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High Temperature Superconducting Cable for Power

Transmission Applications

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Contents

l Design possibilities of superconducting power cables

w Warm and Cold dielectric concepts

w Benefits and drawbacks

w Grid operation of VLI (Very Low Impedance) cables

l Power cable development considerations

w Design drivers and goals

w Trade offs

l Projects

w Major projects for power cables

w Economical benefits

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Warm Dielectric Cable Concept

Former Tube

High Voltage Dielectric

Inner Cryostat Wall

Outer Cryostat Wall

Copper Shield

HTS Tape

Outer Cable Sheath

Inner LN2 Coolant

Outer LN2 Coolant

Protection Layer

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Cold Dielectric Cable Concept

Outer protective covering

Outer Cryostat Wall

Inner Cryostat Wall

Liquid Nitrogen Coolant

Copper Shield Stabilization

HTS Shield Tape

High Voltage Dielectric

HTS Tape

Core / Former

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Cold Dielectric Alternatives

Three phases in one cryogenic envelope

Concentric phases / Triaxial

3 independent phases

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Concentric (Triaxial) Concept

Former Tube

High Voltage Dielectric

Inner Cryostat Wall

Outer Cryostat Wall

Copper Shield

HTS Tape

Outer protective Covering

Inner LN2 Coolant

Outer LN2 Coolant

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Comparison Cold and Warm Dielectric

cryogenic envelope

conductor

LN2cold dielectric

superconducting screen

cryogenicenvelope

conductor

LN2

concept 1:warm dielectric

concept 2:cold dielectric

warm dielectricouter magnetic field

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Design Comparison

outer magn. field

AC-loss

transport current

dielectric

cryostat

HTS-tape amount

accessories

cable inductance

warm dielectric

yes

high

high

conventional

at high voltage

(difficult to access)

low

almost conventional

as conventional cables

cold dielectric

no

low

very high

new type (cold)

at ground potential

(easy access)

high (screen)

new design required

very low

coaxial

no

low

very high

new type (cold)

at ground potential

(easy access)

low

very difficult at high

voltage levels

very low

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LIPA 138 kV HTS Cable Project – Phase 1

345 kV 138 kV

345 kVto ConEd

in NYC

East Garden City Sub-Station

Ruland RoadSub-Station

NewbridgeSub-Station

PilgrimSub-Station

138 kV138 kV138 kV

2005

9.1 km6 km 16.7km

DOE Co-Funded – 610m 138kV 2400A HTS Cable

345/138 138/69610 m

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l Long Island Power Authority – east garden city substationl Electrical operating characteristics

w Operating voltage/current – 138kV/2400A ~ 574MVA

w Design fault current – 69,000A @ 15 line cycles (250ms)l Physical characteristics

w Installation – one 12” pipe (11,7”/ 297mm ID)

w Length – app. 610m

w HTS tape length – 128km

w Cold dielectric design with three individualcryogenic envelopes

l Hardware deliverablesw Three ~ 610m long phase conductors

w Six 161kV outdoor terminations

w One 10kW refrigeration system at one end

w Single joint to be tested in the lab

Worlds First Installation of a Transmission Voltage HTS Cable in the World

Cable design drivers - LIPA Project Fact Sheet

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Cable Design Aspects

Various aspects of cable design need to be traded to reach the optimized design point during

l normal operation as well as

l fault current operation

Cable loss

Former diameter

Cooling stationdistance

Pipe size forinstallation

Pressure drop

Tape Ic

Cable corediameter

Fault current andduration

Optimized cabledesign

Cable rating

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Technical Issue Cable Cooling

l Goal: cable temperature and pressure within specified range

l Trade off:

w Hydraulic diameter determined by

n Cable diameter

n Pipe size

w Distance between cooling stations (Length)

w Cable losses determined by

n HTS-tapes

n Cryostat

n terminations

Hydraulic diameter of the

cooling channel

Cable diameter

High Voltage

Fault conditions

Pipe size

Cable installation

Pumping port

Losses HTS tapes Cryostat

Termination

Length Distance between

substation

Cooling flow of liquid nitrogen 65 K < T < 77 K 3 bars < P < 20 bars

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Cable Cooling Example LIPA Project

l Flow of LN2 in single phase and back in two phasesl Effect of second pump and / or cooling station analyzed

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Technical Issue Fault Current Operation

l Goal: no bubble formation during fault event to avoid dielectric breakdown

l Trade off:

w Choice of materials

n Resistivity

n Thermal conductivity

n Thermal capacity

w Cable design

n Current sharing properties

n Heat exchange properties

Materials Resistivity Current

sharing Temperature

increase

Heat exchange

Cable design

Materials Thermal

properties

No bubble in the

dielectric during the

fault

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Main HTS Cable Projects

Location Main Utilities Cable Use Status

partners Dielectric Number Characterictics

type of phases

U. S. A. Pirelli / ASC Warm 1 50 m / 115 kV / 2 kA Demonstrator Complete

Berlin Pirelli (ex-Siemens) [1] Cold 1 50 m / 110 kV / 2.1 kA Demonstrator Stopped

Italy Pirelli / ASC ENEL / Edison Cold 1 30 m / 132 kV / 3 kA Demonstrator ?

Detroit Pirelli / ASC Detroit Edison Warm 3 120 m / 24 kV / 2.4 kA Network Cryostat Issue

Paris Pirelli / ASC EDF Cold 1 50 m / 225 kV / 2.6 kA Demonstrator Complete

Tokyo SEI TEPCO Cold 30 m / 66 kV / 1 kA Demonstrator Complete

Tokyo SEI TEPCO Cold 3 100 m / 66 kV / 1 kA Demonstrator Complete

Albany (NY) SEI / IGC Niagara Mohawk Cold 3 350 m / 34.5 kV / 0.8 kA Network Ongoing

Japan Furukawa Cold 1 500 m / 77 kV / 1 kA Demonstrator Ongoing

Carrollton (Ga) Southwire / IGC Southern California Edison Cold 3 (rigid) 30 m / 12.5 kV / 1.25 kA Plant supply Complete

Copenhagen NKT / NST [1] Elkraft Warm 3 30 m / 36 kV / 2 kA Network Complete

Columbus (Ohio) Southwire American Electric Power Cold / (Tri) 3 300 m / 12.5 kV / 2.5 kA Network Ongoing

Kunming (China) Innopower / Innova [2] Yunnan Electric Power Warm 3 30 m / 35 kV / 2 kA Network Ongoing

Long Island (NY) ASC / Nexans Long Island Power Authority Cold 3 610 m / 138 kV / 2.4 kA Network Ongoing

[1] Cryogenic envelope supplied by Nexans. [2] Cryogenic envelope and dielectric supplied by Nexans.

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Economical Benefits

l Shorter lengths of insertion – no tying back to existing EHV backbone system (VLI)

l Lower voltage – benefit through cheaper auxiliary equipmentl Greater controlability with use of Phase Angle Regulator – control of

power flow (VLI)l Expanded generator siting options because of lower voltage drop (VLI)l Reduced electrical losses

Superconducting power cables (particularly VLI) do not have to be cost competitive on a stand alone basis. Economical benefits of the „grid

solution“ are of interest

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Conclusion

l Different cable design concepts with their benefits and drawbacks are well understood

l Very low impedance characteristic of cold dielectric cables is of big interest to utilities

l Cable design tradeoffs driven by the specifications are to be managed

l Current ongoing projects enter the step from laboratory setups to grid installations

l The LIPA cable project is the first one on transmission voltage level so far

Material investigation

short cable models

Laboratory setups

Network demonstrators

Market entry

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Thank you for your attention