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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.

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