demo 5 - best paths

DEMO 5:HVDC Superconducting Link

Christian-Eric BRUZEK(Nexans France)

“INNOVATIVE NETWORK TECHNOLOGIES AND THE FUTURE OF EUROPE'S ELECTRICITY GRID”

BEST PATHS DISSEMINATION WORKSHOP

BERLIN, 26 OCTOBER 2016

Normal metal

R (W)

T (K)

R > 0

T = 0 K -273°CAbsolute zero

What is superconductivity?

Superconductors = almost perfect conductors of electricity:no electrical resistance!

Best Paths Dissemination Workshop - Demo 5 - Berlin 26/10/2016

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Superconductor

TcCritical temperature

R 0Superconducting state

Magnetic field

Current density

Temperature

Tc

Jc

Bc

Superconducting domain

Superconducting materials have a huge current rating: at least 150 times greater than copper for HTS materials!

Superconducting cables provide a new way to solve power transmission (voltage x current) issues by increasing the current (up to 5 kA AC or beyond 20 kA DC) rather than the voltage

Requirement of cooling at very low temperatures


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Temperature (K)

Timeline of discovery

T = 0 K -273°CAbsolute Zero

(lowest temperature that canbe reached in the universe)

T = 200 K -73°C

Extreme cold

Industrial cooling

Ambient temperature

T = 0°C 273 K(water becomes ice)

Liquid helium

Liquid hydrogen

Liquid nitrogen

Cryogenic fluids

Superconducting materials

HTS cuprates

MgB2

-200°C

-250°C

(or helium gas @20 K / 20 bar)

How to transmit bulk power 3-5 GW? (examples of corridors)


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15.5 m

Clearing width 45 m

Right-Of-Way width 66 m

47 m

34 m

8 m

Nelson River DC line (Canada)1600+1800 MVA (+2000 under construction)

Geneva, Palexpo Link 2001,

470 m, 220 kV / 2 x 760 MW

Frankfurt Airport,

Kelsterbach Link 2012,

900 m, 400 kV / 2 x 2255 MW

Raesfeld (380 kV AC, Germany)2x 1800 MW

Overhead linesGas insulated lines

XLPE cables

Main objectives of the superconducting demonstrator

10 partners to demonstrate the following objectives

• Demonstrate full-scale 3 GW class HVDC superconducting cable systemoperating at 320 kV and 10 kA

• Validate the novel MgB2 superconductor for high-power electricity transfer

• Provide guidance on technical aspects, economic viability, andenvironmental impact of this innovative technology


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System integration pathways for

HDVC applications

Investigation in the availability of the

cable system

Preparation of the possible use of H2

liquid for long length power links

Cable and termination

development+ manufacturing

processes

Validation of cable operations with

laboratory experiments performed in He gas at variable temperature

Operating demonstration of a

full scale cable system transferring

up to 3.2 GW

Process development to manufacture a

large quantity of high performance MgB2

wires at low cost

10 project partners for an outstanding consortium


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● Losses assessment

● Cable system (terminations)

● MgB2 wires manufacturing

● Optimisation of wires and conductors

● Demo coordination

● Optimisation of MgB2 wires and conductors

● Cable system

● Cryogenic machines

● Testing in He gas

● Integration into the grid

● Scientific coordination

● Dissemination and exploitation

● Optimisation of MgB2 wires and conductors

● Cable system

● Testing in He gas

● Cable system (HV dielectric behaviour)

● Cryogenic machines and cooling systems

● Integration to the grid

● Reliability and maintenance

● Cable system (terminations)

● Integration into the grid

● Socio-economical impact

● Reliability

Conceptual design

Two fluids to guarantee reliable operation


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10 kA MgB2 conductor in He gas

Outer cryogenic envelope

HV lapped insulationin liquid N2

Inner cryogenic envelope

4 wall cryogenic envelope

Liquid N2 (70 K / 5 bar) He gas (20 K / 20 bar)

Demonstrator characteristics

Monopole

3.2 GW

320 kV

10 kA

20 - 30 m

Requirements

Losses < 50 W He gas (@20 K)

