DCS redundancy issues
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Let’s discuss the DCS redundancy issue! For example, if the CPU of a DCS system is dual-redundant, what is the operating status of these two CPUs? Do they operate simultaneously or one works while the other is in standby mode? If one is in use and the other in standby, then when does switching occur, and how does it take place? Could there be delays in timing and discrepancies in data?
Each manufacturer has its own way of operating things. I think Zhejiang University’s Zhongkong redundant main control card operates with two cards running simultaneously; during the switching process, it switches directly to the other main control card with almost no delay. Generally, one in use and one as a backup means a dual-operation state, right?
If two run simultaneously, then there will be two outputs, right? So when a problem occurs, that is, when an error appears in the output, how can we distinguish between the incorrect and the correct values?
Both run simultaneously, but there is only one output – that from the main control card which is in operation; the other one is disabled or does not produce any output. It starts to output data only when it switches from a backup card to a working card……
That can’t be! The risks in this case are the same as those when using one, right?
The risk is reduced because the two operate simultaneously; the probability of one failing is different from the probability of both failing. Otherwise, why would there be control structures such as three-out-of-two or two-out-of-one?
Two CPUs are running simultaneously; one outputs while the other does not. Only in this way can a seamless switchover be achieved. We are using Siemens 414H with dual CPUs in hot standby mode
Redundancy and disturbance-free switching may seem simple, but in practice their implementation and underlying working principles are quite complex; many system manuals only touch on this topic briefly without going into detail. My teacher specialized in the field of disturbance-free switching in *automation during their postgraduate studies