David Knoll

11th EPRI Superconductivity Conference

Houston, TX 2013

Update on AEP/Bixby Project and HTS Cable

Commercialization Prospects

HTS TriaxTM

American Electric Power (AEP)

HTS TriaxTM Cable System

13.2kV ● 3000A ● 69MVA

• 200m cable in duct-bank

• TriaxTM splice

• TriaxTM terminations

• Multiple 90º bends

• Cooling system (open cycle)

Energized: Aug 2006

De-Energized: Oct 2012

Project funded by U.S. DOE

Southwire: Project Lead • Development

• Cable

• Terminations

• Splice

• Installation

• Substation infrastructure

• Operation

AMSC: HTS 1G BSCCO wire

Praxair: Cooling system

HTS TriaxTM

Site Layout

Manhole with splice

North Termination

Liquid Nitrogen Return Line

South Termination

LN Cooling System

HTS TriaxTM Cable

LN

HTS TriaxTM Overview

PH1

PH2

PH3

N

Dielectric

Cryostat

70mm

150 mm

Phase Connections

Neutral

Dielectric

Dielectric

HTS TriaxTM

Open Cycle Cooling

Subcooler

Heat Exchanger

LN2

Supply

Tank 11,000gal

Pulse

Tube(s)

Cable

Backup

LN2 GN2

Nominal temperature = 70K

Nominal pressure = 90-100psia

Truck in LN: 3 or 4 deliveries per week

HTS TriaxTM

Auxiliary System Information

COOLING SYSTEM CONTROL SYSTEM INSTRUMENTATION

Vacuum Pumps HMI Temperature

Heat Exchangers PLC’s Pressure

Valves & Piping Software Flow

Tanks & Vaporizers

Circulation Pumps

Tankers

138 kV

HTS Cable 0.4 W

2

2

1

1

1

3 2 14

3

3

5

112 SPR

Inst.

OC

Inst.

OC

12

11

3

4

4

Bus B

Bus A

3

9

5

7

8

5

3

N.C.

HTS TriaxTM

Substation Circuit

13.2 kV TX

138kV / 13.2kV

Parallel Conventional

feed

HTS TriaxTM

System Operation

COMMUNICATION TO AEP

Status 0: Cable not ready to energize

- not in optimal state

- repair

Status 1: Cable ready to energize

Status 2: Parameter(s) out of range

- Have time to respond

- Fix or switch cable manually

- make-then-break

Status 3: Dangerous condition

- Risk of gas phase in cable

- Major component failure

REQUIRED MANUAL SWITCHING TO ENERGIZE CABLE

System Commissioning DC Current Testing: 6000A High Voltage: VLF 20kV (30 min)

Voltage Soak: 13.2kV (24 hr.)

AEP-Bixby Triax Cable Cooldown

-220

-200

-180

-160

-140

-120

-100

-80

-60

-40

-20

0

20

40

0:02:01 12:03:41 0:05:21 12:07:01 0:08:41 12:10:21 0:12:01 12:13:41

Time

Deg

C

System Operation

1.5 days

AEP-Bixby HTS Cable - Power On

8 August 2006

0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

2600

9:09:00 10:21:30 11:34:00 12:46:30 13:59:00 15:11:30 16:24:00 17:36:30 18:49:00 20:01:30

Time

Am

ps

-210

-208

-206

-204

-202

-200

-198

-196

Tem

pert

ure

P1

P2

P3

N

TI102

TI104

TI105

TI106

System Operation Bixby HTS Cable Load Curve

1Jan2008 - 14July2008

0

500

1000

1500

2000

2500

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

0:00

:00

Date/Time

Cu

rre

nt

(Am

ps

)

Phase 1

Phase 2

Phase 3

Neutral

Bixby Load Curve

August 6 - 10, 2008

0

500

1000

1500

2000

2500

3000

0:00:00 0:00:00 0:00:00 0:00:00 0:00:00

Date/Time

Cu

rre

nt

(Am

ps

)

Phase 1

Phase 2

Phase 3

Neutral

2,715 A

HTS TriaxTM

Transients

27kA

Open

Breaker

17kA

More than 100 transients recorded

Most < 10,000A

Average = 6,500A

Maximum = 27,000A

ΔT not noticeable unless cooling plant went down

HTS TriaxTM

Cable Availability

2008 – 2010 (26,280 hr.)

cable at operating temp: 26,000 hr.

current on cable: 23,000 hr.

