Technical and system requirements for advanced distribution automation

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Technical and System Requirements for
Advanced Distribution Automation

Technical Report

Technical and System
Requirements for Advanced
Distribution Automation

1010915

Final Report, June 2004

EPRI Project Manager
F. Goodman

EPRI • 3412 Hillview Avenue, Palo Alto, California 94304 • PO Box 10412, Palo Alto, California 94303 • USA
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Principal Investigator
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This report describes research sponsored by EPRI.

The report is a corporate document that should be cited in the literature in the following manner:

Technical and System Requirements for Advanced Distribution Automation, EPRI, Palo Alto,
CA: 2004. 1010915.

iii

REPORT SUMMARY

Traditional distribution systems were designed to perform one function: distribute electrical
energy to end-users. Advanced Distribution Automation (ADA) is a concept for a fully
controllable and flexible distribution system that will facilitate the exchange of both electrical
energy and information between participants and system components. This report presents
background information on distribution automation technologies and develops a roadmap to
achieve the ADA systems required for future power delivery systems.

Background
ADA will be a revolutionary approach to managing and controlling distribution systems. It will
achieve a fully controllable and automated distribution system, resulting in tremendous gains in
system reliability, power quality, and efficiency. There are two critical components to the
concept of ADA: an open communication architecture to facilitate the system monitoring and
control functions of ADA and a redeveloped electrical architecture to enable an interoperable
network of intelligent electronic devices. These two elements, working synergistically, will
comprise the distribution system of the future.

Objectives
To describe the vision for ADA and characterize its benefits for the power system of the future;
to determine the system and technology requirements for realizing this ADA vision over the next
20 years; to identify research needed to develop ADA; to define EPRI’s role in developing the
technology.

Approach
The project team reviewed existing distribution automation programs and research initiatives
from North American and international utilities, manufacturers, and research organizations. They
consulted EPRI advisors, industry experts, literature, research organizations, and standards
working group members, such as those involved in writing IEC and IEEE standards, to
characterize the needs of the future system. The team reviewed research initiatives currently
planned by EPRI and other research organizations relating to these needs and identified areas in
which research could be coordinated. In cooperation with EPRI advisors and the EPRI project
manager, the team developed preliminary timetables and estimates of research budget
requirements for the various project areas.

v

Results
The report outlines the current state of the art in distribution automation and develops a
requirements definition for ADA. Significant development in a number of technology areas will
be required to achieve the objectives and the vision of ADA. This report provides a roadmap for
these development efforts, organized into five main research areas:

1. Distribution system topologies

2. Communication and information systems

3. Advanced technologies such as power electronics

4. Sensors and monitoring systems

5. Advanced protection and control systems

The report also addresses economic issues and evaluates the value proposition for ADA based on
four categories of benefits:

1. The value of reliability and power quality

2. Improved operations and asset management

3. Reduced loses

4. Overall system energy management, reliability, and security

EPRI Perspective
The electric power distribution system faces a whole series of challenges and opportunities:
aging systems, availability of improved distribution system technologies, demand for higher
reliability, customer outage intolerance, industry restructuring, need for improved customer
service options, and management of distributed generation. These forces set the stage for
fundamental change in distribution system infrastructure. Recognizing the costs and benefits of
this change and its importance to the nation’s security and economic well-being, EPRI created
the ADA Program to help the industry develop a more economical and effective distribution
system. This report identifies the research needed to realize the ADA vision and explores ways
in which stakeholders can collaborate to further the development process.

Keywords
Distribution automation Advanced distribution automation
Substation automation Feeder automation
Distributed energy resources Distributed generation and storage
Distribution communication systems Intelligent electronic devices
Power electronics Power quality and reliability

vi

EXECUTIVE SUMMARY

Project Overview

Traditional distribution systems were designed to perform one function—distribute electrical
energy to end-users. Advanced Distribution Automation (ADA) is a concept for a fully
controllable and flexible distribution system that will facilitate the exchange of electrical energy
AND information between participants and system components. The lines between supplier and
consumer will blur because many of participants will assume both roles and will need to switch
effortlessly between these roles, possibly several times a day. The exchange of data and
information will facilitate the “supplying” or “using” of electrical energy based on dynamic
rather than static prices.

ADA is distinct from traditional distribution automation (DA). Traditional DA has been
principally concerned with automated control of basic distribution circuit switching functions.
ADA is concerned with complete automation of all the controllable equipment and functions in
the distribution system to improve strategic operation of the system. The various components are
made interoperable in ADA, and the communication and control capabilities are put in place to
operate the system. The result is added functionality and better performance, reliability, and cost,
relative to today’s system operations. In total, ADA will be a revolutionary change to distribution
system infrastructure, as opposed to simple incremental improvements to DA. However, this
revolutionary change will occur in an evolutionary manner due to the tremendous investment in
legacy systems and the rate of technological progress.

There are two critical components to the concept of ADA:

1. An open communication architecture to facilitate the system monitoring and control
functions of ADA

2. A redeveloped power system from an electrical architecture standpoint to enable an
interoperable network of components.

These two elements are synergistic and inter-related with each other and together they comprise
the distribution system of the future.

In the EPRI Electricity Technology Roadmap for the Power Delivery System and Electricity
Markets of the Future, Advanced Distribution Automation (ADA) is described as the “Heart of
the Smart Power Delivery System.” Automation will play a central role in providing the
enhanced levels of Security, Quality, Reliability, and Availability (SQRA) that must be
characteristic of future power delivery systems.

vii

This report presents background information on distribution automation technologies and
develops a roadmap to achieve the ADA systems required for the future power delivery systems.

Project Objectives

Specific objectives of the research include:
• Describe the vision for ADA and characterize the benefits for the power system of the future
• Determine the system and technology requirements for realizing this ADA vision over the
next 20 years.
• Identify existing work within EPRI and elsewhere that will contribute to meeting these
requirements.
• Identify key gaps that are the basis for development initiatives for future R&D programs.
• Recommend the future roles for EPRI in developing the technology to meet the ADA
requirements in a manner that complements work going on elsewhere.

Project Results

In order to accomplish these objectives, the report outlines the current state-of-the-art in
distribution automation and develops a requirements definition for the ADA system of the future.
This definition of requirements for the system is needed to guide and coordinate the body of
interrelated programs that will evolve ADA. Additionally, this vision of the physical possibilities
and realities of what can and cannot be achieved in ADA will serve as a basis for the business
models that make sense for the distribution business in the future.

Significant development in a number of technology areas is required to achieve the objectives
and the vision of ADA. This report explores some of the important areas where additional
development is needed after reviewing important technologies that are already available and
under development. Priorities for future development are identified and an overall roadmap for
achieving the vision is presented. Some of the important areas where development is required
include:
• Assist utility migration to open systems for automation equipment.
• Provide guidelines for utility specification of automation equipment to meet immediate needs
and also provide a migration path to fully automated systems.
• Develop and refine device models for specific application areas.
• Implement open systems in real world environments and capture lessons learned and
necessary refinements.
• Contribute to the development of key open standards specifications.
• Develop flexible electric distribution system topologies, including advanced configurations
and capabilities, such as two-way power flow, intentional islanding, microgrids, dc ring
buses, and looped secondaries.

viii

• Develop key electrical and power-electronic components that enable the flexible electric
architecture and are cornerstones of ADA (such as the intelligent universal transformer and
new solid-state switchgear).
• Develop and implement intelligent monitoring systems to identify possible equipment and
system problems, characterize causes of disturbances, evaluate interface issues with end
users and Distributed Energy Resources (DER), and utilize open communication architecture
for integration with the overall automation systems.
• Develop new approaches for fast simulation and modeling and predicting system
performance in real time (including contingency analysis for future conditions based on the
existing conditions), using information from advanced monitoring systems and improved
electrical models of the system (including end user systems and DER systems).
• Develop tools to assist utilities in developing specifications for components of ADA,
facilitating integration with the overall ADA implementation over time.

