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Coordination of Transmission and Distribution
Planning and Operations to Maximise
Efficiency in Future Power Systems
Luís Castanheira, Graham Ault, Marílio Cardoso, Jim McDonald, J. Borges Gouveia, Zita Vale
Abstract—Transmission and distribution networks have been
historically planned and operated as almost two separate entities.
Future power networks will provide a new framework where this
practice will no longer be desirable or possible. In particular,
achieving maximum efficiency in planning and operating the
transmission system will require the consideration, and possible
coordination and exchange, of functions, services and
information across the transmission-distribution interface. In this
paper the authors review current Transmission System Operator
(TSO) approaches to planning and operations, present possible
visions of future power networks with emphasis on the functions,
services and information exchange across the transmissiondistribution boundary, and finish with a proposal for reviewing
the whole concept of efficiency in future power systems. This
work sets the context for research in the area of efficiency of
T&D planning and operations with the objective of contributing
to the sustainable development of power systems.
Index Terms—Coordination, Efficiency, Operations, Planning,
transmission, Distribution.
I. INTRODUCTION
It is a well known fact that, historically, power networks
have been going through significant changes, mainly in the
years since the beginning of market liberalization.
Nevertheless, functional separation between transmission and
distribution networks in terms of planning and operational
management is still a reality across the world. Some practices
L. Castanheira is with the Department of Electrical and Electronic
Engineering of the Strathclyde University, Glasgow, UK and the Department
of Electrical Engineering of the Enginnering School of the Polytechnical
Institute of Porto, Porto, Portugal (e-mail: lcc@isep.ipp.pt ).
G. Ault is with the Department of Electrical and Electronic Engineering,
Strathclyde University, Glasgow, UK (e-mail: g.ault@eee.strath.ac.uk).
M. Cardoso is with the Department of Electrical Engineering of the
Enginnering School of the Polytechnical Institute of Porto, Porto, Portugal (email: marilio@dee.isep.ipp.pt).
J. MacDonald is with the Department of Electrical and Electronic
Engineering,
Strathclyde
University,
Glasgow,
UK
(e-mail:
j.mcdonald@eee.strath.ac.uk).
J. Gouveia is with the Department of Economy, Enginnering and
Management of the University of Aveiro, Aveiro, Portugal (e-mail:
bgouveia@egi.ua.pt).
Z. Vale is with the Department of Electrical Engineering of the
Enginnering School of the Polytechnical Institute of Porto, Porto, Portugal (email : zav@dee.isep.ipp.pt).
have remained unchanged for the last 50 years. New
perspectives about sustainable development, network security,
power quality and reliability of service are moving power
networks to tackle new challenges, which presents a new
context both for planning and operational management of
power networks. At the same time, the concept/function of
efficiency regarding planning and operations of power
networks may be seen under the new perspectives referred
above, possibly challenging the concepts and practices, seen
today as best practice.
This paper deals with these subjects, starting with a review
of the present state of the art in the planning and operational
practices of TSOs, followed by a statement about the future
power networks context and a discussion of the
concept/function of efficiency under the scope of the future
power systems and transmission operations and planning. It is
expected that this work will lead to further research to bring
new light to the challenge of planning and operational
processes for future power networks. The particular focus of
this research will be in the area of efficiency of planning and
operational processes. This paper will also show that the
efficiency concept needs to be redefined under the future
power networks framework.
II. CURRENT TRANSMISSION SYSTEM PLANNING AND
OPERATIONAL CRITERIA
Transmission system operators have, for a long time now,
been developing their own processes and criteria for planning
and operations. Some reference analysis [1]-[4] on this matter
allows us to understand the basic questions concerning the
planning process.
Traditionally, the basic requirement of a transmission
network was to ensure that the outputs from the utility’s
generation could be transported to the utility’s customers
within specific (and often stringent) targets for security and
power quality. Today, transmission systems have a much
larger mission.
Several years ago, transmission planning was much simpler
than it is today and in turn today’s approaches to transmission
planning are likely to be simpler than those required in the
future. To make matters worse transmission planning today is
conducted within the context of great uncertainty regarding
future power system architecture, generation mixes, and end
use developments.
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For decades the electricity industry was characterized by
vertically integrated utilities. In this scenario utilities could
optimize investments because they owned and operated
generation and transmission. Unbundling generation,
transmission, distribution and retail supply has made the
planning and operations challenge more complex. For
example, the separation of generation and transmission has
presented the problem of the congestion management as an
internal and external problem.
