Subscriber basics

The process step in the system configuration that is called subscribing does allow to connect data of an sending IED to inputs of an receiving IED. The sending data can either be stored in a control block - ReportControl, GSEControl or SampledValueControl, respectively or can be a reference to some data within the data model of the sending IED - for polling. The receiving IEDs input is modelled with the SCL element ExtRef. What we call subscription becomes nothing else than updating/creating ExtRef element in the receiving IED. The connection between the sending data and receiving input is made with the several attributes within the ExtRef element: something is not correct

• iedName: the name of the sending IED
• ldName: the name of the logical device the sending data resides in
• prefix: the prefix of the logical node the sending data receives in
• lnClass: the class of the logical node the sending data resides in
• lnInst: the instance if the logical node the sending data resides in
• doName: the path through the structure of data objects names the data resides in (e.g. Pos or A.phsA for a structured data object)
• daName: the path through the structure of the data attribute names the data resides in (e.g. stVal for simple type of cVal.mag.f for complex types)

For a connection to data send with Report, GOOSE or SMV (Sampled Values) and for projects Ed2 and higher some more attributes can be written:

• srcLDInst: the instance of the logical the sending control block resides in
• srcPrefix: the prefix of the logical node the sending control bloc resides in
• srcLNClass: the class of the logical node the sending control block resides in
• srcLNInst: the instance of the logical node the sending control block resides in
• srcCBName: the name of the sending control block carrying the information
• serviceType: either GOOSE, Report or SMV depending on the service sending the data

NOTE: Report's are rarely connected to receiving IED using the subscription process. OpenSCD does only support to subscribe GOOSE and SMV for the time being

OpenSCD will over three type of basic subscription plugins for GOOSE and three for SMV. They differ in the way/how(many) ExtRefs are created/updated.

Connecting the complete GOOSE/SMV

NOTE: See subscribe to GOOSE or subscribe to sampled value stream to see how to do this with OpenSCD

In this case OpenSCD writes for every data point the GOOSE/SMV is carrying one ExtRef in the receiving IED. It does this in the first logical device in the logical node LN0. Let's see an example for GOOSE further down. There are two ExtRef each for one of the FCDA element in the DataSet connected to the GOOSE control block or GSEControl. FCDA share the date that defines the reference to the data point in the data model: ldInst, prefix, lnClass, lnInst, doName, daName. In addition the sending IED name is written to ExtRef. The rest of the attributes are identifying the control block the FCDAs are connected with/are carried by.

NOTE: The fact that both the FCDA are connected is a matter of choice and must not necessary be done as well as the fact that the ExtRef are allocated to the first logical node LN0 in the receiving IED. This is what differentiates this type of connection to the others further down below.

<IED name="sendingIED" ...>
    <AccessPoint ...>
        <Server>
            <LDevice inst="sendingLD">
                <LN0 prefix="" lnClass="LLN0" lnInst="">
                    <DataSet name="someDS">
                        <FCDA ldInst="CircuitBreaker" prefix="CB" lnClass="XCBR" lnInst="1" doName="Pos" daName="stVal" fc="ST"/>
                        <FCDA ldInst="Meas" prefix="Meas" lnClass="MMXU" lnInst="1" doName="A.phsA" daName="cVal.mag.f" fc="ST"/>
                    </DataSet>
                    <GSEControl name="gooseCB" datSet="someDS">
                        ...
                    <GSEControl>
                </LN0>
                ...
            </LDevice>
        </Server>
    </AccessPoint>
</IED>
...
<IED name="receivingIED" ...>
    <AccessPoint ...>
        <Server>
            <LDevice inst="receivingLD">
                <LN0 prefix="" lnClass="LLN0" lnInst="">
                    ...
                    <Inputs name="someDS">
                        <ExtRef iedName="sendingIED" ldInst="CircuitBreaker" prefix="CB" lnClass="XCBR" lnInst="1" doName="Pos" daName="stVal" serviceType="GOOSE" srcLDInst="sendingLD" srcPrefix="" srcLNClass="LLN0" srcLNInst="" srcCBName="gooseCB"/>
                        <ExtRef iedName="sendingIED" ldInst="Meas" prefix="Meas" lnClass="MMXU" lnInst="1" doName="A.phsA" daName="cVal.mag.f" serviceType="GOOSE" srcLDInst="sendingLD" srcPrefix="" srcLNClass="LLN0" srcLNInst="" srcCBName="gooseCB" />
                    </Inputs>
                </LN0>
                ...
            </LDevice>
        </Server>
    </AccessPoint>
</IED>

Connecting the single data from GOOSE/SMV

NOTE: Not implemented yet in OpenSCD!

