The voltage sag is the power quality problem with most frequent occurrence and the most serious influence and location of its disturbance source plays an important role in solving the disputes between the power supply and the power consumption. In view of current and impedance characteristics of PV power in low voltage ride through（LVRT）

the sag source location method of modified distance impedance relay method is proposed

the correction criterion is given in this paper and the reliability of source location of voltage sags in complex distribution network containing DG is improved. It is shown by the simulation and experimental result that the modified location method can locate more reliably the voltage sag in power distribution grid containing PV.