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SMART GRID
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information and control over their consumption
and, therefore, there are new technologies that
enable energy conservation and efficiency (e.g.,
smart buildings, smart meters, demand response,
etc.). Without investment in the smart grid
infrastructure to support these technologies,
natural limits will be reached as to what can be
achieved. The existing distribution grid
infrastructure is primarily designed for one-way
flow of electricity and limited consumption in
the home. With the growing implementation of
large-scale, intermittent renewable energy
generation, distributed generation and electric
vehicles, the operational limits of the network as
it is currently designed will be reached. To
avoid stalling progress towards a sustainable and
low-carbon future, necessary investments must
be made in power grid and urban infrastructures
that will effectively (without significant
operational constraints) accommodate these
technologies at large-scale deployment.
II. SMART GRID : DEFINITIONAND PURPOSE
In the following section we will describe the
power grid, how it operates today and how a
smarter grid will change the design and
operations to lead to more efficient, effective
power delivery in the future. There are several
challenges, which are leading decision-makers
to consider this technology as an option and in
some cases a requirement. This section will
explore the different capabilities which sit
within the smart grid construct and how they
help respond to those challenges.Current Status
of Power Grid
Todays power grid is composed of two
networks. The first is an actively managedtransmission network, which supplies electricity
over longer distances at a higher voltage; the
other, the distribution network, operates at a
lower voltage and takes electricity the last mile
to individual homes and businesses. The
traditional grid is represented in Fig.1.
Combined, transmission and distribution
networks represent a significant technical
legacy, mirrored in its investment requirements;
Figure.1 Traditional grid and its Features
Unlike other industries, telecommunications
for example, power utility infrastructure is
composed of many analogue/electromechanical
legacy systems that are prone to failure and
blackouts. It is dominated by centralized
generation disseminated via a relatively passive
(limited control), and one-way or limited two-
way communication network between utilities
and the end users. Residential energy
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consumption is often projected rather than
measured. Grid maintenance is time-based and
often reinforced when system components fail
or reach their expected lifetime. Outage
management practice relies on consumers
notifying the utility that a power outage has
occurred. A significant volume of the electricity
that enters the network is lost through either
technical inefficiencies or theft from 4-10% in
Europe to more than 50% in some developing
city environments.
A. Definition of Smart Grid
Smart grids incorporate embedded computer
processing capability and two-way
communications to the current electricity
infrastructure. A smart grid uses sensing,
embedded processing and digital
communications to enable the electricity grid to
be:
--Observable (able to be measured and
visualized)
--Controllable (able to manipulated and
optimized)
-- Automated (able to adapt and self-heal)
--Fully integrated (fully interoperable with
existing systems and with the capacity to
incorporate a diverse set of energy sources).
The smart grid encapsulates embedded
intelligence and communications integrated at
any stage from power generation to end
consumption. To date, the majority of the
industry debate has centered on smart meters
and advanced metering infrastructure devices
designed to accurately measure and
communicate consumption data in the home or
office environment. Confusion can arise if the
term smart meter is used synonymously with
smart grid. One of the objectives of this paper
is to provide some clarity regarding this
misunderstanding. The reality is that, with the
holistic smart grid, the smart meter becomes just
one more node on the network, measuring and
relaying flow and quality data.
Figure.2 Smart grid and its Features
The various fields a smart grid encompasses
is represented below in Fig.3
Figure.3 An artists perception of the Smart
Grid
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II. SMART GRIDS CHARACTERISTICS:
A confluence of factors is driving the need for
investment. Smart grids have the ability to
fundamentally change the way people interactwith their electricity supply. A smart grid will
exhibit seven key characteristics:
B. Self-healing and Adaptive:
A smart grid will perform real time self-
assessments to detect, analyze and respond to
subnormal grid conditions. Through integrated
automation, it will self-heal, restoring grid
components or entire sections of the network if
they become damaged. It will remain resilient,
minimizing the consequences and speeding up
the time to service restoration. The modernized
grid will increase the reliability, efficiency and
security of the power grid and avoid the
inconvenience and expense of interruptions agrowing problem in the context of ageing
infrastructure. In the US alone, interruptions in
the electricity supply cost consumers an
estimated US$ 150 billion a year [4]. It will
reduce vulnerability to the growing threats of
natural disasters (hurricanes, ice storms) as well
as cyber-attacks and terrorism.
