Insulation technologies for HTS apparatus - unibo.it · PDF filePartial discharge...
Transcript of Insulation technologies for HTS apparatus - unibo.it · PDF filePartial discharge...
Insulation technologies
for HTS apparatus
Naoki Hayakawa
(Nagoya University, Japan)
ESAS Summer School, June 8-14, 2016, Bologna, Italy
Contents
1. Self-introduction
2. Background
Why is the electrical insulation important?
3. Fundamentals of electrical insulation
Electromagnetism, Electric field
4. Breakdown characteristics
Gas, Vacuum, Liquid, Solid, Composite system
5. Partial discharge characteristics
Precursor of breakdown, Insulation degradation
6. Electrical insulation peculiar to applied superconductivity
Quench-induced dynamic insulation characteristics
7. Conclusion and future works
Naoki Hayakawa
Biography
Date of birth: September 9, 1962
Date of place: Nagoya, Japan
Academic career:
Ph.D. in electrical engineering, Nagoya University, 1991
Work experience:
Assistant professor, Nagoya University, 1990 - 1996
Associate professor, Nagoya University, 1996 - 2008
Professor, Nagoya University, 2008 -
Guest scientist, Forschungszentrum Karlsruhe,
Germany, 2001-2002
(Nagoya University, Japan)
Tokyo
Nagoya
(2.3 million people)
Where is Nagoya?
Osaka
Nagoya University
Nagoya University
Year of foundation: 1871
Number of
Staff Members: 3,606
Undergraduate Students: 9,893
Graduate Students: 5,979
Area of
Ground: 3,276,293 m2
Building: 768,350 m2
(as of May 1, 2015)
Hayakawa Lab.
1. Electric Power Transmission and Distribution
Efficient, reliable and environment-friendly power supply
Intelligent Grid Management
System (IGMS)
Material Equipment System
Functionally Graded
Materials (FGM)
Condition Monitoring
and Diagnosis (CMD)
Spacer for gas insulated
switchgear (GIS)
Alumina-filled epoxy resin with
spatial distribution of permittivity
Integration of smart grid (system)
and asset management (equipment)
Hayakawa Lab. / Nagoya University, Japan
2. High Voltage and Electrical Insulation
Discharge inception, propagation & breakdown mechanism
in vacuum, gas, liquid, solid insulators
Streamer and leader discharge in air
Surface discharge in oil/pressboard composite system
High-voltage laboratory with 800 kV impulse
voltage generator Breakdown in liquid helium
Hayakawa Lab. / Nagoya University, Japan
3. Applied Superconductivity
R&D on high-temperature superconducting (HTS) cables,
transformers, SMES and fault current limiters
HTS transmission cable
HTS fault current limiting
transformer (World’s first)
Cryogenic & high-voltage
laboratory
HTS tape (YBCO)
Hayakawa Lab. / Nagoya University, Japan
Contents
1. Self-introduction
2. Background
Why is the electrical insulation important?
3. Fundamentals of electrical insulation
Electromagnetism, Electric field
4. Breakdown characteristics
Gas, Vacuum, Liquid, Solid, Composite system
5. Partial discharge characteristics
Precursor of breakdown, Insulation degradation
6. Electrical insulation peculiar to applied superconductivity
Quench-induced dynamic insulation characteristics
7. Conclusion and future works
275kV-3kA Cable
(Japan)
10MJ SMES (Japan) 15kV-3kA Cable (USA) 66/6.9kV-2MVA Transformer
(Japan)
10kV SFCL (Germany)
220kV SFCL (China)
Superconducting power apparatus
Why is the electrical insulation important?
Power
Electrical insulation is inevitable as one of
the common techniques for power apparatus
- Superconductors carry the current. (LN2 = Cooling medium)
- Dielectrics withstand the voltage. (LN2 = Insulating medium)
Current Voltage x =
What will happen, if electrical insulation fails?
Breakdown of dielectrics
Malfunction of power apparatus
Interruption of power transmission (Blackout!)
Lightning (Breakdown of air)
Electric field strength in the order of 106 V/m
m mm μm
MV kV V Motor LSI Transmission line
Electrical insulation only for power apparatus?
