The movable ultra-high-frequency（UHF）antenna array has been applied to partial discharge（PD）monitoring and localization in air-insulated substation（AIS）.Since the antenna array is arranged with small distance

the range of PD source is generally calculated with low-accuracy.This paper presents a direction-of-arrival（DOA）estimation method based on the time difference between antennas.The computation formula of azimuth and elevation angle are derived according to the geometrical relationships between incident angle of UHF signal and azimuth and elevation angles.A simulation model of DOA estimation error based on Monte Carlo method is built to quantify the influence of time difference error.Moreover

the influence of antenna pairs

PD position

distance between antennas and shape of antenna array on DOA accuracy are analyzed.The DOA estimation method is tested with experiments in laboratory.The results indicate that the accuracy of azimuth angle decreases while the accuracy of elevation angle increases when the height of PD source increase.The estimation error of both azimuth and elevation angles decrease when enlarge the distance between antennas.The rectangle array is the optimal configuration for DOA estimation.The estimation error of azimuth angle is less than 4° for rectangle and diamond antenna arrays with size of 4 m×2 m

and the error of elevation angle is less than 10° when it is greater than 20° for rectangle array with size of 0.7 m×0.7 m.