C. Integration of advanced and low-carbon
technologies:
A smart grid will exhibit plug and play
scalable and interoperable capabilities. A smart
grid will permit a higher transmission and
distribution system penetration of renewable
generation (e.g. wind and photovoltaic solar
energy resources), distributed generation and
energy storage (e.g. micro-generation). Case
studies from Belgium demonstrate that as low as
a 7% penetration of distributed wind turbines on
the low voltage network can begin to cause
major problems on the distribution network. To
mitigate the intermittent nature of renewable
generation, the smarter grid can leverage
embedded storage to smooth output levels.
Without a smart grid, diurnal variations in
generation output will typically require
renewables to be backed with fast ramp-up
fossil fuel based plants. Smart grids will also
provide the necessary infrastructure for mass
adoption of plug-in hybrid and electric vehicles,
ultimately enabling both scheduled dispatch of
recharge cycles and vehicle- to grid capability.
Such networks will allow society to optimize the
use of low-carbon energy sources, support the
efforts to reduce the carbon intensity of the
transport sector and minimize the collective
environmental footprint.
D. Enable Demand Response:
By extending, the smart grid within the home
(via a home area network), consumer appliances
and devices can be controlled remotely,
allowing for demand response. In the event of a
peak in demand, a central system operator
would potentially be able to control both the
amount of power generation feeding into the
system and the amount of demand drawing from
the system. Rather than building an expensive
and inefficient peaking plant to feed the spikes
in demand, the system operator would be able to
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issue and demand response orders that would
trigger a temporary interruption or cycling of
noncritical consumption (air conditioners, pool
pumps, refrigerators, etc.).
E. Asset Optimization And Operational
Efficiency:
A smart grid will enable better asset
utilization from generation all the way to the
consumer ends. It will enable condition- and
performance-based maintenance. A smart grid
will operate closer to its operational limits,freeing up additional capacity from the existing
infrastructure; this remains an attractive
proposition when a US study demonstrated that
transmission congestion costs Eastern US
consumers US$ 16.5 billion per year in higher
electricity prices alone. Smart grids will also
drive efficiencies through reductions in
technical and non-technical line losses
estimates are that 30% of distribution losses
could be mitigated.
F. Customer Inclusion:
A smart grid will involve consumers,
engaging them as active participants in the
electricity market. It will help empower utilities
to match evolving consumer expectation and
deliver greater visibility and choice in energy
purchasing. It will generate demand for cost-
saving and energy-saving products. In a world
where consumer expectations and requirements
are growing, smart grids will help educate the
average consumer, foster innovation in newenergy management services and reduce the
costs and environmental impact of the delivery
of electricity.
G. Power Quality:
A smart grid will have heightened power
quality and reductions in the occurrence of
distortions of power supply. As the load
demands increase on an exponential path, power
quality degradation will manifest as more of an
issue, in turn requiring distributed monitoring
and proactive mediation. This will confluence
with a decrease in tolerance for power qualityvariances from modern industry, particularly the
hi-tech sector and the higher costs of such
quality issues as economies grow.
H. Market Empowerment:
A smart grid will provide greater transparency
and availability of energy market information. It
will enable more efficient, automated
management of market parameters, such as
changes of capacity, and enable a plethora of
new products and services. New sources of
supply and enhanced control of demand will
expand markets and bring together buyers and
sellers and remove inefficiencies. It will shift the
utility from a commodity provider to a service
provider.
II. IMPACTOF THE ENABLING TECHNOLOGIES
With all of the Smart Grid research
activity; it is desirable to investigate whether
Smart Grid technologies will have any design
implications for distribution systems. Will the
basic topology and layout of a Smart Grid be
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similar to what is seen today? Alternatively,
will the basic topology and layout of a Smart
Grid look different? To answer these questions,
the design implications associated with the
major technological drivers will be examined.
After this, the next section will examine the
design implications of all of these technologies
considered together.
I. Advanced Metering Infrastructure(AMI)
A Smart Grid will utilize advanced digitalmeters at all customer service locations. These
meters will have two-way communication, be
able to remotely connect and disconnect
services, record waveforms, monitor voltage
and current, and support time-of-use and real-
time rate structures. The meters will be in the
same location as present meters, and therefore
will not have any direct design implications.
However, these meters will make a large
amount of data available to operations and
planning, which can potentially be used to
achieve better reliability and better asset
management.
