Underground Cable: an innovative and reliable Technology Partial Undergrounding as an ecological Solution Integration of Underground Cables in existing Networks New Technologies
Underground Cable: an innovative and reliable Technology
Partial Undergrounding as an ecological Solution
Integration of Underground Cables in existing Networks
New Technologies
XLPE indulated Cables• Commercially used since over 25 years (110 kV)• Since over ten years successfull at 400 kV – even at
long system length (40 km at 500 kV - Japan) • Worldwide established technology • easy to lay and to connect• Environment friendly • Low maintenance/ maintenance free
Underground Cable: an innovative and reliable Technology
Sketch• Conductor Cu
(alternative Al)• Inner Semiconducting
screen• XLPE Insulation• Outer Semiconducting
screen• Cu screen wires
(longitudinal water tightness)
• PE-sheath with integrated Al-Foil
Innovative & Zuverlässige TechnologieUnderground Cable: an innovative and reliable Technology
Accessories: Joints
• 400 kV underground cable are produced and delivered in length up to 1150 m
• Joints will be laid „invisible“under the soil
• Joints can be integrated into underground buildings
Innovative & Zuverlässige TechnologieUnderground Cable: an innovative and reliable Technology
Accessories: terminations
• Outdoor termination as a connection OHL cables system
• Space needed: approx. size of tennis court
Innovative & Zuverlässige TechnologieUnderground Cable: an innovative and reliable Technology
Reliable technology• Good fault statistics, low number of faults• Undergroud cables are protected against
environmental conditions• In operation underground cables are maintenance free
and faults are often caused by external influences
Established Solution• Cable suppliers guarantee a reliable technique with a
homogeneous quality due to international standards (IEC 62067)
• Repair in case of fault– Quick & precise localization of fault– Repair time 2-3 weeks (in case of cable reserve)
Innovative & Zuverlässige TechnologieUnderground Cable: an innovative and reliable Technology
>30 kV DIN VDE 0276-632 45 kV - 150 kV
bis HD 632 45 kV - 150 kV
150 kV IEC 60840 45 kV - 150 kV
> 150 kV DIN VDE 0276-62067 (Entwurf) 220kV - 500kV
bis keine europäische Norm
500 kV IEC 62067 220 kV - 500 kV
Innovative & Zuverlässige Technologie
Standards
Underground Cable: an innovative and reliable Technology
• All systems must be prequalified and/or type tested after the existing standards:This involves a one year system test and a 4 week long sequence of electrical and mechanical tests (type test)
• Each delivered cable or accessories must be subjected to extended routine tests
• Prequalification test: • One year 100m cable and all accessories in
different laying situations, 180 heating cycles under Voltage
• Lightening impulse voltage test after thermal treatment
• At independant test laboratory
Underground Cable: an innovative and reliable Technology
• Type test: • 20 heating cycles under voltage• Tan , lighting impulse, switching impulse, PD• Mechanical and non-electrical tests• at independant test laboratory or with independent
inspector (e.g. KEMA)
Underground Cable: an innovative and reliable Technology
Time of operation• Innovative technology used
since over 10 years• Expected life time of about 40
years• Long term test with higher
field stresses simulate 40 years of operation
Innovative & Zuverlässige TechnologieUnderground Cable: an innovative and reliable Technology
Assorted References 400kV underground cable in EuropeSite Project Cable Systems x Length
(km)Cable/phase
date
Kopenhagen Replacement of existing OHL in urban area 1x221x12
1 19961999
Berlin Connection of east/west systems 2x62x6
1 19982000
York-Tal Area of natural beauty 4x6 2 2000/1
Madrid Barajas airport expansion 2x13 1 2002/3
Jutland Area of natural beauty, waterways and suburbal area
2x14 1 2002/3
London London Ring 1x20 1 2002/5
Rotterdam Randstad water crossing 2x2.1 1 2004/5
Wien Electricity for the city center 2x5.5 1 2004/5
Mailand Suburban part of the Turbigo-Rho-Connection 2x8.5 2 2005/6
Innovative & Zuverlässige TechnologieUnderground Cable: an innovative and reliable Technology
Number of underground systems EHV layed worldwide
Innovative & Zuverlässige TechnologieUnderground Cable: an innovative and reliable Technology
0
1
2
3
4
5
6
7
8
9
10
11
12
94‐9596‐97
98‐9900‐01
02‐0304‐05
06‐07
No.systems
Underground Cable: an innovative and reliable Technology
Partial Undergrounding as an ecological Solution
Integration of Underground Cables in existing Networks
New Technologies
Partial Undergrounding as an ecological Solution
Space needed• Number of systems depending on transfer rate• Width of trace depending on number of systems needed• Max. 2 systems needed for one OHL
Urban Areas• One trench per system: ca. 1.5 meter depth, 1-2 meter width• Heavy equipment needed for civil works along the trench, but
only needed during laying along the trench at joint positions, • Undergrounding under, next and between roads possible• Original state of surface will be restored after installation
Umweltverträgliche LösungPartial Undergrounding as an ecological Solution
Rural Areas• Civil work time depending on
Ground conditions
• Heavy equipment needed for civil works along the trench, but only needed during laying along the trench at joint positions
• Various procedures to undergo sensitive areas or streets
• Landscape restored within 18-24 month
Umweltverträgliche LösungPartial Undergrounding as an ecological Solution
Possible heating of ground• Operating temperature of cable depends on the current carried & load factor• Heat distribution depends on the backfill material around the cable• Impact is “strictly local and very limited“ (Ecofys 2008 report for Irish
government)• Extreme Conditions: Soil directly over the trench can heat up by approx. 2 °C• 5 metre from the cable, no impact
Temperature increase caused by 380kV single-core XLPE cable calculated by FEM modelling temperatures in the conductor plane ( ), in the plane directly above cables ( ), and at the cable surface ( ).
