Abstract：According to the characteristic of the doubly-fed induction generator (DFIG) that the positive sequence impedance is unequal to the negative sequence impedance after the crowbar resistance being activated, the impact of the wind farms′fault characteristic on the relay protection was analyzed in this paper. The difference between the measured impedance and the actual impedance of the line-to-ground protection for zones 1, 2 and 3 are discussed. The zone 2 of the ground distance protection with the traditional setting method would refuse to trip when a line-to-ground fault occurs. Based on the measured impedance when a line-to-ground fault occurs, an adaptive ground distance protection scheme considering the characteristics of the doubly-fed induction generator is proposed. The proposed scheme calculates the adaptive branch coefficient on line and makes the measured impedance reflect the distance from the relay location to the fault point more accurately.Finally, using DIgSILENT, a simulation based on the grid model with wind farms was carried out to verify the conclusion that the adaptive ground distance protection method is more reliable and sensitive while the selectivity is also guaranteed.
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2017, Vol. 32 