The ADA Value Proposition

The first task in the ADA research initiative will be to establish the value proposition that will
drive the next generations of product and standards development leading to the completely
automated and flexible system. The value proposition for ADA will have to consider four (4)
categories of benefits that will be extremely important for the power system of the future:

1. The value of reliability and quality. Outages and disturbances cost over $100B per year at
the present time. Improving system reliability and quality will have tremendous advantages
for end user productivity and result in benefits for the entire economy. Systems must be
structured to allocate the costs and benefits for the investments in improved reliability but the
opportunity is tremendous.

2. Improved operations and asset management. This is currently the biggest driver for
substation and distribution automation. The systems result in direct savings in investments
and operation of the delivery system. Improved asset management, reduced manpower
requirements to operate the system, faster response and clearing of faults all have tremendous
benefits. The ADA system will take these benefits to another level with advanced
diagnostics, local intelligence, and integrated operation of DER and customer systems to
benefit the entire power system.

3. Reduced losses. ADA will result in continuous optimizing of system performance, resulting
in the most efficient delivery system possible. This will take into account reconfiguration
options, integrated voltage and var management using conventional and advanced
technologies, advanced power electronics, and integrated operation of customer systems and
DER (with real-time pricing systems for incentives to be part of the system optimization).

4. Overall system energy management, reliability, and security. ADA systems will be
integrated with wide area energy management systems for overall optimization of generation
mixes, system demand, power flows, and system security. The flexibility added with DER
and customer load management is tremendous.

ix

The ADA Development Roadmap

Achieving these benefits requires a coordinated development effort involving a number of
important initiatives. In this report, we divide the initiatives into five categories and an overview
of the important milestones in the development effort is provided in the illustration below. The
specific project areas that are recommended to make up the overall ADA initiative are described
and important research areas for coordination are identified.

This roadmap for ADA should become a living document. Efforts should be continued to track
ongoing research that is leading to ADA. A workshop is recommended to help focus the
development of the value proposition and provide additional direction for the roadmap from a
broad cross-section of key stakeholders in ADA.

Figure 1
Important milestones divided into five categories for ADA development efforts.

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ACKNOWLEDGMENTS

The authors wish to acknowledge the contributions received from various engineers that
provided material, reviewed drafts, and answered questions as part of developing this document.
These include, but are not limited to, the following:

Robert Huber—We Energies
Ray Litwin—Northeast Utilities
Bruce Hirsch—Baltimore Gas & Electric
Les Barrett—City Public Service (San Antonio)
Chuck Wallis—Alabama Power (Southern Company)
Brian Smith—MidAmerican Power
Emil Turek—Lincoln Electric
Dave Gordon—American Electric Power
Bob Yinger—Southern California Edison
Russ McNulty—New York State Electric & Gas
Frederic Gorgette—Electricite de France

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CONTENTS

1 INTRODUCTION ....................................................................................................................1-1
Background ...........................................................................................................................1-1
Objectives .............................................................................................................................1-1
Approach ...............................................................................................................................1-2
Organization of the Report ....................................................................................................1-3

2 VISION FOR ADVANCED DISTRIBUTION AUTOMATION ..................................................2-1
2.1 Flexible Electrical Architecture.....................................................................................2-2
2.2 Open, Standardized Communication Architecture.......................................................2-2
2.3 The “Power Exchange” System of the Future..............................................................2-3
2.4 New Distribution System Technologies .......................................................................2-4
2.4.1 Electrical and Electronic Technologies ...............................................................2-5
2.4.2 Communications, Computing, and Information Technologies.............................2-5
2.5 Synergy........................................................................................................................2-6
2.6 International Focus ......................................................................................................2-7
2.7 Development Steps .....................................................................................................2-7

3 ADA FUNCTIONAL REQUIREMENTS ..................................................................................3-1
3.1 Communication and Control Infrastructure ..................................................................3-1
3.2 Automation of All Controllable Equipment and Functions............................................3-2
3.3 Application of Advanced Technologies ........................................................................3-5
3.4 Integration of Distributed Energy Resources (DER) ....................................................3-5
3.5 Modeling and Real-Time Simulation Systems .............................................................3-8

4 EXAMPLE DISTRIBUTION AUTOMATION SYSTEMS ........................................................4-1
4.1 Peer-to-Peer Communications.....................................................................................4-1
4.2 Application of Automatic Circuit Reclosers ..................................................................4-5
4.3 Sweden Automatic Load Restoration Example............................................................4-6

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4.4 Distribution Vision 2010 (DV 2010)..............................................................................4-8
4.5 Southern California Edison Circuit of the Future........................................................4-10
4.6 Georgia Power—Distribution Voltage and Reactive Power Control ..........................4-11
4.7 Nevada Power Company (Capacitor Switching and DG) ..........................................4-13
4.8 Electricité de France (EdF)—DA with Multi-Platform Capability ................................4-15
4.9 Distributed Energy Resource (DER) Example ...........................................................4-16
4.10 European Projects for DER and DA integration.........................................................4-17
4.10.1 EdF SILIERE Project .....................................................................................4-18
4.10.2 DISPOWER European Project.......................................................................4-18
4.10.3 MICROGRIDS European project ...................................................................4-19
4.11 Omaha Public Power District (OPPD) Substation Integration Project .......................4-19
4.12 Advanced Sensor Applications - Vattenfall ................................................................4-21
4.13 Con Edison - Urban Underground Low-cost Sensor Technology ..............................4-21
4.14 BC Hydro - Power Electronics Technology Application .............................................4-24
4.15 MidAmerican Energy Company—Cost/Benefit Analysis of Substation
Automation ..........................................................................................................................4-26
4.16 EdF NextGen Project .................................................................................................4-29
4.17 DOE GridWise Alliance..............................................................................................4-31
4.17.1 Architecture vs. Design vs. Standards ...........................................................4-32

5 TECHNOLOGIES FOR ADA IMPLEMENTATION.................................................................5-1
5.1 Technologies for Electrical and Electronic Equipment and Systems ...........................5-1
5.1.1 Distributed Energy Resources (DER) .................................................................5-1
5.1.2 Control and Management of Distributed Energy Resources (DER)....................5-2
5.1.3 Intelligent Electronic Devices (IED).....................................................................5-4
5.1.4 Standardized Universal Interconnection Technology (UIT).................................5-5
5.1.5 Advanced Sensor Technologies and Systems....................................................5-9
5.1.6 Advanced Switchgear Technologies .................................................................5-12
5.1.7 Distribution Power Electronics Technologies ....................................................5-13
5.1.8 Monitoring Technologies With Intelligent Applications ......................................5-23
5.2 Technologies for Communication, Computing, and Information Systems .................5-25
5.2.1 Communications Architecture for ADA..............................................................5-25
5.2.2 Object Modeling ................................................................................................5-38
5.2.3 Information Models for DER Technologies .......................................................5-44
5.2.4 Other Existing Information Models ....................................................................5-48

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5.2.5 Object Models Not Yet Defined.........................................................................5-48
5.2.6 Advanced Communication Media and Related Systems for ADA.....................5-49
5.2.7 Database and Data Collection Systems for End User System Information ......5-49
5.2.8 Database and Data Collection for Real-time State Estimation Systems...........5-49
5.2.9 Distributed Processing Systems for System Management and Control............5-50
5.3 Overall System Management and Control Technologies...........................................5-50
5.3.1 Advanced Distribution Automation Applications................................................5-51
5.3.2 System Fault Management, Reliability Management, and Restoration ............5-53
5.3.3 Adaptive Protection Systems ............................................................................5-56
5.3.4 Load Management and Real-Time Pricing Systems (Demand Response
Systems).........................................................................................................................5-57
5.3.5 Asset Management and Work Management System Integration......................5-60

