Saturday, March 7, 2020

IEC 61850 Is Very Crucial For Semantic Models And Interoperability

IEC 61850 provides a huge number of generic and specific semantic models ... Logical Nodes, Data Objects, Common Data Classes, Instance-Information, Topology Information, Information Exchange, Communication, Protocols, ...

Can you please show me an easy to understand example! Here you are!

The following figure shows how (meta) model information is added to a simple voltage measurement (right upper corner). The value is wrapped with a data object model comprising with many attributes like instCVal.mag.i or units ...
The logical device and and logical node instance information is added next. Finally the semantic of the information exchange (report model) is applied to the value - sure, there is a data set involved as well (not shown here).
All this information (general and specific (instance) semantic) could be described in an SCL document (using an XML based SCL schema). Note that some configuration information, e.g., engineering unit (kV), may be contained in the SCL document only. The device needs to process implicitly the voltage in kV. A device may allow to use the SCL document to configure the device to expose the voltage in V ... or mV ... A client (SCADA or ...) may read out the model at runtime (including the engineering unit, if that is implemented as a model attribute) or may just read locally the SCL document and get the engineering unit from the file. Note: the SCL document is the main document for the models and configuration ... keep it safe!! And check the online read model against the SCL file from time to time to compare the two in order to figure out any change!

Further in our example we have a simple bay topology with electrical equipment like generator, switch gears, voltage and current sensors. This topology could be engineered and documented with the SCL (System Configuration Language) - an XML schema for a whole system. The equipment is assigned to specific information models (MMXU.PhV.phsA. ...).
The system engineering could be managed, e.g., with the Helinks STS Tool. An easy to use tool.
The generic Information Model, e.g., MMXU (defined in IEC 61850-7-4) is concatenated with the application designation (MyGenSets/Gen11).

The various levels of semantics of the Message elements are:
  1. Model Instance: Hierarchical Identification of the specific Model of Semantics (in SCL) 
  2. Message Elements: Service Type, Identification, Value, Quality, and Timestamp (ACSI - Abstract Services)
  3. Message Instance: Service Type, Instance of Identification, of Value, of Quality, and of Timestamp (Report)
  4. Message semantic (ACSI mapped to MMS)
The modeling approach of IEC 61850 could be applied in most automation domains ... especially when electric power is applied.

Let me know please if there is a similar standard model defined for automation systems that may compete with IEC 61850 and IEC 61400-25. 

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