In this case OpenSCD writes for the selected data point in a GOOSE/SMV control block one ExtRef in the receiving IED. The location of the ExtRef can be selected by the user and can be any logical node in the server. Let's see an example for GOOSE further down.

There is only oneExtRef representing the connection to the selected FCDA element in the DataSet connected to the GOOSE control block or GSEControl. FCDA share the date that defines the reference to the data point in the data model: ldInst, prefix, lnClass, lnInst, doName, daName. The allocation to the logical node is done by the user and allows to better sort in the project.

NOTE: The connection of single FCDA element and the free choice fo the allocation of the ExtRef in the receiving IED differentiates this method from the other two.

<IED name="sendingIED" ...>
    <AccessPoint ...>
        <Server>
            <LDevice inst="sendingLD">
                <LN0 prefix="" lnClass="LLN0" lnInst="">
                    <DataSet name="someDS">
                        <FCDA ldInst="CircuitBreaker" prefix="CB" lnClass="XCBR" lnInst="1" doName="Pos" daName="stVal" fc="ST"/>
                        <FCDA ldInst="Meas" prefix="Meas" lnClass="MMXU" lnInst="1" doName="A.phsA" daName="cVal.mag.f" fc="ST"/>
                    </DataSet>
                    <GSEControl name="gooseCB" datSet="someDS">
                        ...
                    <GSEControl>
                </LN0>
                ...
            </LDevice>
        </Server>
    </AccessPoint>
</IED>
...
<IED name="receivingIED" ...>
    <AccessPoint ...>
        <Server>
            <LDevice inst="receivingLD">
                ...
                <LN prefix="someLN" lnClass="CILO" lnInst="1">
                    ...
                    <Inputs name="someDS">
                        <ExtRef iedName="sendingIED" ldInst="CircuitBreaker" prefix="CB" lnClass="XCBR" lnInst="1" doName="Pos" daName="stVal" serviceType="GOOSE" srcLDInst="sendingLD" srcPrefix="" srcLNClass="LLN0" srcLNInst="" srcCBName="gooseCB"/>
                    </Inputs>
                </LN>
                ...
            </LDevice>
        </Server>
    </AccessPoint>
</IED>

Connecting on later binding type inputs

NOTE: Not implemented yet in OpenSCD!

Later binding is a concept that allows to predefine ExtRef elements in the IED configuration Tool (ICT) prior to system configuration. You can see, if a ExtRef is predefined by the attribute intAddr. This is a string set by the ICT to identify which internal function is using this specific input. This means that the OpenSCD does not create a new ExtRef element but updates existing ones.

Let's see an example for GOOSE further down. There is only oneExtRef representing the connection to the selected FCDA element in the DataSet connected to the GOOSE control block or GSEControl. FCDA share the date that defines the reference to the data point in the data model: ldInst, prefix, lnClass, lnInst, doName, daName. The intAddr is already predefined and must not be altered nor can OpenSCD delete such an ExtRef

NOTE: The connection of single FCDA element to an existing ExtRef with instAddr set makes this type of plugin unique compared to the others.

<IED name="sendingIED" ...>
    <AccessPoint ...>
        <Server>
            <LDevice inst="sendingLD">
                <LN0 prefix="" lnClass="LLN0" lnInst="">
                    <DataSet name="someDS">
                        <FCDA ldInst="CircuitBreaker" prefix="CB" lnClass="XCBR" lnInst="1" doName="Pos" daName="stVal" fc="ST"/>
                        <FCDA ldInst="Meas" prefix="Meas" lnClass="MMXU" lnInst="1" doName="A.phsA" daName="cVal.mag.f" fc="ST"/>
                    </DataSet>
                    <GSEControl name="gooseCB" datSet="someDS">
                        ...
                    <GSEControl>
                </LN0>
                ...
            </LDevice>
        </Server>
    </AccessPoint>
</IED>
...
<IED name="receivingIED" ...>
    <AccessPoint ...>
        <Server>
            <LDevice inst="receivingLD">
                ...
                <LN prefix="someLN" lnClass="CILO" lnInst="1">
                    ...
                    <Inputs name="someDS">
                        <ExtRef iedName="sendingIED" ldInst="CircuitBreaker" prefix="CB" lnClass="XCBR" lnInst="1" doName="Pos" daName="stVal" intAddr="someIntAddr" serviceType="GOOSE" srcLDInst="sendingLD" srcPrefix="" srcLNClass="LLN0" srcLNInst="" srcCBName="gooseCB"/>
                    </Inputs>
                </LN>
                ...
            </LDevice>
        </Server>
    </AccessPoint>
</IED>