OVERVIEW OF UNDERGROUND POWER CABLES AT HIGH/EXTRA HIGH VOLTAGE

LEVELS

2008www.europacable.com

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I. Introduction to Europacable

Europacable is:Association of European Cable Manufacturers including:

Europacable aims to:promote of the use of underground cables for electricity transmission;ensure the complete and correct understanding of the technical specifications of underground cables by relevant stakeholders.

Europacable has developed a realistic position for cable transmission solutions:Extra high voltage underground cables are rarely appropriate for an entire new AC power transmission project; When a 100% overhead route is unacceptable, however, underground cables are an appropriate solution to unblock the project. Application of partial undergrounding of a line can provide a compromise to allow a project to proceed without years of legal contests.

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I. Introduction to European Copper Institute

Joint venture between International Copper Association (representing world’s leading mining companies) and European copper industryKey competencies:

– market intelligence and policy analysis– EU regulatory issue management– environment and health science – advocacy & education – market development and defence– media relations

Based in Brussels since 1998

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1. 400 kV XLPE Cable2. 400kV XLPE Cable Joint Bay3. Trench size 4. Constructions issues – urban areas5. Construction issues – countryside trenching6. Transmission losses7. Impact on the network8. Environmental impacts9. Reliability 10. Costs

II. Technical questions on extra high voltage underground cables

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1. 400 kV XLPE Cable

400 kV XLPE Cable:Used for commercial purposes for more than 25

yearscurrent state of the art technology easier installation and jointing environmentally low riskalmost maintenance free

400 kV XLPE cable design1 Copper conductor2 Semiconductor3 XLPE insulation4 Semiconductor5 Waterblocking6 Welded aluminium sheath7 PE outer sheath

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2. 400 kV XLPE Cable Joint BayThe 400 kV cables can be delivered in lengths up to 1000 mCable joint bays - generally unobtrusive underground structuresTemporary tents are set-up only during installationOnly exceptionally are cable joint bays buried in specific

compounds (13m X 3m)

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3. Trench size

Width of trench:Dependent on the number of cablesNumber of cables depends on desiredtransmission capacityTransmission capacity needs to be defined realisticallyIn principle, a trench for underground cables is not as wide as the right of way required for overhead lines

Overhead-Underground Transition Stations:Can be size of tennis court , but in some cases a football fieldAt voltages of 275kV and below, can be applied directly onto a pylon

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4. Construction issues – urban areasTrench per system: ca 1.5 m deep, 1-2 m wideAccess for heavy machinery needs to be available along the lineUnderground cables can easily be placed next to, under or between roads Subsequently the area is re-instated to original condition

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5. Constructions issues - Countryside Trenching

Construction time depends mainly on ground conditions

Trenching requires access for heavy machinery along the line

A variety of “non-invasive” procedures are available to pass under sensitive areas or streets or nature reserves

Depending on the type of vegetation, landscape can be completely re-instated within 18-24 months

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6. Transmission losses

Transmission losses both for overhead lines and underground cables depend upon the system design and loading;

Therefore it is not possible give a generic answer;

An independent study (ForWind) has determined losses for one project:“Underground cable have lower transmission losses than overhead lines under specific parameters because due to thermal reasons underground cables have a larger conductor”

Increased losses in transmission system require additional power generation.

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7. Impact on the networkInsertion of new interconnections in existing networks require detailed planning;Studies on several 400 kV transmission grids show that the characteristics of underground cables can in many cases be beneficial to the overall performance of the network; A grid-study should be carried out for very long cable connections, i.e. more than 20 km, to evaluate whether additional installations for reactive compensation are needed;If needed, these additional measures can be applied at existingsubstations or corridors and do not require any extra compound area for installation.

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8. Environmental impacts

Possible heating of ground:– Operating temperature of an underground cable depends on the

current carried, cable resistance and loss of the resulting heat into the surroundings

– How much heat is distributed to the surrounding soil depends on the filling material used around the cable

– Under extreme conditions of use, the soil directly over the trench can heat up by approximately 2 °C

– This could cause drying of the soil under certain circumstancesThere are no restrictions for the cultivation of land, although vegetation with deep roots must be avoided;Underground cables emit no electric field and can be engineered to emit a lower magnetic field than an OHL;Underground cables do not create any environemntal burden through the creation of noise.

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9. Reliability & Life expectancy

Disturbance of underground cables occurs less frequently than for overhead lines - Underground cables are not affected by severe weather.Only outside influences can disturb and damage underground cablesIn use, cables do not require maintenance;Reliability of XLPE-isolated cables:

– Producers guarantee homogeneous cable quality according to international standards (IEC 62067);

– Repairs caused by damage: • Quick and precise location of errors with modern monitoring

technology• Reparation time 2 - 3 weeks (if, as recommended, spare

parts are kept in stock);Careful long-term testing has been conducted and life expectancy of XLPE-insulated cables is approximately 30 - 40 years.

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10. CostsUnderground cables are – at installation – more expensive than overhead lines due to higher product and installation costs;Cost comparisons often only address costs of installation and ignore lifecycle costs such as losses, outage costs, maintenance, decommissioning, costs of delay in getting authorisations & impact on those affected by the line (e.g. visual amenity, property value);A comprehensive life-cycle analysis should take these into consideration

Furthermore:Every project is different and it is not possible to make generic cost estimates;Depending on ground and surface characteristics, the cost of installation works can increase up to 60%, which will benefit local companies;Partial undergrounding can create predictability for planning and have a positive effect on authorisation procedures and costs;Latest life-cycle analysis confirm that the cost factor compared to overhead lines can be as little as 2–5 times for many situations.