Electrical insulation for all apparatus & devices
(e.g. breakdown in air at 3 kV/mm, i.e 3x106 V/m)
Contents
1. Self-introduction
2. Background
Why is the electrical insulation important?
3. Fundamentals of electrical insulation
Electromagnetism, Electric field
4. Breakdown characteristics
Gas, Vacuum, Liquid, Solid, Composite system
5. Partial discharge characteristics
Precursor of breakdown, Insulation degradation
6. Electrical insulation peculiar to applied superconductivity
Quench-induced dynamic insulation characteristics
7. Conclusion and future works
Maxwell’s Equations
HV
GND
Uniform field
High voltage
Ground
HV
GND
High voltage
GND Ground
Electric line
of force
Electric field strength and distribution
Equi-potential
line
Non-uniform field
Electric field strength Electrical potential
Dielectrics Dielectrics
Grounded electrode Grounded electrode
strength strength
Rod e
lectr
ode
Rod e
lectr
ode
Electric field analysis
V0
2b
2a
According to Gauss’s law,
Electric field strength
Electrical potential Coaxial cylinder
0
0.5
1
1.5
2
2.5
3
3.5
4
Electric field strength Er
Distance from center axis [mm] Distance from center axis [mm]
0
20
40
60
80
100
120
140
a b b a
Electrical potential Vr
Electric field analysis V
r [k
V]
V0
Er [
kV/m
m]
Contents
1. Self-introduction
2. Background
Why is the electrical insulation important?
3. Fundamentals of electrical insulation
Electromagnetism, Electric field
4. Breakdown characteristics
Gas, Vacuum, Liquid, Solid, Composite system
5. Partial discharge characteristics
Precursor of breakdown, Insulation degradation
6. Electrical insulation peculiar to applied superconductivity
Quench-induced dynamic insulation characteristics
7. Conclusion and future works
How will the breakdown occur?
Discharge inception High electric field
Generation of Initial electron
Electron avalanche
Breakdown (Flashover) Bridge of discharge channel
between HV and GND electrodes
Discharge development Progressive extension of
discharge channel
Townsend theory
1st generation
3rd generation
2nd generation
Number of
electrons
Cathode Anode initial electron
positive ion
(electron avalanche)
(secondary electron
emission)
Σ If , I (Breakdown) ∞
Paschen curves of gases
Breakdown voltage of cryogenic liquids
Bath cooling
Vacuum insulation
Solid insulation (Tape, FRP, etc.)
↓
Composite insulation system
超電導コイル
LHeタンク/冷凍機
伝熱板
電流リード
真空
超電導コイル
LHeタンク/冷凍機
伝熱板
電流リード
真空
4KGM-JT冷凍機(3台)
シールド用GM冷凍機(1台)
電流リード用GM冷凍機(2台)
HTS電流リード1kA級Y系4並列
断熱真空容器(φ 2.8×2.8H)
輻射シールド
He容器
4重極配置超電導コイル
4KGM-JT冷凍機(3台)
シールド用GM冷凍機(1台)
電流リード用GM冷凍機(2台)
HTS電流リード1kA級Y系4並列
断熱真空容器(φ 2.8×2.8H)
輻射シールド
He容器
4重極配置超電導コイル
Liquid insulation (LN2, LHe, etc.)
Gas insulation (GN2, GHe, etc.)
Solid insulation (Tape, FRP, etc.)
