Regarding the grounding issue of the DC power supply in DCS or PLC systems
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In a DCS system, in order to provide an electrical reference potential for electronic devices, it is necessary to ground the negative terminal of the DC power supply. So under what circumstances should the DC power supply be designed to be floating?
Refer to HG/T 20513-2014 \"Code for Grounding Design of Instrument Systems\" and SH/T 3081-2003 \"Code for Grounding Design of Petrochemical Instruments\"
The specifications do not contain any instructions regarding floating design; I recall that it is the characteristics of the DCS manufacturer’s system that determine whether floating should be used or not.
1. If the interference from the grounding system is too high (referring to earth currents), it’s better to keep it floating. For example, the DC power supply of SIEMENS PCS has a toggle switch that allows selection between “grounded” and “floating”. 2. Perform \"open circuit/short circuit\" tests on the transmitters and probes on site; generally, this is done by the safety interlock PLC, which requires that the circuits be in an open state, and a \"grounding detection alarm\" should be installed for the 24VDC power supply. It’s very difficult to make a floating system complete; as long as one part is grounded, the entire system becomes \"grounded\". The grounding system is quite practical; grounding serves as your \"backing,\" but it needs to be reliable. @jiaguoyun