Saturday, March 16, 2013

When to use Operate Service and when SetDataValues?

The IEC 61850-7-2 abstract services Operate and SetDataValues are both mapped to MMS Write in IEC 61850-8-1. So, what makes a MMS Write service an Operate or a SetDataValues?

The two services and the mapping are sketched here:


The first mapping is showing the Operate service (as part of the control model):


The Operate service is used in conjunction with the control model (defining state machines, select-before-operate, time-activated control,…). Control service models require a special information model: controllable Common Data Classes, e.g., SPC – Controllable Single Point. The model comprises attributes defined by the CDC and the service parameter ctlVal: these are shown in the MMS Variable as a structure “Oper” with the components: ctlVal, origin, ctlNum, T, Test, Check. These have to written at MMS level. These are always required for Operate even if you need just ctlVal !!

The settable DataObjects require the MMS Write as shown in the following figure:


In IEC 61850-7-3 it is defined exactly which services are to be used for the various attributes in the Common Data Classes. Example for controllable DataObjects:

Note that the FC=CO is defined in 8-1 !

Note also that client user interfaces (like the IEDScout) may use different service names than 7-2 or MMS.


Iqbal said...

Dear Mr. Schwarz,

I'm wondering how do we perform control in IEC 61850 Edition 2 using a client simulator (e.g. IED Scout)? For edition 1 control IEDs which I am having in my lab, using IED Scout, I just simply collapse the data tree until attribute level and perform the control function depending on the control mode(E.g.E01F34LCC1/CSWI1$CO$Pos$Oper$ctlVal). Since in Edition 2 the attribute ctval is no longer assigned to the Functional Constraint CO, I am assuming that I cannot follow the same method to perform the control function. Can you please enlighten me in this matter?

Karlheinz Schwarz said...

Thanks for the question.
The FC=CO is still there. It just Comes into existence with part IEC 61850-8-1 Edition 2.

You have to "Write" ALL components of the Oper-Structure together in one request:

Write (or Control) e.g.E01F34LCC1/CSWI1$CO$Pos$Oper.

That's it.

Iqbal said...

Dear Mr. Schwarz,
Thank you very much for the clarifications!This has been bugging me for a while. Now, I just have to obtain an Edition 2 compliant control IED to test this ^_^.Thanks again!