Logical Nodes - GE UR Series Manual

CHAPTER 3: IEC 61850 COMMUNICATION
contain. A logical node class also defines the name and CDC of each of its data objects. IEC 61850 7-4:2010 clause 6
defines the semantic of standard data object names. For instance, the Instantaneous overcurrent logical node class, which
has class name PIOC, requires an Op data object with the following CDC Protection activation information (ACT) and
semantic:
"Operate (common data classes ACT) indicates the trip decision of a protection function (LN). The trip itself is issued by
PTRC."
Logical node class PIOC also requires the mandatory data object Beh (Behaviour, meaning on, off, test, and so on) and
permits the optional data objects Str (Start), OpCntRs (Resettable operation counter), StrVal (Start value setting) and several
others from the common logical node class. It is possible for a device manufacturer to add data objects in addition to
those specified by a logical node class, but the expansion rules in IEC 61850 7-1:2011 clause 14 must be followed. The UR
series devices in fact do extend the standard logical nodes in many cases; the data objects implemented are as tabulated
in clause 3.4 MICS.
Logical node names are required to be formed from the four-character logical node class name that it implements, a prefix
text, and a suffix instance number. An example is PhsIocPIOC1, in which "PIOC" is the implemented logical node class
name, "PhsIoc" is the prefix, and "1" is the instance number. UR devices adopt the convention that the prefix identifies the
UR element that the logical node is used to model, and the instance number is the UR element number. For instance, all
logical nodes used to model the AC sources use the prefix ACsrc. The logical nodes used to model AC source 1 have logical
node instance 1, the logical nodes used to model AC source 2 have logical node instance 2, and so on. Thus the names for
logical nodes modelling AC source 1 are ACsrcMMXU1, ACsrcMMXN1, and ACsrcMSQI1. Prefixes and instance numbers are
fixed in UR devices, except that three special logical nodes can have user configurable prefixes (GGIO1, GGIO2, and GGIO4).
A collection of related logical nodes are combined into an entity at the next level up in the hierarchy known as a Logical
Device. Logical devices are required to have one logical node implementing logical node LLN0, which addresses common
issues for the containing logical device. Logical devices can also contain as many logical nodes as desired. UR devices
have six logical devices, with logical node instance names and contained logical nodes as generally described in the
following table. The logical device each logical node is assigned to is as specified in clause 3.4 MICS.
Table 3-1: Logical nodes
Logical device instance Generally contains logical nodes modelling...
name
Master communications, including GOOSE, reports, Remote I/O, Direct I/O, Virtual Inputs, Modbus, DNP, and setting
group control
Prot protection and protection-related functions
Ctrl control and monitoring functions
System power system devices: breakers, switches, CTs, VTs, and so on, including interfaces to these, such as AC
inputs, contact I/O, transducer I/O, HardFiber I/O
Meter metering and measurement (other than PMU), including AC sources
Gen FlexLogic, Virtual Outputs, non-volatile latches, FlexElements, recording (for example oscillography), security,
front panel, clock
Logical devices have a product-related name and optionally a function-related name. The product-related name consists
of the logical device instance name (see table) prefixed by the configured IED name. The function-related name is freely
configurable, although the standard strongly recommends use of the IEC 81346 series for the derivation of function related
name. The function-related names are used only when configured by the user, and then only in communications, not in
Substation Configuration Language (SCL). The product-related name is used in SCL, and when no function-related name is
configured, in communications. Note that the symbol "LDName" is used in standard documents to represent either the
function-related or product-related name as appropriate to the context, while "ldName" is used to define the function-
related name. Upper/lower case is critically significant in many 61850 names.
The complete set of logical devices in an IED are combined into an entity at the next level up in the hierarchy known as a
Server. Only one server exists in most IEDs, including UR devices, so a server can usually be considered synonymous with
the IED. The logical devices in an IED can be arranged in a hierarchical structure. Certain entities like revision counters have
a scope that extends to lower levels that do not contain an instance of that entity. UR series devices arrange their logical
devices such that the Master logical device is the root of the hierarchy, and all other logical devices are direct descendants
of Master.
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