How to connect the shield ground and the high voltage ground of the power measurement switch (PMS)?

The connection method between the shielding ground (used for shielded cables and shielding covers) and the high-voltage ground (PE) in a PMS directly affects the shielding effectiveness and safety. The basic principle is that the shielding ground should be connected to the chassis (i.e., PE) at the equipment entry point with low impedance and a large area, and this connection should only occur at this one point. Specific implementation: When all external shielded cables enter the PMS, the shielding layer should be pressed 360° against the metal surface of the chassis using metal cable joints (gland) or shielding clamps. The chassis itself should be reliably connected to the PE line (e.g., via grounding screws and braided tape). Shielding covers on the PCB (if any) should be connected to the chassis via multiple spring fingers or conductive foam.

It is absolutely forbidden to introduce the cable shielding layer into the PCB, connect it to the signal ground, and then transfer it to PE, as this will introduce noise. For sensitive modules with independent internal shielding boxes (such as metering units), the shielding box can be connected to the analog ground of the PCB separately through a high-frequency capacitor (e.g., 10nF), while the box remains insulated from the chassis. In this way, external interference is directly discharged to PE through the shielding layer and does not enter the circuit. Proper connection ensures that the shielding layer suppresses high-frequency interference by more than 30dB while meeting safety grounding requirements.