Redundant system not working when Rack 0 CPU goes stop mode even when rack 1 CPU in run mode

Dear All,

I am using S7 414 - 4H redundant station. Both the CPU (Rack 0 and Rack 1) are going to run mode once we switch on the system and the entire plant is working fine. Even if the master is switched to Rack 1 also the system working fine. 

My problem is when the rack 0 CPU is going to stop mode or any fault/power fail in rack 0 then the rack 1 switching as master but no communication is happening to the rack 1 from my programming device or from my SCADA system. But still the rack 1 CPU in RUN mode. 

I have tried the following things,

1. To check the Rack 1 CPU is really working fine or showing falsely as RUN, when both the CPU is in RUN mode i removed profibus cable from Rack 0 CPU but still the system is communicating to the Slave devices and getting the field values. This confirming that Rack 1 CPU is working fine and communicating to the field devices and synchronizing with Rack 0 PLC.

2. To check my Ethernet communication i performed Switching off of the Rack 0 CPU completely and loaded the PLC program in Rack 1, it was downloading to the CPU. So confirmed my ethernet cable and CP module of the CPU working fine. But couldn't able to go to online. If i tried to go online, it shows no online connection available. 

3. When i switching the mode switch in Rack 0 CPU to stop mode, and when checking from my programming device about the operating modes, It showing that H Station - Solo mode, Rack 0 CPU STOP mode, and Rack 1 CPU - RUN mode. But when i tried to monitor any of the Function calls and when going to online, it shows the System in STOP mode (At bottom right of the window).

Kindly help me to solve the issue.

Note : I can put the entire plant into non-operational for a day or two.

Attached the HW config file.

Hello Arunkpm,

Can you give us any diagram/sketch for your Ethernet network and tell us how you connect both programming device and SCADA to your H station?

I feel you are always connected to a single CPU at a time.

In case you are connected to the  CPU is STOP, can you press Ctrl+D on each CPU to view its diagnostics?

Do you have Siemens SCADA software? or is it a third party SCADA over an OPC server?

Is there a configured fault-tolerant connection with this SCADA?

Regards,

H-H

Dear H-H,

1. Both Rack 0 and Rack 1 CP connected with ethernet network, when trying to ping both the CPs from PC, its pinging. (In my case Rack 0 IP address is 192.168.0.1 and Rack 1 is 192.168.0.2).

2. Am using Siemens SCADA but its not WinCC, but its WinCC OA. It has feature for communicating to redundant device.

3. To check whether Rack 1 CPU is communicating to my programming device, i switched off Rack 0 PLC and tried pinging Rack 1 CP, its working, going online for diagnosing HardWare page, there it is going online, this confirms ethernet connectivity between PG/PD to Rack 1 CPU. 

But when am trying to go online for the Blocks (Function/OB/DB) its showing error that Not able to connect.

I feel there should be no HW issue. some configuration/setting is problem.

awaiting for your guidance.

Hello Arunkpm,

When CPU in rack 0 is in STOP, open your block editor, click on PLC menu and click on "select online CPU". A window will appear allowing you to select CPU in RACK 1.

As for the WinCC OA. I don't know how the connection is configured but you can see in Netpro if there is any configure S7-fault-tolerant connection configured to PC station.

If you can find this connection, then you can monitor connection status online.

Best regards,

H-H

Dear H-H,

Thanks for your reply. 

Yes once changing the CPU for online connection it is communicating. 

And in SCADA it was my stupid mistake, the winCC OA has setting for redundant device, we need to assign IP address of Rack 0 and Rack 1 CPU in that. I have did typo mistake in place of Rack 1 IP address. 

Now everything working fine. Thanks again.