Topic 1: Progress in the understanding of

physical phenomena and materials for use in DC

Professor Dr Ing Ernst Gockenbach, Leibniz Universität Hannover, Germany

1 Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France

1.2 - JIC HVDC 16 Topic 1 Gockenbach

Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France

§  Development status, roadmap, characterisation and criteria of choice for new materials including thermoplastic insulation, nanotechnology, XLPE low by-product

§  Environmental impacts of materials, carbon footprint, pollution and recyclability

§  Understanding of ageing mechanisms and polarity reversals constraints

§  Evaluation of electrical fields at triple points §  Behaviour of DC cables operated in AC for flexible

electrical systems

2

Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France

Development status, roadmap, characterisation and criteria of choice for new materials

including thermoplastic insulation, nanotechnology, XLPE low by-product

Questions and comments New materials available? Voltage limits? Experience?

3

Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France 4

0

4

8

12

16

10 20 30 60 110 132 150 220 275 kV 500 Operating AC voltage

Elec

tric

fiel

d st

ress

Mean field stress Conductor field stress

kV/mm

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Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France 5

Sou

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Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France 6

Sou

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Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France 7

Sou

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w, N

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2

Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France 8

Sou

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Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France 9

Sou

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IEE

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Vol

. 23,

No.

6, p

. 11

-19

Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France

Environmental impacts of materials, carbon footprint, pollution and recyclability

Questions and comments Fluid impregnation material? Recycling of XLPE?

10

Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France

Understanding of ageing mechanisms and polarity reversals constraints

Questions and comments Ageing: thermal, electrical, mechanical, chemical? Polarity reversal: space charges?

11

Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France

1 10 -6 10 -3 10 3 10 6 10 9 s

Electrical breakdown Erosion breakdown

1d 1s 30a

1

10

10 3

time

10 2

kV mm

XLPE 20 °C

ED

E N • t = const

12

Long time behaviour

Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France 13

Electric field

Time

Temperature

Ageing parameter and life time volume

Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France

+ -

+ -

+-

+-

+ - - +

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De-energized AC Cable

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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

DC Cable

- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

50 Hz AC Cable - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

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- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - --

15 ms Sou

rce:

ETG

HV

DC

Col

loqu

ium

, Ber

lin, 2

011

Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France

Evaluation of electrical fields at triple points

Questions and comments Specific for cables? Methods?

15

Workshop Jicable HVDC’16, Friday, August 26, 2016 - Paris - France

Behaviour of DC cables operated in AC for flexible electrical systems

Questions and comments System voltage change AC – DC - AC? What are the determining parameters?

16