When a data type template identifier is shared among multiple devices but their contents are different, the IEC61850 Standard recommends two solutions to overcome this problem:
1. Concatenate the IED name to the identifier string therefore making the data type template identifier unique (see clause 9.5.1, para 2).
2. Use the 'iedType' attribute to uniquely define the 'type' of IED that this data type template is relevant to and do not change the identifier string (see clause 9.5.1, para 2). This is the recommended technique.
This first technique should never cause a problem because the data type template name shall always be unique if the IED Name is appended to the identifier. Even though this solution is well suited, it is a tedious task to rename all data type templates (including references in an IED's model) and could potentially introduce errors due to the large amount of data modification, unless this can be done automatically by a tool.
The second technique is recommended by the standard, but it is not clear where the 'iedType' value is represented in the IED for cross-referencing purposes. It can be assumed that the 'type' attribute in the IED header should equal the value of the 'iedType' attribute in the data type templates but this is not specifically stated. If this is the case, should the 'type' attribute in the IED header not be included in an ICD file because there can only ever be one IED. Or if there is a 'type' attribute in the ICD, should the 'iedType' value be equal to this?
Some clarification is needed.
The 'type' attribute should not be included within the IED header for an ICD file and is only an attribute managed during the substation engineering process therefore removing any confusion for a tool which may have to manipulate data type templates.
26 Sep 06
The 'recommended technique' (point 2 mentioned above) does therefore not work and this point will be removed from part 6. Observe that the purpose of SCL is data exchange between tools, and that therefore it is not an issue that putting the IED type into the LNodeType reference is 'tedious'.
05 Sep 06
It will be made more clear, that iedType= "IED type" refers to the contents of the type attribute at the IED element.
Concerning an ICD file, naturally the use of the iedType attribute is superfluous. However, if it is left empty, then a system configuration tool is allowed to modify the types e.g. for easier reuse across several IED instances of different type, as long as the structure and value resulting at the IED instance keeps the same. Setting the iedType attribute however binds the type template to the IED type and then it is not allowed to be reused on other types.