Borealis degassing

HV XLPE CABLESSTATE OF THE ART

DESIGN / MANUFACTURE ISSUES

Nigel Hampton,Application Manager - Power Cables

Borealis AB, Sweden.

ICC Fall 2003 Education Session

Content

� State of the artStress / thicknessService performanceDownsizing

� DesignTemperatureStrengthLengthAgeing

� ManufactureDegassingScorch


Content

� State Of The ArtStress / ThicknessService PerformanceDownsizing


� ManufactureMoistureDegassingScorchPurity


Thicknesses of Insulation for HV Cables

0

5

10

15

20

25

25 50 75 100 125 150 175

Cable Voltage (kV)

Aver

age

wal

l thi

ckne

ss

(mm

)


Electrical Stresses

0

2

4

6

8

0 2 4 6 8 10 12 14 16

Conductor stress (kV/mm)

Core

Stre

ss (k

V/m

m)

HV

EHV

Mean & 90% Conf Limits

MV


Selected HV Experience

0

500

1000

1500

2000

25 50 75 100 125 150 175VOLTAGE (kV)

CO

ND

UC

TOR

SIZ

E (S

QM

M)

Size Of Bubble Represents Length Of Installed Cores


Thicknesses of Transmission Cables

0

5

10

15

20

25

1965 1970 1975 1980 1985 1990 1995 2000 2005

Thic

knes

s (m

m)

66 110 132 138 154


Use of EHV Technology to Down Size

0,7

0,8

0,9

1

1,1

10 12 14 16 18 20 22

Wall Thickness (mm)

Rel

ativ

e Va

lue

MATERIAL COST

WEIGHT

HV TECHNOLOGY6 / 3 kV/mm

EHV TECHNOLOGY9 / 6 kV/mm

1000SQMM, Pb SHEATH


High Stress Gives Smaller Cables

>15% reduction in weight

5 - 10% reduction in material cost


8

7

6

5

4

3

2

1

012

Wall thickness

Average stress

Volume

Requirement

14 16 18 20 22

Size Affects Electrical Requirement

Reference case - 2000mm2 150kVReference case - 2000mm2 150kV


Content� State of the Art

Stress / ThicknessService PerformanceDownsizing




Breakdown Stress - Design Stress


Breakdown Stress - Design Stress

the winner of the 100mshould complete the marathon in 1 hour 10 mins


Designing Cables

� Design Life� Size� Temperature� Safety

safetytempsizeage

breakdowndesign FFFF

EE =


What Is The Outcome?

safetysizeage

temp@breakdowndesign FFF

EE =



safetysizeage


EE =

40

2,22,2 - 3,8 1,1



safetysizeage


EE =

mmThicknessmmkVEdesign 165.53/150/5.5

1.1*2.2*340

====

40

2,22,2 - 3,8 1,1


Endurance Tests

0

0,3

0,6

0,9

0,1 1 10 100 1000 10000 100000

Time to failure (hours)

Prob

abili

ty o

f fai

lure

50kV/mm33kV/mm

modeltransmissioncables


115kV cables taken from service after 20 Years

UN USEDUSED

Slices Of Insulation Taken From Cables


Endurance Curve - Transmission Cables

05

10152025303540

1,E+

00

1,E+

01

1,E+

02

1,E+

03

1,E+

04

1,E+

05

1,E+

06

Time (Hours)

Mea

n el

ectri

cal s

tress

(kV/

mm

)

FAIL ON TESTNO FAIL ON TESTNO FAIL IN SERVICE

LONG TERM TESTSLONG TERM TESTS

TYPETESTSTYPETESTS


5mm25mm

Size


0

10

20

30

40

50

60

70

10 100 1000 10000Length (m)

Elec

tric

Str

engt

h (k

V/m

m)

Size

5mm25mm


Content

� State Of The ArtStress / ThicknessService PerformanceDownsizing




Water / Moisture Remains A Concern

� Moisture Has ADramatic Effect OnAgeing

� Water Barrier HasTo Be Effective AndProtected

� Oversheaths &Jackets AreImportant Parts OfThe Cable Design

0

10

20

30

40

50

60

1,E-

02

1,E-

01

1,E+

00

1,E+

01

1,E+

02

1,E+

03

1,E+

04

1,E+

05

1,E+

06

TIME (HOURS)

Mea

n El

ectri

cal S

tress

(k

V/m

m)

VIRGIN RAMP BREAKDOWNRAMP BREAKDOWN AFTER DRY AGEINGRAMP BREAKDOWN AFTER WET AGEING


Dielectric Loss Measurements - HV Cable Models

0

10

20

30

0 20 40 60 80 100

Measuring Voltage (kV)

Tang

ent D

elta

(10E

-4) DEGAS 130C DEGAS 22C

AS MADE 130C AS MADE 22C

Industry Standard HV Insulation


110kV Foil Laminate Sheathed Cable

0

1

2

3

4

5

6

0 20 40 60 80 100 120 140 160 180 200

Aus gas ungs konzentration des Methan in der Is o lierung in ppm

Ueb

erdr

uck

in b

ar

Overpressure at 90°C

Overpressure at 23°C

methane concentration in insulation in ppm

Ove

rpre

ssur

e in

bar


Time taken for Degassing

0

5

10

15

20

25

30

5 10 15 20 25

Wall thickness (mm)

Deg

assi

ng ti

me

(day

s)


0

0,5

1

1,5

2

2,5

as made max permitted long degassing GOAL FOR TOMORROW

Wei

ght L

oss

(%)

Degassing Data - TGA Method HD632


Cable Inspection, Hot Oil Test

Lump found in inner semiconductive layer

Width: 0.5 mm

Height: 0.05-0.1 mm


“The Carrot Scorch Test”

Typical “Carrot”

Die

Scorch [vol-%]

Temperature [°C]

0125 130 135 140

20

40

60

80

∆SC=45%

∆T=8°C

- Effect of Temperature -Level and Sensitivity Effected


By product concentration [WT%]

Time to critical scorch evolution [mins]

Increasing Run Length

Optimal Parameters For High Productivity

Decreasing Degassing Requirement

Today

Tomorrow


CLEANLINESS - TAPE TESTSIZE

RANGE(MICRONS)

HVTECHNOLOGY

MVTECHNOLOGY

50 – 70 - -

70 –100 10 -

100 – 200 0 3

NUMBER AND SIZE ISNOT EVERYTHING!

HOW DO WE ALLOW FORDIFFERENT:

MATERIALSSHAPES

0

2

4

6

8

1 10 100

PERMITTIVITY

STRE

SS E

NHAN

CEM

ENT

FACT

OR

R/a=1R/a=0,1

WE NEED ASMARTER SET OFCRITERIA!!


Electrical Stresses

0

2

4

6

8

0 5 10 15 20 25 30 35

Conductor stress (kV/mm)

Core

Stre

ss (k

V/m

m)


Conclusions

� XLPE HV Cables have come a long way and have some exciting challenges ahead

� Much of the technology is well established and known

� Challenges for the futureuse of proven EHV technology to downsizelong lengthsincreased need

ATTENTION TO DETAIL → RELIABILITY

Documents

Borealis degassing