Transcript Dielectric Properties of Insulation

Dielectric Properties of Insulation
 Introduction
 Basic Relations
 Modelling of Dielectrics
 Measurement of Dielectric Parameters
 Conclusions
© Prof.Dr.R.Haller
Dielectric Properties of Insulation
 Introduction
 Basic Relations
 Modelling of Dielectrics
 Measurement of Dielectric Parameters
 Conclusions
© 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
Dielectric Properties
 electrical strength [kV/mm]
 dielectric parameters
permittivity ε
conductivity κ [S/m]
dissipation (loss) factor tanδ
 (other) electrical, thermal, mechanical, chemical
parameters
© Prof.Dr.R.Haller
Dielectric Properties of Insulation
 Introduction
 Basic Relations
 Modelling of Dielectrics
 Measurement of Dielectric Parameters
 Conclusions
© Prof.Dr.R.Haller
Polarization
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 )
 temperature T
© Prof.Dr.R.Haller
el. field
Relative Permittivity εr
gaseous
liquid
solid
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air, SF6, N2, …
~1
Mineraloil
Siliconoil
Rhizinusoil
Water
PVC
PE
Polyamid
Epoxyresin
Hard- paper
paper
Porcelain
BaTiO3
2,2
2,7
5
81
4
2,4
7
3,8 .. 5,8
5
2,8
6
3000 .. 5000
Electrical Conductivity 
physically:
free movable charged particles (electrons, ions)
J = ·E
technically:
depends on
 = (n+q+b+ + n-q-b- + neqebe)
 material (ions, electrons)
 pollutions (H2O, ..)
 operating parameters
(E, t, T)
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Electrical Conductivity 
typical values:
(T = 20 °C)
© Prof.Dr.R.Haller
gaseous
( 10-16 …. 10-19 )
liquids/ solids
( 10- 8 …. 10-15 )
Water
( 10- 4 …. 10- 7 )
Semiconductors
( 10+2 …. 10- 7 )
Conductors
( 10+6 …. 10+8 )
Dissipation Factor



tan δ
characterizing of losses (polarization, conductivity)
Pδ = tan δ · Qc = tan δ · (ωC·U2)
depends on
typical values:
( t (f), E, T)
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)
© Prof.Dr.R.Haller
tan δ and εr vs. frequency
biological tissue
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dispersion area
tan δ and εr vs. frequency
© Prof.Dr.R.Haller
Relaxationszeiten verschiedener Mechanismen
2
1
3
1
insulation
2
conductor
© Prof.Dr.R.Haller
5-10 s Materialpolarisation
30-80 s Grenzschichten
200-500 s Tree-Strukturen
3
outer electrode
inner 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
Dielectric Properties of Insulation
 Introduction
 Basic Relations
 Modelling of Dielectrics
 Measurement of Dielectric Parameters
 Conclusions
© Prof.Dr.R.Haller
Modelling of Dielectrics
a) simple circuit
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Modelling of Dielectrics
© Prof.Dr.R.Haller
Maxwell- Wagner- Model
© Prof.Dr.R.Haller
Modelling of Dielectrics
b) complex circuit
© Prof.Dr.R.Haller
Polarization Effects (i, u)
© Prof.Dr.R.Haller
Dielectric Properties of Insulation
 Introduction
 Basic Relations
 Modelling of Dielectrics
 Measurement of Dielectric Parameters
 Conclusions
© Prof.Dr.R.Haller
Schering- Bridge
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PC- based measuring bridge
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RVM- and IRC- principle
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RecoverVoltageMeasurement
S1
A
HV
DC
D
R
© Prof.Dr.R.Haller
U
testobject
PC
Feuchtigkeitseinfluß in papierisolierten Kabeln
Anstieg des Maximums bei tm und Verschiebung zu kürzeren Messzeiten
Kabel 1: alt gemessen mit 1 kV und 2 kV
Kabel 2: gut gemessen mit 1 kV und 2 kV
Return Voltage (V)
time (min)
© Prof.Dr.R.Haller
Cable 1
701 m
Cable 2
932 m
RVM measurement on 10 kV cabel with paper insulation
Bewertung des Gradienten
im Spannungsanstieg bei
1 und 2 kV :
Qa: 2,0-1,87 trocken
Qa: 1,86-1,65 feucht
Qa < 1,65 nass
© Prof.Dr.R.Haller
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-Messung
CDS
1: Formierung 1800s
testobject
2: Entladung 5s
3: Messung 1800s
1kV
A
I
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D
PC
IRC- Diagnosis on Power Cables
new
© Prof.Dr.R.Haller
(normal) aged
critical
Measurement of Polarization
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Dielectric Properties of Insulation
 Introduction
 Basic Relations
 Modelling of Dielectrics
 Measurement of Dielectric Parameters
 Conclusions
© Prof.Dr.R.Haller
Conclusions
 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
© Prof.Dr.R.Haller
of electrical insulation
Conclusions
 dielectric properties can be determined by
- calculation / simulation
- measurement/ testing
© Prof.Dr.R.Haller
Thank you
Questions ?
& Answers !
© Prof.Dr.R.Haller