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superior performance.powerful technology.

SuperPower, Inc. is a subsidiary of Royal Philips Electronics N.V.

Transmission Level HTS Fault CurrentLimiter

Chuck Weber

8 th

Annual EPRI Superconductivity ConferenceOak Ridge, TNNovember 12, 2008

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8 th Annual EPRI Superconductivity Conference November 12, 2008

SFCL program overview

15.248"

7.362"

15.248"

7.362"

138 kV, 650 kV BILBushings

Vacuum Vessel

Pressure Vessel

Matrix Assembly

Inner diameter

InnerHeight

HTS AssemblyHeight

Assembly diameter

Partners

Specifications

YBCO based, resistive type FCL

138 kV class device

Fault Current

13.8 kA

Load Current

1,200 A rms

Design fault current

37 kA

Design device response

Recover

to superconducting state after a faultcarrying full load current

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TIDD Substation

(Partial) One-Line Diagram

Proposed SFCLInstallationLocation

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Prior accomplishments

Proof-of-Concept demonstrated

MCP 2212 (2004)

2G YBCO (2006)

Beta device testing specificationsestablished

Completed design and testing of HV

bushings (SEI)

Investigated several engineered 2Garchitectures for improved RUL

Design and laboratory testing of shuntcoils to withstand high fault transient loads

Thermal simulation of RUL process

Weibull

plots of standard 2G failures

Conceptual CRS & vessel design

Investigated LN 2 dielectric properties

2G FCL - Probability of failure for 2G tapes as function of energyinput

0.01

0.1

1

10

100

20 25 30 35 40 45 50

Energy [J/cm/tape]

P r o

b a

b i l i t y o

f f a i l u r e

[ % ]

Probability of Failure - Test dataProbability of Failure Calculated using Weibull Distributuon

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6/228 th Annual EPRI Superconductivity Conference November 12, 2008

Improvements to shunt coil and contact design

Shunt coil improvements:

Manufacturing improvements

(easier assembly, more robustcoil)

Mechanical strength

Multi-Layer winding (sizereduction)

Connector improvements:

Shape optimization to avoidcontact hotspots

Improvement in RUL Time

Improvement in RUL Current

Improvement in consistency ofcontact resistance

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Tape heating near contact during fault impactsRUL

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Correlation between different contact geometries

Total Current (80A peak)

Recovery Voltage

Superconductors Current

Straight Thick Contacts

(M3-460 Tape):

I load

= 80 ARUL = 82 sec.


Recovery Voltage

SuperconductorsCurrent


Recovery Voltage

SuperconductorsCurrent

Straight -Tapered Contacts(M3-460 Tape):

I load

= 80 ARUL =

3.5 sec.

Straight -Tapered Contacts

(M3-460 Tape):

I load

= 80 ARUL = 2.8 sec.

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Recent KEMA tests

Recent rounds of KEMA testing focused on critical AEP reclosure sequence onan HTS element

Straight elements wereused

Improved connectordesigns were used

Standard, pre-qualifiedtapes were used

Test Dates: May 2008,July 2008

5 Cycles

Fault13kA/7kA

18 Cycles

Load Current

15 sec

Load Current135 secLoad Current

5 CyclesFault

13kA/7kA

5 CyclesFault

13kA/7kA

5 CyclesFault

13kA/7kABreaker opensand locks-out

Recovery under

NO Load Current

5 Cycles

Fault13kA/7kA

160 secLoad Current

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2G RUL capabilities tested at KEMA

Standard SF12100 2G wire used

Test conditions

-

37 kA fault

-

follows AEP sequence

Test variables

-

Shunt impedance

-

Number of parallel tapes

-

System voltage (v/cm/tape)

-

Load Current

16 Tapes8 Tapes

4 Tapes100V

200V

250V

300V

0

50000

100000

150000

200000

250000

Load Powe r (VA)