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III. Examples of ongoing underground cable projects in Europe

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1. Germany: Lower Saxony

Proposal to build 80km 380kV line from Ganderkesee-St.HulfeProposal (Erdkabelgesetz) adopted in December 2007 by the Parliament of Lower SaxonyLegislation requires use of UGC if proposed OHL is:In proximity of buildings: 200 meters In proximity of residential areas: 400 meters Where crossing environmentally protected areas

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2. Austria: Salzburg link

St Peter

Elixhausen

Kaprun

Eugendorf

Koppel

Bad Vigaun

Bruck

Ongoing debate-opposition to full OHL January 2007: Austrian Energy Agency published a study recommending the use of partial undergrounding to unblock project.August 2007: Minister Eisl asked KEMA to assess whether partial undergrounding of Salzburg part II is technically feasible28 January 2008: Presentation of KEMA study. Cabling is state of the art technology and partial undergrounding(around 40km) would only add €4 to the average bill.

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3. Scotland: Beauly – Denny 400kV line

SSE

TSOarea

ScottishPower

Perth &Kinross

Stirling

Falkirk

PAarea

Beauly

Braco &Muthill

Denny

Stirling

Glen Quaich

CairngormsNational Park

HighlandCouncil

Application for 220km 400/275kV OHL from Beauly to Denny submitted to Scottish Ministers in October 2005 by transmission divisions of Scottish & Southern Energy & Scottish Power;

Significant opposition from a variety of groups wanting partial cable solution (in 5 areas) to safeguard health, preserve visual amenity, cultural heritage & protect nature and tourism;

4 Planning Authorities (PAs) plus CNPA & 17,000 groups/individuals objected;

Scottish Ministers agreed to a Public Inquiry which took place throughout 2007;

TSOs accept viable cabling routes exist;Inquiry Report to be submitted in 2008 &

decision due in 2009.

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4. Italy: The Turbigo-Rho 400 kV Project

Overhead line 380 kV

Underground cable 380 kV

Transition stations

Existing OHL 380 kV

County borders

Milan

Power station2560 MW

Overhead line 380 kV

Underground cable 380 kV

Transition stations

Existing OHL 380 kV

County borders

Overhead line 380 kV

Underground cable 380 kV

Transition stations

Existing OHL 380 kV

County borders

Milan

Power station2560 MW

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4. Italy: the Turbigo-Rho 400 kV Project

The undergrounding of part of 40 km long line led to the speeding up of authorization procedures. The line was necessary for the reinforcement of the transmission grid in a very congested area avoiding the risk of future blackouts. The max. power rating of the circuit is 2.2 GVA.

Benefits of the project:• To overcome the generation limits of the Turbigo power

station and reduce congestion• To improve voltage control in the Milan area• To reduce transmission losses

Timeline:1991 Start of discussions1994 Initial approval of overhead lineUntil 2004 OHL approval blockedJune 2004 Decision on partial undergroundingMarch 2005 Construction of cable (8 months)June 2006 Activation of the line/cable

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5. Number of EHV Cable Installations Globally 1994- 2005

0123456789

101112

94-95 96-97 98-99 00-01 02-03 04-05* Projects started

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6. Length of km of EHV underground cable220-400kV: 1996- 2006

1996 2006 Change %

Austria 48 59 23

Denmark 31 52 68

France 600 914 52

Germany 99 110 11

Ireland 64 106 66

Italy 130 231 78

Netherlands 6 12.5 108

Spain 31 558 1700

UK 553 662 20

Source: CIGRE 338 December 2007

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7. Examples of major 400kV projects in EuropeLocation Project Cable circuits

x Length (km)

Time period

Copenhagen Elimination of OHLs in urban area 1x12, 1x22 1996/9

Berlin Connect West/East systems 2x12 1996-00

Vale of York (UK) Area of outstanding beauty 4x6 2000/1

Madrid Barajas Airport expansion 2x13 2002/3

Jutland, DK Area of outstanding beauty, waterway & semi urban areas

2x14 2002/3

London London Ring 1x20 2002/5

Rotterdam Randstad “ring” waterway crossings 2x2.1 2004/5

Vienna Provide power to centre of city 2x5.5 2004/5

Milan Section of Turbigo-Rho line 2x8.5 2005/6

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IV. DiscussionThe completion of the European internal electricity grid is of fundamental importance:

To stabilize the European electricity grid To create extra transmission capacities (to cover new power stations as well as renewable energies)

XLPE cables are a modern, reliable transmission technology;Europacable believes that extra high voltage underground cables are rarely appropriate for an entire new AC power transmission project; Partial undergrounding is an alternative for: – Land with outstanding natural or environmental heritage or

vulnerable eco-systems;– Areas where land is unavailable or planning consent is difficult to

obtain within an acceptable timeframe;Costs for underground cables can de reduced to a multiple of 2 - 5 times when the whole life-cycle cost is assessed.

OVERVIEW OF UNDERGROUND POWER CABLES AT HIGH/EXTRA HIGH VOLTAGE

LEVELS2008

www.europacable.com