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The Measurement of Very Low Conductivity and Dielectric Loss in XLPE Cables: A Possible Method to Detect Degradation due to Thermal Aging

By John C. Fothergill, T. Liu, Stephen J. Dodd, Len A. Dissado and U.H. Nilson

Abstract

The dielectric response of crosslinked polyethylene (XLPE) insulated, miniature power cables, extruded with inner and outer semicons, was measured over the frequency range 10-4 to 104 Hz at temperatures from 20 to 100 °C. A dielectric spectrometer was used for the frequency range 10-4 to 10-2 Hz. A bespoke noise-free power supply was constructed and used to measure the dc conductivity and, using a Fourier transform technique, it was also used to measure the very low dielectric tanδ losses encountered at frequencies of 1 to 100 Hz. Tanδ measurements of <;10-5 were found in this frequency range and attributed to a β-mode dielectric relaxation lying above 100 Hz due to motion of chain segments in the amorphous region and an β-mode relaxation lying below 1 Hz window due to twists of chains in the crystal lamellae. The dc conductivity measurements were consistent with those of the dielectric spectrometer and indicate lower dc conductivities in vacuum degassed cables than have been previously reported for XLPE (less than 10-17 S.m-1). The conduction process is thermally activated with an activation energy of approximately 1.1 eV. Higher conductivities were found for non-degassed cables. A transformer ratio bridge was used for measurements in the range 1 to 10 kHz; loss in this region was shown to be due to the series resistance of the semicon layers. Thermal ageing of the cables at 135 °C for 60 days caused significant increases in the conductivity and tanδ and it is considered that such measurements may be a sensitive way of measuring electrical degradation due to thermal aging.Peer-reviewedPost-prin

Topics: Cable insulation, Current measurement, Dielectric measurements, Dielectrics, Frequency measurement, Power cables, Temperature measurement
Publisher: Institute of Electrical and Electronics Engineers (IEEE)
Year: 2011
DOI identifier: 10.1109/TDEI.2011.6032823
OAI identifier: oai:lra.le.ac.uk:2381/10061
Journal:

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Citations

  1. Ageing and diagnostics in extruded insulations for power cables,&quot; doi
  2. (1999). Ageing and reliability testing and monitoring of power cables: Diagnosis for insulation systems, doi
  3. (1983). Dielectric Relaxation in Solids”, doi
  4. (1996). Dielectric spectroscopy of a polyethylene in the frequency range of 0.00001 doi
  5. (2009). Effect of thermal aging on the electrical properties of crosslinked polyethylene”, doi
  6. (1992). Electrical Degradation and Breakdown in Polymers, Peter Peregrinus Ltd. for the IEE, doi
  7. (2011). http://www.nationalgrid.com/NR/rdonlyres/C9AF5612-DF25-4FCFABB5-69F237ACB0C5/3411/SPTTS25.pdf (accessed 01
  8. J.C.Fothergill: “Electrical Insulation Systems for a Sustainable Energy Society” Invited opening paper for the 21st Nordic Insulation Symposium,
  9. (2010). L A Dissado, “Dielectric spectroscopy study of thermally-aged extruded model cables” doi
  10. (2004). Polymer Insulated Power Cable” doi
  11. (1987). Rate Theory and Polyethylene Relaxations, doi
  12. (1985). Relaxation processes in crystalline polymers: Molecular interpretation---a review”, Polymer, doi
  13. (1998). Space charge behavior in XLPE cable insulation under 0.2-1.2 MV/cm dc fields,&quot; doi
  14. (1984). Strengths of the Mechanical - - and - relaxation processes in linear polyethylene”, doi
  15. Sub-hertz&quot; dielectric spectroscopy,&quot; in doi

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