GE B30 Communications Manual page 485

CHAPTER 3: IEC 61850 COMMUNICATION G2 IMPLEMENTATION MODEL FOR GOOSE CONFIGURATION VIA SCL
However, this requires that each logical node in the receiving IED that receives a signal via GOOSE needs to be individually
configured with the final application-specific reference. This can be a disadvantage for example when a user wants to pre-
configure a setting template SCL file for the receiving IED. In the template the user can want to define an application-
specific signal, possibly used by multiple devices, that when in-service arrive via GOOSE. The ultimate source of the signal
is not known at the template-building stage, so it is not possible to enter in the template an ObjectReference to it. Also,
while at this stage, the generic semantic to the signal to be received is known; later at the system configuration stage the
signals needed as inputs to the various logical nodes in the receiving IEDs may not be obvious, especially if the signal is
input to user programmable logic.
A complementary example is where first a system configuration tool configures GOOSE connections only to the IED, then
later an IED configurator completes the connection from where the system configurator left it to the destination logical
node.
3.10.8.2 ExtRef
3
Therefore, the G2 implementation model also allows the IED to support in GOOSE connections intermediate objects at the
receiving end, one of which is as shown in the following figure.
Figure 3-19: Intermediate object at the receiving end
Each intermediate object is represented in the SCL as an ExtRef element and a data object (Ind1 in the figure) within the
same logical node. In devices that implement this feature, the ICD file contains ExtRef elements each pre-configured with
the name of the intermediate data object in its intAddr element attribute. The iedName, ldInst, prefix, lnClass, lnInst,
doName, and daName element attributes of the ExtRef elements are user-configured to reference the source of the signal
in the sending logical node, and the iedName, srcLDInst, srcPrefix, srcLNClass, srcLNInst, and srcCBName element
attributes of the ExtRef elements are user-configured to specify the GOOSE control block and thus the GOOSE message the
signal is sent in. The desc element attribute of the ExtRef element is available for the user to give the intermediate object
an application-specific name or description.
In developing a template file, the configurator is used to assign an intermediate object of the appropriate basic data type
for each signal that the IED needs to receive, by putting an application-specific name or description in the desc element
attribute of its ExtRef element. The desc element attribute is used in later stages to make the intended use of this
intermediate object apparent. In each logical node that uses the signal, the configurator is used to set the input ORG data
object to reference the stVal data attribute of the data object referenced by the corresponding intAddr element attribute.
When template configuration is complete, the configurator exports either an IID or CID file depending on the tool used,
which becomes the template file.
UR FAMILY – COMMUNICATIONS GUIDE 3-247