AVAILABILITY (cable ≤ 75K):

26,000 hr. 99% availability

OUTAGE = DE-ENERGIZED CABLE

AVAILABILITY = CABLE ≤ 75K

Dec 2006 – Oct 2012 (51,800 hr.)

44,000 hr. of data recorded

cable at operating temp: 42,500 hr.

current on cable: 35,000 hr.

AVAILABILITY (cable ≤ 75K):

42,500 hr. 97% availability

Cable Outages

Necessary vs. Nuisance

Few necessary outages:

• Circulation pump failure

• Vacuum pump failure

• Leaking valve

Most are nuisance outages.

Redundancy prevented the cable system from being in danger

Health of the cable system was never in danger

Nuisance Examples

• Temperature transmitter failure

- algorithm calculated gas-phase “status 3”

• Tank over-pressure during filling “status 2 or 3”

• House power loss “status 3”

• Improper control system settings “status 2”

• PLC failure “status 2 or 3”

• Operator Error “status 2 or 3”

HTS TriaxTM

End of Service Testing

At this point : HTS TriaxTM Hardware was proven successful

Next Step: Southwire / Ultera took on an effort to commercialize HTS cable Technology

• Utilized DOE funding originally slated for Entergy

• Funding was reduced and to be applied to tackling outstanding commercial barriers

end of service testing on Bixby cable

CABLE TESTS ON AEP-TRIAXTM CABLE

1. Heat load testing: analyze heat loads under different operating conditions

• Analyze historical data

• Higher operating temperatures

• Various flow rates and configurations

2. High voltage testing

• at original operating temperature

• at higher operating temperature

3. High current testing

• Up to 6,000A

• Compare results to original commissioning results

HTS TriaxTM

Heat Load Testing

System Heat Load vs. Time

2007-2011

REFRIGERATION SYSTEM+CABLE+TERM

CABLE + TERM

CABLE ONLY

Loss

(kW

)

Time (hr x 104)

Current (A)

Loss

(kW

)

CABLE ONLY

CABLE + TERM

REFRIGERATION SYSTEM+CABLE+TERM

System Heat Load vs. Current

2007-2011

Heat Load Testing

SYSTEM OPTIMIZATION: IMPACTS OF OPERATING AT HIGHER TEMPERATURE

Cable Inlet Temperature (K)

He

at L

oad

(W

)

RESULTS:

• Difficult to correlate operating temperature and loss.

• Did see correlation b/w ambient temperature and loss

• Need high temperature resolution to get good data

• Largest impact is in termination copper parts

ΔT of 5K adds ~100W

• higher operating temperature has a low impact on system loss

0ºC

1ºC

6ºC

8ºC

20ºC

28ºC

26ºC

27ºC

1720A

18ºC

8

74

A

20ºC

1143A

24ºC

1

14

6A

26ºC

1270A

27ºC

1

61

8A

No Load

With Load

HTS TriaxTM

High Voltage Testing

PURPOSE:

• Partial discharge (PD) baseline at 70K

• Partial discharge (PD) up to 75K

• Compare results

TESTING:

• Voltage on one phase at a time

(other phases grounded)

• PD measurement up to 20kVrms

• Dwell at 20kV

North Termination HTS Cable

LN F

eed

LN F

eed

PH1 PH2 PH3

South Termination HTS Cable

LN F

eed

PD Detector

PH1

High Voltage

PH2 PH3

South Termination HTS Cable

LN F

eed

PD Detector

High Voltage

PH1 PH2 PH3

North Termination HTS Cable

LN F

eed

LN F

eed

PH1 PH2 PH3

South Termination HTS Cable

LN F

eed

PD Detector

PH1 PH2 PH3

High Voltage

North Termination HTS Cable

LN F

eed

LN F

eed

PH1 PH2 PH3

HTS TriaxTM

High Voltage Testing

PD Inception Voltages at 70K supply temperature South Termination North Termination Cable Splice PH 1 4.3 kV 7.6 kV >20 kV >20 kV PH 2 >20 kV >20 kV >20 kV >20 kV PH 3 16 kV 16 kV >20 kV >20 kV

HTS TriaxTM

High Voltage Testing

PD Inception Voltages at 75K supply temperature South Termination North Termination Cable Splice PH 1 ~ 3 kV 13.2 kV >20 kV >20 kV PH 2 >20 kV >20 kV >20 kV >20 kV PH 3 17.3 kV 17.3 kV >20 kV >20 kV

70K

75K

1. Phase 1 terminations show PD at or below operating voltage

• Project ended - not able to determine cause at this time

• Cable withstood 20kV in spite of showing low PD

2. No PD in cable or splice

3. Based on this analysis, the PH1 terminations have operated some time with PD

• Need to study affects of PD on LN impregnated systems

HTS TriaxTM

High Current Testing (by ORNL) PURPOSE: analyze high current-voltage response and compare 2006 vs. 2012 data

looking for performance degradation

• Expected Ic = 7000-7500A for each phase.