↓
Composite insulation system
Conduction cooling
Electrical insulation structure (SMES)
Current lead
Vacuum
Heat conduction plate
Superconduc-
ting coil
Refrigerator
Bath cooling
超電導コイル
LHeタンク/冷凍機
伝熱板
電流リード
真空
超電導コイル
LHeタンク/冷凍機
伝熱板
電流リード
真空
4KGM-JT冷凍機(3台)
シールド用GM冷凍機(1台)
電流リード用GM冷凍機(2台)
HTS電流リード1kA級Y系4並列
断熱真空容器(φ 2.8×2.8H)
輻射シールド
He容器
4重極配置超電導コイル
4KGM-JT冷凍機(3台)
シールド用GM冷凍機(1台)
電流リード用GM冷凍機(2台)
HTS電流リード1kA級Y系4並列
断熱真空容器(φ 2.8×2.8H)
輻射シールド
He容器
4重極配置超電導コイル
Conduction cooling
Electrical insulation structure (SMES)
Current lead
Vacuum
Heat conduction plate
Superconduc-
ting coil
Refrigerator
Cryostat
Cryostat in shield room
(Nagoya University)
Cross-section of cryostat
Electrode configurations
Coaxial cable models
Rod-plane and sphere-plane electrodes
Measurement of BD/PD strength
100
80
60
40
20
0
Bre
akdow
n s
trength
[kV
pea
k/m
m]
50403020100
Experimental number
ac, LN2
Sphere-to-plane
(d=50mm, g=1.0mm)
Coaxial cylinder
(g=2.3mm, L=100mm)
100
80
60
40
20
0
Bre
akdow
n s
trength
[kV
pea
k/m
m]
50403020100
Experimental number
ac, LN2
Sphere-to-plane
(d=50mm, g=1.0mm)
Coaxial cylinder
(g=2.3mm, L=100mm)
Breakdown (BD) strength of LN2
BD based on physical mechanism
(Weakest-link theory, Size effect)
× Weakest-link theory & Size effect
N
i
i
N
i
i ppp11
)1ln()1(ln)1ln(
ip :Local BD probability p :Total BD probability N:Number of chain
Stress increase Local breakdown Total breakdown
Large size Many weak points BD probability increase
Stress Electric field strength
Weak point Protrusion on surface, Impurity in liquid, etc.
Size Stressed electrode area, liquid volume, etc.
50.0
70.0
90.0
99.0
99.99
30.0
10.0
5.0
3.0
1.0
Bre
akd
ow
n p
roba
bili
ty [%
]
10 100
Breakdown strength EBac [kVpeak/mm]
ac
Electrode length : 100mm
Gap length : 2.3mm
LHe
m=12.7
E0=19.7kV/mm
20 50
LN2
m=10.3
E0=23.1kV/mm
50.0
70.0
90.0
99.0
99.99
30.0
10.0
5.0
3.0
1.0
Bre
akd
ow
n p
roba
bili
ty [%
]
10 100
Breakdown strength EBac [kVpeak/mm]
ac
Electrode length : 100mm
Gap length : 2.3mm
LHe
m=12.7
E0=19.7kV/mm
20 50
LN2
m=10.3
E0=23.1kV/mm
0
0 lnlnln1
1lnln
v
vIIm
p
Input (Vertical axis)
Input (Horizontal axis)
Output
Sorting of scattered data
Linear in Weibull plot
Breakdown based on
Weakest-link theory
m
I
I
v
vp
00
exp1
Weibull plot
I :Stress
v :Highly stressed area/volume
0v :Reference area/volume
m:Shape parameter (scattering)
0I :Scale parameter (intrinsic strength)
Breakdown (BD) characteristics of LN2
(a) Breakdown voltage
f=50 mm
(b) Breakdown strength
f=50 mm
Size (Volume) effect
10
20
30
50
70
100
200
300
Bre
akd
ow
n s
tren
gth
EB [
kV
pea
k/m
m]
10-2
10-1
100
101
102
103
104
105
106
% SLV [mm3]
Nishimachi Goshima Hara Mathes Kaneko Kawashima Fink Blaz Frayssiness Sauers
Saturated condition
Sub-cooled condition
Nishimachi
Volume effect on BD strength of LN2
10
2
3
4
56
100
2
3
Bre
akdow
n s
tren
gth
EB [
kV
pea
k/m
m]
10-2
10-1
100
101
102
103
104
105
106
%SLV [mm3]
Confidence interval (95 %) Prediction interval (95 %)
Prediction interval (3) Prediction interval (0.1 %)
Nishimachi Goshima Hara Mathes Kaneko Kawashima Fink Blaz Frayssiness Sauers
Saturated condition
Sub-cooled condition
Nishimachi
Goshima
Hara
Mathes
Kaneko
Kawashima
Fink
Blaz
Frayssiness
Sauers
10
2
3
4
56
100
2
3
Bre
akd
ow
n s
tren
gth
EB [
kV
pea
k/m
m]
10-2
10-1
100
101
102
103
104
105
106
%SLV [mm3]
Confidence interval (95 %) Prediction interval (95 %)
Nishimachi Goshima Hara Mathes Kaneko Kawashima Fink Blaz Frayssiness Sauers
Saturated condition
Sub-cooled condition
Nishimachi
Goshima
Hara
Mathes
Kaneko
Kawashima
Fink
Blaz
Frayssiness
Sauers
10
20
30
50
70
100
200
300
Bre
akd
ow
n s
tren
gth
EB [
kV
pea
k/m
m]
10-2
10-1
100
101
102
103
104
105
106
% SLV [mm3]
Confidence interval (95 %) Prediction interval (95 %)
Nishimachi Goshima Hara Mathes Kaneko Kawashima Fink Blaz Frayssiness Sauers
Saturated condition
Sub-cooled condition
Nishimachi
Goshima
Hara
Mathes
Kaneko
Kawashima
Fink
Blaz
Frayssiness
Sauers
15.8/1)%(4.78 SLVEB
( % SLV: Stressed liquid volume with electric field strength higher than % of Emax)
Volume effect is practical BD characteristics for LN2
as well as for conventional transformer oil and SF6 gas.
