1
Towards CIM Based Control CentersGelli Ravikumar, Student Member, IEEE, S. A. Khaparde, Senior Member, IEEE, Rushikesh K. Joshi
Abstract—New generation of future power system controlcenters need a paradigm shift in their utility IT operations,coordinated use of applications and the architectural designsto meet new challenges. However, literature on comprehensivearchitectural design and implementation towards this direction isscarce. In this paper, an architecture design and implementationaspects are demonstrated for integrating applications and formigrating legacy control centers towards future generation smartgrid. Appropriate adoption of open standards such as thecommon information model (CIM) is endorsed. Though the CIMstandard is matured at model level, many utilities are facingdifficulties in managing data exchanges. As a consequence of thelack of integration capabilities, difficulties are faced in deliveringprompt and accurate decisions in response to grid disturbances.Standards-based integration of systems and applications has be-come imperative. This paper presents an approach for integratinginter-utility and intra-utility application systems through CIMframework. The architecture comprises components for dataintegration & access, CIM based plug-in adapters and third-partyapplication integration. The details of this architecture along withthe intricate relationships between various layers and the opensource technologies are described. The proposed architectureincludes components such as CIM XML creators, CIM XMLdatabase adapters, CIM XML application adapters for powersystem applications. The applications over this architecture workas web applications. A case study involving WR 400 kV networkis illustrated to demonstrate migration strategy. Another casestudy involving load flow and topology processing applications isillustrated to elaborate the proposed architecture on data froma 400 kV 20-substation state network.
Index Terms—CIM, Client-Server model, Control Center,Legacy Migration, Power System Applications, Smart GridArchitecture, SVG.
I. INTRODUCTION
Utility application integration and coordination under the
smart power grid environment can be facilitated more effec-
tively only with standards based implementation of control
center application systems. In order to meet the ever growing
demand for energy and to achieve a competitive electricity
market, the present power utility business all over the world
is moving towards restructuring of the power industry and
towards interconnection of power networks at all levels. But
the existing utility infrastructure encompasses heterogeneous
components in both software and hardware systems. These
components are built on incongruent information models and
communication protocols, thus creating hurdles for integration.
It has been observed that the number and the complexity
of the utility business functions performed by the power
control centers are significantly higher in this power industry
Gelli ravikumar ([email protected]) and S. A. Khaparde([email protected]) are with the Department of Electrical Engineering,and Rushikesh K. Joshi ([email protected]) is with the Department ofComputer Science and Engineering, at Indian Institute of TechnologyBombay, Powai, Mumbai, India.
environment which is enabled by a change towards the smart
power grid architecture [1].
To enable inter-operable environment at intra-utility and
inter-utility control center application systems in the new
smart power grid environment, the development of common
information model (CIM) standard is a core research in this
field. In this paper a brief overview of CIM is presented
and the rationale for the inevitability of the approach in
modern power systems is discussed. In spite of availability
of adequate literature and standards documents on CIM, the
adoption of CIM in coordination with proprietary applications
for integration is still cumbersome at utility level due to a lack
of information on how to implement and manage CIM based
applications. In this context, the focus of this paper has been
to present a framework for integrating utility control center
applications through CIM, and to demonstrate the solution
architecture with case studies. The framework is aimed at
facilitating seamless integration of applications so that system
operators can coordinate with multiple application systems for
performing a grid functionality.
The rest of the paper is organized as follows: Section II
presents the overview of common information model. Section
III explains the high level strategy for migration of control
centers towards adopting CIM. Section IV elaborates the
utility application integration architecture based on the CIM
framework. Finally, two illustrative case studies are presented
in Section V.
II. A BRIEF OVERVIEW OF CIM
The field of power system industry has come across prob-
lems associated with information interoperability at conven-
tional control centers since electrical utilities relied on in-
house or proprietary systems and non-ISO standard protocols
to achieve information exchange. Therefore, the power system
architecture discipline is motivated by the need to address
information interoperability with the standard information
model such as Common Information Model (CIM) [2], which
has been designed to model the power system domain and its
applications. The goal, however, is to make minimum effort
and get maximum benefit in terms of non functional quality
attributes such as flexibility, accessibility and re-usability over
power grid applications.
