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Dielectric Properties of Insulation

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

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  1. Dielectric Properties of Insulation • Introduction • Basic Relations • Modelling of Dielectrics • Measurement of Dielectric Parameters • Conclusions

  2. Dielectric Properties of Insulation • Introduction • Basic Relations • Modelling of Dielectrics • Measurement of Dielectric Parameters • Conclusions

  3. 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 ) ?

  4. Dielectric Properties • electrical strength [kV/mm] • dielectric parameters permittivity ε conductivity κ [S/m] dissipation (loss) factor tanδ • (other) electrical, thermal, mechanical, chemical parameters

  5. Dielectric Properties of Insulation • Introduction • Basic Relations • Modelling of Dielectrics • Measurement of Dielectric Parameters • Conclusions

  6. 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

  7. Relative Permittivity εr

  8. 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)

  9. 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 )

  10. 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)

  11. tan δ and εr vs. frequency biological tissue dispersion area

  12. tan δ and εr vs. frequency

  13. conductor Relaxationszeiten verschiedener Mechanismen 2 1 5-10 s Materialpolarisation 3 1 insulation 30-80 s Grenzschichten 2 200-500 s Tree-Strukturen 3

  14. outer electrode inner electrode water tree

  15. water tree & electrical tree

  16. 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)

  17. Dielectric Properties of Insulation • Introduction • Basic Relations • Modelling of Dielectrics • Measurement of Dielectric Parameters • Conclusions

  18. Modelling of Dielectrics a) simple circuit

  19. Modelling of Dielectrics

  20. Maxwell- Wagner- Model

  21. Modelling of Dielectrics b) complex circuit

  22. Polarization Effects (i, u)

  23. Dielectric Properties of Insulation • Introduction • Basic Relations • Modelling of Dielectrics • Measurement of Dielectric Parameters • Conclusions

  24. Schering- Bridge

  25. PC- based measuring bridge

  26. RVM- and IRC- principle

  27. RecoverVoltageMeasurement testobject S1 HV DC A PC D U R

  28. 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)

  29. 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

  30. 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

  31. CDS 1: Formierung 1800s testobject 2: Entladung 5s 3: Messung 1800s A D 1kV PC I Meßprinzip der IRC-Messung

  32. IRC- Diagnosis on Power Cables new (normal) aged critical

  33. Measurement of Polarization

  34. Dielectric Properties of Insulation • Introduction • Basic Relations • Modelling of Dielectrics • Measurement of Dielectric Parameters • Conclusions

  35. 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

  36. Conclusions • dielectric properties can be determined by - calculation / simulation - measurement/ testing

  37. Thank you Questions ? & Answers !

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