How to suppress low-voltage power distribution interference in intelligent low-voltage monitoring units?

Low-voltage power distribution systems suffer from various interferences, including harmonics, surges, and switching overvoltages. The solution employs a multi-stage filtering and protection approach. A CMZ3225A-501T common-mode inductor (500μH) is installed at the power input, along with a CY-X2-224K X capacitor (0.22μF/305V) for differential-mode filtering. On the secondary side, a PBZ2012E600Z0T ferrite bead (600Ω@100MHz) is used to suppress high-frequency noise. For surge protection, a three-stage architecture is employed: the first stage uses a 2R600L-8×6 gas discharge tube (600V/5kA), the second stage uses a 14D511K varistor (510V/4kA), and the third stage uses an SMBJ24CA TVS diode (24V/600W). Simultaneously, the monitoring circuit utilizes an ISO7240C isolation amplifier with an isolation voltage of 3kVrms. This solution can reduce low-voltage power distribution interference by more than 35dB, maintain monitoring accuracy at level 0.5, and meet the IEC 61000-4-5 4kV surge and IEC 61000-4-4 4kV EFT test requirements.