When a fault occurs in wind farms based on doubly fed induction generators（DFIG）

the characteristics of DFIG short-circuit current is differences from conventional power system

which is mainly not power frequency

and makes pitch extraction and calculation incorrect in constant frequency-fourier method.For understanding of the characteristic of short circuit current for doubly-fed wind farm

the paper is combined with the equal circuit of DFIG wind farm

which analyses the frequency components of short circuit voltage and current with the fault

which the result is validated by the pectrum analysis technique. Following the frequency’s feature of voltage and current

simulations based on PSCAD is made to verify the adaptive failings of distance protection in wind farms. Through the simulation of wind farms in actual situation

the short-circuit current offsetting constant frequency

which makes traditional distance protection based on Fourier power frequency algorithm does not accurately measure the impedance resulting in the malfunction of the component.