Funded by

Installation and Testing of Helium Gas Cooled

Superconducting DC Cable at FSU-CAPS

Sastry Pamidi, Chul Han Kim, Lukas Graber, Danny Crook, Steve Ranner,

Bianca Trociewitz, and Steinar Dale The Florida State University - Center for Advanced Power Systems

Tallahassee, Florida

David Knoll, Dag Willen, Carsten Thidemann, and Heidi Lentge Ultera

19-Pamidi

11th EPRI Superconductivity Conference, October 28-30, 2013,

Houston, TX

Team Members

Sastry Pamidi

Chul Kim

Steinar Dale

Superconductivity Cryogenics

Danny Crook

Sastry Pamidi

Chul Kim

Facilities/

Electrical

Steve Ranner

Bianca Trociewitz

CAPS

NSWCCD, Philadelphia

Brian Fitzpatrick

Advice on Navy needs & relevance

Ultera/Southwire

David Knoll

Cable Fabrication

Cryo Dielectrics

Lukas Graber

Horatio Rodrigo

Steinar Dale

Benefits of Helium Gas Cooled

Superconducting Power Devices

Flexibility in operating temperatures (30 K–80 K)

Enhanced superconducting properties at lower temperatures

Lower temperatures allow higher power densities when

necessary

Larger temperature gradients can be maintained without

accompanying a phase change

Easier to integrate with other superconducting devices

operating under helium gas cooling

Increased flexibility in power system design optimization

Helium Gas Based Systems - Challenges

Low heat capacity of helium gas – requires high

pressures and flow rates for efficient heat removal

Helium gas has low dielectric strength – dielectric design

has to depend on the solid dielectric medium

Little experience on helium gas cooled superconducting

power devices

Commercial cryocoolers are inefficient –technological

developments necessary

Current Phase – Validate cryogenic and thermal issues

Monopole

Current rating: 3 kA and @ 77 K (up to 10 kA @ 40 K)

Voltage rating: 1 kV

Long-term Goal

100 MW -10 kA @ 50 K; voltage rating: 5 kV

Superconducting DC Cable Nominal Specifications

2G HTS - Cryoflex insulation – Ultera Triax Cable Design

Cryogenic Helium Circulation Systems

Operating Pressure: up to 250 psi, Expected flow rate: up to 10 g/s

AL 330

1

4

3

2

Cryo Fan

Stirling System

340 W @ 50 K

Cryozone Bohmwind Fan

50 psi 300 psi

Design Validation Studies on 1 m Cable Sections

The prototype cables performed well in gaseous helium

At 300 psi, PDIV is 7.4 kV peak

He inlet

Vacuum LN2

T- Sensors Cable

Current

Terminal

Schematic of the Terminations

G10 bar Temperature Sensors

TS #1

TS #8

TS #2

TS #5 TS #7 TS #6

TS #3 TS #4

G10 bar

Temperature Sensors

TS #9 TS #10 TS #11

TS #12

Cryostat

GHe In GHe Out 1 m or 30 m

cryostat

T Across the Terminations and the Cryostat

Without The Cable

∆T

30 m cryostat

Estimated Heat Leak From The Termination Tanks

Temperature Sensors

TS #1

TS #8

TS #2

TS #5 TS #7 TS #6

TS #3 TS #4

G10 bar

Temperature Sensors

TS #9 TS #10 TS #11

TS #12

GHe In GHe Out

Pictures of Cable Installation

As mass flow rate increases, the T decreases; T < 4 K @ 8 g/s for 3 kA

@ 50 K inlet T

Temperature Gradients Across the 30–m Cable

Little resistance between clamshell and cable terminal. 10 µ between the

current lead and the clamshell – room for improvement

@ 55 K

Resistances of the Current Contacts

Voltages measured on each of the three HTS layers

Only white noise measured up to 3000 A

No Voltage Rise Up To 3 kA

A Screenshot During One of The Tests

Current Voltage – HTS

layers

Voltage –

Copper layers

Summary

Cryogenic helium circulation system maintains a T<4 K

from inlet to outlet of the 30 m cryostat

Thermal load tests using simulated cable did not create large

temperature gradients

Experimental data on temperature gradients matched with

that of the thermal model

30 m cable performed well in GHe up to 3 kA

What is next?

We will attempt 4-5 kA with modified current feed throughs

High voltage tests in November/December 2013

We will look for funding for ±5 kV, 10 kA cable design