How to improve interference immunity in the grounding of an electrical power measurement switch (PMS) system?

As a complete system, the grounding architecture of the PMS directly determines its resistance to external electromagnetic interference (such as EFT, surges, and RF fields). Grounding design to improve system immunity must adhere to the principles of "layering, equipotentiality, and low impedance." At the equipment level, the chassis and all accessible metal components are reliably connected to the PE (protective earth) layer, forming the first layer of shielding and discharge path. At the board level, the PCB ground plane is connected to the chassis at multiple low-impedance points, ensuring that interference current flows directly to the ground and does not enter the circuit.

At the circuit level, sensitive analog circuits use floating ground or are connected to the chassis at a single point via a common-mode inductor CMZ2012A-900T to block ground noise intrusion. At the cable level, the shielding layers of all incoming and outgoing cables are connected to the chassis at a 360° angle at the entry point. At the system level (such as the entire control cabinet), the PMS is equipotentially connected to other devices via copper busbars. Simultaneously, a common-mode inductor CMZ1211-501T and a Y-capacitor are placed at the power input to provide a low-impedance return path for common-mode interference. With its systematic grounding design, PMS can easily pass rigorous immunity tests such as IEC 61000-4-4 EFT Level 4 (4kV), IEC 61000-4-5 Surge Level 4 (4kV CM, 2kV DM) and IEC 61000-4-6 CS 10V.