The CIM standard is a power systems domain model which
has been evolving for more than two decades of collaborative
efforts by experts from multiple domains world wide [3]. CIM
has evolved into an overarching domain model that represents
the entire value chain of power sector covering wide range
of concepts. The inception, need, semantic understanding, the
static and dynamic data exchanges through CIM/RDF/XML
files, evolution of CIM, and more such case studies have
2
been reported in [2], [4]–[7]. Converters from proprietary to
CIM format using object oriented methodologies [8] and using
database methodologies [9] have also been developed. With
these CIM developments, it becomes an attractive choice for
flexible and persistent representation of data in both object-
oriented and relational database paradigms.
Although CIM has been developed as an exhaustive model
in the last two decades span, efforts are still being made to
extend the CIM to account for various factors such as market
models and graphics models [10]–[13]. CIM is already gaining
worldwide recognition and acceptance as a standard for power
system domain [14]. The power system applications of CIM
at transmission and at distribution level are described in [15]–
[17]. Thus CIM plays a significant role in the power system
industry. An implicit list of several benefits from development
and utility perspectives are as follows.
A. Benefits from Development Perspective
1) Model driven approach and a systematic development
paradigm comprising of common structure and common
semantics improves application design time complexity
and achieves better compatibility. This approach can
also avoid many semantic compatibility errors which are
otherwise difficult to find and correct.
2) CIM oriented software systems (COSS) store informa-
tion in CIM format, which removes the extra layer of
CIM translation during information exchange among
applications.
3) Improves the confidence level in information retrieval
since standard mapping is followed, eliminating the need
for interpretation of values for which documentation is
incomplete.
4) Faster implementation of application functionality and
business processes in a model driven paradigm due to
the use of proven existing technology and architectural
solutions.
5) Smoother processes for maintaining and extending ex-
isting applications due to openness and standardization
in architecture.
6) Redundancy due to replicated or overlapping data in
multiple applications can be avoided following a model
driven approach.
B. Benefits from Utility Perspective
1) Rapid integration of application systems and information
will improve utility’s capability to respond quickly to
business changes.
2) Due to standardized commercial-off-the-shelf (COTS)
applications, integration of utility functionality and busi-
ness applications can be faster and smoother.
3) Flexibility to plug-in and change third party applications.
4) Easy and fast access to intricate relationship of every
object or asset of a utility.
With this foundation of CIM, the application integration
architecture with CIM-oriented database for control centers
is described in the subsequent sections of the paper.
Fig. 1. Migration Architecture for Movement Towards Future Control Centers
III. CONTROL CENTER MIGRATION
In the above sections we have identified the problems faced
by present control centers. While addressing these problems,
it is desirable to establish a migration architecture to pave
the way towards a smooth migration of legacy control centers
to seamless control centers. Therefore the paper contemplates
on the present control center issues, and envisions an archi-
tecture for future control centers with design objectives such
as seamless integration of utility applications, availability of
information in a common model, ability to integrate third-party
applications, and seamless data exchange in inter-utility and
intra-utility application networks.
A bird’s-eye-view of the proposed architecture is depicted
in Fig. 1. The picture shows a vertical and horizontal section
looking like the mathematical symbol ∞ (infinity). The shape
infinity is depicted to suggest that every layer is open to
unbounded extension due to standardization. Further they can
inter-operate through the utility integration bus (UIB). The
vertical infinity ring is envisaged to accommodate power
system applications and third-party applications. The hori-
zontal infinity ring accommodates more general information
exchangers and CIM based adapters. These infinity layers are
integrated through a standardized UIB.
