eirgrid's grid25 report 3b/reference material/… · fuels and are thus a call to action in...

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25A Strategy for the

Development of Ireland’s

Electricity Grid for

a Sustainable and

Competitive Future

www.eirgrid.com

EirGrid is a state-owned company and is the independent electricityTransmission System Operator (TSO) in Ireland and the Market Operator(MO) of the wholesale electricity trading system. EirGrid's role is to deliver quality connection, transmission and market services to electricitygenerators, suppliers and customers utilising the high voltage electricitysystem. We are responsible for the Grid infrastructure required to supportthe development of Ireland's economy, as well as connecting the IrishGrid to the European Grid. EirGrid plays a key role in the operation of the Single Electricity Market (SEM) which services the island of Ireland.

EIRGRID’S MISSION IS TO DEVELOP, MAINTAIN AND OPERATE A SAFE, SECURE,RELIABLE, ECONOMICAL ANDEFFICIENT TRANSMISSIONSYSTEM FOR IRELAND.

1

Contents

3 Foreword by the Minister for Communications,Energy and Natural Resources, Eamon Ryan, T.D.

5 Introduction by Dermot Byrne, Chief Executive, EirGrid

6 Executive Summary

11 Introduction to GRID25

13 Vision

19 Future Grid Requirements

21 The Grid Development Strategy

23 A Regional View

Appendices

44 Technical Options for Grid Development

47 Glossary

A Strategy for the Development of Ireland’s Electricity Grid 2

for a Sustainable and Competitive Future 3

The last few years have seen extraordinary changes in global electricity markets, as climate change and energy security have moved to the top of policy imperativesat home, in Europe and across the world.

These issues are likely to continue to put upward pressure on the price of fossilfuels and are thus a call to action in energy policy. EirGrid’s Grid DevelopmentStrategy, GRID25, is a critical element in future-proofing Ireland’s electricity needsby facilitating more sustainable, competitive, diverse and secure power supplies insupport of economic and social development and renewable energy deployment.

The Strategy, when implemented in full, will provide a platform so that in eachregion of Ireland we can harness our abundant renewable energy resources andprovide clean and competitively priced electricity for homes, businesses and newhigh-tech industries.

GRID25 builds on the significant investment that has already been made in ourtransmission network and moves us towards a cutting-edge intelligent electricitysystem. We are also extending that network by connecting to the UK and in duecourse to the European Grid. This will enable us to participate in the Europeanmarket and facilitate both the export and import of electricity.

GRID25 has been informed by the findings of the ground-breaking All-Island Grid study which demonstrates the feasibility of at least 40% renewable electricityin our system by 2020 if we develop our Grid in a smart manner. This level ofrenewable supplies will help us meet our domestic targets and support theEuropean Union’s 2020 climate change targets. However, in developing such long-lasting infrastructure we must be cognisant of the future when larger emissionsreductions will be needed and the supply of fossil fuels may be much less secure.

EirGrid is taking on the challenge on behalf of Irish business and consumers, ofbuilding a network fit for the 21st century. Doing so is the first crucial step to allowus to position Ireland as a world leader in clean energy production. Getting our Grid development right can give other developers the confidence to invest in thejobs and plant that will power our future. The Grid to be delivered by GRID25 willensure our transition to a low-carbon economy.

The delivery of GRID25 is a collective enterprise and requires all stakeholdersincluding enterprise, local communities and the regions to work with each other. I have every confidence that together we can deliver.

FOREWORDBY THE MINISTER FOR COMMUNICATIONS, ENERGY AND NATURAL RESOURCES,

EAMON RYAN, T.D.

Eamon Ryan, T.D.Minister for Communications, Energy and Natural Resources

EirGrid is takingon the challengeon behalf of Irish business and consumers, of building anetwork fit for the 21st century.


I am pleased to present EirGrid’s Grid Development Strategy, GRID25. This is a majorinitiative to put in place safe, secure and affordable electricity supply throughoutIreland, supporting economic growth and providing a roadmap to a bright future for renewable and sustainable energy.

Electricity is a vital service for domestic, business, farming and industrial customersand this Strategy is designed to ensure that the transmission network has the capacityto provide for growth in electricity demand between now and 2025.

A strong transmission grid is essential for Ireland to attract and retain high-techindustrial investment, for the country to have competitive energy supplies and balancedregional development and in order to reduce our dependence on fossil fuels in light ofthe major issue of climate change.

It results from a robust and stringent analysis of the long term needs of electricityusers nationwide and includes very practical and progressive solutions to deliver highquality, secure and economic power supplies in line with best international practice.

Putting in place infrastructure is never easy and does require sensitivity to differingneeds and concerns and this document addresses those issues in a comprehensive way.

It is vital that Ireland has the electricity supply infrastructure to ensure oureconomic growth and maximise our competitiveness. EirGrid is committed to thedelivery of this Strategy for the national good and will consult widely on the Strategyand its implementation.

The implementation of GRID25 is essential if Ireland is going to meet its targets for generating electricity from renewable sources. It also enables Ireland to link to Britain and further afield with potential to both export and import electricity.

The Strategy reflects the output of the All-Island Grid Study and is consistent with theGate 3 process for connection of wind generation. I am very grateful for the support ofthe Minister for Communications, Energy and Natural Resources, Eamon Ryan, T.D., inlaunching this Strategy.

GRID25 also enables the different regions to develop their potential in attracting new high-tech industry and to accommodate population growth and represents a totalinvestment of €4 billion, which has been carefully considered and will be delivered in a responsible and cost-effective way. The Commission for Energy Regulation (CER) willhave an overall monitoring and approval role to ensure the investment is deliveredeffectively and efficiently.

There are very significant opportunities and challenges over the coming years. The Irish power system has successfully provided the energy for major economicgrowth in the past 20 years and I am convinced that this Strategy will set the stage forfurther growth. Developing the National Electricity Grid requires support from allstakeholders and the importance of progress in delivery cannot be over-emphasised.

Putting this Strategy in place will ensure that Ireland has the best possible platformin terms of a world-class, competitive and sustainable electricity system.

It is vital thatIreland has theelectricity supplyinfrastructure to ensure oureconomic growthand maximise ourcompetitiveness.

INTRODUCTIONBY DERMOT BYRNECHIEF EXECUTIVE, EIRGRID

Dermot ByrneChief Executive, EirGrid


The Transmission Grid provides a vitallink between all generators and theusers of electricity. It provides physicalaccess to all generators to a centralmarket and it enables all users to availof electricity from the central market at the most economic rates.

Over the next 15 to 20 years, majorchanges will take place in Ireland’selectricity needs, in its sources of fueland in its fleet of power stations.

Change will increasingly be drivenby issues of energy security,competitiveness, climate change and by the need to move away from imported fuels.

GRID25 will bring new levels of wind generation, both on and off-shore and an introduction ofcommercial ocean technology-basedgeneration to Ireland. It will alsorequire flexible conventionalgeneration, as well as marketstructures and networks thatencourage competition, and whichenable consumers to benefit fromeconomic electricity.

What will remain constant throughthis period will be the requirement of all consumers – householders,farmers, small and medium sizedbusinesses and large industries – forhigh quality, reliable power supplies.

The National Electricity Grid willremain a vital channel for essentialsupplies delivered reliably, forsustainable and renewable energy andfor open competition within the sector.A strong grid will bring the energysupplies which will enable Ireland toprosper economically and to providegood quality of life to its people.

The Grid will be a key pillarsupporting balanced regionaldevelopment, linking parts of thecountry rich in renewable energy or

EXECUTIVESUMMARY

conventional generation, to the rest ofthe country, enabling all market usersto benefit from reliable electricalenergy at the most economical price.

