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Alarm acknowledge

Created by: Alejandro Barraza at: 7/20/2011 10:20 PM (9 Replies)

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7/20/2011 10:20 PM	Rate (0)
Alejandro Barraza Advanced Member Joined: 9/22/2010 Last visit: 11/20/2024 Posts: 14 Rating: (0)	It happened that a voltage drop caused a power failure in a S7-400 PLC (416 CPU). In diagnostic buffer there was a message of power failure, and the reboot process. The situation we noticed is the following: After the voltage was restored and rebooted the PLC, there were issues in the WinCC communication, the alarm handling was incorrect, The alarms were not generated, and the existing ones didn't dissapear when acknowledged, in fact if we acknowledge any alarm it caused an error in wincc, making it freeze for a couple of seconds and then dropping the connection, then the connection eventually came back as long we do not ack any alarm, we were able to change a setpoint in a faceplate, or the operating mode from manual to auto, and also see the process variables but no alarms or messages were generated, the solution was to make a clear/reset and the the alarms and WinCC acknowledge worked fine, the question is: Is the PLC damaged?

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7/21/2011 12:45 AM	Rate (0)
Phantom75 Posts: 2661 Rating: (279)	I do not think the PLC is damaged. The worst I can think of is, there is a problem with the RAM. Is the backup battery ok?
Phantom75 Posts: 2661 Rating: (279)
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7/21/2011 4:58 AM	Rate (0)
Alejandro Barraza Advanced Member Joined: 9/22/2010 Last visit: 11/20/2024 Posts: 14 Rating: (0)	No RAM issues, but the diagnostic buffer shows an entry regarding a batt failure, at least one batt is faulty, should be just replace the battery, does a battery failure causes this strange behavior for the alarms? how is related?

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7/21/2011 7:05 AM	Rate (0)
SVg Posts: 50 Rating: (1)	Hi, Keep the battery selection for 1 battery and check..........
SVg Posts: 50 Rating: (1)
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7/21/2011 5:49 PM	Rate (0)
Phantom75 Posts: 2661 Rating: (279)	Alejandro Barraza No RAM issues, but the diagnostic buffer shows an entry regarding a batt failure, at least one batt is faulty, should be just replace the battery, does a battery failure causes this strange behavior for the alarms? how is related? There should not be any relation. I agree RAM issues will result in an entirely different behavior, like PLC stop. Can you attach the diagnostic buffer? Also, look for CPU firmware updates: may be this is a known issue. Have you logged-in a Support Request? Regards
Phantom75 Posts: 2661 Rating: (279)
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10/2/2012 1:28 PM	Rate (0)
tomorrow Advanced Member Joined: 4/20/2010 Last visit: 11/19/2024 Posts: 38 Rating: (4)	Did someone had a solution? I have the same problem, PCS 7 V7.1 SP1 and I have invalid messages(timestamp) and I'm not able to acknowledge them. If I try to acknowledge them the connection to this AS breaks down and after short time it comes back. The Actual values are coming from the AS as they should, changing of alarm limits is working but acknowledging is impossible and from this AS I don't get new messages generated. Even the emergency acknowledge function is not working.... Does somebody have some hints for me? SR is already created, but help from this side is up to now not working or not usefull... thanks

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10/2/2012 4:17 PM	Rate (0)
Alejandro Barraza Advanced Member Joined: 9/22/2010 Last visit: 11/20/2024 Posts: 14 Rating: (0)	Certainly I didn't get a proper solution from Support. But in my case I was using PCS7 v7.1 no SP. What we did was to reset the PLC (cold factory reset) and reload the entie program (Hwconfig, connections, charts). And the problem hasn't re-appeared since that. Batteries were ok. (currently using 2). Altough I would recommend doing a CPU firmware upgrade.
	Last edited by: Alejandro Barraza at: 10/2/2012 4:26 PM
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12/3/2014 7:56 AM	Rate (0)
Gedas Bronze Member Joined: 6/27/2008 Last visit: 7/6/2021 Posts: 43 Rating: (4)	The same problem. CPU 417-4 FW 5.3.2, PCS7 V8.0 SP1. In our case the problem appeared after OS server restart. We now had it four times (on different PLCs in the same project) and Siemens support so far has not told us something meaningfull. We now updated FW (to 5.3.4) and can only hope that this will solve the problem, but as Siemens has not said that this is FW problem we are not sure. Maybe someone has experience on this ? Some solutions ?

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12/3/2014 8:47 AM	Rate (0)
mark1507 Platinum Expert Joined: 6/23/2008 Last visit: 11/20/2024 Posts: 1168 Rating: (283)	Hi, we had exactly the same behavior, but the reason was different. When "disable" or "enable" of alarms (by the lock in the faceplate) was used and at the same time an other oprator was aknowleding alarms, it came to the same problem. In our case the support confirmed that this is solved with update to V5.3.4 and it is even mentioned in the update description. We couldn't perform the update yet, but we believe that it will be solved with the update. Regards...
	"Expert" does not necessarily mean Siemens employee. Please cross-check your requirements always with official Siemens documentation. Also "Experts" are pleased about feedback. Please don't send support requests as PM. Questioners who don't follow up their thread will be put to my list of users to be ignored.
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This contribution was helpful to 1 thankful Users Gedas

7/20/2016 4:52 PM	Rate (0)
Hijaq_ltd Advanced Member Joined: 2/13/2013 Last visit: 4/19/2024 Posts: 2 Rating: (0)	Hi Gents, We have exactly the same issue on our plant. PCS7 8.0 SP2. One server pair, 3 PLCs. 1st and 2nd PLCs have firmware 5.3.1. The third PLC has version 5.3.3. We have these issues only with third PLC with firmware 5.3.3. Does anybody have any solution/suggestion? Thank you in advance.

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