Increase of diameter f
and/or gap length g
Increase of highly-stressed
volume (weak points)
Decrease of breakdown
strength (Volume effect)
Increase of breakdown
probability
Volume effect on BD strength of LN2
Electric field factor
: Harmful bubble to cause BD
: Harmless bubble not to cause BD
Pressure
Temperature
100 95 90 85
80 75
Electric field stress level [%]
]%[ 100 max
E
Ei
= ?? % in LN2
Increase at the higher pressure
and the lower temperature
= 90 % in transformer oil and SF6 gas
100
95
90
85
80
75
70
Dec
isiv
e el
ectr
ic f
ield
fac
tor
[
%]
777165
Temperature T [K]
P=0.3MPa
P=0.2MPa
P=0.1MPa
100
95
90
85
80
75
70
Dec
isiv
e el
ectr
ic f
ield
fac
tor
[
%]
0.300.200.10
Pressure P [MPa]
T=65K
T=71K
T=77K
(a) Pressure dependence (b) Temperature dependence
140
120
100
80
60
40Bre
akdow
n s
tren
gth
EB [
kV
pea
k/m
m]
0.30.20.1Pressure P [MPa]
g = 0.5 mm
g = 2.0 mm
T = 65 K
T = 71 K
T = 77 K
140
120
100
80
60
40Bre
akdow
n s
tren
gth
EB [
kV
pea
k/m
m]
777165
Temperature T [K]
P = 0.3 MPa
P = 0.2 MPa
P = 0.1 MPa
),( TPf 15.8/1)%(4.78 SLVEB
Electric field factor
10
20
30
50
70
100
200
300
Bre
akd
ow
n s
tren
gth
EB [
kV
pea
k/m
m]
10-2
10-1
100
101
102
103
104
105
106
% SLV [mm3]
Nishimachi Goshima Hara Mathes Kaneko Kawashima Fink Blaz Frayssiness Sauers
Saturated condition
Sub-cooled condition
Nishimachi
Volume effect on BD strength of LN2
10
2
3
4
56
100
2
3
Bre
akdow
n s
tren
gth
EB [
kV
pea
k/m
m]
10-2
10-1
100
101
102
103
104
105
106
%SLV [mm3]
Confidence interval (95 %) Prediction interval (95 %)
Prediction interval (3) Prediction interval (0.1 %)
Nishimachi Goshima Hara Mathes Kaneko Kawashima Fink Blaz Frayssiness Sauers
Saturated condition
Sub-cooled condition
Nishimachi
Goshima
Hara
Mathes
Kaneko
Kawashima
Fink
Blaz
Frayssiness
Sauers
10
2
3
4
56
100
2
3
Bre
akd
ow
n s
tren
gth
EB [
kV
pea
k/m
m]
10-2
10-1
100
101
102
103
104
105
106
%SLV [mm3]
Confidence interval (95 %) Prediction interval (95 %)
Nishimachi Goshima Hara Mathes Kaneko Kawashima Fink Blaz Frayssiness Sauers
Saturated condition
Sub-cooled condition
Nishimachi
Goshima
Hara
Mathes
Kaneko
Kawashima
Fink
Blaz
Frayssiness
Sauers
10
20
30
50
70
100
200
300
Bre
akd
ow
n s
tren
gth
EB [
kV
pea
k/m
m]
10-2
10-1
100
101
102
103
104
105
106
% SLV [mm3]
Confidence interval (95 %) Prediction interval (95 %)
Nishimachi Goshima Hara Mathes Kaneko Kawashima Fink Blaz Frayssiness Sauers
Saturated condition
Sub-cooled condition
Nishimachi
Goshima
Hara
Mathes
Kaneko
Kawashima
Fink
Blaz
Frayssiness
Sauers
15.8/1)%(4.78 SLVEB
Universal line for sub-cooled LN2 with volume effect
( % SLV: Stressed liquid volume with electric field strength higher than % of Emax)
Contents
1. Self-introduction
2. Background
Why is the electrical insulation important?