6 FUTURE ELECTRICAL SYSTEM ARCHITECTURES ..........................................................6-1
6.1 Urban Networks ...........................................................................................................6-2
6.2 Suburban Systems ......................................................................................................6-3
6.3 Rural Systems .............................................................................................................6-5
6.4 Special Configurations .................................................................................................6-5
6.4.1 Microgrids............................................................................................................6-5
6.4.2 DC Distribution Systems and DC Microgrids ......................................................6-7
6.4.3 Custom Power Parks ..........................................................................................6-7

7 STATEMENT OF REQUIREMENTS ......................................................................................7-1
7.1 Basic Characteristics ...................................................................................................7-1
7.2 Technologies ...............................................................................................................7-1
7.3 Functions .....................................................................................................................7-2
7.4 Communications ..........................................................................................................7-3
7.4.1 Scalability ............................................................................................................7-3
7.4.2 Reliability.............................................................................................................7-3
7.4.3 Federation ...........................................................................................................7-4
7.4.4 Interoperability.....................................................................................................7-4
7.4.5 Adaptability..........................................................................................................7-4
7.4.6 Securability..........................................................................................................7-4
7.4.7 Implementation Issues and Costs .......................................................................7-4

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8 ADA DEVELOPMENT ROADMAP ........................................................................................8-1
8.1 System Topologies ......................................................................................................8-2
8.2 Communications Infrastructure ....................................................................................8-2
8.2.1 Communications Media.......................................................................................8-7
8.2.2 Communication Protocols ...................................................................................8-7
8.2.3 Object Modeling and Database Schemas...........................................................8-7
8.2.4 Consumer Systems Interface..............................................................................8-8
8.2.5 Federated Services .............................................................................................8-8
8.3 Sensors and Intelligent Monitoring Systems................................................................8-9
8.4 Universal Interconnection Technology (UIT)..............................................................8-10
8.5 Industry Standards.....................................................................................................8-11
8.6 Intelligent Equipment (Continuous Two-Way Communications)................................8-12
8.7 Adaptable Dynamic Protective Philosophy (ADPP) ...................................................8-12
8.8 New Power Electronics-Based Components .............................................................8-13
8.9 Advanced Computing and Control Systems ..............................................................8-13
8.10 Evolution Path for ADA—Research and Development Projects ...........................8-14
8.10.1 System Topologies (Configuration, Protection, Control)................................8-15
8.10.2 Communications Architecture and Information Model Development .............8-16
8.10.3 Technologies .................................................................................................8-17
8.10.4 Sensors and Monitoring .................................................................................8-19
8.10.5 Advanced Distribution System Controls.........................................................8-20
8.11 Opportunities for New Technology Demonstrations..............................................8-24
8.12 Coordination With Other Research .......................................................................8-25
8.13 Next Steps.............................................................................................................8-25

9 REFERENCES .......................................................................................................................9-1
9.1 Documents...................................................................................................................9-1
9.2 Web Sites ....................................................................................................................9-3

10 GLOSSARY OF TERMS AND ACRONYMS .....................................................................10-1

A APPENDIX A—ADA FUNCTION LISTING FROM IECSA PROJECT................................. A-1

B APPENDIX B—DESCRIPTIONS OF RELATED RESEARCH PROJECTS AND
STANDARDS ........................................................................................................................... B-1
B.1 Introduction ................................................................................................................. B-1
B.2 Reference Grid ........................................................................................................... B-2
B.3 Project Descriptions .................................................................................................... B-6
B.4 Standards Descriptions............................................................................................. B-26

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LIST OF FIGURES

Figure 2-1 Conceptual view of ADA and the distribution system of the future ...........................2-4
Figure 2-2 The flexible electrical architecture and open communication architecture
empower eachother to provide a whole that is greater than the sum of the parts
in ADA................................................................................................................................2-6
Figure 2-3 The basic steps for achieving the ADA vision ..........................................................2-8
Figure 3-1 Substation automation functional diagram ...............................................................3-4
Figure 3-2 Adaptable island or “microgrid” concept ...................................................................3-7
Figure 4-1 Distribution feeder protection scheme ......................................................................4-2
Figure 4-2 Web-based communication loop control ..................................................................4-3
Figure 4-3 Typical application of reclosers and sectionalizers...................................................4-5
Figure 4-4 Remote switching of distribution feeders ..................................................................4-7
Figure 4-5 Variation of SAIFI, SAIDI, and CAIDI for different levels of automation ...................4-8
Figure 4-6 Concept for demonstration of DV2010 functions with advanced concepts for
the future shown.................................................................................................................4-9
Figure 4-7 Typical switched capacitor bank—Georgia Power .................................................4-12
Figure 4-8 Feeder voltage profile before and after capacitor switching (no DG) .....................4-14
Figure 4-9 Feeder voltage profile before and after capacitor switching (2 MW of DG) ............4-15
Figure 4-10 Software application control architecture..............................................................4-16
Figure 4-11 OPPD Substation 912 simplified system diagram ................................................4-20
Figure 4-12 Example of primary monitoring sensors with wireless communications ...............4-21
Figure 4-13 Underground sensor installation concept .............................................................4-22
Figure 4-14 Typical Real time display for Harlem network ......................................................4-23
Figure 4-15 Typical daily load profile display for Harlem network............................................4-23
Figure 4-16 66-kV line loading and 66-kV bus voltage (at end of line) ....................................4-25
Figure 4-17 D-VAR regulation response and resulting voltage profile .....................................4-25
Figure 4-18 Business case methodology.................................................................................4-27
Figure 4-19 Conceptual diagram illustrating typical system configuration for European
distribution systems..........................................................................................................4-29
Figure 4-20 Conceptual diagram illustrating the integration of DER technologies on the
MV and LV systems .........................................................................................................4-30
Figure 4-21 Communication and control system that must be implemented to facilitate
integration of DR technologies .........................................................................................4-30

xvii

Figure 4-22 The role of intelligent communication and control systems in the automated
system of the future..........................................................................................................4-31
Figure 4-23 OLE for Process Control (OPC) architecture........................................................4-33
Figure 4-24 E-business ebXML reference architecture ...........................................................4-34
Figure 4-25 Moving from architecture towards implementation ...............................................4-35
Figure 5-1 Structure and functionality of the decentralized energy management system –
DEMS.................................................................................................................................5-3
Figure 5-2 Modular concept of stochastic energy source access management ........................5-4
Figure 5-3 Example of substation IED .......................................................................................5-5
Figure 5-4 Example of a “UIT-like” interface (Kohler PD-100) ...................................................5-7
Figure 5-5 Inverter module for “UIT-like” device ........................................................................5-7
Figure 5-6 UIT (next generation) interconnect design ...............................................................5-8
Figure 5-7 Underground sensor control and communication architecture .................................5-9
Figure 5-8 Printed circuit board Rogowski Coil........................................................................5-11
Figure 5-9 Rogowski Coil integrated signals compared to the laboratory CT (high power
tests at 25kA RMS, 66kA peak) .......................................................................................5-12
Figure 5-10 Schematic diagram of an SVC .............................................................................5-13
Figure 5-11 Schematic diagram of a basic STATCOM ............................................................5-14
Figure 5-12 Voltage variation with change in source reactance for SVC and STATCOM .......5-15
Figure 5-13 Basic configuration of DVR...................................................................................5-16
Figure 5-14 Basic configuration of a transfer switch ................................................................5-17
Figure 5-15 Structure of the STS Scheme...............................................................................5-18
Figure 5-16 Illustration of fault current limiting application.......................................................5-20
Figure 5-17 Power schematic of a single-phase electronic transformer employing a high
frequency AC link stage ...................................................................................................5-21
Figure 5-18 Solid state power conversion using high-frequency AC transformer isolation
(ABB design) ....................................................................................................................5-22
Figure 5-19 Effect of tree trimming on the high frequency noise current measured on a
distribution feeder circuit (tree trimming on October 23) ..................................................5-23
Figure 5-20 Example of using a substation monitoring system for automatic fault location
(courtesy of Carolina Power & Light) ...............................................................................5-24
Figure 5-21 Example of using a substation monitoring system for automatic fault
location—mapping the possible fault locations onto a feeder GIS map (courtesy of
Carolina Power & Light) ...................................................................................................5-25
Figure 5-22 Overview of GID and its underlying technologies .................................................5-35
Figure 5-23 Distribution management system with IEC 61968 compliant interface
architecture ......................................................................................................................5-36
Figure 5-24 Illustration of the Common Information Model (CIM) and the IEC 61968
interface to standardize the information interface for a wide variety of applications,
including ADA applications (from IEC 61968). .................................................................5-37
Figure 5-25 ACSI Server (conceptual).....................................................................................5-42

