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| 6/14/2011 4:49 PM | |
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Posts: 30 Rating:
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Dear All, I want to designe my network based on Redundant F.O. for communicating between CCR and Remote I/O's using OLM. My plant is a power plant that DCS shall send trip commands to the main feeders ( in SS) to be shed within 0.2 second from the detection of generator trip. what's the best configuration. I have attached my plant overview as attach. In this config i have 2 rings,(4.2 Km & 6.15 Km) i have another option to merge them and have a ring with 10.35 Km lenght. Which of them is better? i think for this spec, it's better to us CPU 417-H and using OLM G12. i want to know which item's are important to design this nework. For exampne BIT Times,......? Is there any good refrence for design this type of config? AttachmentDouble-Ring.pdf (268 Downloads) |
| 6/14/2011 7:46 PM | |
Joined: 9/27/2006 Last visit: 3/17/2025 Posts: 12344 Rating:
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Hello Behrooz; You will find much information on OLM topologies and parameters in the following manual: OLM operating manual:http://support.automation.siemens.com/WW/view/en/30006392 Please make sure you read chapter 3, on OLM topolgies, and especially chapter 5, on power budgets and link power margin. This will be crucial to your design, and you might find that your maintaining the 2 loops you had in mind could be beneficial to your project. Here is also a small FAQ on redundant ring implementation: http://support.automation.siemens.com/WW/view/en/19758281 Hope this helps, Daniel Chartier |
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| 6/14/2011 9:10 PM | |
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Posts: 148 Rating:
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| 6/15/2011 6:36 AM | |
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Posts: 30 Rating:
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Dear Daniel, Thanks for ur quick reply, As you can see in following document, an important item to design a nework is BIT TIMES: I want more information about it:(Page 32,33) SIMATIC NET Twisted-Pair and Fiber-Optic Networks Link: https://support.automation.siemens.com/WW/llisapi.dll?query=SIMATIC+NET+Twisted-Pair+and+Fiber-Optic+Networks&func=cslib.cssearch&content=adsearch%2Fadsearch.aspx&lang=en&siteid=cseus&objaction=cssearch&searchinprim=0&nodeid0=10805951&x=0&y=0 [schnippschnapp] new question is splitted to what''s the best configuration to have these two ring on one profibus path. Regards, Behrooz |
Last edited by: O_Moderator at: 6/15/2011 1:40 PM |
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| 6/15/2011 2:26 PM | |
Joined: 10/7/2005 Last visit: 3/18/2025 Posts: 3042 Rating:
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Hello Behrooz "Bit Time" (aka "Tbit") on Profibus is simply1/baudrateand the offcial definition for it is (ref www.profibus.com --> Products --> Glossary): The bit time Tbit is the time which elapses during the transmission of one bit measured in ns (nanoseconds). It depends on the Baudrate and is calculated as follows Tbit = 1 (bit) / Baudrate (bit/s). Examples: 12 Mbit/s --> Tbit = 83 ns 1,5 Mbit/s --> Tbit = 667 ns. So the higher the baudrate you choose for your Profibus, the shorter the bit time. My question to you is: Why do you believe it is an important design aspect of the Network? |
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| 6/16/2011 2:07 AM | |
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Joined: 10/7/2005 Last visit: 3/18/2025 Posts: 3042 Rating:
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Hello Behrooz even though an OLM causes a signal delay of <=6.5 Tbits, it will be the least of your worries when estimating the overall system response/reaction time. Example: You run your bus at 1.5Mbps which means aTbit of 667 ns and have 4 OLM's in your signal path,your OLM based delay will be a miniscule 17 microseconds (4 * 6.5 * 667 ns). To get an idea of thesystem response/reaction time, you'll need to take a number of things into account and evalute the whole signal chain starting withsignal source and ending with thedevice that executes the action. Have a look at the thread below where the pricinples are further explained and links to the relevant manuals can be found: Choosing decentral periphery for time critical applications Note too the advise given in your other thread HERE. Question: Is this a safety relevant application (Process or Machine safety) and are safety I/O's involved in this? If so, the relevant safety manualswill contain additional information about reaction times calculation. I hope this helps |
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