Power distribution issues in DCS
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I would like to ask everyone: apart from the regulations for thermal power plants, why don’t the instrument power distribution standards in the chemical industry standards specify that DCS systems must be powered by two separate power sources – one from a UPS and the other from another power source on a different bus section? Is this requirement optional in the chemical industry? Is it determined by whether the project causes safety accidents during power outages? Do you know anyone from a paper mill? Does the paper industry use only one power supply to supply power to the DCS?
As far as I know, petrochemical facilities use two power supplies: mains electricity and UPS
We have the same doubt: one of our projects here is powered by a single-channel UPS. We asked the designers, and they said it complies with the specifications. There has always been a question regarding single-channel power supply: since the power supplied comes through rectifiers-inverters, and the UPS operates 24 hours a day, isn’t that meant to require very high standards for the quality of the UPS?
Reply to 3# njutzdh13: My question is what to do when the UPS needs maintenance?
Two power supplies do not refer to one supply from the mains and another from a UPS; rather, it means that there are two power sources leading from the distribution room to the system, so that in the event of a problem with one source, the other can provide power. Both circuits need to be powered by a UPS to ensure that the manufacturing process is not interrupted.
To ensure stable and reliable power supply for the DCS, two power supplies are necessary. Moreover, since DCS cards can be damaged by unstable voltage, at least one of the two power supplies should be an UPS-powered supply. The design specifications allow for power supply from a single source, but DCS manufacturers or design firms will require users to use two separate power supplies, with at least one of them being provided by a UPS.
According to technical discussions with Eaton UP, all UPS systems use two power supplies
Maintenance is no problem; UPS units all come with a maintenance bypass, so it’s sufficient to switch to the bypass during maintenance.
UPS batteries typically provide power for about 30 minutes. What if the UPS fails and cannot be repaired within those 30 minutes? This is something that needs to be considered.