Proceedings of 2005 International Symposium on Electrical Insulating Materials, 2005. (ISEIM 2005). 2005
DOI: 10.1109/iseim.2005.193505 View full text |Buy / Rent full text
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Abstract: Dielectric spectroscopy measurements below 1 Hz are often dominated by "conduction-like" effects. For this reason, they often appear to be dismissed as being of little interest. In this paper two "sub-hertz" responses are considered that give insights into the insulating systems concerned. The first system is that of cross-linked polyethylene, taken from a power cable system. Measurements at temperatures between 60˚C and close to melting at 100˚C show a change in characteristic from a percolation process to a … Show more

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“…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
“…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
“…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
“…Because of the expected changes to trapping centres, one would also expect the conductivity to change (although one could argue that almost anything would change the conductivity!). This was measured accurately using low-frequency dielectric spectroscopy [39] as a function of temperature for both cables, before and after ageing. An Arrhenius plot is shown in Figure 4.…”
Section: Ageingmentioning
“…From [39] Laurent et al have advocated the use of electroluminescence (EL). Electrical ageing of insulating polymers would involve dissipation to the lattice of the energy of mobile or trapped space charges.…”
Section: /T Ln(conductivity)mentioning