For the Grid to play its part fully, it must be developed. The bulktransmission system, comprisingcircuits at 220 kV or higher,represents the motorways and dualcarriageways of the electricitytransport system. Capacity hasremained largely unchanged in thelast 20 years, a period that has seen a growth of 150% in the electricitydemand being carried by the system.EirGrid calculates that to facilitate the necessary increase in renewablegeneration and to adequately meetthe demands of the electricitycustomer, the capacity of the bulktransmission system will need to be doubled by 2025.

This will be achieved through major reinforcements to the existingnetwork using the best technologicalsolutions available. The Grid will bedeveloped taking account of thecontinuing need to balance thereliability and security objective withthe costs and environmental impact ofdevelopments in a sustainable way.

The Strategy described here willinvolve upgrading the high voltagesystem and an investment ofapproximately €4 billion over the period to 2025. This new infra-structure is every bit as essential to the future growth of the country as any investment in road, rail and broadband.

GRID25 strikes a balance betweencosts, reliability and environmentalimpact. It examines the totality ofdevelopments and considers avariety of options to minimise the netlength of new line build in a region


through a number of initiativesdesigned to maximise the use of the existing network.

This level of new and upgradedinfrastructure represents a majorshift in the scale of grid developmentfrom today’s levels and will presentsignificant challenges to all involvedin its delivery. We will have todevelop innovative methods forupgrading existing network so thatthe disturbance and the costs tocustomers can be minimised. And we will need to find quicker ways ofprogressing through all the variousphases of planning and constructionto deliver a system capable ofaccepting large amounts of newrenewable and conventionalgeneration. EirGrid is committed toensuring that these developments are completed on time and in a cost-effective way.

MW

GRID25 is essential to:

■ Supporting growth in the regionsand ensuring continuedreliability and security of supply;

■ Providing high-quality, high-voltage bulk power supply forIreland that will enable thedifferent regions to attract infuture industry and boostexisting industry;

■ Exploiting Ireland’s naturalrenewable sources of energy(wind and wave);

■ Reducing Ireland’s carbonemissions by transmittingrenewable energy in line with Government policy;

■ Increasing Ireland’s connectivityto the European Grid, allowingfor both bulk exports ofelectricity and imports ofelectricity when appropriate.

The consequences of non-action are:

■ Within the next five to ten years keyparts of the Grid will have reachedcapacity and will be in danger ofoverloading, resulting in loss ofsupply to customers;

■ High-tech industry that requiressecure, high quality energysupplies will be limited to locationswith strong grid infrastructure;

■ The needs of new and currentresidential clients will not be met;

■ The power system will not be ableto guarantee security of supply;

■ Access to the market will not be possible for all low-costgenerators limiting competitive-ness in the electricity market;

■ The drive to reduce Ireland’s CO2emissions and meet its targets for the use of renewables incompliance with legislation will be seriously undermined;

■ Ireland will not be stronglyconnected to the European Grid andwill be unable to participate fully ina pan-European electricity market.

DEMAND GROWTH 1985-2025

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1985 1988 1991 1994 1997 2000 2003 2006 2009 2012 2015 2018 2021 2024

for a Sustainable and Competitive Future 9A Strategy for the Development of Ireland’s Electricity Grid 8

GRID25 IS AN ESSENTIAL INFRASTRTO FACILITATE RELIABLE, SECURE AELECTRICITY SUPPLIES THROUGHO

UCTURE INITIATIVE ND AFFORDABLE UT IRELAND.

Without it, within the next five to ten years key parts of the Grid will have reached capacity and will be in danger of overloading, resulting in ‘blackouts’.


The need for changeElectricity is a fundamental componentof life in the modern world. Ireland, likemany countries, faces the challenge ofproviding the platform on which wewill continue to support reliable andaffordable electricity services in thecoming decades.

The world’s energy industry ischanging significantly to counter thedeclining stocks of fossil fuels and to limit the production of harmfulgreenhouse gasses. The Governmentin its White Paper on “Delivering a Sustainable Energy Future forIreland”, published in 2007, has settargets for the electricity industry inIreland to meet these challenges. A significant contribution to oursustainable energy future will comefrom renewable energy sources.

Energy efficiency will be increasinglyimportant in moderating growthdriven by population numbers andeconomic development. EirGrid willcontinue with active campaigns to encourage savings in power usewhere possible and will also supportsmart metering which will enableconsumers to more directlyparticipate in managing their own consumption.

The transmission network plays animportant role in transporting thepower from the variety of generationsources, both conventional andrenewable, to the towns and cities, foronward distribution to every home,farm and business across the country.EirGrid is responsible for developingthe transmission network in Ireland. It does this to ensure that there isadequate network capacity to carrypower from new generation stationsand to ensure a reliable supply tomeet growing demand for electricity.

A balanced forward-thinkingapproach will be adopted to minimisethe impact on the environment while

01 INTRODUCTION TO GRID25

providing the necessary capacity fortransporting power from source topoint of use.

GRID25 provides an outline designfor how the transmission network willbe developed in the long-term to meetthe challenges ahead.

The overall goal of GRID25 is todevelop the network economically toreliably meet anticipated transportneeds of users of the Grid. Inachieving this goal GRID25 supportsthe Government’s priority actions of increasing the penetration ofrenewable energy technologies and of improving energy efficiency and energy savings.

The reasons for GRID25

GRID25 provides a common under-standing of how the development ofthe Grid should be undertaken tosupport a long-term sustainable andreliable electricity supply.

The long-term view of transmissioninfrastructure requirements provides aguide to the scale of grid developmentrequired to correctly match theanticipated long-term needs. In theabsence of a long-term view, thedevelopments may otherwise beplanned piecemeal to only meet the short-term needs as they arise,resulting in inefficient investment andin many cases an ineffective grid.

High voltage networks providemuch greater capacity than lowervoltages. For instance a 400 kV lineprovides about three times thecapacity of a 220 kV line. Another way of expressing this is that it wouldtake three 220 kV lines to provide thesame capacity as a 400 kV line. So,where the long-term need may be for a 400 kV line, without foresight,three 220 kV lines may be installed.Developments based on a long-termview are therefore more economic andhave less impact on the environment

Grid25 provides a common under-standing of howthe developmentof the Grid shouldbe undertaken tosupport a long-term sustainableand reliableelectricity supply.


and the communities through whichthe circuits pass.

Next stepsGRID25 provides an approach to griddevelopment over the next decadeand beyond. It also provides a scale tothe necessary infrastructure requiredon a national and regional level. As a matter of priority, EirGrid willprogress network development tomeet anticipated needs in line withthe GRID25 Strategy.

EirGrid has begun to undertakedetailed studies to more clearly

specify reinforcement projectrequirements. The studies will assessenvironmental impact, technicalissues and route identification for the many necessary schemes.

Once the information alreadycontained in this Strategy, such as the needs of a region, is collated withthe information from the studies, plansfor specific projects will be drawn upand implemented in consultation withthe public and all key stakeholders,and subject to regulatory oversight by the Commission for EnergyRegulation (CER).

01INTRODUCTION

proposedsolutions

briefing + feedback consultation

projectdevelopment

THE GRID25 PROCESS


The demands for transmission serviceswill be far different in 2025 to whatthey are today. We must plan now tomeet these changing needs.

Our vision is of a grid developed tomatch future needs, so it can safelyand reliably carry power all over thecountry to the major towns and citiesand onwards to every home, farm and business where the electricity is consumed and so it can meet theneeds of consumers and generators in a sustainable way.

The drivers of grid investment arecomplex in nature and require careful analysis.