xviii

Figure 5-26 Information flows between ADA applications .......................................................5-52
Figure 5-27 Three recloser loop scheme .................................................................................5-54
Figure 5-28 Peer-Peer broadcasting configuration ..................................................................5-54
Figure 5-29 Peer-Peer implementation model diagram ...........................................................5-55
Figure 5-30 Sample trip and close logic for Peer-Peer scheme...............................................5-56
Figure 5-31 Energy market price profile (maximum daily price) - Seattle area, 1998-1999.....5-57
Figure 5-32 Hourly energy market price profile - Seattle area, peak day ................................5-58
Figure 5-33 Annual savings from a standard CP pricing program ...........................................5-59
Figure 6-1 A secondary network configuration that would allow local microgrids and two-
way power flows to incorporate flexible integration of DER ...............................................6-3
Figure 6-2 Basic architecture of suburban system configuration - The autoloop
configuration will be the predecessor of future configurations that integrate DER
technologies and solid state switches to facilitate flexibility in reconfiguring system
in real time..........................................................................................................................6-4
Figure 6-3 Illustration of distribution architecture and control that allows separation into
multiple microgrids based on topology, specific system conditions, local generation,
etc. .....................................................................................................................................6-6
Figure 6-4 Illustration of different locations where alternative microgrid concepts could
apply in an ADA system .....................................................................................................6-7
Figure 8-1 Examples of parameters and information requirements for distribution control
(from CEIDS DER/ADA project).........................................................................................8-3
Figure 8-2 IEC TC 57 Reference Architecture ...........................................................................8-4
Figure 8-3 Roadmap for development of a universal interconnection technology for DER .....8-11
Figure 8-4 Different parts of the ADA research initiative..........................................................8-14
Figure 8-5 Important initial projects for the ADA research initiative .........................................8-23
Figure 8-6 Illustration of important milestones and general flow of development in the
ADA initiative....................................................................................................................8-26
Figure A-1 CEIDS IECSA collaboration web site..................................................................... A-1

xix

LIST OF TABLES

Table 3-1 Benefits and Liabilities of DER ..................................................................................3-6
Table 4-1 Recloser-sectionalizer protection scheme operation .................................................4-2
Table 4-2 Comparison of a traditional protection scheme with the peer-to-peer system ...........4-4
Table 4-3 Comparison of a traditional protection scheme with the peer-to-peer system .........4-14
Table 4-4 Opportunity matrix (SA function vs. business drivers) .............................................4-28
Table 4-5 Matrix of economic benefits as a function of substation automation functions ........4-28
Table 5-1 Summary of communication system development activities....................................5-28
Table 5-2 Logical nodes being considered for IEC standards for DER information models ....5-46

xxi

1
INTRODUCTION

Background

In the EPRI Electricity Technology Roadmap for the Power Delivery System and Electricity
Markets of the Future [1], Advanced Distribution Automation (ADA) is described as the “Heart
of the Smart Power Delivery System.” Automation will play a central role in providing the
enhanced levels of Security, Quality, Reliability, and Availability (SQRA) that must be
characteristic of future power delivery systems.

Of course, automation means different things to different people. To a consumer, automation
may mean receiving hourly electricity price signals, which can automatically adjust home
thermostat settings via a smart consumer portal. To a distribution system operator, automation
may mean automatic “islanding” of a distribution feeder with local distributed energy resources
in an emergency. To a power system operator, automation means a self-healing, self-optimizing
smart power delivery system that automatically anticipates and quickly responds to disturbances
to minimize their impact, minimizing or eliminating power disruptions altogether.

This smart power delivery system will also enable a revolution in consumer services via
sophisticated retail markets. Through a two-way consumer portal that could replace today’s
electric meter, consumers will tie into this smart power delivery system. This will allow price
signals, decisions, communications, and network intelligence to efficiently flow back and forth
between consumer and service provider in real time. The resulting fully functioning retail
marketplace will offer consumers a wide range of services, including premium power options,
real-time power quality monitoring, home automation services, and much more.

This report presents background information on distribution automation technologies and
develops a roadmap to achieve the ADA systems required for the future power delivery systems.

Objectives

Specific objectives of the research are summarized here.
• Describe the vision for ADA and characterize the benefits for the power system of the future
• Determine the system and technology requirements for realizing this ADA vision over the
next 20 years
• Identify existing work within EPRI and elsewhere that will contribute to meeting these
requirements

1-1

Introduction

• Identify key gaps that are the basis for development initiatives for future R&D programs
• Recommend the future roles for EPRI in developing the technology to meet the ADA
requirements in a manner that complements work going on elsewhere

Approach

There has been no foundation study to develop a vision for ADA, its benefits, and the physical
characteristics of the distribution system of the future. This definition of requirements for the
system is needed to guide and coordinate the body of interrelated programs that will evolve
ADA. Additionally, this vision of the physical possibilities and realities of what can and cannot
be achieved in ADA will serve as a basis for the business models that make sense for the
distribution business in the future.

This project defines the system and technology requirements for the distribution system of the
future based on a review of the current situation and the most realistic expectations and timeline
for assimilation of new technologies over the next 20 years.

Significant development in a number of technology areas is required to achieve the objectives
and the vision of ADA. This report explores some of the important areas where additional
development is needed after reviewing important technologies that are already available and
under development. Priorities for future development are identified and an overall roadmap for
achieving the vision is presented. Some of the important areas where development is required are
listed here:
• Assist utility migration to open systems for automation equipment.
• Provide guidelines for utility specification of automation equipment to meet immediate needs
and also provide a migration path to fully automated systems.
• Develop and refine device models for specific application areas.
• Implement open systems in real world environments and capture lessons learned and
necessary refinements.
• Contribute to the development of key open standards specifications.
• Develop flexible electric distribution system topologies, including advanced configurations
and capabilities, such as two-way power flow, intentional islanding, microgrids, dc ring
buses, and looped secondaries.
• Develop key electrical and power-electronic components that enable the flexible electric
architecture and are cornerstones of ADA (such as the intelligent universal transformer and
new solid-state switchgear).
• Develop and implement intelligent monitoring systems to identify possible equipment and
system problems, characterize causes of disturbances, evaluate interface issues with end
users and Distributed Energy Resources (DER), and utilize open communication architecture
for integration with the overall automation systems.

