How to eliminate interference at the power acquisition interface of a power DTU?

Eliminating interference at the DTU power acquisition interface requires isolation and filtering measures. An isolation transformer is used on the secondary side of the PT/CT, with the turns ratio set according to the signal amplitude, and a primary-to-secondary withstand voltage of 3000VAC. An RC low-pass filter is deployed on the secondary side with a cutoff frequency of 2kHz, using precision resistors and C0G capacitors. For common-mode interference, a differential amplifier is used in conjunction with an instrumentation amplifier. In terms of PCB layout, the acquisition interface is kept away from digital circuits and shielded with a ground plane. Interference coupling paths are analyzed through simulation to optimize the design. In actual measurements, the acquisition error should be less than 0.2%. Eliminating interference ensures metering accuracy, meeting the 0.5S class requirement.