In many cases growth in demand forelectricity results in higher power flowson the transmission network. Wherethe power flows exceed the capabilityof the Grid, reinforcement is necessary.Demand forecasts are therefore a good indicator of the need for grid investment.

In general, the addition ofgeneration creates a much greater and immediate impact on the Grid than demand increases because of the size of a generator relative to the more gradual increases in localdemand. The Grid often has to bereinforced to facilitate the flow ofpower from the generator to the rest of the system. This is true whether the generator is connected to thetransmission system or to thedistribution system.

Customer demand close to agenerator can reduce the amount ofpower that must be transported awayfrom the area. In certain parts of thenetwork, therefore, higher demandlevels may result in a reducedinfrastructure build.

Demand for electricityDemand for electricity has grown

steadily since the early days of anational electricity supply. Electricityis a safe, versatile and economic form

02VISION

of energy favoured by industrial,commercial and domestic customers.A well established relationship existsbetween economic growth andelectricity consumption. The forecastfor demand levels in 2025 are basedon the Economic and Social ResearchInstitute’s long-term forecast ofmoderate growth in economic activity.

One of the Government’s mainpriorities towards creating a sustain-able energy future is the area ofenergy efficiency and savings. Asuccessful energy efficiency campaignwill improve performance across all energy sectors including theelectricity sector. One plausibleoutcome of the energy efficiencycampaign is an increase in the shareof electricity in the transport market.While GRID25 is designed to meetincreasing demand for electricity,albeit at a slower growth thanexperienced over the previousdecade, EirGrid will continue tomonitor the success of theGovernment’s National EnergyEfficiency Action Plan and adapt its transmission developmentprogramme as appropriate.

This Strategy envisages the use ofnew ‘Smart Grid’ technology in theform of smart metering, which willplay a key role in giving customerscontrol over their consumption and in efficient use of grid infrastructure.

The trend in geographicaldistribution of loads is regularlymonitored by EirGrid. Analysis of the current distribution indicates that about 58% of the demand is inthe gateway cities and towns. TheNational Spatial Strategy (NSS)defines gateways as having a strategiclocation, nationally and relative totheir surrounding areas and providingnational-scale social and economicinfrastructure and support services.GRID25 supports the NSS goal ofdeveloping gateways and achieving

By 2025, the Gridwill carry 60%more power tocities and townsacross Ireland.


balanced regional developmentthrough planning for an increased65% share of the total system demandfigure for the gateways and throughgrowing other demands at an equalrate across the country.

Renewable generationGeneration from renewable energysources is a key plank in the Strategyto reduce carbon emissions and tomaintain a sustainable energy supply.The Government has set a target ofmeeting at least 33% of electricitydemand from renewable generation by2020. It also intends setting furthertargets jointly with the relevantNorthern Ireland authorities.

It is recognised in the Government’sWhite Paper on “Delivering a Sustain-able Energy Future for Ireland” thatwind energy will play a pivotalcontribution to meeting that goal.Ocean technologies and biomass arealso expected to contribute.

Many of the locations suitable for renewable energy generationschemes are in areas where there have been little or no generationdevelopments heretofore. Theaggregate of renewable generationcapacity in some areas is equivalent tolarge conventional generation stationsand in many cases the network is notcapable of carrying the power fromthese generation sources. Significantreinforcement of the Grid will thereforebe required to cater for the new powerflows from renewable generation. Itwill not be possible to utilise Ireland’snatural resources of renewable energywithout the essential upgradesoutlined in GRID25.

The power flow analysisunderpinning this Strategy consideredthe impact on grid developmentrequirements of two distinct levels ofrenewable generation:

■ Meeting 33% of electricityconsumption from renewableenergy;

■ Meeting 40% of consumptionfrom renewables.

The following diagram illustrates theexpected regional distribution of therenewable generation capacity.

Conventional generationIf 40% of electrical consumption is metby renewable generation, it followsthat 60% must be supplied from non-renewable “conventional” generation

or imports from abroad. Given thatwind is expected to make up most ofthe renewable portfolio, the amount ofconventional generation capacity mustbe adequate to ensure a reliable powersupply for those hours when windgeneration output is low.

GRID25 provides for a range ofconventional generation scenarioslocating close to:

• principal sea ports;

• existing station sites;

• strong transmission nodes.

REGIONAL DISTRIBUTION OF RENEWABLE CAPACITY

north west35%

north east4%

west8%east

4%

midlands3%

south west30%

south east16%

02VISION


FUTURECONVENTIONALGENERATIONLOCATIONS *

limerick (killonan)

dunstown

carlow

kellis

great island

waterford

kilkenny

aghada

whitegate

barrymore

shannonbridge

cushaling

drogheda (drybridge)

ennis

tynagh

dublin

tarbert

aughinish

moneypoint

coolkeeragh

newry

coleraine

moybellacorick

castlebar

louth

cashla

kilroot

ballylumford

mullingar

lanesboro

flagford

sligo

shankill

athlonekinnegad

cahir

Large

Medium

Small

Natural Gas Network


GRID25 ENABLES THE DIFFERENT RTHEIR POTENTIAL IN ATTRACTING NINDUSTRY AND TO ACCOMMODATE Without it, high-tech industry that requires secure, high quality energy supplies will be unlikely to locate in regions which have inadequate supplies.

EGIONS TO DEVELOP EW HIGH-TECH POPULATION GROWTH.


InterconnectionThe East-West interconnectionproject currently being progressed by EirGrid will provide a 500 MW link with the UK Grid. It is likely that by 2025 at least one furtherinterconnector from this system toanother off-shore system, eitherBritain or France, will be in place.Greater penetration of renewablesources may provide a case for stillfurther interconnection projects.

GRID25 will provide for theconnection of further interconnectorsalong the south-east or southerncoast as these are the most likelyregions for interconnectors to connect to the system.

These interconnectors could play asignificant role in internationalisingthe Irish energy market and infacilitating the anticipated high levels of renewable generation on the island by providing a means to export excess generation whenoutput from renewable generation is high and to import power when it is low.

02VISION


Additional grid capacity requiredThe Transmission Grid in Ireland ismade up of circuits and equipment atthree voltage levels 400 kV, 220 kVand 110 kV. The 400 kV network andthe more extensive 220 kV networkare the main means of transportingbulk power around the country.

The 220 kV network was firstintroduced in the early 1960s and the400 kV network was built in the early1980s. Since the mid-1980s this bulkpower network has changed little whiledemand in the same period has grownby over 150%, leaving little capacity for further growth. The anticipatedincreasing power flows on the systemmeans that between now and 2025 the capacity of the bulk transmissionsystem will need to be doubled.

The key factors that will causepower to flow and that therefore drivefuture investment in the Grid are:

■ Higher demand levels, up to and including maximum forecast demand of 60%distributed throughout every region;

■ Significantly higher renewablegeneration capacity levels;

■ Location of new conventionalgenerators and output levels;

■ Connection point of furtherinterconnectors and transfer levels.

The 110 kV network, which bringspower from the bulk networks toindividual towns and large loads, alsoneeds to be substantially upgraded.

Estimated grid developmentrequirementsThe following indicates the amount ofinfrastructure development required to strengthen the Grid1.

■ Approximately 1,150 km of newcircuits will be required. Thisrepresents an increase of about20% on the total length of theexisting network. Of this, 800km will need to be at 220 kV orhigher; the other 350 km will be at 110 kV. In addition to these circuits, others will beneeded to connect many of thenew generators to the Grid;

■ 2,300 km of the existingtransmission network will needto be upgraded to providegreater capacity. This includes1,100 km or 70% of the existing220 kV network and 1,200 km of the 110 kV network.