Perhaps the biggest change that advanced
meters will enable is in the area of real-time
rates. True real time rates will tend to equalize
distribution system loading patterns. In
additions, these meters will enable automatic
demand response by interfacing with smart
appliances. From a design perspective, peak
demand is a key driver. If peak demand per
customer is reduced, feeders can be longer,
voltages can be lower, and wire sizes can be
smaller. Most likely, advanced metering
infrastructure will result in longer feeders. A
prototype of Smart Meter is shown in Fig.4.
Figure.4 Example of a smart meter in use in
Europe that has the ability to reduce load,
disconnect-reconnect remotely, and interface to
gas & water meters
J. Distribution Automation:
Distribution automation (DA) refers to
monitoring, control, and communication
functions located out on the feeder. From a
design perspective, the most important aspects
of distribution automation are in the areas of
protection and switching (often integrated into
the same device). There are DA devices today
that can cost-effectively serve as an intelligent
node in the distribution system. These devices
can interrupt fault current, monitor currents and
voltages, communicate with one-another, and
automatically reconfigure the system to restore
customers and achieve other objectives. The
ability to quickly and flexibly reconfigure an
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interconnected network of feeders is a key
component of Smart Grid. This ability, enabled
by DA, also (1) requires distribution
components to have enough capacity to accept
the transfer, and (2) requires the protection
system to be able to properly isolate a fault in
the reconfigured topology. Both of these issues
have an impact on system design. Presently,
most distribution systems are designed based on
a main trunk three-phase feeder with single-
phase laterals. The main trunk carries most
power away from the substation through the
center of the feeder service territory. Single-
phase laterals are used to connect the main
trunk to customer locations. Actual distribution
systems have branching, normally open loops,
and other complexities, but the overarching
philosophy remains the same.
A Smart Grid does not just try to connect
substations to customers for the lowest cost.
Instead, a Smart Grid is an enabling system that
can be quickly and flexibly be reconfigured.
Therefore, future distribution systems will be
designed more as an integrated Grid of
distribution lines, with the Grid being connected
to multiple substations. Design, therefore, shifts
from a focus on feeders to a focus on a system
of interconnected feeders. Traditional
distribution systems use time-current
coordination for protection devices. These
devices assume that faster devices are
topologically further from the substation. In a
Smart Grid, topology is flexible and thisassumption is problematic. From a design
perspective, system topology and system
protection will have to be planned together to
ensure proper protection coordination for a
variety of configurations.
K. Distributed Energy Resources:
Distributed energy resources (DER) are
small sources of generation and/or storage that
are connected to the distribution system. For
low levels of penetration (about 15% of peak
demand or less), DER do not have a large effect
on system design as long as they have properprotection at the point of interconnection. A
Smart Grid has the potential to have large and
flexible sources of DER. In this case, the
distribution system begins to resemble a small
transmission system and needs to consider
similar design issues such as non-radial power
flow and increased fault current duty. Other
design issues related to the ability of a
distribution system to operate as an electrical
island, the ability of a distribution system do
relieve optimal power flow constraints, and the
ability of DER to work in conjunction as a
virtual power plant [8].
L.Microgrids:
Microgrids are generally defined as low
voltage networks with DG sources, together
with local storage devices and controllable
loads (e.g. water heaters and air conditioning).
They have a total installed capacity in the range
of between a few hundred kilowatts and a
couple of megawatts. The unique feature ofmicrogrids is that, although they operate mostly
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connected to the distribution network, they can
be automatically transferred to islanded mode,
in case of faults in the upstream network and
can be resynchronized after restoration of the
upstream network voltage. Within the main
grid, a microgrid can be regarded as a
controlled entity that can be operated as a single
aggregated load or generator and, given
attractive remuneration, as a small source of
power or as ancillary services supporting the
network.
Figure.5 Evolution of Smart Grid incorporating
distributed generation resources and virtual
utilities
M. Virtual Utilities:
Virtual utilities (or virtual electricity
market) adopt the structure of the internet-like
model and its information and trading
capability, rather than any hardware. Power is
purchased and delivered to agreed points or
nodes. Its source, whether a conventional
generator, Renewable Energy Source (RES) or
from energy storage is determined by the
supplier. The system is enabled by modern
information technology, advanced power
electronic components and efficient storage.
Fig.5 shows future grid system with all above-
mentioned smart features.
N. Other technologies:
Advanced power electronics will allowvariable-speed operation of electric generators
and motors to increase the overall efficiency of
the electricity supply chain as well as to
increase the quality of the power supply. They
may also extend the application of HVDC lines-
for example with superconducting cables- that
could enhance transmission and distribution.
I. SHAPINGUPFORTHE FUTURE :
COMMUNICATIONISTHE KEY
Throughout the development of the new
grids, communication at every level is essential.