The architecture comprises of CIM oriented database repos-
itory (CIMODB) layer encompassing the third-party applica-
tion database layer. The development of CIMODB for third-
party databases mainly include three steps of identification of
third-party objects to be migrated, their mapping on the CIM
class model, and the development of converters which can
be plugged into the CIMODB to convert a third-party non-
standardized database into CIMODB. If a mapping fails to
identify CIM classes due to lack of suitable CIM classes, a
local or global extension in CIM can be proposed.
With this model as the basis, the paper demonstrates a spe-
cific solution architecture which is applied to two case studies.
The first case study brings out a process of smooth integration
of information, application and the graphical displays, while
the second case study suggests a migration path from legacy
3
Fig. 2. Architecture for CIM Integrated Applications in a Control Center
to seamless control centers.
IV. UTILITY APPLICATION INTEGRATION ARCHITECTURE
The architecture depicted in Fig. 2 demonstrates a model
for integrating power system applications with CIM oriented
database in a web enabled framework. Solution characteristics
such as service orientation, openness, seamless application
integration, interoperability, flexibility, scalability, extensibility
and semantic message payload formats are identified as signif-
icant aspects of future power system control centers. The pro-
posed architecture comprising four services with eight layers
is designed keeping view the aforementioned solution charac-
teristics. The input services include configuration, CSV-XML
conversion, CIM RDF XML and database adapter layers. The
output services include application and presentation layers.
The data services manage the storage layer over a relational
database. The validation service includes CIM conformance
through a CIM XML validation adapter to validate CIM RDF
XML files.
The implementation of this architecture is carried out via
a coordinated use of various standards and open source tech-
nologies such as Common Information Model (CIM), Unified
Modeling Language (UML), eXtensible Markup Language
(XML), Comma-separated Values (CSV) [18], Scalable Vector
Graphics (SVG) [19], PHP [20], MySQL [21], JAVA and
Python [22]. These are supported by consortia such as IEC
TC 57, W3C, OMG and the open source community. The
description of the eight layers in the proposed architecture
shown in Fig. 2 is given below.
1) Configuration & Stream Layer: This layer consists of
configuration information pertaining to network static data,
network graphical coordinates, network profile data and net-
work dynamic data streams. This layer facilitates customiza-
Fig. 3. Sequence Diagram for CIM/XML, SLDx Generator
tion to the users of the software system. In our implemen-
tation, we have used the CSV file format for representing
the information in the configuration layer as shown in the
figure. Network static data includes information about static
configurations. Network dynamic data represents dynamic
values of the components included in network static data such
as breaker and disconnecter status, and values of frequency,
voltage, phase angle, current and power flow. Network graphi-
cal coordinates represent position of each power system object
on a canvas. Network profile data includes the corresponding
static information such as CIM classes, CIM attributes, and
CIM relationships of the above mentioned network static and
dynamic information.
2) Platform Specific CIM Classes and Validation Layer:
The layer includes CIM related processors, converters, and
validator. The CIM XML validator validates the CIM XML
files for conformance in accordance with the standard IEC
61970-552 [23]. Any power system application would only
be needing some of these UML classes. A profile structure is
4
Fig. 4. Sequence Diagram for CIM/XML Graphic Generator
created for each application. A profile represents application
requirement in CIM. The real world online power system
data can then be incorporated into XML bindings confirming
to these associated schema corresponding to the profiles. A
schema file represents rules and definitions of XML tags. The
user creates the CIM profiles using CIM profile creator of
which the output is sent to XSD generator. The XSD format is
used to represent the schema files corresponding to the domain
profile models.
3) CSV-XML and CIM/XML Layers: The layer CSV-XML
imports CSV configurations and converts them into the
CIM XML format. It uses XSD schema files which capture
structural representation of the XML. The layer includes
CIM/XML static file creator, CIM/XML dynamic file creator
and CIM/XML graphic file creator for converting the config-
uration fils defined in the above configuration layer. The con-
verters import the configuration files and refer schema file to
generate the corresponding CIM/XML files. The interactions
of CIM/XML converter are shown in Fig. 3. The CSV/XML
layer includes CIM XML static files, dynamic files and graphic
files. This CIM XML database will be used to exchange the
information across control centers.
