential protection of adaptive variable data window is proposed, and the method is validated by RTDS simulation platform. This work is supported by Natural Science Foundation of Inner Mongolia Autonomous Region (No.2018LH05032).