3. Fundamentals of electrical insulation
Electromagnetism, Electric field
4. Breakdown characteristics
Gas, Vacuum, Liquid, Solid, Composite system
5. Partial discharge characteristics
Precursor of breakdown, Insulation degradation
6. Electrical insulation peculiar to applied superconductivity
Quench-induced dynamic insulation characteristics
7. Conclusion and future works
Electrical insulation of HTS cable
HTS layer
HTS shielding layer
PP laminated paper
PP laminated paper Butt gap
→ LN2/PP laminated paper composite insulation system
Butt gap
(f=5mm)
Partial discharge (PD) in butt gap
Volume effect on PD inception strength 70
60
50
40
30
20
10
PD
IE [kV
rms /m
m]
5 6
10 2 3 4 5 6
100 2 3 4 5 6
1000
Statistical stressed liquid volume SSLV [mm3]
P=0.1MPa
BD strength
PD & BD traces
Coaxial cable models
Contents
1. Self-introduction
2. Background
Why is the electrical insulation important?
3. Fundamentals of electrical insulation
Electromagnetism, Electric field
4. Breakdown characteristics
Gas, Vacuum, Liquid, Solid, Composite system
5. Partial discharge characteristics
Precursor of breakdown, Insulation degradation
6. Electrical insulation peculiar to applied superconductivity
Quench-induced dynamic insulation characteristics
7. Conclusion and future works
Quench of superconducting coil in LHe
Superconducting coil (NbTi)
LHe
High-voltage electrode
LHe: Pressure = 0.1 MPa, gap length = 9 mm
Applied voltage = 0 kV
-100
-50
0
50
100
Ap
pli
ed v
olt
age
Va
[kV
]
1.51.00.50.0time [s]
Bubble generated
BD
-100
-50
0
50
100
Appli
ed v
olt
age
Va
[kV
]
1.51.00.50.0
Energizing time th [s]
Applied voltage Heater current
Nichrome sheet electrode
H.V.
(ϕ = 6 mm)
Quench-induced dynamic BD of LN2
P = 0.1 MPa
1.51.00.50.0time [s]
-100
-50
0
50
100
Ap
pli
ed v
olt
age
Va
[kV
]
Bubble generated
BD
-100
-50
0
50
100
Appli
ed v
olt
age
Va
[kV
]
1.51.00.50.0
Energizing time th [s]
Applied voltage Heater current
Nichrome sheet electrode
H.V.
(ϕ = 6 mm)
Quench-induced dynamic BD of LN2
P = 0.15 MPa
80
70
60
50
40
30
20
10
0
BD
E [
kV
pea
k/m
m]
6050403020100
Electrode diameter f [mm]
P = 0.10 MPa
Static
Dynamic
Stable heating
80
70
60
50
40
30
20
10
0
BD
E [
kV
pea
k/m
m]
6050403020100
Electrode diameter f [mm]
P = 0.12 MPa
Static
Dynamic
Stable heating
Static BD strength
Static BD strength
P = 0.1 MPa P = 0.15 MPa
Dynamic BD strength Dynamic BD strength
Static and dynamic BD strength of LN2
1.0
0.8
0.6
0.4
0.2
0.0
Ele
ctri
cal
loss
[W
/m]
PPLP-C Tyvek/PE
Total loss
Dielectric loss
AC loss
1.0
0.8
0.6
0.4
0.2
0.0E
lect
rica
l lo
ss [
W/m
]
PPLP-C Tyvek/PE
Total loss
Dielectric loss
AC loss
275 kV – 3 kA HTS cable
(M-PACC project, Japan)
Dielectric loss 20 %
Total loss 41 %
Dielectric loss reduction for HTS cable
Contents
1. Self-introduction
2. Background
Why is the electrical insulation important?