Independent System Operators and utilities are developing
transmission planning processes to accommodate the needs of
a rapidly evolving and increasingly fragmented electricity
industry. Transmission planning must be conducted in
coordination with the power generation companies and
according to the location of power generating units. In
addition, transmission planning must consider to a far greater
extent than at present the interface with distribution.
In future, transmission planning must have some important
characteristics like:
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Stakeholder participation throughout the planning
process
Broad range of alternatives considered
Effects of transmission on generation market power
and congestion costs
Comprehensive risk assessment of transmission plan
Proactive, rather than reactive
Economies of scale
New technologies
Development of a practical and robust transmission
plan
Consideration of distribution system developments in
transmission planning
Likewise, the operation of transmission grids must pay
attention to many issues such as:
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Generation-demand balancing
Frequency control
Voltage and reactive power control
Inter-area exchange
Ancillary network services
Analysis of network security
Stability issues
Safeguard measures
Network reconfiguration
To achieve the objective of secure and stable operation it is
fundamental that information exchange is carefully managed
between all entities involved and that the information is
available for real-time control of networks. To this end the
importance of information and communication technologies
(ICT) will likely grow prolifically.
Nowadays almost all electrical systems in the world have
connections to other neighbouring systems, often in other
countries. This means that the grid operation should be
multilaterally coordinated. In the full paper the authors will
explain how this can be done and what models of transmission
systems are most appropriate, e.g., transmission capacity
model based on power transfer distribution factors.
Nevertheless there are still many questions to be solved
even under the present scenario, as is the case stated in [5]
where a divestment solution in transmission networks in the
EU is defended, showing that the present market organization
does not maximize economic efficiency.
In the full paper the authors will review the current status
of planning and operational practices for transmission power
networks, as a basis for the novel approaches suggested for
future transmission planning and operations. As will be
discussed later, the issue of achieving a global efficiency in
the planning and operation of future power systems will be
central to these developments.
III. FUTURE POWER NETWORKS FRAMEWORK
Recent advances in ICT, new power generation devices and
other relevant issues have been driving many important
research projects in order to preview the expected changes in
future power systems. In particular, the work developed under
the scope of [6] and [7] relates to two of the major projects
presently ongoing.
At the moment it is already possible to present some
common themes evident in both the future power system
projects referenced above. Specifically there are several
relevant aspects in these projects relating to changes in
planning and operational approaches for future power
networks. Among those changes, some of the most relevant
ones is the possible existence of exchange of functions,
information and services across the transmission-distribution
interface. Some examples of this are:
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Demand-side participation
Distributed power generation
Advanced control and FACTS (and D-FACTS)
Energy storage
In each of these examples it is evident that broad
implementation of these technologies and devices in
distribution systems will necessitate the passing of
information relating to their existence and status in both
planning and operational time scales.
Likewise, their
existence in large numbers will provide the opportunity for
supporting services to be provided to the transmission system
from distribution connected equipment. The functional split
in the planning and operation of these devices between
transmission and distribution entities is a critical issue.
In the full paper the authors will present a structured
approach to planning and operations in future power systems
with particular reference to the functions, services and
information exchange between transmission and distribution
networks to achieve maximum global efficiency.
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IV. EFFICIENCY CONSIDERATIONS
VI. REFERENCES
[1]
Concerns with efficiency have always existed side by side
with power networks planning and operations and assume
different aspects as we consider the planning or the
operational processes. The changes that will be imposed on
power networks under the future framework will also certainly
impose new definitions of efficiency and new functions
related to planning and operating for maximal efficiency. In
particular, it is likely that, along with new definitions for
efficiency, there will be a requirement for new metrics or
indexes to measure efficiency.
Efficiency in planning and operating power systems is
commonly attributed as economic efficiency of market
structures, cost efficiency of network investment, or losses
related efficiency in planning or operations terms. In future,
efficiency will encompass expanded definitions in these areas
plus aspects of environmental efficiency in terms of carbon
emissions and sustainability. In this regard, new tools will
likely be required to analyse the efficiency of planning and
operational options across a broad spectrum of efficiency
measures. In particular, achieving global efficiency of
transmission combined with distribution systems plus
independent generation and load customers is a major
challenge – particularly in deregulated power markets.
However, even though the challenge is great, the benefits are
thought to be vast, and therefore new approaches to assessing
efficiency and to combining the assessment across the
transmission-distribution interface are necessary.
