PLC control system grounding - Solutions - Huaqiang Electronic Network

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The ground of the plc control system includes system ground, shield ground, AC ground and protection ground. The disturbance of the grounding system to the PLC system is mainly due to the uneven distribution of potential at each grounding point. There is a ground potential difference between different grounding points, causing ground loop current and affecting the normal operation of the system. For example, the cable shielding layer must be grounded at one point. If both ends A and B of the cable shielding layer are grounded, there is a ground potential difference, and a current flows through the shielding layer. When an abnormal state such as a lightning strike occurs, the ground current will be larger.

In addition, the shielding layer, the grounding wire and the earth may constitute a closed loop. Under the action of the changing magnetic field, an induced current may appear in the shielding layer, and the signal loop is interfered by the coupling between the shielding layer and the core wire. If the system is confused with other grounding, the generated ground loop may generate unequal potential distribution on the ground, which affects the normal operation of the logic circuit and analog circuit in the PLC. The logic voltage interference tolerance of PLC operation is low, and the distribution interference of logic ground potential easily affects the logic operation and data storage of PLC, resulting in data confusion, program running or crash.