dielectric properties of insulation

© Prof.Dr.R.Haller© Prof.Dr.R.Haller

Dielectric Properties of InsulationDielectric Properties of Insulation

Introduction

Basic Relations

Modelling of Dielectrics

Measurement of Dielectric Parameters

Conclusions

© Prof.Dr.R.Haller© Prof.Dr.R.Haller

Dielectric Properties of InsulationDielectric Properties of Insulation

Introduction

Basic Relations

Modelling of Dielectrics

Measurement of Dielectric Parameters

Conclusions

© Prof.Dr.R.Haller© Prof.Dr.R.Haller

Insulation Materials (Dielectrics) gaseous [air, SF6, N2, …]

liquid [Oil (mineral, silicon, ..), H2O, Glycerin, ..]

solid [Cellulose (Paper), Thermoplastics (PVC, PE, …),

Duroplastics (EP, Siliconrubber, ..),

anorganic materials (Porcelain, Ceramics, ..)] which are the most important electrical properties

for manufacturing, design, construction, operation,

diagnosis ( Recycling ) ?

© Prof.Dr.R.Haller© Prof.Dr.R.Haller

electrical strength [kV/mm]

dielectric parameters

permittivity ε

conductivity κ [S/m]

dissipation (loss) factor tanδ

(other) electrical, thermal, mechanical, chemical

parameters

Dielectric PropertiesDielectric Properties

© Prof.Dr.R.Haller© Prof.Dr.R.Haller

Dielectric Properties of InsulationDielectric Properties of Insulation

Introduction

Basic Relations

Modelling of Dielectrics

Measurement of Dielectric Parameters

Conclusions

© Prof.Dr.R.Haller© Prof.Dr.R.Haller

PolarizationPolarization

D = ε0·E + P bzw. P = ε0·E·(εr – 1) = ε0·E· χ

Polarization requests time (relaxation time )

and losses (dissipation factor tan δ)

Polarization depends on material (kind of polarization)

frequency f ) of applied

amplitude Emax ) el. field

temperature T

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Relative Permittivity Relative Permittivity εεrr

gaseousgaseous air, SFair, SF66, N, N22, …, … ~ ~ 11

liquidliquid MineraloilMineraloil 2,22,2

SiliconoilSiliconoil 2,72,7

RhizinusoilRhizinusoil 55

WaterWater 8181

solidsolid PVCPVC 44

PEPE 2,42,4

PolyamidPolyamid 77

EpoxyresinEpoxyresin 3,8 .. 5,83,8 .. 5,8

Hard- paperHard- paper 55

paperpaper 2,82,8

PorcelainPorcelain 66

BaTiOBaTiO33 3000 .. 50003000 .. 5000

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Electrical Conductivity Electrical Conductivity

physically: free movable charged particles (electrons, ions)

J = · E = (n+q+b+ + n-q-b- + neqebe)

technically: depends on material (ions, electrons)

pollutions (H2O, ..)

operating parameters

(E, t, T)

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Electrical Conductivity Electrical Conductivity

typical values: gaseous ( 10-16 …. 10-19 )

(T = 20 °C) liquids/ solids ( 10- 8 …. 10-15 )

Water ( 10- 4 …. 10- 7 )

Semiconductors ( 10+2 …. 10- 7 )

Conductors ( 10+6 …. 10+8 )

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Dissipation Factor tan Dissipation Factor tan δδ characterizing of losses (polarization, conductivity)

Pδ = tan δ · Qc = tan δ · (ωC·U2)

depends on ( t (f), E, T)

typical values: mineral oil (10-3 …. 10-1)

(T = 20 °C) oilimpregnated paper (10- 3 …. 100)

( f = 50 Hz) PVC, PA, paper (10- 2 …. 10-1)

PE, PTFE (10-4 …. 10- 5)

EP, porcelain (10-1 …. 10-2)

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tan tan δδ and and εεrr vs. frequency vs. frequencybiological tissue dispersion area