Effective dialogue between stakeholders will
ensure that relevant information influences the
system design. The latest technologies will be
incorporated into the network and the approach
will remain flexible to accommodate further
developments. Once the networks are up and
running, two-way flows will exist between
provider and user.
It is important to emphasize the role of
Information and Communication Technology
(ICT) in particular telecommunications in
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adapting electricity networks to the real time
actions and managing control distributed in the
network, which may not be fully supported by
the present internet generation. Even if the
internet protocol is universal, a serious effort is
needed to effectively use communications
equipment for a distributed real-time control of
electricity networks.
The real time performance of the internet as
communication means is known to be very
difficult to assess and it is critical given the
power balance needed at any instant in time. It
is possible to conceive such a network but the
real hardware, protocols, standards and markets
at all levels are more difficult to realize. The
question of international regulation must be
addressed, not only at the technical but also at
the political level.
A. A Period of Transition
In managing the transition to the internet-
like model, it may be useful to consider
concepts under development in a number of
projects under the European Commissions
Framework Programs: for example, active
distribution networks.
The function of the active distribution
network is to efficiently link power sources
with consumer demands, allowing both to
decide how best to operate in real time. The
level of control required to achieve this is much
greater than in current distribution systems. It
includes power flow assessment; voltage
control and protection require cost-competitive
technologies as well as new communication
systems with more sensors and actuators than
presently in the distribution system. The
increase in required control leads to a dramatic
rise in information traffic derived from status
and ancillary data. This, along with the ability
to re-route power, means that the active
network represents a step towards the internet-
like model.
B. Active Management
The evolution of active management,summarized in the next figure Fig.6, can be
described as follows:
--Initial stage: Extension of Distributed
Generation (DG) and RES monitoring and
remote control to facilitate greater connection
activity. Some connections will rely on bilateral
contracts with distributed generators for
ancillary services. Rules will have to be defined
to outline physical and geographical boundaries
of contracting.
--Intermediate stage: A management regime
capable of accommodating significant amounts
of DG and RES has to be defined: local and
global services and trading issues, adaptability
without information overload, control issues.
--Final stage: Full active power
management. A distribution network
management regime using real-time
communication and remote control to meet the
majority of the network services requirement.
The transmission and distribution networks are
both active, with harmonized and real-time
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interacting control functions and efficient power
flow.
The three stages are represented in the Fig.3
below:
Figure.6 Stages in Active Management
II. AN INTEGRATED SMART GRID
Smart Grid solutions, including
Distribution Automation, Asset Management,
Demand Side Management, Demand Response,
Distributed Energy Management and Advanced
Metering Infrastructure, allow utilities to
identify and correct a number of specific system
issues through a single integrated, robust, and
scalable Smart Grid platform.
Consider a distribution system with
pervasive AMI, extensive DA, and high
levels of DER. As mentioned in the
previous section, each of these
technologies has certain implications
for system design. However, a true
Smart Grid will not treat these
technologies as separate issues.
Rather, a Smart Grid will integrate the
functions of AMI, DA, and DER so that
the total benefits are greater than the
Figure.7.An Integrated Smart Grid
sum of the parts. Much of the integration
of functions relates to communication systems,
IT systems, and business processes. System
design of a distribution system, when it can take
full advantage of AMI, DA, and DER working
together, a Smart Grid will increasingly look
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like a mesh of interconnected distribution
backbones.
This Grid will likely be operated radially
with respect to the transmission system, but
non-radially with respect to DER. Protection on
this backbone will therefore have to be smart,
meaning protection setting can adapt to
topology changes to ensure proper coordination.
Radial taps will still be connected to the
backbone, but lateral protection will gradually
move away from fuses cutouts. DA on laterals
will become more common and laterals will
increasingly be laid out in loops and more
complex network structure.
Currently, distribution systems are designed
to deliver power to customers within certain
voltage tolerances without overloading
equipment. In a Smart Grid, these criteria are
taken for granted. The driving design issues for
Smart Grid will be cost, reliability, generation
flexibility, and customer choice. Networks are
evolving and Smart Grids incorporate the latest
technologies to ensure that the networks will be
flexible, accessible, reliable and economical.
An integrated Smart Grid is shown in Fig.7
Smart Grid Benefits:
The goal of the Smart Grid is to use advanced
information-based technologies to increase grid
efficiency, reliability and economy. Consumers,
utilities, the environment and society as a whole
will benefit from better use of new and existing
energy delivery infrastructure.
