How to avoid ground loops in a hybrid grounding system for an electrical power measurement switch (PMS)?

In a PMS system, low-frequency circuits require single-point grounding to avoid ground loops, while high-frequency circuits and shielding layers require multi-point grounding to reduce impedance. This contradiction needs to be resolved using a hybrid grounding strategy. A typical application of hybrid grounding is as follows: the shielding layer of the signal cable is connected to the chassis ground at the PMS device end via a capacitor (e.g., 1nF/2kV) to achieve high-frequency multi-point grounding; simultaneously, it is connected to the internal signal ground via a 100kΩ resistor in parallel with a CMZ2012A-900T common-mode inductor (90μH) to achieve low-frequency single-point grounding.

For the PCB, the analog circuit area uses a single-point grounded star topology, while the digital circuit area uses a grid ground plane. The two are connected at one point via a ferrite bead (e.g., PBZ1608E600Z0T). The power ground (PGND) is connected to the chassis ground via a 0Ω resistor or directly. This structure can both prevent power frequency ground loop currents and provide a low-impedance discharge path for high-frequency noise. With proper design, hybrid grounding can reduce the noise voltage induced on the signal line by 40dB by the ground loop, while ensuring that the grounding impedance of the shielding layer is less than 1Ω at 100MHz.