There are a number of technicaloptions to achieve this increase innetwork capacity. These are furtherdiscussed in Appendix A, “TechnicalOptions for Grid Development”.

This level of new build andupgrading represents a major shift inthe scale of infrastructure developmentfrom today’s levels and will presentsignificant challenges to all involved in its delivery.

Upgrading existing lines generallyrequires taking the lines out of servicefor lengthy periods of time to makechanges to conductors and /or thestructures supporting them. Thereason the lines are being upgraded isthat the power trying to flow on themexceeds their existing capabilities.Taking them out of service for

1 These figures do not include the current development programme as detailed in the “TransmissionDevelopment Plan 2007-2011”, or any new interconnectors, or the circuits that will be required to connect new generation stations, both renewable and conventional, to the Grid.

03FUTURE GRIDREQUIREMENTS

Through forwardplanning we willachieve increasedcapacity with onlya 20% increase inthe total length ofthe network.


upgrading will put a severe strain on the operability, reliability andefficiency of the power system. EirGrid will have to develop innovativeupgrading methods to limit the impacton customers both in terms of costsand supply security.

Building 800 km of 220 kV or 400 kV lines will present its ownchallenges. In many cases, the newcapacity provided by these lines willneed to be in place before some ofthe existing lines can be upgraded. We will have to find quicker ways of progressing through all the various phases of planning andconstruction to deliver a systemcapable of accepting large amounts of new renewable and conventionalgeneration.

03FUTURE GRID REQUIREMENTS


GRID25 will deliver an efficienttransmission network for Ireland’ssocial and economic development. It will have the necessary capacity to reliably transport the futureanticipated power levels fromrenewable and conventionalgenerators and interconnectors to thecities and towns and the villages andhomes where the power is required.

We will follow international bestpractice and innovative methods toprovide the necessary transmissioncapacity. The technology optionsavailable to implement GRID25 willincrease as research and developmentis carried out. We will be proactive in investigating and adopting newtechnologies taking due considerationof the cost and effectiveness of the technology.

New transmission lines will be builtat 400 kV and at 110 kV. Building at

400 kV rather than 220 kV is moreefficient and provides greater powercarrying capability. Building one 400kV circuit avoids the need for buildinga multiplicity of 220 kV lines and sohas less long-term impact on theenvironment and on local communities.

In the longer term it may beappropriate to upgrade the 220 kVnetwork to 400 kV for similar reasonsof efficiency and capacity. We willexamine each case as the need toupgrade arises and consider the optionof using a higher capacity conductor at 220 kV or rebuilding at 400 kV.

Striking a balanceEirGrid has a statutory obligation to balance the provision of reliabletransmission services with the coststo the final customer and with theimpact of transmission infrastructureon the environment.

04THE GRID DEVELOPMENTSTRATEGY

New bulktransmission lineswill be built at400 kV. Buildingone 400 kV circuitavoids the needfor building amultiplicity of220 kV lines andso has less long-term impact onthe environmentand on localcommunities.

costs and

efficiency

securityand

reliability

environment


GRID25 strikes a balance betweencosts, reliability and environmentalimpact. It examines the totality ofdevelopments and considers socialacceptance at an affordable price inthe context of the overall long-termnetwork development. In particular we will endeavour to minimise the netlength of new line build in a regionthrough a number of initiatives:

■ We will utilise the existingnetwork where possible to avoidbuilding new overhead circuits.In many cases re-utilising theexisting network is more costlythan building new circuits butthe Strategy results in lessimpact on the environment;

■ We will seek to up-rate existinglines by using a higher capacityconductor, where appropriate.Using traditional conductortypes would generally involvemodifying or taking down andchanging the towers or polesthat support the conductor. A change that involves a long circuit outage of one ormore years will have seriousramifications for the security ofsupply during the outage. Wewill therefore use new light-weight high capacity conductorsas they become commerciallyavailable and where possible to avoid the need for majorstructural changes and so tominimise security issues;

■ Where the required increase incapacity cannot be provided by a new conductor operating at the same voltage, we willconsider upgrading the circuit to a higher voltage;

■ Where appropriate, we willconsider replacing an existingline with a double circuit line toprovide the required additional

capacity. This is a more costlyoption and is somewhat lessreliable than having twoseparate lines but it avoidsbuilding a new line on aseparate route;

■ In certain limited circumstanceswe will put selected 110 kVcircuits underground tominimise the impact of newbuild in a region. This will beconsidered in areas where there is congestion of urbandevelopment, a multiplicity ofoverhead lines, a relatively wideexpanse of water or an area ofunique natural beauty. A 110 kVunderground solution would notbe advanced where the groundconditions were unsuitableeither because of the risk to theenvironment or because ofconstruction difficulties;

■ We will examine the potentialfor using HVDC technology forappropriate applications such as transporting high volumes of power over long distances;

■ We will consider theappropriateness of new towerdesigns and other mitigatingmeasures outlined in theGovernment-sponsored reportrecently issued on “TheComparative Merits of OverheadElectricity Transmission LinesVersus Underground Cables” inorder to minimise the landscapeand visual impact of necessaryinfrastructure. We will also take account of the NationalLandscape Strategy when it is published.

04THE GRID DEVELOPMENT STRATEGY

PROPOSED EXPENDITURE BY REGION

north west €750m

north east€300m

west€315m

midlands€310m

south west €730m

south east€830m

east€800m


sligo

donegal

mayo

cavan

monaghan

louthroscommon

longford

westmeath

meath

galway

kildare

clare

limerick

tipperary n.r.

tipperary s.r.

kilkenny

offaly

laois

carlow

wicklow

wexford

kerrywaterford

cork

leitrim

dublin

north west

west

south west

east

south east

north east

midlands

northernireland

EirGrid has divided up the network into seven regions. It is emphasisedthat the maps here are illustrative only. All areas and regions of Irelandwill be covered by GRID25.

05A REGIONAL VIEW

NORTHWESTREGION


sligo

donegal

mayo

cavan

monagha

roscommonlongford

westmeath

galway

kil

clare

offaly

laois

leitrim

northernireland

castlebar

dalton

tonroe

flagford

gilra

gortawee

shankill

arva

to enniskillen lisdrum

ratrussan

kingscourt

mehi

turleen

knock

dunfirth

kinnegad

derryiron

mullingar

lanesboro

arigna

richmond

srananagh

sligo

corderry

corraclassy

carrick-on-shannon

cathleen’sfall cliff

golagh

binbane

tievebrack

to strabane

drumkeen

meentycat

letterkenny

kiltoy

trillicksorne hill

bunbeg

bellacorick

tawnaghmore

moy

cunghill

cloon

cashla

galway

tynagh

somerset

athlone

shannonbridge

oldstreetdallow

agannygal

ikerrin

thornsberry cushaling blake

newbridge

athyportlaoise

derrybrien

A

CB


This area is particularly rich in wind andocean renewable energy resources. The planned gas pipeline, connectingthe Corrib gas field off Mayo to Galway, will provide the opportunity for gasfired generation along the route of the pipeline.

The transmission network in theNorth West is predominately at 110 kV,with very little 220 kV and no 400 kVnetwork in the region. There are two110 kV circuits linking the NorthernIreland and Republic of Irelandtransmission systems, Letterkenny toStrabane and Corraclassy-Enniskillen.These provide standby supportbetween relatively weak parts of the two systems.

