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Dielectric Properties of Insulation. Introduction Basic Relations Modelling of Dielectrics Measurement of Dielectric Parameters Conclusions. Dielectric Properties of Insulation. Introduction Basic Relations Modelling of Dielectrics Measurement of Dielectric Parameters
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Dielectric Properties of Insulation • Introduction • Basic Relations • Modelling of Dielectrics • Measurement of Dielectric Parameters • Conclusions
Dielectric Properties of Insulation • Introduction • Basic Relations • Modelling of Dielectrics • Measurement of Dielectric Parameters • Conclusions
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 formanufacturing, design, construction, operation, diagnosis ( Recycling ) ?
Dielectric Properties • electrical strength [kV/mm] • dielectric parameters permittivity ε conductivity κ [S/m] dissipation (loss) factor tanδ • (other) electrical, thermal, mechanical, chemical parameters
Dielectric Properties of Insulation • Introduction • Basic Relations • Modelling of Dielectrics • Measurement of Dielectric Parameters • Conclusions
Polarization D = ε0·E + P bzw. P = ε0·E·(εr – 1) = ε0·E· χ Polarizationrequests time (relaxation time ) and losses (dissipation factor tan δ) Polarizationdepends on material (kind of polarization) frequencyf ) of applied amplitudeEmax ) el. field temperatureT
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)
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 )
Dissipation Factor tan δ • 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)
tan δ and εr vs. frequency biological tissue dispersion area
conductor Relaxationszeiten verschiedener Mechanismen 2 1 5-10 s Materialpolarisation 3 1 insulation 30-80 s Grenzschichten 2 200-500 s Tree-Strukturen 3
outer electrode inner electrode water tree
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)
Dielectric Properties of Insulation • Introduction • Basic Relations • Modelling of Dielectrics • Measurement of Dielectric Parameters • Conclusions
Modelling of Dielectrics a) simple circuit
Modelling of Dielectrics b) complex circuit
Dielectric Properties of Insulation • Introduction • Basic Relations • Modelling of Dielectrics • Measurement of Dielectric Parameters • Conclusions
RecoverVoltageMeasurement testobject S1 HV DC A PC D U R
Feuchtigkeitseinfluß in papierisolierten KabelnAnstieg 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) Cable 1 701 m Cable 2 932 m time (min)
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
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
CDS 1: Formierung 1800s testobject 2: Entladung 5s 3: Messung 1800s A D 1kV PC I Meßprinzip der IRC-Messung
IRC- Diagnosis on Power Cables new (normal) aged critical
Dielectric Properties of Insulation • Introduction • Basic Relations • Modelling of Dielectrics • Measurement of Dielectric Parameters • Conclusions
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 of electrical insulation
Conclusions • dielectric properties can be determined by - calculation / simulation - measurement/ testing
Thank you Questions ? & Answers !