Underground Cable: an innovative and reliable Technology ... · HV Cable. AB Bern 100414 ... • Cable systems allow to shield the magnetic field around the trench • Superconducting

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


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


Accessories: terminations

• Outdoor termination as a connection OHL cables system

• Space needed: approx. size of tennis court


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)


>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


• 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


• 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)


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


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


Number of underground systems EHV layed worldwide


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




New Technologies


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


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





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


Partial undergrounding as a economical Solution


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!


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!


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


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




AB Bern 100414

Monitoring and Rating by nkt cables

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

Real Time Thermal Ratingand Power Cables combined in one

New Technologies




conductor

XLPE insulation

APL sheath

earth conductors

magnetic screening

wire armour

PE pipe

Valfit+ Cable up to 245kVXLPE insulated cable in PE pipe


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)


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

Thank you!

Underground Cable: an innovative and reliable Technology ... · HV Cable. AB Bern 100414 ... • Cable systems allow to shield the magnetic field around the trench • Superconducting

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