Source: University Duisburg-Essen
Umweltverträgliche LösungPartial Undergrounding as an ecological Solution
Underground Cable: an innovative and reliable Technology
Partial Undergrounding as an ecological Solution
Integration of Underground Cables in existing Networks
New Technologies
Integration of cables in existing networks
Impact of underground cables in existing Networks
Geplanter Netzausbau gemäß Vorrangiger Verbundplan und dena-Netzstudie I
• Integration of new cable systems needs detailled planning
• Quicker realization of network extansion
• There might be compensation systems needed at length longer than 20 km
Underground Cable: an innovative and reliable Technology
Partial undergrounding as a economical Solution
Integration of Underground Cables in existing Networks
New Technologies
New Technologies
Superconducting cables
RTTR (Real Time Thermal Rating)
Electromagnetic shielding (EMC)
Cable Developments new
2005
1930 1940 1950 1960 1970 1980 1990 2000 2010 2015
VALfit plus (EMV) up to 170 kV2007
Low Pressure Oil filled cables
High Pressure Oil filled cables
Internal Gas Pressure cables
External Gas Pressure cables
PE cables
XLPE cables
City cables (3 core) up to 145 kV
Superconducting
Paper insulated
XLPE insulated 2009
Superconducting cables 2001
VALfit (city cable in plastic tube) up to 145 kV
City cables up to 245 kV
No new technology nkt cables has more than 9 years of operation experience!
• Copenhagen, Denmark
• 30 m, 2.0 kA, 30 kV
• 104 MVA
• 12,000 h at 100% load
• Years 2001 … 2003
• DK utilities
• Supplied 50,000 users
• 2 years operation!
Superconducting cables
nkt cables - Certificates of Approval
Southwire, Carrollton, Georgia• Carrollton, U.S.A
• 30 m, 1.25 kA, 12.5 kV
• 27 MVA
• 50,000 h at 100% load
• Years 2000 … 2006
• Supplied energy to Southwire Co’s cable factories
• Converted to test station
• 6 years operation!
Superconducting cables
Unique cable design
HTS Triax™ Energy CableThree phases in one cable
Common neutral screen
Cryostat duct (thermal insulation)
10 kV … 72.5 kV
30 MVA … 400 MVA
Made in Cologne, Germany
Superconducting cables
26
HTS Triax™ Energy CableSuitable for medium voltages (10-72 kV)
Former Dielectric Dielectric Dielectric Cryostat
Phase 1 HTS Phase 2 HTS Phase 3 HTS Copper Neutral
LN
LN
New Technologies
Superconducting cables
RTTR (Real Time Thermal Rating)
Electromagnetic shielding (EMC)
AB Bern 100414
VALCAPHard-/Software Package
Load Control Software
- RTTR -developed by nkt cables
Fiber Optic Temperature Monitoring
DTS Controller
Service and Engineering
by nkt cables
AB Bern 100414
Our System thinking !
Load Control Software - RTTR -
developed
by nkt cables
Fiber Optic Temperature
Monitoring Device
DTS Controller
Service
Engineering
by nkt cables
Fiber Optic
Tubes/CableOverhead
LinesFiber Optic
Accessories
Fiber Optic
Accessories HV Cable
AB Bern 100414
The Specification
• Temperature Monitoring along an Optical Fiber (Raman effect)
• Optical Fibre integrated in Cable/Conductor or placed upon
• Max measuring length: 18km (36km)
• Multichannel option - up to 8 channels
• Spec. of Optical Fiber: Multimode
• Hot spots can be detected – Resolution up to 1m
• RTTR Software
for load prediction and grid control assistance!!!
1. SafetyAvoidance and reaction on critical load status
2. EfficiencyUtilize the existing capacity of your net to an optimum
3. Dynamic and FlexibilityWith Dynamic Rating to a flexible energy highway
4. TransparancyAnalysis of condition, requirements and planning
New Technologies
Superconducting cables
RTTR (Real Time Thermal Rating)
Electromagnetic shielding (EMC)
conductor
XLPE insulation
APL sheath
earth conductors
magnetic screening
wire armour
PE pipe
Valfit+ Cable up to 245kVXLPE insulated cable in PE pipe
Electromagnetic shielding (EMC)
Cable with internal magnetic screening
0,0
0,5
1,0
1,5
2,0
2,5
0 1 2 3 4 5 6 7 8 9 10
T
m
Distance from centre of trench
Mag
netic
Indu
ctio
n
110 kV XLPE-cablel 1 System473 A / 90 MVA
Three core cable in plastic pipe
Single core cable in plastic pipe
Three core cable in steel pipe
• 3-core Valfit plus: screening without steel pipe to approx. 0.2 µT in 1.2 m distance (1000 A, 150 kV)
Electromagnetic shielding (EMC)
Summary• 400 kV cable systems are state of the art, reliable and
environment friendly solutions for energy transfer
• Cable systems can be equipped with RTTR systems such as VALCAP to maximize flexibility and the overall transfer rate
• Cable systems allow to shield the magnetic field around the trench
• Superconducting cables are reliable alternatives for energy transfer in special situations