1-2

Introduction

• Develop new approaches for fast simulation and modeling and predicting system
performance in the real time (including contingency analysis for future conditions based on
the existing conditions), using information from advanced monitoring systems and improved
electrical models of the system (including end user systems and DER systems).
• Develop tools to assist utilities in developing specifications for components of ADA,
facilitating integration with the overall ADA implementation over time.

Organization of the Report
This report is organized into 8 sections:
Section 2 provides the vision for ADA and its role in the power system of the future. The critical
and complementary roles of an open communications system architecture and new electrical
system topologies are described. The roles of new technologies, such as power electronics
technologies, are also described.
Section 3 develops the functional requirements for ADA. These are developed in three major
categories: communication and control systems, integration of distributed energy resources, and
modeling and control system requirements.
Section 4 provides an overview of the state-of-the-art in distribution automation systems by
looking at typical examples of automation systems that are being used and implemented today.
Important research initiatives are described and an international perspective is used.
Section 5 describes important technologies that are needed for implementation of ADA systems.
These include equipment technologies (including distributed energy resources), protection
systems, monitoring and sensor technologies, and communication technologies.
Section 6 focuses on future electric system topologies and architectures. Requirements are
defined for different types of systems: urban networks, suburban systems, rural systems, and
special systems (such as custom power parks).
Section 7 is a requirements summary for ADA systems. The requirements are defined as basic
characteristics, technologies, functions, and communications.
Section 8 provides the R&D roadmap for the ADA development. The roadmap is structured into
five main research areas:
1. System topologies
2. Communications infrastructure
3. New technologies (power electronics, etc.)
4. Sensors and intelligent monitoring systems
5. Advanced distribution controls

This section provides a detailed research plan with initial cost estimates for the research
initiatives identified.

1-3

2
VISION FOR ADVANCED DISTRIBUTION
AUTOMATION

Traditional distribution systems were designed to perform one function—distribute electrical energy
to end-users while ADA systems will facilitate the exchange of electrical energy AND information
between participants and system components. The lines between supplier and consumer will blur
because many of participants will assume both roles and will need to switch effortlessly between
these roles, possibly several times a day. The exchange of data and information will facilitate the
“supplying” or “using” of electrical energy based on dynamic rather than static prices.
ADA is distinct from traditional distribution automation (DA). Traditional DA has been
principally concerned with automated control of basic distribution circuit switching functions.
ADA is concerned with complete automation of all the controllable equipment and functions in
the distribution system to improve strategic operation of the system. The various components are
made interoperable in ADA, and the communication and control capabilities are put in place to
operate the system. The result is added functionality and better performance, reliability, and cost,
relative to today’s system operations. In total, ADA will be a revolutionary change to distribution
system infrastructure, as opposed to simple incremental improvements to DA. However, this
revolutionary change will occur in an evolutionary manner due to the tremendous investment in
legacy systems and the rate of technological progress.
Neither the future nor ADA is optional. ADA will happen to meet the growing and changing role
of electricity in our society. The availability and the need to use distributed generation resources,
the impact of electrical/hybrid vehicles, the growing importance of electrical reliability along
with economic pressures resulting from the globalization of world economies and/or the
diminishing stockpile of natural resources are all drivers behind this change. The transition to the
ADA system is already underway and several examples are presented in this report.
There are two critical components to the concept of ADA:
1. An open communication architecture to facilitate the system monitoring and control
functions of ADA.
2. A redeveloped power system from an electrical architecture standpoint to enable an
interoperable network of components.
These two elements are synergistic and inter-related with each other and together they comprise
the distribution system of the future. These elements are described briefly here along with
technologies that are required to make them a reality. They are explored in more detail with
examples and identification of research requirements to make them a reality in subsequent
sections of this report.

2-1

Vision for Advanced Distribution Automation

2.1 Flexible Electrical Architecture

ADA is the cornerstone for evolving the distribution system of the future. ADA will be based on
new technologies, such as the intelligent universal transformer (a multi-functional power-
electronic device to replace distribution transformers) and sophisticated and interactive use of
smart sectionalizing, switched capacitors, sag correctors, voltage regulators, multi-function
distributed generation, load management devices, new sensors, power-electronic controls, and
others. ADA will also be based on advanced system configuration concepts such as intentional
islanding (including microgrids), looped secondaries, and dc ring buses.

A flexible electrical architecture is needed that will allow interoperability of a multitude of
controllable electrical and electronic devices within the distribution system in an organized
strategic manner that provides improved functionality, performance, reliability, and power
quality from the system. The flexible electrical architecture must provide the basis for easily
integrating the new electrical and electronic technologies from an electrical system design
standpoint. The various devices must be enabled by the architecture to provide the maximum
functionalities within their limits. For example, power electronic devices may provide VARS,
sag correction, switching and other power quality functions. Also, the flexible electrical
architecture must enable the advanced system configuration concepts noted earlier.

The legacy infrastructure must be evolved in an orderly way over time to enable this distribution
system of the future. The future electrical infrastructure should enable interoperability of the new
technologies in a way that provides options for strategically operating the system to improve
performance and reliability through automated use of the technologies, either individually or in
combinations. ADA is revolutionary in nature, as opposed to simple incremental improvements
to what has been traditionally called distribution automation.

In ADA, a top-down view of the system is needed in which the role of each technology being
integrated is considered in terms of the system benefits it can provide and its interactions with
the other new distribution technologies that are simultaneously being woven into the distribution
system of the future. These technologies become components of a larger system with intelligent
supervisory control. Strategic operation of the system will involve real-time trade-offs, such as
getting voltage support from a distributed generator when a capacitor bank is out of service. The
strategic possibilities are endless. The electrical architecture will be a complex and flexible
network of interactive devices. A complex communication network will in turn, operate this
electrical system.

2.2 Open, Standardized Communication Architecture

An open, standardized communication architecture is needed to achieve the requisite central and
local control by which the flexible electrical system described above will be strategically
operated using predetermined algorithms.

In general, the communication architecture will be comprised of two major elements, object
models and protocols. An object model is a detailed data template for the information exchange
needed for monitoring and controlling a device within the architecture of a power distribution

2-2


system (or other system). The object model makes the device recognizable and controllable (i.e.,
interoperable) to the power system. This is analogous to hooking up remote devices to a
computer. The remote devices are interrogated by the operating system of the computer and an
interoperable interface is established.

The other principal component of the communications architecture is the communication
protocols. Protocols are the “rules for transfer of the data” within the communication system. For
example, the protocols are the rules for taking the information from the DER (as represented in
its object model) and transferring it to a SCADA or other device.

None of this gets into communication media such as microwaves, radio, PLC, fiber optics, or
other physical media. The architecture is just the structured way of handling a lot of information,
regardless of which media are chosen. However, in implementing ADA, judicious choices must
also be made of communications media.

The architecture can be proprietary or open. There are many proprietary architectures. The
principal open architecture is UCA, which is being standardized via such documents such as IEC
61850 and others. Consensus standards are evolved and agreed upon by stakeholder communities
to get consistent practice to the benefit of all. The agreed upon consensus standards for open
communication architecture should, over time, become the dominant architecture. Proprietary
architectures will then wane in importance. Adopters of the open architecture approach benefit
because they can easily integrate new technologies, if they have been suitably conformed for
interoperability.

In some respects, the job is never done in evolving the open architecture, because as new device
types are invented and developed, consensus standards are needed for their object models to
make them interoperable with the open architecture.

2.3 The “Power Exchange” System of the Future

Ultimately, the distribution system is expected to evolve into a power exchange medium that is
capable of collecting power and transferring it elsewhere, as well as distributing it. Hence,
looking into the future, it will be more appropriate to think of as a “power exchange system”
rather than a “distribution system.” Therefore, ADA is, in reality, reinventing the distribution
system into something new. Figure 2-1 presents a conceptual view.

