Dual ProfiBus Network for Redundancy

[natirm]

Hi

I like to know how the cable redundancy work in profibus. In order to provide cable redundancy I like to use two bus network for each slave.

Q1. Field instrument need to have special functionality?
Q2. On the controller side, are there two Profibus Master modules for each bus line? So how can a slave response two masters in a serial protocol?

I realy cant picture the configuration in my mind??

Thx!

 

[Hydro Power Guy]

Are you referring to Profibus DP and an I/O network, or Profibus PA and an instrumentation network?

Here is a link for DP: http://www.automation.siemens.com/d...442011/pub/de/simatic-s7-400-h-excerpt_en.pdf

 

[natirm]

Ok so the difference between DP and PA is the device that you connect? This is new info for me. So according to pdf file it's possible to make redundant connection to remote I/O not field instrument itself.

So here I once again like to ask if there are any field instruments with redundant Profibus Port? I never saw anything like this.

 

[Hydro Power Guy]

Ok so the difference between DP and PA is the device that you connect?

No, they are different protocols. You can not hook up a Profibus DP device to a Profibus PA network. (or vice versa)

So according to pdf file it's possible to make redundant connection to remote I/O not field instrument itself.

I don't have that much Profibus PA background, but in my experience I am not aware of cable redundancy as an option. You can create a redundant ring using Siemens OLM's OR ELM's as an option, but this only gives you a ring structure which turns into a linear network if any one segment fails.

 

[Hydro Power Guy]

This .pdf gives a pretty good overview of how Profibus PA can be implemented.
http://www.krohne.com/fileadmin/med...munications/Fundamentals/FU_PROFIBUS_e_72.pdf

 

[Hydro Power Guy]

Can you give a little more detail of what the Profibus PA network will be connected to?
I have a feeling that you have a redundant PLC with a redundant Profibus DP I/O network and you want to integrate a Profibus PA segment into it.

 

[natirm]

To be honest I dont know the differeance between DP and PA. According to what you say I believe DP is used to communicate with remote IO and PA for field enstrument. Im not trying to achive anything right now. I have been told that emerson has valves which supports dual profibus networks but I dont think that is possible. I made some search and think its only redundant master modules where there is only one of them actively communicating with slaves. As soon as primary module fails other one takes control but they all connected to same segment.

 

[Longhorn]

Have a look at this document, section 2.5 explains redundancy configuration using DP/PA Coupler.

http://faziliao.jonweb.net/siemens/ET200/ET200M_E.PDF

PA is more frequently used in EX class areas, PA has the capability to loop power the instrument (dependant on instrument) and therefore doesnt require an aux supply. the lower baud rate of 45.45kbps means cabling lengths can go up to 2km including all spurs but is dependant on the DP/PA coupler spec. Fault disconnection electronics (FDE) in each device prevents the device from pulling the bus down by limiting the fault current to +/- 9 mA.

Hope this helps

 

[natirm]

Ok, I believe we all saying same thing. Looking at document links you provided I do NOT see two purpule cable going into Field Instrument (Valve, flow transmitter or any intelligent device that internally include profibus slave protocol).

 

[Longhorn]

Ok, I believe we all saying same thing. Looking at document links you provided I do NOT see two purpule cable going into Field Instrument

This is because the instrument side of the DP/PA Coupler is PA Profibus which is not purple cable (Commonly black), i think you will struggle to find instrumentation with build in redundancy. You would usually find that the master of the bus can be configured as a redundant module like the IM153-2