In the operation of air separation plant, in order to ensure the accuracy of DCS control system monitoring and the safety and stability of operation, it is necessary to do well of DCS system grounding.
Grounding is to connect the circuit and unit with an equipotential or equipotential surface as the common reference point of signal to realize low impedance value, so as to ensure that when the signal, power supply or DCS system equipment entering DCS system is abnormal, it can bear overload current and quickly lead the overload current to the earth, provide shielding layer for DCS system, eliminate electronic noise interference, and provide the whole control system with a shielding layer The system provides reference zero potential of common signal.
The grounding of DCS control system shall follow the following principles:
1.The logic grounding, signal grounding and shielding grounding in DCS system shall meet the requirements of "one point grounding". Insulated copper stranded wire or cable shall be used to connect to the general grounding copper bar.
2.The DCS system shall be insulated from the foundation by installing insulation pads and insulation bolts, and the insulation resistance to ground shall be greater than 50m Ω.
3.When the insulation between power supply cabinet, operation console, relay cabinet and foundation is uncertain, they shall not be connected to the general grounding copper bar, but shall be connected to the nearby indoor electrical protection grounding trunk line.
4.When selecting the access point of DCS system for public grounding grid, the grounding resistance of common grounding grid shall not be greater than 4 Ω, and the connection resistance shall not be greater than 1 Ω, and the access point of DCS shall be far away from the current entry point.
5.The shielding layer of DCS system signal shielding cable shall not float in the air and must be grounded.