Key developmentsIt is expected that demand in theregion will grow by up to 60% by2025. Area A (Donegal) is expected tohave up to 691 MW of wind generation, with Areas B (Mayo/Galway) and C(Leitrim/Roscommon) having 880 MWand 269 MW respectively. Area B isalso expected to have up to 240 MWof wave generation and 31 MW of off-shore wind. If ocean technologies, for whatever reason, do not developsufficiently for such large scaledeployment by 2025, the networkcapacity that might have beenattributed to it could be utilised byother more established renewabletechnologies such as wind generation.

Grid development in the region will include:

€750m

Benefits

■ The North West canbecome a net exporter ofpower to the rest of theisland, reducing itsreliance on generationfrom outside the region;

■ Plans will facilitate thegrowth of renewablegeneration connections in the region;

■ The increased powersupply will accommodateand help attract futureindustry.

Consequences of non-action

■ By the second half of thenext decade, there will beno capacity in the networkto cater for new customersand the reliability of supplyto existing customers will fall below normalinternational standards;

■ There will be not be enoughcapacity in the network toconnect further renewablegeneration; as the northwest is a renewable-richregion this will have severeconsequences on the abilityof Ireland to meet itsrenewable targets and itslong-term sustainableenergy supplies.

estimated total GRID25

investment in the North West Region

■ An additional investment of approximately €750m toupgrade almost 700 km of theexisting transmission networkand to build new circuits;

■ Extension of the 220 kV networkinto Sligo, already in progress;

■ 110 kV reinforcements betweenKillybegs (Binbane station) andLetterkenny and Ballaghadreen(Tonroe station) and Castlebar;

■ Major infrastructuraldevelopment from Mayo to themain bulk transmission systemin the eastern part of the region;

■ Further integration of theDonegal and Northern Irelandnetworks.


IT IS VITALELECTRICITO ENSURAND MAXIWithout GRID25,be able to guarancompetitiveness

THAT IRELAND HAS THE TY SUPPLY INFRASTRUCTURE E OUR ECONOMIC GROWTH, MISE OUR COMPETITIVENESS.the power system will not

tee security of supply or in the marketplace.


gal

cavan

monaghan

louth

longford

westmeath

meath

kildareoffaly

laois wicklow

dublin

northernireland

**

gortawee

shankill

arva

to enniskillen lisdrum

ratrussan

kingscourt

meathhill

dundalk

tandragee

turleenan

275kV

mullagharlinlouth

drybridge

gormannavan

knockumber

platin

baltrasna

stevenstown

corduff

glasmore

huntstownkilmore grange

north wall

poolbeg

finglasmacetown

rinawade shellybanksirishtown

fassaroe

charlesland

carrickmines

college park

cookstown

inchicore

kilteel

pollaphuca

maynoothdunfirth

kinnegad

derryiron

woodlandmullingar

richmond

rraclassy

gh

to strabane

drumkeen

eentycat

letterkenny

kiltoy

ridge

allow


monread

barodanewbridge

dunstown

athyportlaoise stratford

ballybeg

turloughhill

east west hvdc interc

NORTHEASTREGION

AB


This region has some potential for on-shore wind generation and highpotential for off-shore wind.

The area shares a border withNorthern Ireland, which makes theregion and the interconnector that willrun through it significantly importantto the All-Island Single ElectricityMarket. The 220 kV and planned 400kV transmission network in the regionprovides a strong power corridorbetween Dublin and Belfast.

A high capacity gas pipeline runs between north Dublin and the Northern Ireland gas system,providing potential for gas-firedgeneration in the north east.

Key developmentsBetween 1995 and 2005 the demand in the region has grown by about 55%.It is expected that by 2025 the demandwill have grown by a further 60%.Renewable generation connections are expected to include up to 145 MWwind generation in Area A and 125 MWoff-shore wind generation in Area B.


■ An additional investment ofapproximately €300m in the region;

■ The North-South Interconnector(400 kV) connecting Kingscourtin Cavan to Turleenan in Tyrone;

■ A new 400 kV circuit fromWoodland in Meath toKingscourt in Cavan;

■ Strengthening of power circuitsbetween the North West regionand the North East regionfacilitating power flows;

■ Reinforcement of 110 kVnetworks supplying Cavan and Monaghan;

■ Upgrading about 240 km of theexisting transmission network.

€300m

Benefits

■ The North-Southinterconnector and theWoodland-Kingscourt linewill provide long-termcapacity between theNorthern Ireland and theRepublic of Irelandsystems and ensuresecurity of supply to theNorth East region;

■ Provides for substantialincrease in electricitydemand in the region;

■ There will be increasedopportunities to providerenewable energy in the region;

■ Increased opportunities forgas-fired generationtechnologies.


■ Within a matter of yearsthere will be no capacity in the network to cater for new customers and the reliability of supply to existing customers will fall below normalinternational standards;

■ The network will not beadequate to allow efficientoperation of the All-Islandmarket, meaning thatcustomers will not benefitfrom the cheapestelectricity available;

■ There will be no capacity inthe network to allow furtherrenewable generation to beconnected; this will denyIreland the opportunity toexploit its off-shore windresources and will havesevere consequences on the ability of Ireland to meet its renewabletargets and its long-termsustainable energysupplies.


investment in the North East Region

WESTREGION


galway

clare

limerick

tippera

tipp

kerry

cork

cloon

cashla

galway

tynagh

somerset

athlone

shan

oldstreet

agannygal

westmidland

nenagh

ardnacrusha

ahane

killonan

ennis

booltiagh

drumline

mungretprospectsealrock

moneteen

castlefarm

tullabrack

moneypoint

tarbertaughinish

rathkeale

ballycummin limerick

atheatrien

clahane

tralee

oughtragh

knockearagh

coomacheo

clonkeen knockraha

barrymore

mallow

glenlara

c

tippe

charleville

derrybrien


This region features an availability ofnatural resources for wind and oceantechnologies. Hydro-generatedelectricity is already produced on the Shannon Estuary.

The area already has large-scalepower stations in Tarbert, Moneypointand Tynagh and a gas transmissionpipeline from Galway to Limerickwhich passes close to a number ofpotential locations suitable for gas-fired generation projects.

There are 400 kV, 220 kV and anumber of 110 kV circuits in the region.

Key developmentsBy 2025, peak demand for electricityis expected to increase by 60%(estimated in 2007). The region isexpected to have up to 440 MW ofwind generation and 75 MW of wave generation.


■ An additional investment ofapproximately €315m inregional transmission network;

■ Upgraded networks supplyingthe large urban centres of Ennisand Limerick;

■ Up-rating over 250 km ofexisting networks to facilitatehigher capacity power flows,using existing corridors where possible;

■ Strengthening the transmissioncapacity across the ShannonEstuary.

Benefits

■ Provides for substantialincrease in demand intothe future;

■ Allows for renewableresources from both windand wave to feed into theNational Electricity Grid.


■ Within the next five to tenyears there will be nocapacity in the network tocater for new customersand the reliability of supplyto existing customers will fall below normalinternational standards;

■ There will be no capacity inthe network to allow furtherrenewable generation to beconnected; this will havesevere consequences on theability of Ireland to meet itsrenewable targets and itslong-term sustainableenergy supplies.

€315m estimated total GRID25

investment in the West Region


EASTREGION

louth

rd

stmeath

meath

kildare

kilkenny

laois

carlow

wicklow

wexford

dublin

arva kingscourt

drybridge

gormannavan

knockumber

platin

baltrasna

stevenstown

corduff

glasmore


north wall

poolbeg

finglasmacetown


fassaroe

charlesland

carrickmines

college park

cookstown

inchicore

kilteel

pollaphuca

maynoothdunfirth

kinnegad

derryiron

woodlandmullingar

cushaling blake

monread

barodanewbridge

dunstown


ballyraggetcarlow

kellis

kilkenny

londgewood

ballycaddenbanoge

crane ballywater

sheltonabbey

arklow

ballybeg

turloughhill

east west hvdc interc


This region has the potential for highlevels of conventional generation as a result of the existing gas grid andthe proximity of Dublin Port. Windresources are confined mainly to off-shore locations. There are large-scale thermal generating stations atPoolbeg, North Wall, Huntstown andIrishtown and a pumped storagefacility at Turlough Hill in Wicklow.