Total Recovered Pow er, 2x5 cycles Faults at 37kA with 10mOhm

P a r a l l e l T a p e s

V o l t a

g e

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3 x Base-Line Voltage

w/o Load

w/ Load

Achieving RUL is a difficult task

Without load current recovery is very fast

Adding load current makesrecovery much more difficult

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Base-Line Voltage

RUL

1.5 x Base-Line Voltage

RUL

3 x Base-Line Voltage

RUL

Electrical stress on the tapes can limit RUL

RUL time can affected byincreasing the V/cm on thetape

Limits of the designoptimization are understood

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Factors impacting RUL defined by test results

1.67 m-Ohm

5 m-Ohm

100 V200 V

250 V300 V

0

10000

20000

30000

40000

50000

60000

70000

80000

Load Power (VA))

Total Recovered Power, 2x5 cycles Faults at 37kA with 4 Tapes

S h u n t I m p e d a n c e V o l t a g

e

Sample surface plot of RUL conditions

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Ability to predict RUL over wide design space

1 . 6

7 m - O

h m

5 m - O

h m

4 T a p e s ,

1 0 0 V

4 T a p e s ,

2 5 0 V

8 T a p e s ,

1 0 0 V

8 T a p e s ,

2 5 0 V

1 6 T a p e s ,

1 0 0 V

1 6 T a p e s , 2 5

0 V

0

100

200

300

400

500

600

700

800

900

1000

Maximun RecoveredLoad Current

Recovered Current with 2 Asymmetrical 37kA Faults, 5 cycles each

I m p e d a n c e V o l t

a g e, # T a p e s

Maximum Load Current as a function of shunt impedance, operating

voltage & number oftapes

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RUL with 90% of the Power recovered withinthe 2 nd

and the 3 rd

37 kA Faults

Worst case conditions at Tidd

can achieve RUL

Full recovery expected with optimal bath conditions

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Bath Conditions Impact on Ability to Recover

100 150 200 250 300 350 400 450 500 5500

100

200

300

400

500

600

Heat OutHeat In

No Recovery Due to Film Boiling

Temperature (K)

P o w e r

( W )

Lowering the shunt coil value orincreasing the resistance of thestabilizer layer will help with film boiling.

Lower Z shunt

,Higher Z

tape

Boiling Heat Transfer for LN2

0.1

1.0

10.0

100.0

1.0 10.0 100.0 1000.0

T wall - T sat (K)

q / A ( W / c m

2 )

During the fault transient, tape heats up to film boiling region.Bath conditions (pressure, subcooling) shift boiling heat transfer curveBath conditions have an impact on the dielectric strength of LN2

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19 Managed by UT-Battellefor the Department of Energy DOE Peer Review 2008

Introducing bubbles in LN lowersbreakdown strength: FCL recovery

Two experiments

Open bath LN

Pressurized cryostat

Nitrogen gas provided

by fused silica capillarytube

Varied flow rates

Parallel plane profiledSS electrodes

BD strength of LN is

~5x the gas at 1 bar

Bubbles form thermally or electrically and can affect the breakdown strength

2 mm gap0.5 mm capillary tube

Important for FCL Recovery under Load

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Effect of externally provided bubbleson LN Breakdown: AC breakdown

all data w and w/o bubbles

Breakdown Field (kVrms/mm)5 6 7 8 9 20 3010

C u m u

l a t i v e

F a

i l u r e

P r o

b a

b i l i t y ( % )

1.0

5.0

10.0

20.030.040.050.060.070.080.090.095.0

99.099.9

Effect of Bubbles

Presence of bubbleswithout bubbles with bubbles

A v e r a g e

E l e c t r i c

F i e l d ( k V r m s / m m

)

0

2

4

6

8

10

12

14

16

18

Liquid nitrogen at 1 bar

Bubbles in LN lowers breakdown strength

Change in slope at lower probability indicates change in BDmechanism

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Summary

Significant progress in understanding and impacts of:

RUL

Variables impacting RUL studied and understood

Worst case conditions at TIDD can be met

Impact of device design and cost under evaluation

LN2

Dielectrics

Impact of bubbles on breakdown mechanism and dielectricstrength

Loss of cryogenic partner a setback, but not fatal

Next step: Alpha detailed design

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8 th Ann l EPRI S percond cti it Conference No ember 12 2008

Thank You for your attention!

For more information:

www.superpower-inc.com

or [email protected]

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