IEEE Power & Energy Magazine - January/February 2016 - 54

the variant model part types also plug into the eQ foundation model parts:
✔ steady-state hypothesis (ssh) model parts define the
input choices for power flow, consisting mainly of
* component status
* generation and load values
* regulation targets
* limits.
✔ topology (tp) describes the bus-branch topology that
results from eliminating switches from the model.
✔ state variables (sv) describe the steady-state solution.

Maintaining Model Parts Through Time
Network cases need to be assembled to take account of the
future view. a future view for invariant model types is normally
the present plus the set of new construction plans that should be
considered for a particular study. the ciM approach is to use
plans stored in an "incremental" form-that is, stored as a set of
changes to an eQ model part. then, any future state of an eQ
model part is the latest version of the as-built model part plus the
latest versions of each appropriate plan's incremental changes.
variant data is normally set up differently. setup processes
differ for different study assumptions and are often customized to pull data from outage schedules, market outcomes,
load forecasts, etc. such setup processes will, however, always
produce standard ciM variant model parts, which will then
plug directly into the invariant eQ model part bases.

Operations, Procedures, and Audit Trails
the ciM architecture facilitates the definition of generic
operators on ciM data sets. For example, because all model
parts follow a similar pattern, it is straightforward to define
"composition" as a generic operation that merges the model
parts as a step in preparing a case. similarly, "apply incremental" can be an operation that adds a plan to a model part as a
step in preparing a case. even steps like "run my power flow"
or "run my network equivalent procedure" can be expressed
as operations on ciM model parts.

this aspect of ciM work is still in development, but the result
is expected to be a language that may be used in the future tense
for defining case assembly procedures and in the past tense for
expressing a precise audit trail of the operations that produced a
given network analysis case. this latter is an extremely important goal because one of the most manual chores for engineers
today is the painstaking process of assuring that exactly the
right input has been used in producing a given case.

Using CIM to Design
Effective Business Processes
grid operation today employs some very complex analytical
procedures. in europe, for example, one procedure involves
daily setup and execution of 24 hourly simulations of the
european grid for the following day. running these successfully, day in and day out, requires the ability to assemble
cases involving many sources of data quickly and with low
probability of mistakes.
the ciM architecture summarized in the previous section enables such automation. the ciM generally does not
prescribe either the processes that should be run (which vary
considerably) or the design of processes. its focus is on standardizing the agreements about exchanged data structures
on which these processes depend. however, in setting those
agreements, it has considered how to enable simple errorfree composition of data parts from many sources, which is
the most difficult element of the process.
despite its not being prescriptive about processes, the
ciM work provides some very useful guidance toward managing network analysis processes. in current practice, very
complex processes have evolved based on little or no underlying data architecture. by contrast, the main ciM idea is
simple: establish a strong data architecture and build processes on it.
the proper approach can be viewed in four layers, as shown
in Figure 4. ciM standards are at level 0. everything else builds
on the ciM as the common language of network modeling. iec
standards provide the core, but it is important to understand that

Level 3:
Network Model Business Processes

* Integrate Sources and Consumers with Network Model Management
* Automate Business Processes Based on Network Model Management

Level 2:
Network Model Management

* Repositories for Model Parts
* Facilities for Managing Model Parts and Assembling Cases
* Hub for CIM Compliant Exchange of Data

Level 1:
Data Management Responsibilities

* Organize Modeling Responsibility Among Cooperating Entities
* Define CIM Framework Agreements
* Define Case Assembly Procedures

Level 0:
CIM Semantic Standards

* Shared Definition of Data Structure and Meaning
* Standards for Model Part Data Exchange
* Methodology for Network Model Management

figure 4. The four-layer approach to establishing a network model data architecture.
54

ieee power & energy magazine

january/february 2016

Table of Contents for the Digital Edition of IEEE Power & Energy Magazine - January/February 2016