How to design a multi-rack shared-ground intelligent controller PAC?

In multi-rack systems, the common ground design of the intelligent controller PAC must ensure potential balance among racks and avoid ground loops. First, a main grounding copper busbar (cross-sectional area not less than 25mm²) is established. Each rack is connected to the main grounding busbar in a star configuration via an independent grounding wire (cross-sectional area not less than 6mm²), with the grounding wires being of equal length and less than 2m. Shielded twisted-pair cables are used for signal connections between racks, with the shield grounded at a single point to the local rack at the transmitting end to avoid ground loops.

For long-distance communication, optical fibers or isolators (such as the ADuM series) are used for electrical isolation. Simultaneously, isolation transformers or common-mode inductors (such as CMZ7060A-701T) are installed at the power input of each rack to suppress common-mode noise conduction. Testing and verification show that this common ground design can reduce the ground potential difference between multiple racks to less than 0.5V (at 50Hz-1MHz), and the system passes the IEC61000-4-25 HEMP immunity test with a communication bit error rate below 10^-9.