4) Database Adapter and Database Layers: This layer
is defined in order to provide data integrity, management
and consistent access to other plug-in applications. The first
purpose is to accept data from data sources in CIM XML
format and send it to data archives. The second purpose is to
retrieve the data from archives and make it available in CIM
XML format for plug-in applications. The database adapter
layer includes CIM XML converters for converting CIM XML
file database to relational database with the database operations
such as create, read, update and delete. The database layer
includes relational database storage system to archive CIM
XML file database. We have earlier presented the CIM oriented
database schema in [24].5) Application layer: The data configuration and data in-
tegration layers form a major portion of the proposed archi-
tecture. On the basis of these layers, plug-ins can be built
independently by third party developers. Thus the architecture
addresses the problem of achieving interoperability at the ap-
plication level mentioned in above sections. This layer includes
applications such as scalable vector graphics (SVG) converter
for generating graphic network diagram files, cascade style
sheets (CSS) [25] theme generator for defining styling arti-
facts, topology processor for obtaining bus branch model from
node breaker model of a power system network and load
flow adapter for integrating proprietary load flow softwares
that compute power flows over lines. The interactions of SVG
converter which generates SVG files are shown in Fig. 4.
6) Presentation Layer: The purpose of this layer is to
provide web enabled aforesaid services for integrating widely
spread power system applications. This approach is aimed
at facilitating remote execution, access and management the
myriad power system software application systems. The layer
comprises of components which act as front-end clients and
a back-end presentation server. The presentation server for-
mulates and forwards the concerns of the presentation clients
to the application layer. We have used a pull model approach
wherein the client sends a request in order to obtain a response
from the server. The request is sent in an encrypted form of
XML-http-request and the data is decrypted by the server-side
php scripts. The application programs located at the server
side are executed in accordance with the decrypted request
and subsequently the results are sent back to the client in a
html format.
V. CASE STUDY AND RESULTS
A. Case Study: WR 400 kV Network
In accordance with the scheme of developing CIMODB
from third-party databases discussed in Section III, in this
case study, we analyzed western region (WR) 400 kV network
for migration of third-party database into the proposed CIM
based architecture. The western region load dispatch center
(WRLDC) maintain their network through a GE SCADA
system. As per the proposed architectural solution strategy,
the following three steps were followed. Firstly, every ob-
ject in the WR 400 kV network under consideration was
analyzed to identify the objects that need to be mapped
to CIM, specifically those which are exchanged with other
control centers. Secondly, these objects were mapped to CIM
classes identifying the relevant attributes and relationships.
The second step is referred to as CIM profile creation. From
the profile, the XML schema was derived from the CIM
profile of the network model by using the XSD generator as
shown in Fig. 2. Thirdly, for the data conversion which is
represented in PSS/E system format, a format-specific adapter
was developed for converting PSS/E format into CIM format
to finally generate CIM XML objects. The resulting CIM
XML objects are then stored into the CIMODB which was
mentioned in the Section IV.
The prototype system was implemented using Python and
XML. It is noted that the process of analyzing and mapping
5
Fig. 5. Maharashtra 400 kV Network
needed domain experts having a coherent knowledge of the
GE system and its functionality. Once the mapping process is
done, the remaining exercise mainly involves implementation
of the format-specific adapter. In this way as prescribed in
Fig. 2, migration towards CIM can be achieved.
B. Case Study: Maharashtra 400 kV Network
An objective of this study has been to demonstrate the
generation of CIM/RDF/XML domain data for the existing
400 kV Maharashtra network so that they can be processed
by applications. Also graphics information for the network
was generated as graphics data files which are then translated
into SVG format so that the entire network is visualized. The
case study was carried out by deploying actual but offline
data traces over a laboratory implementation confirming with
the proposed CIM oriented architecture. A description of two
applications implemented in this case study is provided below.
