How should the shield of the sampling cable of the power measurement switch (PMS) be grounded?

The grounding method of the shielding layer of the PMS external sampling cable (connecting to the CT/VT or sensor) is crucial for suppressing interference; incorrect grounding can introduce ground loop noise. The principle of correct grounding is "single-point grounding, connected to a clean ground." Typically, the shielding layer should be grounded at the PMS device end, specifically connected to a "clean analog ground" (AGND) at the same potential as the sampling circuit reference, or directly connected to the chassis ground (PE), depending on the system grounding strategy. If the PMS internal analog ground is isolated from the chassis ground (connected via an inductor or resistor), the shielding layer should be connected to the chassis ground to provide a direct discharge path for common-mode noise, preventing noise from entering the circuit ground. Connections must use a 360° crimping method, such as using a metal cable connector (gland) or shielding clip, ensuring good contact throughout the circumference. "Pigtail" connections are strictly prohibited, as their lead inductance will severely degrade high-frequency shielding effectiveness. At the sensor end, the shielding layer should be left unconnected unless the sensor housing is already grounded. For environments with long cables or severe high-frequency interference, consider grounding the PMS shielding layer through a capacitor (e.g., 1nF) to accommodate both high and low frequencies.