• Power supplies limited to 6000A cannot measure Ic of cable

• Two phases were measured simultaneously – minimizes inductance

ph1

ph2

ph3

ph1ph2ph3

gnd

gnd

North termination

South termination

DC 6 kA power source (Two 3 kA dc power

supplies)

Undergroundcable splice

0

0.05

0.1

0.15

0.2

0.25

0.3

0.35

0.4

0.45

0 1 2 3 4 5 6 7

Vo

lta

ge [

V]

Current [kA]

ph3 June 2006

ph3 August 2012

High Current Testing (by ORNL)

2006

2012

2012

2012

PHASE 3 : V-I CURVE

RESULTS:

1. Total resistance of circuit = 0.15 – 0.17mΩ

- resistance at superconducting-to-normal transition estimated at 15mΩ

2. Similar V-I characteristics before and after 6 years of service

very little (if any )degradation

PHASE 2 : V-I CURVE

HTS TriaxTM

Lessons Learned

CABLE, TERMINATIONS, SPLICE

1. Technology is robust: thermal cycles and high current transients do not damage the system.

2. HTS wires show no degradation.

3. Need to study effects of PD - does not seem to degrade the system in the short-term.

• Next generation TriaxTM Termination: PDIV > 20kV (2.5U0) in full scale tests.

4. Need to consider higher operating temperatures

• Up to and above 75K

• Data shows no performance degradation

• Enable more efficient cooling systems

5. Ambient temperature has an effect on system heat load

• Improve thermal insulation systems

• Improve current lead designs

HTS TriaxTM

Lessons Learned

INSTRUMENTATION

1. Sensors themselves are robust

• RTD, Thermocouple, Rosemount pressure sensor, differential flow meter: all good

2. Instrumentation transmitters need to be industrial type

• Harsh outdoor environments

• Need protection against transients which are typical in substations

3. Need redundancy

• Protection systems should have more than one point of reference

• Eliminate nuisance trouble alarms and unnecessary shut-downs.

CONTROL SYSTEM

1. Most important: build redundancy into algorithms

• Conservative design for safety is okay, but need to prevent nuisance shut-downs.

HTS TriaxTM

Lessons Learned

COOLING SYSTEM

1. Systems are robust today

• Cryogenic systems are not new, so they are inherently reliable

2. Need full redundancy on active components

• Maintainable / replaceable without system shutdowns

3. Need to monitor and maintain thermal insulation systems

• Source of significant heat load, thus risks to efficiency

• Maintainable without system shutdowns

4. Vibration can be for fixed components

• Mechanical fatigue and failure

5. Simple is good

• Generally, cryogenic experts are required to operate such systems

• Can the LN supply systems be simplified so that anyone can operate it?

6. Need a lot of work on efficiency.

HTS CABLE COMMERICIALIZATION

COMMERCIAL BARRIERS

1. Capital cost still very high

• Today: $15M-$20M per mile

• 5+ Years: $10M-$15M per mile

2. Cryogenics not optimized for cables

• Size reductions are necessary

• Need to be simple to operate

• Expensive to operate – both open and closed-cycle need better efficiency

3. Need factory test capability for cable, terminations and splices

4. Need long-length system studies (greater than 1km)

• Figure how to manage cool-down / recovery times

• Managing heat load

5. Need optimized repair and maintenance schemes

• Today, system repair is on the order of months

• Need to optimize component designs for efficient repair

HTS CABLE COMMERICIAL PROSPECTS

CONGESTED URBAN AREAS

1. Retrofit existing duct-bank

• replace low capacity MV with ultra-high capacity medium voltage

2. Remote substation

• move high voltage facilities to remote areas

• pipe in transmission-level power at medium voltage

3. Substation Inter-tie

• Share substation equipment (transformers)

• Increase redundancy and reliability.

• Avoids the need for extra high voltage infrastructure to meet reliability