How to eliminate leakage current monitoring interference in intelligent low-voltage monitoring units?

Interference elimination in leakage current monitoring requires a balance between high sensitivity and anti-interference capabilities. The secondary side of the zero-sequence current transformer uses a high-permeability magnetic core, paired with a low-noise operational amplifier (AD8629). Signal processing employs bandpass filtering (10Hz-1kHz) to suppress power frequency harmonics.

PCB layout: The leakage current monitoring circuit is kept away from power supplies and digital circuits.

Housing shielding: The zero-sequence current transformer (CT) is equipped with a metal shield.

Software algorithm: Moving average and threshold comparison are used.

Through this elimination, the leakage current monitoring sensitivity reaches 30mA, with a false alarm rate of less than 0.1%, meeting the IEC 61008-1 residual current device standard.