The 220 kV network within Dublinand the 220 kV and 400 kV networklinking the East region with the rest of the island will require significantdevelopment to increase the flow ofpower to and from the region and toaccommodate future imports andexports of power through theinterconnector between Ireland(Woodland, Co. Meath) and GreatBritain (Deeside, Wales), due to beoperational during 2012.

Key developmentsThe demand for electricity in the Eastregion is expected to increase by over80% by 2025 and will then be 30% ofthe demand of the island. Up to 240MW of wind generation is expected tobe connected to the Grid in this region.


■ An additional investment of approximately €800mthrough upgrading approximately 450 km of the existing networkand building new circuits;

■ Strengthening of network intoand out of the region to allowthe demand to be met byrenewable generators locatedmainly in the west of the country;

■ Strengthening of networkserving Dublin City load;

■ Development to allow north-south flows to by-pass thenetwork serving the Dublin load;

■ Construction and connection ofnew 220 kV stations in northand West Dublin to cater for therapidly growing developmentsin these areas;

■ Reinforcement of the network to cater for strong growth inKildare and North Wicklow.

Benefits

■ Improvements will ensuresecurity of supply to the region;

■ Infrastructure to attractfuture industry;

■ Provision for the use ofrenewable energy in the region.


■ In the medium term, therewill be no capacity in the network to cater fornew customers and thereliability of supply toexisting customers will fallbelow normal internationalstandards;

■ There will not be adequatecapacity in the network toallow for excess renewablegeneration to be exportedover the planned East-West interconnector; thiswill curtail renewablegeneration at times,reducing the commercialityof renewable developmentsand consequently thelikelihood of necessaryprogression.


investment in the East Region


GRID25 WILL ENSURE THAT IRELANPOSSIBLE PLATFORM IN TERMS OF COMPETITIVE AND SUSTAINABLE EL

D HAS THE BEST A WORLD-CLASS,

ECTRICITY SYSTEM.Without it, the needs of new and current residential clients will not be met.


roscommonlongford

westmeath

me

galway

kildar

merick

tipperary n.r.

tipperary s.r.

kilkenny

offaly

laois

carlow

w

navan

knockumber

maynoothdunfirth

kinnegad

derryiron

woomullingar

lanesboro

richmond

cloon

cashla

tynagh

somerset

athlone

shannonbridge

oldstreetdallow

agannygal

ikerrin


monread

barodnewbridge

dunstown

athyportlaoise stratfor

ballyraggetcarlow

kellis

lisheen

westmidland

nenagh

ardnacrusha

ahane

killonan

e

mungret

oneteen


cahir

tipperary

doon

annerballydine

cullenagh killoteran

killmurry

great island

kilkenny

waterford

charleville

thurles

derrybrien

MIDLANDSREGION


The main Dublin-Galway gastransmission pipeline passes through the Midlands region close totransmission stations at Athlone,Edenderry, Kinnegad and Mullingar.

There are modest wind resourcesavailable in the Midlands region.There are three peat-burning stationsat Lanesboro, Shannonbridge andCushaling stations. Supply in theregion is served mainly through the110 kV meshed network, although anumber of higher capacity 220 kV and 400 kV lines pass throughproviding potential for substantialincreased supplies.

Key developmentsBy 2025, the demand in the Midlandsregion is expected to grow by over40%. It is expected to have up to 160 MW of wind energy.


■ An additional investment of approximately €310mthrough upgrading 225 km of transmission network and new circuit build;

■ Tapping in to the existing 400kV line to strengthen the 110 kVnetwork around Portlaoiseproviding capacity to supply the continuing strong growth in Kildare and Laois;

■ Reinforcement to cater forcontinued demand growth in the gateway towns of Athlone,Mullingar and Tullamore;

■ Upgrading will facilitate powerflows from both renewable and conventional sources andmaximise the use of existingpower corridors.


investment in the Midlands Region

Benefits

■ Future growth in demandwill be accommodated;

■ There will be increasedsecurity of supply to the region;

■ Increased transmissioncapacity will allow forgrowth of renewablegeneration connections in the region;

■ Network capacity to allowfor small-scale thermalgeneration in the region.


■ Over the next five to tenyears, there will be nocapacity in the network tocater for new customersand the reliability of supplyto existing customers will fall below normalinternational standards;

■ There will be no capacity inthe network to allow furtherrenewable generation to be connected.


kildare

erary n.r.

ipperary s.r.

kilkenny

offaly

laois

carlow

wicklow

wexford

waterford

dublin


north wall

poolbeg

finglasmacetown


fassaroe

charlesland

carrickmines

college park

cookstown

inchicore

kilteel

pollaphuca

maynoothdunfirth

kinnegad

derryiron

athlone

shannonbridge

dallow

ikerrin


monread

barodanewbridge

dunstown


ballyraggetcarlow

kellis

lisheen

dungarvan

cahir

tipperary

doon

annerballydine

cullenagh

cullenagh

killoteran

killmurry

great island

wexford

kilkenny

londgewood

ballycaddenbanoge

crane ballywater

sheltonabbey

arklow

ballybeg

turloughhill

waterford

thurles

SOUTHEASTREGION

A

B


This region has good wind resources.There is at present a 220 kV networkpassing through the region providinghigh-capacity supply to the region andan underlying 110 kV networkthroughout.

There are existing large-scalegeneration facilities with fuel-handling capabilities at Great Islandstation. The main Cork to Dublin gastransmission network passes throughthe region. There is a possibility ofconnecting the Great Island facilityand other potential generation sitesto the gas transmission network in the future.

Key developmentsDemand in this region is expected toincrease by over 45% by 2025. Area A on the map is expected to have 335 MW of on-shore and 445 MW off-shore wind generation, while Area B should have 210 MW on-shore windgeneration. A new interconnector fromthis region to either Great Britain ormainland Europe will enable the exportand import of power when appropriate.

Grid developments in the region will include:

■ An additional investment of approximately €830m will be required to upgradeapproximately 490 km of theexisting network and to buildnew infrastructure;

€830m

Benefits

■ Proposals will ensuresecurity of supply to majorurban areas and to theregion as a whole;

■ Will allow for substantialgrowth in renewablegeneration connections inthe region;

■ Future growth in demandfrom both industry anddomestic users can beaccommodated.


■ Over the next five to tenyears, there will be nocapacity in the network tocater for new customersand the reliability of supplyto existing customers will fall below normalinternational standards;

■ There will be no capacity inthe network to allow furtherrenewable generation to beconnected; this will havesevere consequences on theability of Ireland to meet itsrenewable targets and itslong-term sustainableenergy supplies;

■ Further interconnection will not be possible in this region.


investment in the South East Region

■ Strengthening of the 220 kVlinks to both Dublin and Cork tofacilitate increased power flows;

■ Strengthening the networkssupplying the major cities andtowns in the region;

■ Reinforcement of currentinfrastructure, including up-rating 110 kV and 220 kVcircuits, while maximising the use of existing corridorswhere possible.


clare

limerick

tipperary

tippera

kerry

cork

agannygal

ikerrin

westmidland

nenagh

ardnacrusha

ahane

killonan

ennis

booltiagh

drumline

mungretprospectsealrock

moneteen

castlefarm

tullabrack

moneypoint

tarbertaughinish

rathkeale


atheatrien

clahane

tralee

oughtragh

knockearagh

coomacheo

clonkeen

coomagearlahy

glanlee

clashavoon

macroom

hartnett’scross

ballylickey

dunmanway

bandon

brinny

carrigadrohid

inniscarrakilbarry

coolroetrabeg

marina

raffeenwhitegate

aghada

knockraha

barrymore

mallow

glenlara

cahir

tipperary

charleville

SOUTHWESTREGION

BA


€730m

Benefits

■ Increased security ofsupply to the region;

■ Greater number ofrenewable generatorsconnected;

■ Improved network willallow for exports ofrenewable generation from the region;

■ Significant future growth indemand from both industryand domestic users can beaccommodated.


