How does the equipotential bonding of the power measurement switch (PMS) suppress common mode?

In electrical cabinets where PMS is installed, potential differences between the equipment's metal casing, cable shielding, and grounding busbar can create common-mode voltage-driven interference currents. Equipotential bonding aims to eliminate or reduce these potential differences and is a fundamental measure for suppressing common-mode interference. During implementation, copper busbars or braided strips with a cross-sectional area of not less than 16mm² are used to connect the PMS casing, adjacent circuit breaker cabinets, motor casings, sensor casings, etc., at close range, and finally connect them all to the grounding busbar.

The connecting wires should be short and straight, with a length not exceeding 0.5m, and should avoid forming loops. For cable shielding entering the PMS, it should be tightly connected to the casing at the entry point using 360° crimped shielding terminals or metal cable gland. If there are multiple circuit boards inside the PMS, their shielding grounds should also be connected to the same casing grounding point through a low-impedance path. After equipotential bonding, the power frequency potential difference between the various metal components should be less than 1V, and the high-frequency (above 1MHz) impedance should be less than 0.1Ω. This can reduce common-mode interference voltage caused by external induction or ground potential difference by more than 90%, significantly improving the system's immunity to surges and EFT.