See figure 8 for a graphical representation of
potential Smart Grid benefits
8: Smart Grid Benefits
Improved System Reliability:
The Smart Grid will provide dynamic,
real-time monitoring, control and optimization
of grid operations and resources in a number of
ways:
Advanced network visualization,
distribution applications and outage defense
systems will give utilities the capacity to detect,
analyze and restore system faults before they
jeopardize system integrity.
Greater coordination among all
participants in the system will trigger better
price signals and a more efficient balance
between demand and supply.
Increased physical and cyber security, as
well as special protection systems, will warn of
security threats before they escalate.
Significant reductions in residential peak
demand energy consumption will be achieved
by providing real-time pricing and
environmental signals in conjunction with
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advanced in-home and distributed generation
technologies.
Advanced outage management systems and
distribution automation schemes will result in
fewer blackouts and local power disruptions
along with faster recovery times.
Increased Consumer Participation:
As an integral part of the Smart Grid,
homeowners will have the tools and
information to actively manage their power
consumption. Using smart meters and in-home
automation, utilities will be able to provide their
consumers with the next generation of energy
services. DSM programs in particular will
satisfy two basic consumer needs: the need to
understand the cost of ones consumption
habits, and the need for greater choice in energy
services. At the utility end, DSM programs
allow utilities to reduce or shift peak demand,
minimizing capital expenditures and operating
expenses. Peak shifting also translates to
substantial environmental benefits in terms of
reduced line losses and improved dispatching of
generation units. Over time, DSM will also
encourage consumers to replace inefficient end-
use devices such as incandescent lighting and
embrace emerging products such as plug-in
hybrid electric vehicles.
Increased Efficiency:
Improving the operational efficiency
of the electric power system is one of thegreatest potential benefits of the Smart Grid.
Advanced power electronics will improve the
quality of the power supply by allowing for
variable-speed operation of electric generators
and motors, controlling reactive power. Utilities
may also extend the application of High
Voltage Direct Current (HVDC) lines to reduce
line losses in long-distance, interregional power
transmission. Broadband communications will
be used connect power producers and loads at
every voltage level at a very low cost,
permitting utilities to implement new strategies,
such as virtual power plants or power markets
for small producers or consumers.
Environmental Benefits:
The threat of global warming, air
pollution and resource degradation are forcing
government policy makers, the general public
and the utility industry to question the
sustainability of our present energy
infrastructure. The Smart Grid will allow
modern society to address these challenges as
they become ever more pressing. In particular,
greater efficiencies in the grid will help
alleviate the need for new generation,
transmission and distribution facilities, and
result in massive amounts of avoided emissions.
The mass deployment of Advanced Metering
Infrastructure (AMI) adopted by leading
utilities has already shed light on the ability for
Smart Grid technologies to reduce
consumption. Likewise, improved integration ofsmaller generators in the distribution system
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will increase the role of renewable energy
supplies in meeting regional demand.
Economic Benefits:
Improved load estimates and reduced
line losses will improve asset utilization and
translate to long-term avoidance of capital
expenditure for generation, transmission and
distribution projects. Operationally, the
advantages of automated operations, predictive
maintenance, self-healing mechanisms and
reduced outages will bring about major
reductions in labor costs, particularly those
associated with maintenance and outage
recovery. From a macroeconomic perspective,
the wide-scale implementation of the Smart
Grid will create new jobs, spur competitive
technology development and revitalize a sector
of the economy that is traditionally slow to
change.
Conclusions:
In conclusion, the smart grid brings bothbenefits and design challenges to the utility, its
customers, and the associated technologists.
The electric power system is arguably the
worlds largest machine, if one defines a
machine as a series of interconnected parts that
form a common system. Transient stability, I2R
losses, communications, security, system
architecture and modeling are all parts of the
complex picture. There are several points to
progress toward the smart grid. Operational
Technology and Information Technology
departments should become closer. Security has
to be considered from the beginning of the
project. Data communications is often the
largest missing piece. The project needs to be
done in well-defined phases. Phase 0 is learning
of all existing and in-flight projects within the
utility. Systems integration is essential to
realizing benefits. The primary mission is still
to keep the lights on. The data deluge must be
managed. Knowledge capture is part of smart
grid planning and results. The work is not all
technical; there are strategy and change
components for the employees. To
accommodate a more flexible, dynamic, secure,
and diverse system, the smart grid is an
essential component on the path to the energy
future of 2030.