Siemens Simatic S5 Problem

[sns]

I am facing a problem with a siemens s5 system, the topology of which is attached. This PLC basically controls are drawline and has two buses (profibus). One for controlling the DC drives (Siemens 6RE24) and the second for the remote ET stations, of which there are 19. The diagram of their topology is also attached.

The problem is that on the CPU 2 (Interlock CPU, with a red dot), QVZ fault comes up after the drawline/processing line starts. This fault comes up after about 10 mintues or so of running operation.

After checking the QVZ status bit using the iStack, the fault comes down to station 16, 17, 18 or 19, although always from these four but is random at each occurence.

Also, we're using a Softing PBT3 profibus tester. When the drawline is running we get some signal strenght (more on that later), from each station but when the fault QVZ, all the signals die out.

Actions Taken so far,

-Changed the profibus connecters are 16,18 and 19 which has significantly increased the profibus signal strength (using Softing PBT3 profibus tester).
-Changed the IM/ET station modules at 18,19 ET stations

But the fault is still persisting, comes up after about 10 or so minutes of operation.


Actions planned
- Check the field instrumentation connected to these four stations (switches, valves)
- Increase the QVZ timeout time. My question is that will this help? Also can anyone guide me how to change that time?
- Changing the IM Card from the converter bus as no fault comes on that.
Any other tips, help would be greatly appreciated.

 

[moggie]

After checking the QVZ status bit using the iStack, the fault comes down to station 16, 17, 18 or 19, although always from these four but is random at each occurence.

.

Check the "power supply" to the station and modules at 16, 17, 18 & 19 - if possible trend it so you can see what it is like over time.
As well as checking all the profibus connections.

 

[KalleOlsen]

Hi!

Common issues are:

- Power Supply as moggie says.

- Equipotential differences between cabinets.
Use big cupper lines to fix it (best) or use fiber optic bus connection. Fx. this: http://www.helmholz.de/prod,80_107_109.html Click Pofibus/ProfibusFO.

- El. noise induced from power cables.
Separate bus cable and power cable as described in the 'Profibus installation guidelines' (www.profibus.com)

- And of course bad connedtions.

If your analyzer does not provide trending or scope function, this popular analyzer cold be worth a closer look:
http://www.procentec.com/profitrace2/

Kalle

 

[sns]

Sorted it out. Rerouted the profibus cable over a smaller route, some of it was going near power cables, although working fine for 15 years now.