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I/O communication Network for SCADA

Created by: DeltaX at: 4/28/2009 10:35 AM (4 Replies)

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4/28/2009 10:35 AM	Rate (0)
DeltaX Posts: 10 Rating: (0)	Dear all, For SCADA network architecture, the I/O communication network there are two options: Either all the RTU are connected on the PLC remote I/O communication network and the SCADA server are connected via another link to the PLC that as the role of interface; or all the RTU and PLC are directly connected to the SCADA servers via the I/O communication network. could you plz clarify the main difference between use the first one or the second one, and what you recommended. the cost is big issue for my design. Your help is highly appreciated
DeltaX Posts: 10 Rating: (0)
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4/28/2009 11:16 AM	Rate (0)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 3/22/2025 Posts: 12344 Rating: (2707)	Hello DeltaX; There is no single answer to this question, it will depend on the project details. We have done both, depending on the number of I/O and the number and projectcomplexity of the SCADA/HMI units. Cost is always an issue, especially in the present economic situation, but there are others: reliability being one of the most important. In our present projects, we average more than a 1000 I/Os (digital and analog) with 2 SCADA systems and 3 HMIs. We will systematically segregate the two, I/Os on a separate network to ensure that the flow of data to the PLC is never interrupted or limited. Then the SCADA and HMIs are setup on their own link,because they can cause a much greater load on communication functions, and are not necessarily as time-critical (a half-second delay between the pressing of a button on the screen and reaction from the floor is generally not conductive to ulcers...). Often Profibus-DP will be used for the I/O comms, Ethernet for the SCADA/HMI. Hope this helps, Daniel Chartier

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4/28/2009 12:13 PM	Rate (0)
DeltaX Posts: 10 Rating: (0)	It was great to hear from you Daniel. Let me first clarify sth to make sure there is not missunderstanding or NOT unserstand the meaning of the world "from my side" First of all,This is my first project for SCADA, so I'm alittle bit new in this feild. Secondary, This is Gas SCADA project, so if you think there are special points that should be taken in considration plz let me know. dchartier reliability being one of the most important. one of means that other factor very important, could you plz notify? I/Os on a separate network to ensure that the flow of data to the PLC is never interrupted or limited. do you mean kind of redundancy or kind of design for the project. Then the SCADA and HMIs are setup on their own link,because they can cause a much greater load on communication functions Can I conclude from that you have one network that links the control devices, and other one that links the Operator station, printers ..etc Often Profibus-DP will be used for the I/O comms, Ethernet for the SCADA/HMI. what is the limitation for using ProFibus, the distance i mean? Finally, from my basic research on the web and some books for specific requirments with regard to amount of data, bandwidth, response time and longest distannce for large area a DNP 3.0 and IEC 870-5-101 can be used. DNP 3.0 sends small number of large sized data while IEC 870-5-101 send a large number of small sized data. my confusion comes from this artcle: "The choice of the protocol between options is made depending upon what country the target application will be in, i.e in North America DNP 3 would be the obvious choice, while in Europe IEC 60870 would be the clear winner" whatyour advice for using the DNP or IEC. what is the factors that affect to choose one of these? Thanx in advanced Omar
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4/28/2009 1:31 PM	Rate (1)
dchartier Grandmaster-Expert Joined: 9/27/2006 Last visit: 3/22/2025 Posts: 12344 Rating: (2707)	Hello Omar; First, I have not much information on DNP 3.0 or the IEC substation protocols. It is rare that we use them, and if we have to we use gateways (for example, from IEC to Profibus-DP: see Prolinx gateways, from Prosoft Techologies). The fact is that the Automation and Drives division of Siemens (the one which hosts this forum) has no drivers for substation protocols in their controllers, as we generally work in the process and manufacturing industries, nort in power generation and distribution,. This is a very different world of automation, and Siemns has a division that does work with these equipments. the powerQuality division (http://www.powerquality.de/pq_da/index_e.htm). In their offerings there is a product called Sicam (http://www.sicam.de/index_e.htm) that comprises controllers, RTUs, protection relaysand communicatuion modules suited for the power industries. Please have a look, you will find drivers for IEC 60870 and IEC 61850 in the Sicam PAS documents, for example. In our projects, like I mentionned, we use Profibus-DP, for the I/O links. It is a high-speed RS-485 or fiber-optic link for remote I/O monitopring abnd control. The copper link length limitations vary with the speed selected for the bus. At highest speed (12 MB), the bsu segment can be 100m; it can be extended to 1 km with the use of repeaters (9 maximum). Fiber optics can transmit the signal over a much longer distance, up to 25 km if required. Please go to the Profibus Internationaal site for a more complete description of Profibus networks: http://www.profibus.com/pb/technology/description/ Industrial Ethernet is used for high-level networking between PLCs and SCADA stations, for example, and carry large loads of data. The basic length of a segment is limited to 100m, but switches extend this in a star topology as required..The following manual will give you an idea of the communication processors,and related equipment Siemens offers for Indusatrial Ethernet: http://support.automation.siemens.com/WW/view/en/8763736 I know this is a lot of information and can look confusing, but study it at your rythm to grasp the basics of the communication offerings from Siemens Automation and Drives. Hope this helps, Daniel Chartier

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4/28/2009 3:25 PM	Rate (0)
DeltaX Posts: 10 Rating: (0)	Thank you for your time and your kindness, that's was very helpfull. I appreciate your help so much, I'll finish study then if i have question i'll posted here. Omar Bukra
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