Issue with remote start/stop of the pump
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For starting and stopping pumps via DCS, the start/stop signals are generally connected directly to the electrical secondary circuit, which operates at 220V. As a result, the start/stop signal wires carrying 220V voltage travel from the power distribution room to the DCS cabinet. According to regulations, should the start/stop signal cables be routed in separate cable trays from other signal cables? Is a tray and partition required at the very least?
It is best to add a relay on the electrical side to achieve voltage isolation
According to the specifications, the start/stop signal cables and other signal cables should be laid separately, preferably using different tray systems. This is to avoid mutual interference and failures caused by such interference. For remote start/stop signal cables and other low-voltage signal cables, partitions can be added to the cable tray to provide further isolation and protection. This ensures the stability and reliability of signal transmission. .
It’s specified in the standards; a partition needs to be added.
The DCS provides passive (dry contact) signals to the electrical department, which uses these passive (dry contact) signals to configure the electrical secondary circuits.
Here, I usually use DCS to provide 24VDC active contacts; a 24VDC relay is installed in the distribution cabinet for isolation, with the relay contacts being used to control start and stop. On the one hand, inside the DCS cabinet, all cards are powered at 24V, which is safer. On the other hand, slot box cables are also below 24V, ensuring the quality of the signal, so there is no need to worry about installation issues. Since I run a small business and am in charge of both control instruments and electrical systems myself, there is no need for standard procedures such as design or modification; I think this approach is safer and more convenient!
It is also common to use passive dry contacts to connect to the secondary circuit of a distribution cabinet. As long as one pays attention to making distinctions and ensuring safety while working in the DCS cabinet, avoiding electric shock as well as ground faults and short circuits, etc., it will be fine. As for the laying of the cables, let me tell you – it has no impact at all. Although it is 220V, the dry contacts have no load, and the signal wires are all shielded, so they have no impact on the signals at all; they are all laid directly in a trunking.