Accurate measurement of voltage in the distribution network fault indicator is one of the important basis for fault identification. By analyzing the voltage characteristics of various ground faults under different grounding modes of the distribution network, it is pointed out that the voltage variation characteristics of the fault phase or non-fault phase can be used as one of the criteria for fault identification of fault indicators when the system has a ground fault. A voltage sensor based on the mechanical structure of the fault indicator is designed. Through theoretical analysis and simulation research, the influence of the temperature and different heights of the distribution line on the measurement results of the voltage sensor are analyzed. The prototype test results show that the linear error of the sensor in the measurement range is within ±3.8%, and its accuracy as a characteristic of voltage variation is acceptable.