"Sub-hertz" dielectric spectroscopy

Fothergill, J.C.; See, K. B. A.; Ajour, Mohammed N.; Dissado, L.A.

doi:10.1109/iseim.2005.193505

Cited by 12 publications

(8 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…It can be seen that the activation energy has increased after ageing for both homo-and copolymer cables. A similar result was found for the same kind of XLPE measured as thin films [7] where the activation energy for unaged films was 0.89 eV and 1.06 eV for aged samples. The results on aged cables of the spectroscopic measurements using FRA and time domain measurements can be merged together to obtain the spectra over a wider frequency range.…”

Section: DC Conductivity Measurement Resutlssupporting

confidence: 83%

Dielectric spectroscopy study of thermally-aged extruded model power cables

Liu

Fothergill

Dodd

et al. 2010

2010 10th IEEE International Conference on Solid Dielectrics

View full text Add to dashboard Cite

F. (2010). Dielectric spectroscopy study of thermally-aged extruded model power cables. 2010 10th IEEE International Conference on Solid Dielectrics (ICSD), pp. 1-4. doi: 10.11091-4. doi: 10. /ICSD.2010 This is the accepted version of the paper.This version of the publication may differ from the final published version. Abstract-"Model" extruded power cables, having a much reduced geometry but using the same extrusion techniques and materials as full-sized cables, have been examined using dielectric spectroscopy techniques to study their thermal ageing effects. Cables insulated with homo-polymer XLPE and co-polymer of XLPE with micron-sized ethylene-butyl-acrylate (EBA) islands were studied by both frequency-domain and time-domain dielectric spectroscopy techniques after accelerated thermal ageing under 135°C for 60 days. In the frequency domain, a frequency response analyzer (FRA) was used to measure the frequency range from 10 -4 Hz to 1Hz at temperatures from 20C to 80C. In the time domain, a special charging/discharging current measurement system was developed to measure the frequencies from 10 -1 Hz to 10 2 Hz. These techniques were chosen to cope with the extremely low dielectric losses of the model cables. The results are compared with those from new model power cables that were degassed at 80°C for 5 days. Thermal ageing was found to increase the low-frequency conductivity, permittivity and the discharging current. Both homo-and copolymer cables have substantial increase of dielectric loss after ageing. Permanent

show abstract

Section: DC Conductivity Measurement Resutlssupporting

confidence: 83%

Dielectric spectroscopy study of thermally-aged extruded model power cables

Liu

Fothergill

Dodd

et al. 2010

2010 10th IEEE International Conference on Solid Dielectrics

View full text Add to dashboard Cite

show abstract

“…As a result the ion transport, both within and between clusters will be facilitated and the process will move to higher frequencies. A similar frequency increase has been observed in the q-dc response of aged micro-particle filled epoxy resin [32] and glass fibre reinforced epoxy resin [33]. In these cases microscopic examination showed the increase in frequency to be associated respectively with de-binding of the micro-particle and the fibre from the resin, i.e.…”

Section: Influence Of Ageingsupporting

confidence: 75%

Charge transport in thermally aged paper impregnated with natural ester oil

Abdelmalik

Dodd

Dissado

et al. 2014

IEEE Trans. Dielect. Electr. Insul.

View full text Add to dashboard Cite

This is the accepted version of the paper.This version of the publication may differ from the final published version. Permanent repository link ABSTRACTSamples of a dried composite oil-paper system were thermally aged in the laboratory under N 2 in a sealed container and analysed using their dielectric response. The contributing loss processes were separated using an equivalent circuit model containing constant high frequency capacitances, dc-conductances, a dispersive capacitance, and a low frequency quasi-dc (q-dc) dispersion process as circuit elements. This low frequency dispersion in oil-paper samples is a bulk property of the system that is often mistaken for a dc conduction process when only the imaginary capacitance or acconductance is measured. The Dissado-Hill response function is proposed for the frequency dependence of the dispersive capacitance in the mid-frequency range rather than the Debye function because its cluster concepts correlate with the sample morphology of a matrix of oil-filled cavities. The quasi-dc dispersion is assigned to the transport of mobile charges between charge-clusters associated with locally connected oil filled cavities, which is a process that can be represented on a global scale by the form of hierarchical circuit system that leads to constant phase angle responses, and is here modelled by the Dissado-Hill q-dc function. It was found that the two dispersions moved together to higher frequency with thermal ageing of the composite material. The characteristic frequency common to the dispersions had an activation energy that decreased with thermal ageing, whereas their amplitude increased. This behaviour is discussed in terms of possible changes to the oil-paper composite caused by the ageing process.

show abstract

“…Fothergill et al [13] published work on the change of conductivity of full-sized cables electro-thermally aged as part of the EU ARTEMIS project [14]. These cables had an insulation thickness of 18 mm and were aged at 90 kV rms for 6 months (4380 h) at a temperature of 80C.…”

Section: /1000t [K]mentioning

confidence: 99%