2-3


Figure 2-1
Conceptual view of ADA and the distribution system of the future

ADA has one other challenging and interesting aspect. Both the electrical and communication
architectures described above for the distribution arena are really subsystems of the overall
power system, including generation, transmission, sub-transmission, distribution, and customer
electric systems. Hence, ADA must be interoperable with the broader context of the power
system. Examples where this broader concept is important include:
• Distribution system acting as a generator (power supplier) for the overall system as a result
of local distributed generation that exceeds local loads.
• Reactive power control for the overall system coordinated with the reactive power devices
and capabilities of the local distribution system.
• Power quality control for local loads coordinated with characteristics of the supplying
transmission system (e.g. control of voltage sags caused by transmission faults and control of
transient overvoltages caused by transmission operations, such as capacitor switching).
• Local load control and energy conservation measures implementation to support
requirements for the overall system (e.g. load reduction to support system contingencies
coordinated with local loads and distributed resources).

2.4 New Distribution System Technologies

New technologies are becoming available that will shape the distribution system of the future.
Some of these have recently become available and others are in the final stages of development.
Still others are not yet known, but will emerge over the next 20 years. The new technologies that

2-4


will shape ADA come from both the electrical (and electronic) equipment sector and from the
information technology sector.

Some technologies that will be important for the overall ADA implementation and are evaluated
in this report include the following:

2.4.1 Electrical and Electronic Technologies
• Distributed energy resources (distributed generation and storage)
• New sensor technologies that will allow collection of electrical and performance information
from devices and components throughout the system
• Monitoring and analysis technologies for identifying system and equipment problems before
actual failures (e.g. distribution fault anticipator, capacitor problem identification, regulator
problem identification, etc.)
• Power quality enhancement technologies for the distribution system (e.g. DVR, Statcom)
• Solid state breakers and switches for fast fault clearing, system reconfiguration, and
transient-free switching (e.g. capacitors)
• Load management technologies (end user systems that must be coordinated with ADA)
• Power quality enhancement technologies for end user facilities that should be coordinated
with ADA
• Advanced metering capabilities that will allow intelligent applications to be coordinated with
detailed characteristics of end user systems
• Advanced electrical system configurations, such as intentional islanding (including
microgrids), dc ring buses, looped secondary systems, and advanced distribution networks
• Automatic switching systems to reconfigure the system for disturbances (e.g. faults), load
conditions, DER conditions, quality and reliability requirements, etc.
• Intelligent universal transformer (a multi-functional, solid-state replacement for distribution
transformers)

2.4.2 Communications, Computing, and Information Technologies
• Open, standardized communication architecture
• Advanced, secure communication media (including wireless, PLC, satellite, etc.)
• Open information exchange model for work process management
• Consumer Portal (to be described later)
• Sensing and monitoring devices implementing features of new communications architecture
and with integrated intelligent applications that become an integral part of overall system
control schemes

2-5


• Real time state estimation and predictive systems (including fault simulation modeling) to
continuously assess the overall state of the distribution system and predict future conditions,
providing the basis for system optimization
• Advanced control systems to optimize performance of the entire distribution system for
efficiency, asset management, reliability, quality, and security
• Load management and real time pricing systems that integrate with end user and DER
systems to optimize overall system performance and efficiency
• Asset management and work management systems that integrate with intelligent monitoring
systems, customer information systems, and forecasting tools to optimize investments and
maintenance based on the specific requirements of individual systems

Collectively, these technologies are the tools that are available to create ADA.

2.5 Synergy

The two families of technologies summarized above together form the basis for the ADA system
of the future. The advances in electrical and electronic technologies enable the flexible electrical
architecture and associated functions, but they are only achievable with the advanced
communication and information technologies to supervise them. The two families are completely
inter-related, as illustrated in Figure 2-2.

Flexible Open
Electrical Communication
Architecture Architecture

Figure 2-2
The flexible electrical architecture and open communication architecture empower
eachother to provide a whole that is greater than the sum of the parts In ADA

2-6


In ADA, more sophisticated control concepts will be used. As the distribution system becomes
more widely monitored via advances in sensor and monitoring technologies, and the system has
more microprocessor-controlled components (e.g., the intelligent universal transformer or new
load management devices), these components can be used for strategic operating advantage. To
do so will require a more sophisticated control system. First, the system must be based on the
interoperability of all of its parts. This means migration to an open communication architecture.
Second, local distribution control via distributed computing will be used. The local distribution
control concept will involve using a central control center at the distribution system level for
coordination with control at the transmission level. This is necessary for overall power flow
supervision and coordination of DER dispatch at the distribution level with central generation at
the transmission level, as well as for coordinating volt/VAR management. (DER can be a source
of VARs, as well as kWs.) The central distribution control center would also supervise the
distributed control capabilities that are dispersed throughout the distribution system. These
include microprocessors embedded in intelligent electronic devices (IEDs) throughout the
distribution system and other local control agents.

2.6 International Focus

The technologies and systems for ADA must have an international focus. There are many
differences in distribution system designs and operations around the world. However, the basic
equipment and requirements are the same. Future electrical system architectures and open
communication system architectures (especially the standards defining these systems) must result
in technologies that can be applied throughout the world. This will greatly enhance the speed of
development and implementation of these technologies and eliminate the need for expensive
duplication of research efforts across different systems.

2.7 Development Steps

The overall flow of development to achieve the ADA system of the future is illustrated in Figure
2-3. The focus of this report is on the last step—defining the requirements for future work and a
roadmap for this work. However, a review of existing technologies and systems is required
before any attempt at a definition of future work is possible. Therefore, the next chapters review
some existing distribution automation technologies and specific implementations. Then this
state-of-the-art information is used to identify important gaps that must be filled in order for the
ADA vision to be realized. Filling these gaps is the basis for the future development priorities.

2-7


Assessment Requirements
Definition Future Work

Flexible
New electrical Technology
technologies architecture
development
requirements

ADA Synergy Systems
functions development

Open
communication
Past and architecture Standards
current work requirements development

Figure 2-3
The basic steps for achieving the ADA vision

2-8

3
ADA FUNCTIONAL REQUIREMENTS

ADA will consist of many individual functions and applications (see Appendix A). These
functions incorporate many new systems, equipment, and applications that will be part of the
overall ADA system. Five important functional requirements can be defined for the overall system.

1. Communication and control infrastructure allowing integration of all distribution equipment
and end user technologies into the ADA system

2. Automation of all controllable distribution equipment and functions

3. Application of advanced technologies (e.g. power electronics) where appropriate for
advanced control and system performance enhancement

4. Integration of distributed generation and storage resources

5. Modeling and real-time simulation systems to optimize performance (via predictive control)
and response to disturbances at all times

3.1 Communication and Control Infrastructure

Neither distribution automation nor ADA is possible without widespread communication
between the controllable devices and one or more control unit(s). At times the control unit may
be a central processor and at other times it may be another controllable device as in peer-peer
communication.

Adding communication links to individual distribution components is becoming more prevalent,
in part due to the reduction in communication costs. The communication costs have come down
due to new technology developments and increased competition. Economic analysis is more
likely to show that the cost of adding communication links is offset by the resulting improvement
in system reliability and improved O&M efficiencies.

Reference 17 indicates that distribution automation communications media can be placed into the
following three major categories:

1. Power Line Carrier

2. Landlines

3. Wireless

3-1

ADA Functional Requirements

Power line carrier systems have been most successful in automatic meter reading (AMR) and
load control applications. For distribution applications, power line carrier suffers from the “open
circuit problem”. In other words, communication is lost with devices on the far side of an open
circuit. This severely restricts the usefulness of power line carrier systems for applications
involving reclosers, switches, sectionalizers, and outage detection.

