IEEE Power & Energy Magazine - January/February 2016 - 71

envelope for the payloads that can then be exchanged by virtually any transport. a full description of the standard envelope and the various messaging infrastructures that can be
used are in the Iec 61968-100 standard.
now, we see the tendency for transmission utilities needing to integrate their enterprise systems, and they are taking advantage of the standard canonical cIm model and
experience from the distribution world. The inverse is also
true, i.e., larger distribution utilities see the advantage in
leveraging distribution network models within many of their
business processes, and they are actively taking advantage of
the canonical cIm model and experience from the transmission world. The same type of parallelism exists within the
energy markets. The definition of both wholesale and retail
markets leverage the energy market business processes as
well as the network and distribution models.
This expansion is ongoing, and extensions continue to be
added. currently, extensions to support demand response for
markets and environmental data are in the process of being
added to the cIm model. In the european Union, the adoption of the common energy market, increased renewable
production, and the reduction of co2 emissions resulted in
accelerated use of the cIm. when the european network
of Transmission system operators for electricity started to
use the cIm in its common Grid model exchange standard,
further cIm extensions were created.

The Canonical Model
The cIm canonical model is represented in Unified modeling language (Uml) diagrams. The cIm includes a very
large number of classes, and each class has associations
describing relationships with other classes. most classes also
have attributes describing characteristics of the class. There
are three base packages contained in the canonical model:
✔ Iec 61970 contains the base power system model
including all base domain data types and the classes
and attributes used to model the electrical characteristics necessary for network analysis. These classes
and attributes are used by the other two packages as
needed to fully specify the power system models used
by their domains.
✔ Iec 61968 contains the classes and attributes used
to model the distribution system and the operational
systems within the utility. These systems include
the customer information system, oms, Dms, GIs,
advanced metering infrastructure, and mobile device
management.
✔ Iec 62325 contains the classes and attributes used to
model the market systems for the north american and
european style markets. These systems include the
day ahead and real-time markets, financial transmission rights, and settlements.
each package contains a set of objects/classes that describes
things in the real world. an object or class is a noun or thing that
is owned or operated by an entity such as an aclinesegment,
january/february 2016

PowerTransformer, or substation and is defined in terms of attributes and relationships (associations both within and between
other packages). a class attribute describes significant aspects
about the class such as the rating or resistance. The aclinesegment class has the attribute "r" for resistance. associations
connect classes and are assigned a role that describes the relationship in each direction. a PowerTransformer has an association to the substation that contains it. a single class in the
canonical cIm can have multiple relationships, but most relationships in the cIm simply carry the referenced class name as
the role.
Besides the packages and classes, there is a specific set of
concepts that are also expressed in the Uml symbols:
✔ inheritance/specialization
✔ simple association or relationship.
The rules and conventions for naming of packages,
classes, attributes, associations, and data types are fully
defined in the document "cIm model management," which
will become an Iec technical report. a draft of the document can be found at http://iectc57.ucaiug.org/modelmgrs/
shared%20Documents/.

Inheritance/Specialization
In Uml, an arrow with an enclosed arrowhead is used to
represent both inheritance and specialization. an example
of this symbol is shown between the equipment class and
the Powersystemresource class in figure 1. In the figure,
the equipment class inherits from the Powersystemresource
class and therefore "inherits" all the attributes and associations of the Powersystemresource or any classes that are in
that lineage. The equipment class is also a specialization of
the Powersystemresource class. In that same figure, conductingequipment is a specialization of the equipment class.

Simple Association/Relationship
a simple association is shown in Uml as a single line with
no arrowhead on either end. each association has a role name
and a multiplicity. The multiplicity defines how many of the
opposite class can be associated to the far end. for example,
if you have 0..n Tapchangers that have an association to 0..1
regulationschedules, it means a tap changer can have zero
or one regulation schedules or zero or one regulation schedules can apply to zero or many tap changers.

CIM Evolution
The scope of the cIm canonical model has been expanding since its inception. originally, it was interoperability
between applications, and that was expanded to interoperability between systems. a further expansion included business
processes and energy markets within a utility and additional
network analysis and distribution applications exchanges.
This has resulted in a reputation that the cIm is continuously changing, which is actually true with respect to all
extensions. The early parts, however, have been stable, particularly in recent years. when a new information model is
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Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - January/February 2016