Fault current < 35 kAduring 100 ms

AC Ripples on 10 kA DC current < 1% amplitude @ 50 Hz

Polarity reversal = 100 MW/sup to 10 GW/s

Cu

MgB2

Schedule: 2 Work Packages divided in 11 Key Tasks


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Extension of KT 7.1 to develop very high performance wire

in revised DOW

October 2016

MgB2 wires manufacturing (Columbus SpA process)

Industrial machines to roll, draw, swag and anneal


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Clean synthesis of powders

20 meter long in-line furnace Multistep drawing machine 4 meter furnacefor annealing HT

High power straightdrawing machine

WP 7Task 7.1

• 39 new machines• 15 existing machines in use• 10 main upgrades to the technical

infrastructures• 1 new two-floor building• 2280 m2 of covered workshop area• 20 direct production units

MgB2 wire design and characterisation


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WP 7Task 7.1

MgB2 wires

Diameter (mm) 1.3 1.0 1.5 1.5

Materials Monel, Ni Monel, Ni, Nb Monel, Ni Monel, Ni, Nb

MgB2 volume fraction 17 % 12 % 30 % 12 %

Ic (A) @ 20 K & 1 T 500 300 > 650 > 650

Ic (A) @ 4.2 K & 3 T 280 400 > 700 600

rc (mm) 125 100 200 150

already optimised for fault “tolerant” requirements

New design proposed for project-specific fault

“transparent” requirements

❹❸❷❶

MgB2 wires – Towards kilometric piece lengths


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WP 7Task 7.1

Next steps

Implement the new wire (#4) layout into the production process to manufacture a cable conductor on industrial cabling machine

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Wire diameter homogeneity achieved along the entire batch length of about 2 km

Confirmation of the wire process capabilityto stay within the specification limits

10 kA MgB2 cable conductor


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WP 7Task 7.2

Strategy 1: Control quenching during the fault

Cable already manufactured by Nexans

Measurements of extracted wires performed after cabling after bending on 1.2 m diameter drum by Columbus SPA show no degradation

Ongoing electrical characterization of cable prototypes at CERN:Measurements of the critical current of 2 meter long prototype cable tested in liquid (at 4.3 K) and gaseous helium (at temperatures between 15 K and 30 K)

Cu MgB2

18 MgB2 wiresIc = 14000 AIop/Ic = 0.72D= 9.6 mm

Modeling: transient phenomena(= thermal losses)

• Power inversion from 100 MW/s up to 10 GW/s

• Fault current: 35 kA during 100 ms

• Ripple losses due to current source into the MgB2 wire

But possible at 5 GW/s

Risk of quench identified at 10 GW/s ramp

Fault tolerant cable conductor design validated:• For the controlled quench cable design,

the temperature after a fault has been estimated (≈ 90 K)

• Time to recover ≈ several seconds

Ripples are acceptable:• 1 % 50 Hz ripples generate coupling

losses in the same order of magnitude as the cryo-envelop (0.1 W/m) manageable with the cooling system



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WP 7Task 7.2

• Several possible designs to accept current higher than 35 kA without quenches

• Possible by the unique properties of the MgB2 superconductor: high current and good stability at low cost

• With a maximum diameter of 20 mm to limit the losses of the inner cryogenic envelope (< 0.15 W/m)

Strategy 2: Fault transparent MgB2

cable configurations(=no quench during the fault)

MgB2 wires

Diameter (mm) 1.5

Design Simple stage

Cable diameter (mm) 19

Number of MgB2 wires 36

❹

Very high currents can be withstood within an acceptable cable size, when using the “fault transparent” design. This could save the power grid from a blackout.