In the full paper the authors will review the present new
concepts regarding network planning efficiency and
operational efficiency, and the drivers necessitating change in
this area.
V. CONCLUSIONS
This paper presents four main ideas that are inextricably
linked:
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There is an emerging body of literature regarding
possible future power system architectures
This future context implies new procedures and
approaches to power networks planning and
operations
Transmission and distribution planning and
operations must be coordinated much more closely in
future
The concept of efficiency in power system planning
and operations needs to be reviewed in the context of
future power systems
To this end the authors have embarked on research
programmes that seek to develop new analytical
techniques and concepts to address the issues discussed in
this paper. The outline of these new concepts and
techniques are presented in this abstract and will be
presented in more detail in the full paper.
[2]
[3]
[4]
[5]
[6]
[7]
UCPTE, "Summary of the current operating principles of the UCPTE”,
http://www.ucte.org/pdf/Aboutus/Mission/Summary-English.pdf
Nordel ad hoc group, "Reliability standards and system operating
practices”,http://europa.eu.int/comm/energy/electricity/florence/doc/flor
ence9/position_paper/nordel_reliability_2002.pdf
E. Hirst and B. Kirby, “Transmission planning and the need for new
capacity”, U.S. DOE National Transmission Grid Study,
http://www.eh.doe.gov/ntgs/reports.html#reports
REN, “Plano de Investimentos da Rede Nacional de Transporte 20042009,”, REN, www.ren.pt
J. Bower, "Electricity Infrastructure & Security of Supply : Should EU
Governments Invest in Transmission Capacity", in Oxford Energy
Comment. March 2004,
http://www.oxfordenergy.org/comment_prn.php?0403
EPRI, Intelligrid Architecture,
http://www.intelligrid.info/IntelliGrid_Architecture/Overview_Guidelin
es/index.htm
Graham Ault, Ian Elders, Stuart Galloway, James McDonald, Matthew
Leach, Efterpi Lampaditou, Jonathan Koehler, ‘Electricity Network
Scenarios for 2050’, SuperGen Future Network Technologies
Consortium Report EPSRC/SGFNT/TR/2005-001, July 2005.
VII. BIOGRAPHIES
Luís Castanheira received the B.Sc. degree in 1996 and the M.Sc. degree in
2002 from the University of Porto, Porto, Portugal. He is currently an
Assistant Professor of Electrical Power Systems with the Polytechnic Institute
of Porto, Porto, Portugal. He is also a PhD student with the University of
Strathclyde, Glasgow, UK and his research interests include energy and
sustainable development, distributed generation and future power systems
Graham Ault graduated from the University of Strathclyde in 1993 with a
first class honours degree in Electrical and Mechanical Engineering. He
returned to the Centre for Electrical Power Engineering (now Institute for
Energy and Environment) at the University of Strathclyde in 1996 to fill a
PhD research post focusing on the impact of small scale generation on
electricity networks. Gaining his PhD in 2000 he has expanded his research
portfolio to span several aspects of distributed generation, asset management,
and power system planning and development.
Luís Castanheira received the B.Sc. degree in 2001 from the Polytechnic
Institute of Porto , Porto, Portugal and he is currently an Assistant Professor of
Electrical Power Systems with the same school. He is also a PhD student with
the University of Vila Real, Vila Real, Portugal and his research interests
include future power systems
Jim McDonald received his BSc, MSc and PhD degrees from the University
of Strathclyde. His research activities lie in the areas of: power system
protection and measurement; Artificial Intelligence, renewable generation, and
energy management. He has published over 200 technical papers and is coauthor of two books. He is currently Head of the Electrical and Electronic
Engineering department at Strathclyde and actively involved in energy matters
at national and international levels.
Joaquim Borges Gouveia received the B.Sc. degree in 1973 and the Ph.D.
degree in electrical engineering in 1983 from the University of Porto, Porto,
Portugal. He is currently a Full Professor with the University of Aveiro,
Aveiro, Portugal. His research areas include energy efficiency, innovation, and
services operation management.
Zita Vale received the B.Sc. degree in 1986 and the Ph.D. degree in electrical
engineering in 1993 from the University of Porto, Porto, Portugal. She is
currently a Coordinator Professor with the Polytechnic Institute of Porto,
Porto, Portugal. Her research areas include power systems operation and
control, electricity markets, decision support, and artificial intelligence.