To solve the problem of limiting the accuracy of double-end traveling wave ranging by the existing traveling wave monitoring device, a traveling wave monitoring device for nanosecond time-precision grounding fault based on 4G DTU is developed. Firstly, the high-speed data acquisition card and DSP, is used to collect，analyze and storage fault voltage. Then the GPS nanosecond timing module is used to calculate the voltage reference time. Finally, 4G DTU is used to send fault data to the background computer. This paper introduces the method of collecting and storing fault voltage data and calculating voltage reference time of the device. The debugging results show that the data acquisition, analysis and transmission functions meet the requirements of the online monitoring device, and the fault voltage reference time accuracy calculated by the device is nanosecond, and the fault data can be used for subsequent fault location work.

4G DTU, GPS timing module, Nanosecond precision, Single-phase ground fault, Traveling wave ranging.