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In order to improve the fault location accuracy of overhead line and underground cable combined transmission line, a new method of transmission line fault location based on discrete wavelet transform (DWT) is proposed. Multi resolution analysis (MRA) is carried out on the transient signals measured at one end of the transmission line through DWT. Under the condition of low fault starting angle, the line mode current and zero mode current are used to detect the fault, and the traveling wave arrival time from the fault point to the substation is solved in combination with the wavelet modulus maximum (WMM), so as to accurately locate the transmission line fault. The method of half sine voltage response overcomes the shortcomings of limited sampling frequency and low fault starting angle. The fault distance is calculated by using the difference between the sending time of 100kHz half sine signal and the time of receiving derivative signal. Taking into account the harmonic distortion and the changes of fault resistance, grounding resistance, fault location and starting angle, the test results show that for 100km transmission line, even when the fault is close to the bus (<2%) and the fault starting angle is low, the fault location error obtained by the proposed method is only 0.14km.