Logical Device (LD)

Basics

A Logical Device (LD) is an element that allows to group Logical Nodes (LN) with a Server. It does a similar job as a folder does in Windows explorer. Just imagine an IED with 1000 LNs without any way to group them in a meaningful way. The LD does not come with a lot of restriction to give users a much freedom as possible:

Name/instance definition is restricted to an alphanumeric pattern to max 64 characters
Each logical node must have at least on logical nodeLLN0and one other logical node.

Typical examples for logical devices grouping:

A protection scheme grouping all logical nodes that are needed. E.g. overcurrent protection with 4 stages each modeled with a PTOC
A circuit breaker modeled at simplest by CSWI, XCBR and CILO
…

SCL implementation

In the SCL file the element LDevice is representing a LD. It comes with two attributes: inst or name.

<IED name="..." >
<AccessPoint name="...">
...
<Server>
  <LDevice inst="P50" name="OCP51">
    <LLN0 lnClass="LLN0" ...>
    <LN ... lnClass="PTOC" inst="1" ...>
    <LN ... lnClass="PTOC" inst="2" ...>
    <LN ... lnClass="PTOC" inst="3" ...>
    <LN ... lnClass="PTOC" inst="4" ...>
  </LDevice>
  <LDevice inst="CBR" name="Circuitbreaker">
    <LLN0 lnClass="LLN0" ...>
    <LN ... lnClass="CSWI" inst="1" ...>
    <LN ... lnClass="XCBR" inst="1" ...>
    <LN ... lnClass="CILO" inst="1" ...>
  </LDevice>
  ...
</Server>
</AccessPoint>
</IED>