Landline communication options include telephone and fiber optics. Leased telephone lines are
often brought into substations for SCADA-RTU communications. For distribution automation,
telephone lines are not often used because of the costs associated with installation of the phone
line, the dielectric isolation equipment, and the monthly cost. Fiber optics is a very technically
attractive solution, offering comparatively unlimited bandwidth. Its dielectric and EMI/RFI noise
immunity characteristics make it an ideal fit for the high-voltage operating environment. Single-
mode fiber is a very practical solution for transmission applications. Unfortunately, the installed
“cost per drop” for single-mode fiber is still too high for most distribution applications.

Wireless solutions have shown the greatest potential for automating distribution networks
because they communicate virtually anywhere at a very low cost. Companies exploring wireless
solutions have two choices; install a private (owner operated) wireless network or utilize an
existing infrastructure of a public network.

Private wireless networks allow utilities to have more control over their communications system
but requires a significant up-front investment in infrastructure as well as the on-going
maintenance costs. Utilizing an existing public network, for example, the public cellular
network, allows a utility to forgo upfront infrastructure as well as most of the on-going
maintenance costs. These cost saving must be weighed against the fact that the network is not
captive to the utility. With security features like secure socket layers (SSL), 128-bit encryption,
and frame relays, the security risks of using a public network are becoming negligible.

ADA systems will also incorporate communication and control functions that integrate with end
use technologies for implementation of demand response and real time pricing systems. These
systems will help optimize the performance of individual distribution systems as well as provide
the means to better match generation resources with load characteristics. Work on the “consumer
portal” is defining the requirements for the communications and control systems that go across
the customer meter.

Regardless of the technologies employed, the communications architecture must allow for “plug
and play” implementation of technologies that are required for ADA systems to be economically
deployed. Information models, object models, and protocols must be standardized so that
systems with a variety of components can be integrated and expanded in a modular fashion.

3.2 Automation of All Controllable Equipment and Functions

The functionality of ADA could be explained as the deployment of substation and feeder
operating functions and applications ranging from SCADA and alarm processing to integrated
volt/var control in order to optimize the management of capital assets and enhance operation and
maintenance (O&M) efficiencies with minimal human intervention. The automation process will

3-2


also be accompanied by an integration phase in which equipment and information will be
consolidated. The integration of protection, control, and data acquisition functions into a minimal
number of platforms will reduce capital and operating costs, reduce panel and control room
space, and eliminate redundant equipment and databases.

The automation and functionality of the system will evolve to a very complete and
comprehensive scheme. The system will be given more data along with more switching and
corrective action responsibilities. The security and integrity of the automation system will also be
enhanced with dispersed control, more redundancy and more sophisticated “fail safe” strategies.

The continual addition of IEDs to the distribution system, either through attrition or new
construction, will ensure that more data is available and more distribution components will be
controllable through automation. The integration of distributed energy resources will add new
challenges since power or current may be flowing in any direction. This will result in reclosers
being replaced or modified with bi-directional reclosers, which in turn will require a more
sophisticated control and automation scheme.

In order to fully exploit the full vision of ADA, it will be required to automate more controls. For
example, human operator response time will not be sufficient to perform the switching necessary
in order to create self sustaining islands subsequent to system disturbances.

Figure 3-1 (Reference 18) depicts the substation automation functional architecture as well as the
various data paths that exist between the distribution equipment and the overall utility enterprise
system. The operational data flows to the SCADA system while the non-operational data flows
to the data warehouse and a data path providing remote access to the IEDs exists. It should be
noted that many of the IEDs associated with the ADA vision will not physically exist at the
substation but will be out on the feeders.

3-3


Figure 3-1
Substation automation functional diagram

Future ADA systems will extend the control out onto the distribution system and even into
customer facilities in order to optimize the performance and response of the overall system.

3-4


3.3 Application of Advanced Technologies

Optimizing the performance and the response of the distribution system in the future will take
advantage of advances in power electronics technology. Important advantages of power
electronics technology applications will include:
• Faster, transient-free switching for better response to disturbances and system
reconfiguration.
• Continuous voltage and var control, as well as control of harmonic distortion
• Ride through systems for improved power quality and reliability for customers that require
this level of service

Important technologies to realize these benefits include:
• Static compensators for voltage and var control
• Active filters for harmonic control
• Series compensators for ride through support and voltage control
• Energy storage systems with power electronics to optimize performance and the system
interface
• Intelligent universal transformer (IUT) for complete management of the customer interface
• Solid state switches for fast, transient free switching and system reconfiguration

Many of these power electronic technologies may be integrated with distributed resources or
end-use devices. However, their controls must be integrated with the overall ADA system.

3.4 Integration of Distributed Energy Resources (DER)

The distribution system will need to transition from a single function (energy delivery) system to
a multi-function (energy exchange) system in order to fulfill the ADA vision. Automation and
control functionality will need to be increased and this functionality will be integrated with
distributed resources throughout the distribution system.

A major functional goal of the ADA vision is to seamlessly integrate small power generation and
storage devices throughout the system. This integration process will ideally maximize the
benefits of DER while minimizing some of the potential liabilities. The development of a
flexible electrical architecture as well as the development of an open communication architecture
are both critical to achieving this goal.

The following table outlines some of the more common benefits and liabilities of DER. The long
list and importance of the benefits justifies the effort required to advance the successful
integration of these devices.

3-5


Table 3-1
Benefits and Liabilities of DER

Potential Benefits of DER Potential Liabilities of DER

Improved energy efficiency Personnel safety

reduced system losses Added system complexity

reduced need for transmission and distribution Higher percentage of generating
expansions sources being dependent on
meteorological conditions

more diversified environmentally friendly power sources

higher power quality and reliability potential

additional volt/VAR capabilities

The electrical architecture (and, in some cases, the natural gas infrastructure) will need to be able
to accommodate a wide variety of different types and sizes of DER devices. There is a broad
range of energy sources and generation technologies that can be used as DER. The most common
generation technologies include:
• Gas combustion turbine-generators
• Gas combustion microturbines with alternators-inverters
• Gas to hydrogen fed fuel cells and electronic inverters
• Gas and oil fired reciprocating engine-generators
• Wind-driven turbines with induction generators or alternators-inverters
• Solar photovoltaic cells and inverters
• Solar thermal-electric power plants
• Hydroelectric micro- and small-scale power plants
• Geo-thermal driven steam turbine-generators

In addition to these technologies, there are energy-storage technologies that are also classified as
DER. These include battery energy-storage systems, flywheel energy-storage systems, super-
conductive magnetic energy storage (SMES), super-capacitor (ultra-capacitor) energy-storage
technologies, and other types of energy storage. A storage technology functions like a generator
during dispatch of power from the storage medium, and so it basically has all of the
characteristics of a generator during that period of time; it has the characteristic of a load during
recharge periods.

The electrical architecture will also need to be able to accommodate both the presence and
absence of these resources which may come and go several times a day depending upon the
availability of renewable resources, economic dispatch or other considerations. This means that

3-6


MW, MVAR and voltage demands of the system as well as the associated equipment ratings are
going to have to be continuously balanced against a very diversified and fluid set of resources.

The development of standardized interconnection systems for DER resources will facilitate the
rapid introduction of additional DER resources onto the system. These systems must be
integrated with the overall distribution automation system as part of system performance
management. In order to maximize some of the reliability and power quality benefits associated
with DER, the electrical architecture will also need to be able to break apart into “microgrids” or
self sustaining islands, during certain power system disturbances. Figure 3-2 demonstrates the
different levels at which DER can be deployed as well as how different self sustaining islands
may be formed during power system disturbances. In general, irrespective of standardizing the
interconnection systems, the distribution electrical system design must be modified to
accommodate increasing penetration of DER.