■ In the short to mediumterm, there will be nocapacity in the network tocater for new customersand the reliability of supplyto existing customers will fall below normalinternational standards;

■ There will be no capacity in the network to allowfurther renewablegeneration to beconnected; as the SouthWest is a renewable-richregion this will have severeconsequences on theability of Ireland to meet itsrenewable targets and itslong-term sustainableenergy supplies.


investment in the South West Region

■ Strengthening of the Corknetwork to allow power to beexported from the two large gas-fired generators in East Cork;

■ Planned grid reinforcements toconnect significant amounts ofwind generation;

■ Significant strengthening ofcapacity between the SouthWest and the South East toallow excess power to flow from both renewable andconventional sources to supply demand in other parts of the country.

Cork and Kerry in particular feature anabundance of natural renewableresources for wind and oceantechnologies. Hydro-generation on theRiver Lee also contributes renewableenergy to the National Electricity Grid.

There are thermal generationfacilities at Marina in Cork City andAghada in East Cork with plans for new generators at Aghada and nearby Whitegate well in advance. The gas network passes close to thetransmission system at numerousother points providing further potentialfor gas-fired generation in the region.

The transmission network in theregion consists of both 220 kV and 110 kV circuits.

Key developmentsDemand in the region is expected to rise by 60% by 2025. Area A isexpected to have up to 730 MW ofwind power and 145 MW of wavegenerated power, with Area B havingup to 880 MW and 40 MW of bothtechnologies respectively. Large partsof the network will be upgraded toaccommodate this growth in demandand renewable generation.


■ €730m will be invested in theinfrastructure of the region, to include the upgrading ofapproximately 130 km oftransmission network and newtransmission developments;


THE IMPLEMENTATION OF GRID25 IESSENTIAL IF IRELAND IS GOING TO ITS TARGETS FOR GENERATING ELEFROM RENEWABLE SOURCES.Without it, the drive to reduce Ireland’s C02 emissions andmeet it’s targets for the use of renewables in compliancewith legislation will be seriously undermined.

S MEET

CTRICITY

As outlined above the future gridcapacity requirements will bedetermined by the customers’ long-term demands for electricity, by theoutput from generators built to supplythat demand and by the flows acrossinterconnections with other systems.EirGrid has calculated that, based on its vision of 2025, a significantincrease in grid capacity will berequired. The following sectionsdiscuss the technical options fordelivery of the necessary capabilityand the research and developmentinitiatives that EirGrid is undertakingto ensure that best practice is used.

Overhead and underground electricity linesOverhead lines are the standard form of transmission throughout theworld. Lines are made up of threeconductors that carry the power fromgenerators to loads and in many casestwo earth wires that help protect thecircuit from lightning faults. Thesewires are supported on either woodpole or steel mast structures.

High voltage (HV) circuits can onlybe laid underground using special HV cables designed specifically forunderground use. The conductors in underground HV cables must beheavily insulated to avoid a shortcircuit between the conductor and the ground around the cable. As aresult, the installation costs for anunderground cable are far higher than for a simple overhead line.

Overhead lines cost significantlyless to construct than undergroundcables. They are easier to pinpointfaults on and quicker to repair and soprovide a cheaper and more reliablealternative to underground cables.While they do have an impact on the local visual environment, this is minimised as far as possible in construction and planning.

Only where it is not possible to finda route for overhead lines are highvoltage (HV) underground cables usedworldwide. Such situations arise, forexample, when the area that has to be traversed consists of one or moreof the following:

■ A built-up urban area wherethere is no space for supportstructures;

■ An area with a multiplicity ofexisting overhead power lines;

■ A relatively wide expanse ofdeep water;

■ An area of unique natural beauty.

There are two main reasons whyunderground cables are used so rarelyat transmission voltages (110 kV, 220kV and 400 kV). Firstly the capital costof installing a cable is many times thatof an equivalent overhead line andsecondly the operating performance ofan underground cable is not as good asthat of an overhead line. The higher theoperating voltage the stronger will bethe case in favour of an overhead line.

While some lines are placed under-ground internationally, this is only asmall proportion of the amount in place.

Statistics from the 23 Europeancountries that make up the Union forthe Co-ordination of Transmission ofElectricity (UCTE) show that in 2006only 1.7% of their combined ExtraHigh Voltage grids (i.e., 220 kV andabove) consisted of undergroundcable. The comparable figure for theRepublic of Ireland was 4.7%. Bycontrast at transmission voltagesbelow 220 kV the level of usage ofunderground cable in Ireland is lowerthan our European neighbours. It istherefore at this voltage, 110 kV, thatEirGrid can give greater considerationto the use of cable.

When considering a transmissionproject in isolation however, neither atechnical nor an economic case can

TECHNICAL OPTIONS FORGRID DEVELOPMENT

APPENDIX A


be made for installing undergroundcable, even at 110 kV, unlessconfronted with a built up area, a vastexpanse of water or an area wherethere is a multiplicity of overheadlines. In some countries lower voltagelines have been placed undergroundbut, for the reasons given above, nocountry has adopted a policy ofundergrounding high voltage lines.

Reasons for building at 400 kV A 400 kV line typically provides threetimes more capacity than a 220 kV lineand will meet long-term needs moreeffectively. Therefore one way ofreducing the number of new lines in thelong-term is to use the 400 kV voltage.

Power flow on a 400 kV lineexperiences much lower losses thanthe equivalent flow on a 220 kV line.Building at 400 kV therefore supportsthe EU and the Government’scommon objective of increasingenergy efficiency.

Upgrading an existing 220 kV line to400 kV can achieve similar efficiencyand capacity gains. However, thiswould involve taking the existing 220kV line out of service and dismantlingit and building a new 400 kV line onthe same route. The system could notoperate without one 220 kV line for anextended period, it could not operatewith a number of lines out of servicesimultaneously as would be the case if all 220 kV lines were upgraded to400 kV by 2025.

Up-rating existing circuitsIn recent years, a number of factors,including financial constraints anddifficulties obtaining planningpermissions for new infrastructure,have intensified interest in increasingthe ability of existing circuits to carryhigher levels of power.

A transmission line’s ability to carrypower depends largely on the type of


conductor used, the height of theconductor above ground and theoperating voltage. Up-rating is aprocess where the current carryingcapacity of existing high voltage lines is increased by using variousstrategies or techniques.

There are a number of different up-rating scenarios that can be applied to the Irish situation.

Some transmission lines can be up-rated by simply raising some of the support structures so that morepower can be transmitted through the conductors without infringingelectrical ground clearances. Thismethod will be limited by the capacityof that particular conductor to carrythe required power.

To overcome this conductor capacitylimit, up-rating can be carried out byreplacing the existing conductors withhigher capacity conductors and bystrengthening and/or raising thesupport structures. There are anincreasing number of conductor typesavailable, each with different currentcarrying capabilities, costs and serviceexperience. It is our intention to usenew high-capacity conductors whereappropriate and affordable.

