profibus Control 1

[HamidEle]

Can Profibus replace the hardwired for the motor contro? As a plant operator, I haven't got convinced not to use hardwired control for start-stop of the motors, especialy for large motors.
Can somebody make some commments?
Thanks in advance.

 

[86ed]

Hard wired start/stop commands is still and will continue to be the preferred method for breaker control. My company has started experimenting with IEC 61850 commands from our plant DCS to various IEDs. We would implement start/stop motor commands via IEC61850 before ever using/considering profibus--especially for large motors.

 

[jraef]

If you are referring to Safety systems, there is ProfiSafe, which is a Safety qualified subset of ProfiBus. It must be implemented with the correct power hardware however.

If we are not speaking of Safety Systems, there are ways to implement Profibus control with a quasi-manual system that can take control if the Profibus comm signal is lost. One nice thing about Profibus is its ability to self-monitor. I use Siemens Simocode relays on large motors as the protection device and control interface. They have the ability to be controlled by a Profibus network on normal operations, but they use the network monitoring function to automatically allow for manual hard-wired control if the network ever goes down. In fact I set them up to be seamless transfer in most cases and I always program them to allow a hard wired E-stop to override any Profibus command, unless a disorderly shutdown will have worse consequences than an E-stop.


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[HamidEle]

Thanks for the inputs. Are there any safety concerns with Profibus system? We are trying both IEC61850 ethernet and Profibus for the motor relays. Is there any way we can communicate with both?

 

[86ed]

Both is possible. It all depends on the hardware/software capabilities of the DCS you are planning on using. However, it would probably be more elegant to stick with a single protocol for your protection & control system--if possible.

 

[jraef]

61850 is typically used for sub station automation, so you must be using some high end relays. If you've already gone to that level of relay, you are probably thinking of sticking with that protocol because the relays will be optimized for it. You would likely need a gateway of some sort to make a 61850 relay talk to a ProfiBus network.

But in my opinion, ProfiBus might be better for motor controls because it is deterministic and most Ethernet TCP/IP based networks are not. An exception to that I know of is the ProfiBus version of Ethernet, called ProfiNet. They add deterministic data to the standard TCP/IP protocol packets to make it more deterministic, but most people consider it slightly less so than ProfiBus because of the inherent nature of Ehternet to start with. In sub-station automation this may not be an issue, with motor controls it might. You would have to evaluate what that means to you.


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[HamidEle]

Thanks, Jaref,

Would you consider to use Profibus to control the motor only without any hardwired control?