Design and manufacture a mockup of a 10 kA cable conductor built with 9 to 12 wires #4 around a flexible copper core at Nexans

Electrical characterisation of cable prototypes at CERN and Columbus:• Measurements of the critical current of extracted

wires and 2-meter long “mockup” cable tested in liquid (at 4.3 K) and gaseous helium (at temperatures between 15 K and 30 K)

• Very high current expected Ic > 800 A at 20 K and 1 T for wire

• Ic > 35 kA!!! for cable conductorToo high to be measured



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WP 7Task 7.2

Next steps

1. Manufacture a cable conductor (Type 4) based on the results of wire 4 characterization and on the specifications from the modeling task

2. Measure the critical current of cable conductor (Type 1) (expected Ic ~ 14 kA)

3. Measure the critical current of a mockup cable conductor (Type 4) (expected Ic ~ 18 kA)

Cable system: termination


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WP 7Task 7.3

High Voltage parts

For injection of:1. Cryogenic fluids He & Liq N2

2. Current

70 K flow (inlet/outlet)

Liquid nitrogen

Grounded parts

20 K flow (inlet/outlet)

Helium gas

Principle of HVDC termination

• Withstand the full testing voltage

• Should inject the current into the cable conductor with an hybrid current leads

• Should allow the Liq N2 cryogenic fluid injection

Height ≈ 8 m

Principle of CryogenicHV insulated line

• Withstand the full testing voltage

• Should allow the cryogenic fluid circulation (tightness / resistance to pressure 20 bar)

• Should have a good radial thermal insulation

Cable system: hybrid current leads


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WP 7Task 7.3

Hybrid current leads benefit from high temperaturesuperconductor tapes

Welding tocable cryostat

(tightness 20 K)

20 K20 bar

cable cryostat

20 K – 77 KThermal insulated area / Low thermal

conduction area

High temperature superconductor tapes

Brazed connection to MgB2 cable

70 K5 barLN2

Transition 70 K - Ambient

not represented in this scheme

(copper rod is foreseen…)

Welding totermination cryostat

(tightness 70 K)

10 kA current

Total heat load expected per current

leads at 70-77 K500 W

Total heat load expected per current lead in He gas at 20 K

≈ 6 W

< 1 W calculated by KIT by FEM modeling

based on the design

In accordance with the calculation, prototype of current lead tested is able to transfer 10 kA at 77 K in Liq N2 in superconducting state.Ready for demonstration

Current leads are a heat inlet point within the system (Joule + thermal conduction)

Cable system: HV cable insulation


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WP 7Task 7.3

A versatile and quick lapping line has been designed for preparation of short model 1 samples• Different tapes’ material (paper, PP, PPLP, etc…)• Different dimensions (thickness, width,…)• Different pitches and gaps between the tapes

HV cable insulation= lapped tapes impregnated with liquid nitrogen

Cryogenic HV testing equipment for space charge measurements close to operating conditions of the cable HV insulation was designed and is operational

Select the best equipment to limit the space charges in DC with the highest voltage breakdown

Commissioning of testing equipment for cable insulator is completed• Submitted up to 60 kV

(possible upgrade to 120 kV)• In LN2 under 5 bar pressure

with a slow fluid flow• Temperature regulation by

exchanger

Cable system


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WP 7Task 7.3

HV cable insulation • 40 kV are applied across a 2 mm thick Kraft

paper impregnated with Liq N2

• A good elastic wave propagation through the sample is found

No trapped charge carrier is found

HV insulation made using paper impregnated with Liq N2 looks like a good candidate for HVDC superconducting cable

Next steps

1. Manufacture and test the cryogenic He injection tube

2. Manufacture HV cable samples with different lapping layouts

3. Verify the charge carrier distributions within the insulation to assess the insulation design with PPLP

4. Finalise cable HV insulation design (Paper or PPLP)

5. Design termination cryostat and bushing after definition of cable HV insulation

Cryostat and cooling system


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WP 7Task 7.4

Cryogenic system design• Correlations for the evaluation of the pressure

drop and heat losses of the cryogenic envelope around the superconducting cable were reviewed

• A program flow chart of the thermohydraulicmodel has been proposed

Commissioning of the 20 K cooling machine has started in May 2016

Next steps

1. A dedicated thermo-hydraulic model has to be programmed to evaluate the pressure drop and heat losses of the superconducting cable (conductor and insulation pipes)

2. As a result of the modeling, dedicated design charts involving various parameters the cable will be provided

3. A cooling concept for a kilometric superconducting cable will be proposed

Availability of the system


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WP 7Task 7.5

Concept designs of different systems• Conceptual design of the cooling system

including redundancy for a superconducting cable several kilometer long: a modular system keeping a temperature well where the cable lays down