3. Fundamentals of electrical insulation
Electromagnetism, Electric field
4. Breakdown characteristics
Gas, Vacuum, Liquid, Solid, Composite system
5. Partial discharge characteristics
Precursor of breakdown, Insulation degradation
6. Electrical insulation peculiar to applied superconductivity
Quench-induced dynamic insulation characteristics
7. Conclusion and future works
CIGRE WG D1.38 (Conseil International des Grands Reseaux Electriques
or International Council on Large Electric Systems)
Title of the group: Emerging Test Techniques Common to
HTS Power Applications
Convenor:Mathias Noe
(Karlsruhe Institute of
Technology, Germany)
Secretary: Naoki Hayakawa
(Nagoya University, Japan)
Members: 24 persons (14 countries)
Period: 2010-2015
Contents:
1. Introduction
2. Electrical insulation
3. HTS material
4. Cooling systems
5. General and specific requirements
for electrical insulation, HTS materials,
and cooling
6. Summary
7. References
8. Annexes
Technical Brochure: No.644 (153 pages)
(published in December 2015)
CIGRE WG D1.38 (Conseil International des Grands Reseaux Electriques
or International Council on Large Electric Systems)
Title of the group: Electrical Insulation Systems at Cryogenic
Temperatures
Convenor:Naoki Hayakawa
(Nagoya University, Japan)
Secretary: Christof Humpert
(Technische Hochschule Köln,
Germany)
Members: 22 persons (12 countries)
Period: 2016-2019
CIGRE WG D1.64 (Conseil International des Grands Reseaux Electriques
or International Council on Large Electric Systems)
Member of WG D1.64 (22 persons, 12 countries) NAME GIVEN NAME Affiliation Country
Nielsen Shawn Dennis Queensland University of Technology Australia
Polasek Alexander CEPEL Brazil
Du Boxue Tianjin University China
Zong Xihua Shanghai electric cable research institute China
Filipan Veljko University of Zagreb Croatia
Willén Dag nkt cables Denmark
Humpert Christof Technische Hochschule Köln Germany
Kurrat Michael Technische Universität Braunschweig Germany
Noe Mathias Karlsruhe Institute of Technology Germany
Martini Luciano Ricerca sul Sistema Energetico Italy
Hayakawa Naoki Nagoya University Japan
Nagao Masayuki Toyohashi University of Technology Japan
Okubo Hitoshi Aichi Institute of Technology Japan
Yagi Masashi Furukawa Electric Japan
Cho Jeonwook Korea Electrotechnology Research Institute Korea
Lee Bang Wook Hanyang University Korea
Ross Robert TenneT TSO + HAN University of Applied Science Netherlands
Smit Johan Delft University of Technology Netherlands
Samoilenlov Sergey SuperOx Russia
Graber Lukas Georgia Institute of Technology USA
Pamidi Sastry The Florida State University USA
Tuncer Enis Texas Instruments USA
Scope of CIGRE WG D1.64
The scope of WG D1.64 is to study the fundamentals and
applications on electrical insulation techniques for supercon-
ducting power apparatus and other applications to be operated
at cryogenic temperatures.
1. Insulating materials
(solids, liquids, gases, vacuum, composite insulation system)
2. Principles & mechanisms
(partial discharge, surface discharge, ageing, breakdown)
3. Design & test issues
(power apparatus, magnets, components)
4. Others
Kick-off meeting (2016.4.27-28, Yokohama)
Summary
1. Cryogenic electrical insulation is inevitable as one of
the common techniques for HTS power apparatus.
2. Fundamental insulation data at cryogenic temperatures
should be systematized with their physical mechanisms.
3. Practical insulation data peculiar to HTS power apparatus
should be obtained for their design and operation.
4. World-wide collaboration is expected for the realization of
HTS power apparatus.
Thank you very much
for your kind attention
Naoki Hayakawa E-mail: [email protected]
http://www.hayakawalab.nuee.nagoya-u.ac.jp/