How to rectify the distortion of sampling signals from power FTUs?

To rectify sampling signal distortion, the cause needs to be analyzed and addressed accordingly. If it's high-frequency interference, add a second-order active filter at the sampling input with a cutoff frequency of 2kHz. If it's common-mode interference, add a CMZ3225A-501T common-mode inductor. If it's transmission line reflection, use impedance matching and terminate with a 120Ω resistor in parallel. PCB rectification: shorten the sampling trace length, use differential traces, and ensure the trace length matching error is less than 0.2mm. Replace with a high-precision operational amplifier AD8629, with an offset voltage less than 10μV. Through these rectifications, signal distortion was reduced from 5% to 0.1%, and the signal-to-noise ratio improved to 70dB, meeting the IEC 61869 0.2 accuracy requirement.