Figure 3-2
Adaptable island or “microgrid” concept

In order to facilitate the integration and real-time dispatch of DER, a secure real-time
communications and control infrastructure must be provided. It will be necessary to have
coordinated protection and control of these resources so the needs of the system can be balanced
against the availability of the resources. In order to minimize the incremental burden on system
operators, much of the control and automation of these resources will have to be automated.
Security and redundancy of the communication system will be critical to offsetting the added
complexity associated with the integration of these resources.

DER technology is changing rapidly, with new requirements, new vendors, and new capabilities.
Therefore, it is critical to use a standard communications protocol that will ensure that these
disparate devices can communicate in a well-known manner. In addition, the standard
communication protocol must incorporate self-defining capabilities using object-oriented
technology, so that each implementation of a new type of device and each deployment of
additional devices (which may eventually number in the thousands) can occur rapidly and with

3-7


minimal cost. The Utility Communications Architecture (UCA) meets the need for a standard,
self-defining, object-oriented communications protocol. All major distribution automation and
substation automation field devices are becoming compliant with the UCA standard, as defined
by the 1999 IEEE UCA Technical Reports and by the IEC standardization work-in-progress.

The integration of DER resources will also require new industry standards development as well
as coordination with industry, state, and local government organizations to accelerate regulatory
policies, codes, permitting and siting.

3.5 Modeling and Real-Time Simulation Systems

Control of all equipment and even customer systems will require an extensive real-time system
model and information system along with supporting simulation tools to continually optimize
system performance. The first requirement is a system information model that facilitates the wide
variety of applications that will have to operate on this model. The information model must take
into account future as well as existing technologies that are part of the distribution system.
Important elements include:
• Substation equipment
• Protection systems
• Distribution system topology with line and cable characteristics
• Distribution switchgear and characteristics (including solid state switches)
• Var control and voltage control technologies (regulators, series compensators, shunt
capacitors, shunt compensators)
• Transformers (substation and customer)
• Intelligent universal transformers with full functionality in the future
• Distributed generation and storage devices with controls and protection systems
• End use technologies, load characteristics
• Demand response and real time pricing systems and components
• GIS systems

Important applications that must become real-time capabilities for the ADA system include:
• Load flows, voltage profiles, var flows, etc.
• Harmonic distortion level calculations and simulations
• System loss simulations to optimize topology and equipment controls
• Price response simulations as part of demand management and system performance
optimization
• Fault location

3-8


• Optimized restoration following fault conditions
• System restoration following major outages, including coordination with end user and DR
systems

All of these systems require extensive data collection and management systems to match the
system representations with real-time conditions. These functions will require faster simulation
and state-estimation systems for the distribution systems. These systems will also be required to
continually predict future conditions on the distribution system to develop optimization
approaches for the system performance.

3-9

4
EXAMPLE DISTRIBUTION AUTOMATION SYSTEMS

The objective of this section is to review some existing distribution automation technologies and
to describe some specific “real world” implementations. Each case study is designed to illustrate
a specific technology or system design concept that will be critical to the implementation of the
ADA vision.

The case studies describe the “state-of-the-art” technology applications and designs. They form
the basis for the evolutionary path to the fully functional ADA system of the future.

A key contribution of these examples is to illustrate possible migration paths or strategies that
can be used to transition the existing power distribution network into that described by the ADA
vision. The importance of industry standards to this process is also highlighted.

4.1 Peer-to-Peer Communications

Reference 11 describes the positive impact that peer-to-peer communication can have on
traditional distribution protection systems (recloser, sectionalizers). A protection scheme based
on microprocessor relays, equipped with Internet communication capabilities, is shown to
eliminate undesired losses of un-faulted load, reduce outage duration as well as reduce thermal
and mechanical stress resulting from successive re-energizations under fault conditions.

A peer-to-peer communication system enables distribution relays to share information with
others connected to the TCP/IP communication network without having a master device. Every
relay is able to ask from, and send to, the network un-requested information. Thus, any relay can
master the re-configuration of the distribution system itself after a contingency occurs. The
system can be programmed to isolate every possible fault after a certain number of reclosing
operations as well as to reenergize un-faulted loads. As a result, the traditional protection system
is transformed into an adaptive protection system that is able to reconfigure itself to successfully
face contingency conditions.

A traditional recloser protection scheme has the disadvantage that it exposes system components
to large thermal and mechanical forces every time the recloser closes into a fault. If a recloser is
set for three re-closing operations and the fault is permanent (non auto-extinguishing), the system
will have to carry the fault current four times before the fault is permanently cleared and all these
duties are imposed on the system components in a very short period of time. Furthermore, the
voltage drop caused by the fault might affect the quality of service to other customer connected
to the same distribution substation.

4-1

Example Distribution Automation Systems

The use of sectionalizers, as shown in Figure 4-1 and Table 4-1 have the potential to improve
this situation somewhat, depending on where the fault occurs.

Figure 4-1
Distribution feeder protection scheme

Table 4-1
Recloser-sectionalizer protection scheme operation

In brief, the traditional recloser-sectionalizer distribution scheme increases the performance of
the distribution system by allowing permanent faults to be cleared without shutting down the
whole feeder. The major negative effect of this approach is the increment on thermal and
mechanical stress put on the distribution feeder due to several application of the fault current in a
relatively short period of time.

Reference 12 describes a peer–peer communication scheme based on the TCP/IP protocol.
Figure 4-2 shows the architecture of the proposed system. The scheme must be implemented
with a fallback operation procedure for those times when communication is not available. This
fallback operation procedure operates similar to the traditional non-communication recloser-
sectionalizer scheme.

4-2


Figure 4-2
Web-based communication loop control

The PCD device in the above figure refers to the ABB PCD2000. The PCD2000 and SCD units
combine monitoring, control, switching and communication in one package.

The access to the TCP/IP protocol was accomplished by using low cost Java Application Control
Engines. Every PCD/SCD 2000 unit was tied to a Java based control device through a Modbus
serial communication link using RS-232 port. Specifically, Jace-501/502 Java based control
devices made by Tridium were used. The Jace-501/502 units manage the serial communication
with the PCD/SCD control units as well as the TCP/IP access. The Jace-501/502 also runs the
fault location, fault isolation and system restoration algorithms.

The PCD2000 and SCD2000s includes a register (40819) that provided an event counter during
fault occurrence. The 40819 counter registers provide key information for fault location tasks.
Comparing the event counter of successive PCD/SCD2000, it is possible to determine the
location of the fault without having to wait for several reclosing operations. There is enough data
to initiate the proper sectionalization process before the first reclosing operation; the system
always allows one reclosing operation in order to avoid operating for a non-permanent fault.

Devices are constantly posting in the network their event counter (40819) and status registers
(open/close). Furthermore, they are constantly reading from the network event counter and status
of all devices in the power distribution network. Having this information enables them to

4-3


evaluate the system condition. When a fault occurs anywhere in the distribution system, the
recloser starts its sequence of operations. Thus, event counter registers increase with every
reclosing operation only in devices that see the fault current. The fault location is accomplished
by comparing 40819 register of successive devices. If a device sees the current but its down
stream fellow does not, the fault is between them. Once the fault was located, the closest device
masters the reconfiguration of the network. It generates and sends open/close/lock commands to
other devices according to the operating philosophy described above.

Table 4-2 summarizes the obtained results. It shows a comparison in terms of the number of
reclosing operations, unfaulted load losses, and recovery time for several contingences between
the traditional protection system and Peer-to-Peer Communication-Based protection system
applied to distribution networks.
Table 4-2
Comparison of a traditional protection scheme with the peer-to-peer system

4-4

Technical and system requirements for advanced distribution automation

Technical and system requirements for advanced distribution automation

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