• Radial inward heat flow is removed by a cooler at the end of each the cryostat module, which is filled by a cryo-fluid below 25 K

• Different thermal shields (liquid, gas or solid) are proposed to increase the availability of the system even during repairs or maintenance operation

Next steps

1. Selection of the best solutions based on the evaluation of the energy efficiency and cost estimation

2. According to the selection, redundancy strategies will be developed

Expected results and impact


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1000

2000

Transmitted power (MW)

100 200 300 400

Voltage(kV)

3000

4000

5000

Eco-friendly Innovations in Electricity Transmission and Distribution Networks, Woodhead Publishing Series in Energy: Number 72; 2015 Edited by Jean-Luc Bessede P158

Best Paths Demo 5

Increased powerat a reduced voltage level

Reduced power transmission losses

Consequent reduction of raw materials


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Copper 2000 mm² Conductor

Superconducting wires

MgB2

XLPE extruded cable

56 mm

1.1 mm

> 10 000 A

≈ 1 800 A

(One € coin)

Demo 5 conductor

Reduced space for cable installation and substations


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Significant reduction of right-of-way corridors and of excavation work

No thermal dependence to the environment

Example: 6.4 GW DC power link with XLPE cables

1,30 m

2,00 m

Foot print = 7 m

Resistive cables ( 8 x 400 kV - 2 kA)

Foot print = 0.8 m

Our Best Paths Demo 5(2 x 320 kV - 10 kA)

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Favourable scenario: 15°C, soil 1 K.m/W

Recent DEMO 5 conference presentations


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Date Presentation Title Meeting

May 2016An MgB2 superconducting cable for very high DC power transmission

16th IERE General Meeting & China Forum

July 2016Space charge measurements at very low temperatures

International Conference on Dielectrics (ICD)

August 2016An MgB2 superconducting cable for very high DC power transmission

Cigré Session 2016

September 2016

Midterm update on the high-power MgB2

DC superconducting cable project within BEST PATHS

27th Applied Superconductivity

Conference (ASC 2016)

September 2016

MgB2 round wires for the high power superconducting cable demonstrator in the Best Paths project

27th Applied Superconductivity

Conference (ASC 2016)

November 2016

Numerical model for quench calculations in a 10 kA MgB2 superconducting cable

17th Conference on Electromagnetic Field

Computation (CEFC 2016)

DEMO 5 publications in 2016


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Date Publication Title Journal

March 2016An MgB2 HVDC superconducting cable for power transmission with a reduced carbon footprint (Invited)

Proceedings of the ED2E Conference

April 2016The BEST PATHS Project on MgB2

Superconducting Cables for Very High Power Transmission

IEEE Transactions onApplied

Superconductivity

April 2016 3-D Numerical Modeling of AC Losses in Multifilamentary MgB2 Wires (Invited)

IEEE Transactions onApplied Supercond.

June 2016Space charge measurements at very low temperatures

Proceedings of the International Conference

on Dielectrics (ICD)

August 2016 An MgB2 superconducting cable for very high DC power transmission

Proceedings of the Cigré Session 2016

September 2016

Midterm update on the high-power MgB2

DC superconducting cable project within BEST PATHS (Under peer review)

IEEE Transactions onApplied

Superconductivity

Conclusion: Highlights and critical issues

A good momentum of the team is now achieved

Exciting collaborative works are carried out within the Demo 5 teams

1. Demo 5 is very innovative and based on systems to be developed

2. Difficulties to measure the performances of the MgB2 wires (Ic, losses..) or testing high voltage at cryogenic temperatures.

Limited number of experimental set-ups available but collaborations beyond the Best Paths consortium are started (IEC TC 90, Cigré, universities, etc…)

3. Conceptual design of the critical parts is now validated

No blocking point has been identified so far

4. In 2017 the project will enter a new phase, the demonstration, which will require significant engineering developments…


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Contacts

• Christian-Eric BRUZEK

[email protected]

• Adela MARIAN

[email protected]

• Frédéric LESUR

[email protected]


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