Thursday, November 12, 2015

Question & Answer: Are “valKind” and “valImport” related?

The configuration of systems and IEDs with IEC 61850 tools (system tools, IED tools, protocol stacks) is a challenge for people involved in power system protection, monitoring, and automation.

I guess that you have some experience with the many rules and the underlying philosophy that are crucial for the correct operation of interconnected IEDs.

Quite often it is obvious how to apply a given rule in the configuration language (IEC 61850-6 SCL). First of all: You have to take into account the standard document AND the green tissues!

Example on the relation between “valKind” and “valImport”. Tissue 804 introduces the new attribute “valImport” in an SCL document:

The need for that “valImport” attribute is discussed at the bottom of the tissue 804. The solution is well defined.

The two attributes can be applied for data attributes configured in an SCL file. There are two different categories of data attributes:

1. Models of “process” related information, e.g., scale factor of an Integer modeled measurement.

2. Models of “communication service” related information, e.g., Trigger options or integrity period of a report control block.

If in a SCL document (SCD) the process related values (e.g., scale) SHALL be fixed, these values must be set and declared as fixed. It is not allowed by an IED tool nor online to change these (fixed) values: Here are the corresponding attribute settings (valKind=RO AND valImport=false).

We have to be careful with rules (not defined in the standards) like the following:

If valKind=Set THEN valImport=true (if I can overwrite a value with a service, it makes sense to allow to configure a value at tool level; it may be useful for communication service related information of a control block, but not for process related information).

Be careful with the combinations of these two attributes … they are independent of each other. And: Not all tools may understand the philosophy below.

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