In the case that raising structures and replacing conductors will not meet requirements, further increases in power transfer capability can beachieved by replacing an existingtransmission line with a higher voltageline along the same route. Replacing a 110 kV line with a 220 kV line willnormally mean using steel latticetowers in place of wood pole structures.

Opportunities also becomeavailable to up-rate existingtransmission lines duringrefurbishment programmes whereextensive work would have to becarried out in any case on these lines.

Our policy is to examine all up-rating opportunities using existing

infrastructure and line routes so as tominimise new build where possible.

As part of the process a rigorousexamination of new technologies thatcan be employed will be initiated.Such opportunities may presentthemselves in the form of newconductor types or in utilisingmonitoring techniques which enableexisting circuits to carry more power.

Tower designTransmission tower design has beenevolving over the last 70 years fromthe early double wood pole lines stillin operation today to the steel latticeand monopole designs.

For all new projects, efficient andoptimally designed towers are beingdeveloped, where the main feature of these towers is the reduced visualimpact due to lower towers, a lowernumber of steel struts in the structureor new slimline monopole structures,all in various shapes and sizes.

With the availability of modernmaterials there are now numerousoptions available for the internalconfigurations, size, materials, colourand finish of each structure whilsthaving regard to the environmental,planning and practical consequencesof each option.

As part of all new developments an investigation into the appropriatestructure design taking into accountall current and emerging designs willtake place so as to minimise theimpact on the existing environment.

The objective is to limit any impactof new transmission infrastructure onthe landscape by combining towerdesign and robust route selection.

High Voltage Direct Current (HVDC)In Ireland, like in all other countries ofthe world, the electricity that isdistributed to electricity consumers isof the alternating current (AC) variety.

The electricity that is generated bythis country’s power stations is alsoAC. The link between the powerstations and the distribution networkis provided by the high voltageTransmission Grid. Therefore theTransmission Grid also operates with AC electricity.

If a transmission grid was to beoperated with direct current (DC) itwould be necessary to install anAC/DC converter station at everypower station and at every point ofconnection to the distributionnetwork. Such AC/DC converterstations typically cost many tens ofmillions of Euro. Although the cost perkm of HVDC underground cable andoverhead line is cheaper that their ACequivalents the excessive cost of theconverter stations makes thewidespread use of HVDC unattractive,other than for bulk transfers over longdistances where the savings in line orcable outweigh the additional costs ofconverter stations.

The need of the power system torespond instantaneously to increasesin supply and demand, mean thatHVDC technology is not feasible for amain grid system, although it mayhave a role in a few limitedcircumstances:

■ An AC to DC to AC connectioncan be used when twoindependent AC networks are to be linked together and therespective operators want theirsystems to continue to operateat different frequencies. Theoperator of the converter stationwould have complete controlover the quantity and directionof flow of electrical powertransferred between the twosystems. An example of thiswould be EirGrid’s planned East-West Interconnectorbetween Ireland and Wales.

New 220 kV line design


■ DC transmission is moresuitable than AC when a largeamount of power is to betransferred over a very longdistance on a radial (i.e., notmeshed) circuit. HVDC overheadlines would typically be used tomove 1,000 MW or more overdistances in excess of 650 km.HVDC underground or sub-marine cables are typicallyused to move 250 MW or moreover distances in excess of tens of kilometres. A long sub-sea crossing, such as thatproposed for the East-WestInterconnector, would be anexample of where this would arise.

EirGrid always investigates and stays up to date on all newtechnologies. EirGrid can see potentialfor HVDC in transmitting the bulkenergy generated by clusters ofrenewable energy generators from theremote areas where they are normallylocated and where one would expectthe existing Transmission Grid to beweak to areas where the existingTransmission Grid is already strong. As a result EirGrid, in partnership with Northern Ireland Electricity (NIE),has commissioned a technical studyinto the possible application of HVDCcircuits on the island of Ireland.

Research & developmentThe technology options available toimplement GRID25 will increase asResearch and Development is carriedout. EirGrid will be undertakinginitiatives in the following areas whichwill facilitate implementing the Strategytaking account of best practice:

• Dynamic monitoring of line loading;

• Conductor types;

• Tower design;

• ‘Smart Grid’ concepts;

• Underground cable technologyand use.

Dynamic monitoring of line loadinginvolves installing devices to monitorthe loading of a line and the climaticenvironment. Combining dynamicknowledge of the environment, theline design and the system conditionsmay enable an existing circuit to carrymore power. EirGrid has selected aspecific line and is implementing apilot project.

New technologies facilitate thedevelopment of new conductor types.High capacity lightweight conductortypes are being developed. With lightweight and reduced thermalexpansion properties, it may bepossible to install such conductors on existing structures and gainincreased capacity without visualchanges to a line or additional rights-of-way. The availability andapplicability of such technologies to the Irish Grid will be examined.

Investigation into the appropriatestructure design, taking into accountthe emerging and current designs willtake place so that each developmentuses the appropriate structure tominimise the impact on the existingenvironment. The ability to convertexisting 220 kV structures to 400 kVoperation will also be explored.

The ‘Smart Grid’ concept is a termused to refer to grids that use robusttwo-way communications andintelligent equipment and supportgreater participation of users of theGrid in contributing to the efficiency,reliability and safety of the operationof the Grid and power delivery. SmartGrids includes electronic controlmeasures such as SCADA and remotecontrol switching which have been ineffective operation in Ireland fordecades. Further developments inSmart Grids such as the integration

and use of smart meters in systemoperation will be monitored andintroduced as technology solutionswhen appropriate.

Underground cable technology and use will be kept under review. In partnership with NIE, EirGrid hascommissioned a technical study intothe possible application of HVDCcircuits on the island of Ireland.EirGrid is participating in work beingcarried out through the internationalorganisation CIGRE on cables in power systems.

APPENDIX A TECHNICAL OPTIONS FOR GRID DEVELOPMENT


GLOSSARYAPPENDIX B

AAC Alternating current

AC/DC converter An interface between AC and DCsystems comprising electronicequipment that rectifies AC current to DC or inverts DC current to AC

CCircuitAn electrical circuit is a closed pathformed by the interconnection ofelectrical components, such as anoverhead line or transformer, throughwhich an electric current can flow.

Conductor A metal wire capable of carryingelectrical current.

Conventional Generation Types of generation technologies inexistence prior to emergence ofrenewable energy generators

EEirGrid A state-owned company, EirGrid is theindependent electricity TransmissionSystem Operator (TSO) in Ireland and the Market Operator (MO) in thewholesale electricity trading system.

GGrid The transmission system is a meshednetwork of high voltage lines andcables (400 kV, 220 kV and 110 kV) forthe transmission of bulk electricitysupply around Ireland. The Grid,electricity transmission network and transmission system are usedinterchangeably in this document

HHVAC High Voltage Alternating Current – thestandard for electricity generation,transmission and distributionworldwide.

HVDC High Voltage Direct Current

OOverhead line A circuit comprising conductors andtower or pole support structures.

RRenewable Generation Generation from renewable energysources such as wind, wave, tidal,biomass and photovoltaic cells.

SSmart Grid A transformed electricity transmissionand distribution network or “Grid” that uses robust two-waycommunications, advanced sensorsand distributed computers to improvethe efficiency, reliability and safety of power delivery and use.

TTransmission SystemSee “Grid”

UUnderground cable A reinforced insulated electricityconductor placed underground.

Up-rating Changing the conductor, the towers or the voltage of an overhead line toincrease its power-carrying capability

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EIRGRID Plc

The Oval160 Shelbourne RoadBallsbridgeDublin 4

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