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tan tan δδ and and εεrr vs. frequency vs. frequency

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5-10 s Materialpolarisation

conductor

2

311

2

3

30-80 s Grenzschichten

200-500 s Tree-Strukturen

Relaxationszeiten verschiedener Mechanismen

insulation

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inner electrode outer electrode

water tree

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water tree & electrical tree

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Knowledge of dielectric properties is necessary for whole life cycle of electrical equipment

Dielectric properties can be determined by

calculation (modelling, simulation)

measurement ( diagnostic/ testing)

© Prof.Dr.R.Haller© Prof.Dr.R.Haller

Dielectric Properties of InsulationDielectric Properties of Insulation

Introduction

Basic Relations

Modelling of Dielectrics

Measurement of Dielectric Parameters

Conclusions

© Prof.Dr.R.Haller© Prof.Dr.R.Haller

Modelling of DielectricsModelling of Dielectricsa) simple circuit

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Modelling of DielectricsModelling of Dielectrics

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Maxwell- Wagner- ModelMaxwell- Wagner- Model

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Modelling of DielectricsModelling of Dielectricsb) complex circuit

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Polarization Effects (i, u)Polarization Effects (i, u)

© Prof.Dr.R.Haller© Prof.Dr.R.Haller

Dielectric Properties of InsulationDielectric Properties of Insulation

Introduction

Basic Relations

Modelling of Dielectrics

Measurement of Dielectric Parameters

Conclusions

© Prof.Dr.R.Haller© Prof.Dr.R.Haller

Schering- BridgeSchering- Bridge

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PC- based measuring bridgePC- based measuring bridge

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RVM- and IRC- principleRVM- and IRC- principle

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RRecoverecoverVVoltageoltageMMeasurementeasurement

S1

AD PCHV

DC

RU

testobject

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Feuchtigkeitseinfluß in papierisolierten Kabeln Anstieg des Maximums bei tm und Verschiebung zu kürzeren Messzeiten

Cable 1 701 m

Cable 2 932 m

time (min)

Return Voltage (V)

Kabel 1: alt gemessen mit 1 kV und 2 kV

Kabel 2: gut gemessen mit 1 kV und 2 kV

© Prof.Dr.R.Haller© Prof.Dr.R.Haller

RVM measurement on 10 kV cabel with paper insulation

Qa: 2,0-1,87 trockenQa: 1,86-1,65 feuchtQa < 1,65 nass

Bewertung des Gradientenim Spannungsanstieg bei 1 und 2 kV :

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RVM Diagnose an 1 kV Papierkabel - Stromversorgung der Löschwasseranlage eines großen Chemie-Unternehmens

• Speisekabel mit hoher Wichtigkeit für Löschwasserpumpen• 700m Zuleitung im Elbdüker NAKRAA 3x185• T-Muffe und 300 m bzw. 560 m NAKBA 3x185 bis zu den Pumpenhäusern

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Meßprinzip der IRC-MessungMeßprinzip der IRC-Messung

1: Formierung 1800s

I

1kV

CDS

2: Entladung 5s

3: Messung 1800s

testobject

PCAD

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new (normal) aged critical

IRC- Diagnosis on Power Cables

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Measurement of PolarizationMeasurement of Polarization

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Dielectric Properties of InsulationDielectric Properties of Insulation

Introduction

Basic Relations

Modelling of Dielectrics

Measurement of Dielectric Parameters

Conclusions

© Prof.Dr.R.Haller© Prof.Dr.R.Haller

ConclusionsConclusions

dielectric properties will be characterized by:

relative permittivity εr

electrical conductivity

dissipation factor tan δ

knowledge of dielectric properties is important

for manufacturing, design, operation (diagnosis)

and recycling of electrical insulation

© Prof.Dr.R.Haller© Prof.Dr.R.Haller

ConclusionsConclusions

dielectric properties can be determined by

- calculation / simulation

- measurement/ testing

© Prof.Dr.R.Haller© Prof.Dr.R.Haller

Thank you

Questions ?

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