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Accurate Multipoint Synchronous Measurement Scheme of AC Electric Fields

Based on the measured electric field data at several appropriate points adjacent to AC transmission lines, the voltages on the lines can be inversely calculated, which will greatly facilitate the condition monitoring of overhead transmission lines. The difficulty of the technique lies in the accurate synchronous measurement of multipoint electric fields. When the measurement is started by sending a command to the measuring device, there will be a problem of unsynchronization in the process of receiving and processing instructions by the measuring device, which will lead to the failure to realize the requirement of synchronous starting. And when the frequency of the oscillator crystal mounted on multiple measurement devices drifts, the synchronization accuracy of the measured electric field data is not high due to the different time rhythms, which leads to inaccurate voltage inversion. In this paper, 1PPS from the GPS receiver is used to provide a unified time standard for the measurement device. In the FPGA, the accumulation method is used to divide the 1PPS into the sampling clock of the required frequency, and the sampling pulse starts to be generated on the next 1PPS rising edge after the starting command. This scheme can not only realize the simultaneous start of acquisition by multiple measurement devices, but also reduce the time error caused by the oscillator crystal. The measurement error and its influence factors are analyzed by simulation and experiment. Finally, three electric field measurement devices are applied in the experiment, and the validity of the multipoint synchronous measurement scheme is verified.