Overview Of Ehv Underground Power Cables Feb 2008
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OVERVIEW OF UNDERGROUND POWER CABLES AT HIGH/EXTRA HIGH VOLTAGE LEVELS 2008 www.europacable.com
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.
2
I. Introduction to European Copper Institute Joint venture between International Copper Association (representing world’s leading mining companies) and European copper industry Key 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
3
II. Technical questions on extra high voltage underground cables 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
400 kV XLPE Cable 400kV XLPE Cable Joint Bay Trench size Constructions issues – urban areas Construction issues – countryside trenching Transmission losses Impact on the network Environmental impacts Reliability Costs 4
1. 400 kV XLPE Cable 400 kV XLPE Cable: Used for commercial purposes for more than 25 years current state of the art technology easier installation and jointing environmentally low risk almost maintenance free 400 kV XLPE cable design 1 Copper conductor 2 Semiconductor 3 XLPE insulation 4 Semiconductor 5 Waterblocking 6 Welded aluminium sheath 7 PE outer sheath
5
2. 400 kV XLPE Cable Joint Bay The 400 kV cables can be delivered in lengths up to 1000 m Cable joint bays - generally unobtrusive underground structures Temporary tents are set-up only during installation Only exceptionally are cable joint bays buried in specific compounds (13m X 3m)
6
3. Trench size Width of trench: Dependent on the number of cables Number of cables depends on desired transmission capacity Transmission capacity needs to be defined realistically In 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 field At voltages of 275kV and below, can be applied directly onto a pylon
7
4. Construction issues – urban areas
Trench per system: ca 1.5 m deep, 1-2 m wide Access for heavy machinery needs to be available along the line Underground cables can easily be placed next to, under or between roads Subsequently the area is re-instated to original condition
8
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 reinstated within 18-24 months
9
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.
10
7. Impact on the network Insertion 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 existing substations or corridors and do not require any extra compound area for installation.
11
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 circumstances
There 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. 12
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 cables In 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. 13
10. Costs
Underground 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); ¾ 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.
14
III. Examples of ongoing underground cable projects in Europe
15
1. Germany: Lower Saxony
Proposal to build 80km 380kV line from Ganderkesee-St.Hulfe Proposal (Erdkabelgesetz) adopted in December 2007 by the Parliament of Lower Saxony Legislation 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
16
2. Austria: Salzburg link
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 feasible 28 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. 17
St Peter
Eugendorf Elixhausen Koppel
Bad Vigaun
Kaprun Bruck
3. Scotland: Beauly – Denny 400kV line 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. 18
TSO area
PA area
Beauly
Highland Council Cairngorms National Park SSE
Perth & Kinross Glen Quaich Braco & Muthill Scottish Power
Stirling Denny
Stirling Falkirk
4. Italy: The Turbigo-Rho 400 kV Project
Power station 2560 MW Existing OHL 380 kV
Overhead line 380 kV Underground cable 380 kV Transition stations
19
County borders
Milan
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.
Timeline: 1991 1994 Until 2004 June 2004 March 2005 June 2006
Start of discussions Initial approval of overhead line OHL approval blocked Decision on partial undergrounding Construction of cable (8 months) Activation of the line/cable
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
20
21
5. Number of EHV Cable Installations Globally 1994- 2005 12 11 10 9 8 7 6 5 4 3 2 1 0 94-95
96-97
98-99
00-01
* Projects started
22
02-03
04-05
6. Length of km of EHV underground cable 220-400kV: 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
23
7. Examples of major 400kV projects in Europe Location
Project
Cable circuits x Length (km)
Copenhagen
Elimination of OHLs in urban area
Berlin
Connect West/East systems
1x12, 1x22
Time period 1996/9
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
24
IV. Discussion The 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. 25
OVERVIEW OF UNDERGROUND POWER CABLES AT HIGH/EXTRA HIGH VOLTAGE LEVELS 2008 www.europacable.com
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.
2
I. Introduction to European Copper Institute Joint venture between International Copper Association (representing world’s leading mining companies) and European copper industry Key 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
3
II. Technical questions on extra high voltage underground cables 1. 2. 3. 4. 5. 6. 7. 8. 9. 10.
400 kV XLPE Cable 400kV XLPE Cable Joint Bay Trench size Constructions issues – urban areas Construction issues – countryside trenching Transmission losses Impact on the network Environmental impacts Reliability Costs 4
1. 400 kV XLPE Cable 400 kV XLPE Cable: Used for commercial purposes for more than 25 years current state of the art technology easier installation and jointing environmentally low risk almost maintenance free 400 kV XLPE cable design 1 Copper conductor 2 Semiconductor 3 XLPE insulation 4 Semiconductor 5 Waterblocking 6 Welded aluminium sheath 7 PE outer sheath
5
2. 400 kV XLPE Cable Joint Bay The 400 kV cables can be delivered in lengths up to 1000 m Cable joint bays - generally unobtrusive underground structures Temporary tents are set-up only during installation Only exceptionally are cable joint bays buried in specific compounds (13m X 3m)
6
3. Trench size Width of trench: Dependent on the number of cables Number of cables depends on desired transmission capacity Transmission capacity needs to be defined realistically In 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 field At voltages of 275kV and below, can be applied directly onto a pylon
7
4. Construction issues – urban areas
Trench per system: ca 1.5 m deep, 1-2 m wide Access for heavy machinery needs to be available along the line Underground cables can easily be placed next to, under or between roads Subsequently the area is re-instated to original condition
8
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 reinstated within 18-24 months
9
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.
10
7. Impact on the network Insertion 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 existing substations or corridors and do not require any extra compound area for installation.
11
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 circumstances
There 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. 12
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 cables In 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. 13
10. Costs
Underground 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); ¾ 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.
14
III. Examples of ongoing underground cable projects in Europe
15
1. Germany: Lower Saxony
Proposal to build 80km 380kV line from Ganderkesee-St.Hulfe Proposal (Erdkabelgesetz) adopted in December 2007 by the Parliament of Lower Saxony Legislation 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
16
2. Austria: Salzburg link
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 feasible 28 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. 17
St Peter
Eugendorf Elixhausen Koppel
Bad Vigaun
Kaprun Bruck
3. Scotland: Beauly – Denny 400kV line 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. 18
TSO area
PA area
Beauly
Highland Council Cairngorms National Park SSE
Perth & Kinross Glen Quaich Braco & Muthill Scottish Power
Stirling Denny
Stirling Falkirk
4. Italy: The Turbigo-Rho 400 kV Project
Power station 2560 MW Existing OHL 380 kV
Overhead line 380 kV Underground cable 380 kV Transition stations
19
County borders
Milan
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.
Timeline: 1991 1994 Until 2004 June 2004 March 2005 June 2006
Start of discussions Initial approval of overhead line OHL approval blocked Decision on partial undergrounding Construction of cable (8 months) Activation of the line/cable
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
20
21
5. Number of EHV Cable Installations Globally 1994- 2005 12 11 10 9 8 7 6 5 4 3 2 1 0 94-95
96-97
98-99
00-01
* Projects started
22
02-03
04-05
6. Length of km of EHV underground cable 220-400kV: 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
23
7. Examples of major 400kV projects in Europe Location
Project
Cable circuits x Length (km)
Copenhagen
Elimination of OHLs in urban area
Berlin
Connect West/East systems
1x12, 1x22
Time period 1996/9
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
24
IV. Discussion The 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. 25
OVERVIEW OF UNDERGROUND POWER CABLES AT HIGH/EXTRA HIGH VOLTAGE LEVELS 2008 www.europacable.com
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