Good day all.

I am experiencing a problem in our plant. We have 5 S7-400 PLCs for 5 different units using PCS7 SCADA system. Every 8 days we experience a problem that seems to affect all PROFIBUS (PB) device on the network. 1 unit is different from others and the rest 4 are identical. The set up with the 4 units is 1 PB network from the CPU and two separate networks using profibus cards. The one unit is affected first and the next follows. The fault in the end is picked up on the SIMOCODE Pro V devices that goes into a DEVICE and GEN. FAULT which can only be reset by power cycling each and every SIMOCODE device. 

Hello,

maybe first basic hint, is any chance to check some diagnostic buffers for events? They must include something important in my opinion.

Duris_I

Hello,

maybe first basic hint, is any chance to check some diagnostic buffers for events? They must include something important in my opinion.

 Hello Duris,

Thank you for the suggestion. I have had a look in the CPU Diagnostic buffer. The devices just starts to disappear one by one giving a message 'Distributed I/Os. station failure' as if the had been switched off but the haven't.

Hello Alexander;

With so few details on your installation, it is difficult to provide useful replies to your situation.

It might be helpful to show us the contents of the CPU's diagnostic buffer; use the Save AS... button on the diagnostic buffer page to transfer all messages to a text file that can be attached to your posts.

One thing I would like to look at is the timing of the station losses; if they are lost at the exact same time, it could be either (just a few possibilities):

- a power problem on the Profibus nodes(if they are all powered from the same source and it becomes unstable),

- a termination problem; both end stations (the first and last physical nodes on your network) must have termination resistors set to ON and must remain powered at all times to activate the termination circuit. if the termination is lost (power is removed from the station) reflections appear on the network and the CPU master can be submerged by erroneous messages that overwhelm it, and the network fails.

- EMC issues, where the Profibus cable is too close to an electric field, such as a motor turning on; this may induce voltage on the network connections and make it fails also.

See if any of these ideas help you, check all cable runs and verify every Profibus connectior for adequate wiring (validate especially the shield connection, proper grounding is imperative). And see if the links below can be helpful.

TOP 5 REASONS YOUR PROFIBUS NETWORK FAILED

https://us.profinet.com/top-5-reasons-your-profibus-network-failed/

A short guide to addressing EMC on PROFIBUS – Procentec

https://procentec.com/about/news/2016/a-short-guide-to-addressing-emc-on-profibus/

Tips for trouble shooting on the PROFIBUS-DP | SMAR

http://www.smar.com/en/technical-article/tips-for-trouble-shooting-on-the-profibus-dp

Installation guides- Profibus.com

https://www.profibus.com/download/?tx_solr%5Bfilter%5D%5B0%5D=technology%3APROFIBUS&tx_solr%5Bfilter%5D%5B1%5D=targetgroup%3AUser&tx_solr%5Bfilter%5D%5B2%5D=group%3AInstallation+Guide

Hope this helps,

Daniel Chartier

dchartier

Hello Alexander;

With so few details on your installation, it is difficult to provide useful replies to your situation.

It might be helpful to show us the contents of the CPU's diagnostic buffer; use the Save AS... button on the diagnostic buffer page to transfer all messages to a text file that can be attached to your posts.

One thing I would like to look at is the timing of the station losses; if they are lost at the exact same time, it could be either (just a few possibilities):

- a power problem on the Profibus nodes(if they are all powered from the same source and it becomes unstable),

- a termination problem; both end stations (the first and last physical nodes on your network) must have termination resistors set to ON and must remain powered at all times to activate the termination circuit. if the termination is lost (power is removed from the station) reflections appear on the network and the CPU master can be submerged by erroneous messages that overwhelm it, and the network fails.

- EMC issues, where the Profibus cable is too close to an electric field, such as a motor turning on; this may induce voltage on the network connections and make it fails also.

See if any of these ideas help you, check all cable runs and verify every Profibus connectior for adequate wiring (validate especially the shield connection, proper grounding is imperative). And see if the links below can be helpful.

TOP 5 REASONS YOUR PROFIBUS NETWORK FAILED

https://us.profinet.com/top-5-reasons-your-profibus-network-failed/

A short guide to addressing EMC on PROFIBUS – Procentec

https://procentec.com/about/news/2016/a-short-guide-to-addressing-emc-on-profibus/

Tips for trouble shooting on the PROFIBUS-DP | SMAR

http://www.smar.com/en/technical-article/tips-for-trouble-shooting-on-the-profibus-dp

Installation guides- Profibus.com

https://www.profibus.com/download/?tx_solr%5Bfilter%5D%5B0%5D=technology%3APROFIBUS&tx_solr%5Bfilter%5D%5B1%5D=targetgroup%3AUser&tx_solr%5Bfilter%5D%5B2%5D=group%3AInstallation+Guide

Hope this helps,

Daniel Chartier

 Hello Daniel,

Thank you for the help. I would not like to believe it is a installation issue since it affects SIMOCODES on 4 different PLCs each with its own network and affected at a more similar interval. We do have parts of the installation that we should still bring to conformance with the guidelines.

The problem has since not happened the past two weeks, thus I don't have CPU diagnostics log yet.

Yes, we do have a number of erroneous messages coming in on some of the units which we are also trying to attend to. But this messages are mainly coming from the field PA devices.

Yes the SIMOCODES are powered from the same power source however there is a time difference of ±10 minutes between each PLC when the SIMOCODES goes down.

Hello Alexander;

Glad to know your system has not dropped off for a few weeks. Let's hope things stabilize for some time to come.

In your maintenance procedures, keep the installation guidelines in mind, and come back whenever you get diagnostic messages from your Simocides or any other node on your network.

What about the Profibus PA diagnostic messages, do you use PA couplers or PA links to connect the PA instruments to the Profibus network? Any visible link between the PA diagnostic messages and problems on other nodes?

Hope this helps,

Daniel Chartier