1) Web-enabled Network Topology Processing (NTP): The
topology processor is implemented in python environment in
accordance with the algorithmic schemes presented in [26]–
[28]. The web enabled NTP application is provided as a
service by integrating it with Apache server and PHP scripts.
A database schema presented in [24] is used for storing static
and dynamic network data (switch statuses, load and genera-
tion values), topology, and graphical coordinate information.
AJAX technology is used for facilitating asynchronous calls
to be sent to the server from the client, such as calls to report
status changes of circuit breakers manually initiated by the
user by clicking through the interactive display shown in Fig.
5. The strategy of integration of CGI, AJAX and SVG into
client-server systems that is followed in this work is as de-
scribed in [29]. Common gateway interface (CGI) is a software
technology which is used to interface external applications
to the server. In this work, AJAX technology was used to
track the user initiated changes in the substation or network
diagrams and then the CGI scripts are used accordingly to
Fig. 6. Queries for Load Flow API
trigger the associated application such as topology processing
and load flow.
In the example shown in Fig. 5, as a result of toggling
status of a few switches, three islands are formed on the
network. The islands are visualized in different colors. In this
case study, the size of configuration file is 1428 KB, and the
elapsed time of generating CIM-RDF-XML and CIM graphics
XML files are 0.164 seconds and 0.128 seconds respectively.
The sizes of these generated files are 1562 KB and 1872 KB
respectively. The SVG files for the network diagram and for
all the substation diagrams are generated on-line whenever
the user triggers the click event on the browser. The SVG file
sizes and their generation times are as follows: The elapsed
time of generating the graphics SVG file for the network
diagram is 0.143 seconds and the file size is 72.9 KB. The
elapsed time of generating the graphics SVG file for each
substation diagram varies from 0.109 to 0.137 seconds, and
the file sizes are 23.4 KB to 39.8 KB in accordance with the
number of graphical objects in the diagram. In addition, the
6
time of taken by only the topology processor component is
0.112 seconds. A computer with the dual operating system
(windows 7 and ubuntu 13.04) and 4GB RAM is used for
executing the developed programs, and preparing the set-up
of both the database and the web server.
2) Load Flow Application: A load flow analysis is also
carried out by integrating Matpower, a load flow software
Matlab package into the framework. The example queries
shown in Fig. 6 are used to retrieve the required values from
the database (schema presented in [24]) for use by the load
flow application. An adapter is developed for conversion of
CIM/XML files to MatPower compatible format.
VI. CONCLUSION
Though the concept of CIM standard for coordinated use
of SCADA/EMS application systems has been dealt with
in the literature, the information on smooth migration and
implementation is scarce. Such a migration to open design and
implementation needs a paradigm shift in the basic structure.
Utilizing the recent advancements in technologies and archi-
tecture philosophy, the paper demonstrated an architecture and
related implementation aspects for migration and subsequent
application development towards future control centers. The
proposed architecture is CIM based. The solution organizes
into horizontal and vertical extensible rings with database
layers at the core.
A demonstration implementation of the architecture has
been developed with a coordinated use of open source, pro-
prietary (PSS/E) and in-house (code developed) software. A
case study of WR 400 kV network is implemented as a
demonstration of migration of a legacy utility to a CIM
based seamless utility. Another case study of 400 kV 20-
substation Maharashtra network model is implemented over
this implementation to elaborate integration of application and
web enabled visualization. Also a case study of 400 kV 20-
substation Maharashtra network model is implemented over
this implementation to elaborate integration of application
and web enabled visualization. The design of CIM oriented
application integration architecture is envisaged to be advan-
tageous from the perspectives of developers and the utilities
from the point of view of compatibility, interoperability, user-
friendliness, extensibility and openness.
ACKNOWLEDGMENT
The authors like to thank the officials of Maharashtra
State Load Dispatch Center (MSLDC) and Western Region
Load Dispatch Center (WRLDC) for providing the data of
the practical power system networks. Thanks are due to Dr.
Pradeep for his valuable technical suggestions.
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