Lanca, M. C., M. Fu, E. Neagu, L. A. Dissado, J. Marat-Mendes, A. Tzimas, and S. Zadeh,
"Space charge analysis of electrotherinally aged XLPE cable insulation",
Journal of Non-Crystalline Solids, vol. 353, no. 47-51, pp. 4462-4466, 2007.
AbstractCross-linked polyethylene (XLPE) is currently widely used as an insulating material for power cables due to its good physical properties, however when in use it undergoes an electrical ageing process. Its ability to trap electric charge can give rise to space charge accumulation in the bulk of the polymer and produce localised electric stresses that can lead to cable failure, since the electric field will be increased above the design stress in some regions favouring the initiation of degradation there. In this work the PEA (pulsed electro-acoustic) method was used to compare the charge dynamics in three samples (XLPE cable peelings) aged in different ways (electrothermally in the laboratory, field aged in service and thermally aged in the laboratory). Very different transient behavior was found depending upon the ageing history. This is related to differences in the migration of chemical species in the insulation layer, which are known to act as charge traps. All materials showed heterocharge peaks when the space charge reached stability, the magnitude of which seems to be related to the severity of the ageing. (c) 2007 Elsevier B.V. All rights reserved.
MC, L., F. M, N. E, D. LA, M. - M. S. J, T. A, and Z. S,
"Space charge analysis of electrothermally aged XLPE cable insulation",
Journal of Non-Crystalline Solids, vol. 353, pp. 4462-4466, Jan, 2007.
Abstractn/a
MC, L., F. M, N. E, D. LA, M. - M. S. J, T. A, and Z. S,
"Space charge analysis of electrothermally aged XLPE cable insulation",
Journal of Non-Crystalline Solids, vol. 353, issue 47-51, 2007.
AbstractCross-linked polyethylene (XLPE) is currently widely used as an insulating material for power cables due to its good physical properties, however when in use it undergoes an electrical ageing process. Its ability to trap electric charge can give rise to space charge accumulation in the bulk of the polymer and produce localised electric stresses that can lead to cable failure, since the electric field will be increased above the design stress in some regions favouring the initiation of degradation there. In this work the PEA (pulsed electro-acoustic) method was used to compare the charge dynamics in three samples (XLPE cable peelings) aged in different ways (electrothermally in the laboratory, field aged in service and thermally aged in the laboratory). Very different transient behavior was found depending upon the ageing history. This is related to differences in the migration of chemical species in the insulation layer, which are known to act as charge traps. All materials showed heterocharge peaks when the space charge reached stability, the magnitude of which seems to be related to the severity of the ageing.
Neagu, E. R., M. C. Lanca, C. J. Dias, and J. N. Marat-Mendes,
"Space Charge and Dipolar Charge Contribution at Polar Polymers Polarization",
Ieee Transactions on Dielectrics and Electrical Insulation, vol. 22, no. 3, pp. 1419-1426, 2015.
Abstractn/a
MC, L., N. ER, N. RM, D. CJ, M. - M. JN, and D. - G. DK,
"Space charge studies in LDPE using combined isothermal and non-isothermal current measurements",
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION, vol. 11: Univ Wales, Univ Nova Lisboa, pp. 25-34, Jan, 2004.
Abstractn/a
Lanca, M. C., E. R. Neagu, R. M. Neagu, C. J. Dias, J. N. Marat-Mendes, and D. K. Das-Gupta,
"Space charge studies in LDPE using combined isothermal and non-isothermal current measurements",
Ieee Transactions on Dielectrics and Electrical Insulation, vol. 11, no. 1, pp. 25-34, 2004.
AbstractUsing a recently developed procedure combining isothermal and non-isothermal current measurements space charge trapping and transport in LDPE was successfully studied. Unaged, thermally and electrically aged samples were investigated. The samples were conditioned before each measurement in order to obtain reproducible results. In the non-isothermal measurements appeared a broad peak (40degreesC to 50degreesC) that was possible to decompose into two or three peaks (35, 45 and 65degreesC). At even higher temperature another peak was sometimes present (85degreesC) depending on the prior sample conditioning. The space charge is trapped near the surface in deep traps (maximum depth of approximate to 15 mum). Relaxation times, mobilities and activation energies have been calculated for different charging/discharging conditions. For unaged samples the reproducibility of the results was poor while for the aged polyethylene it was quite good, meaning that aging helps conditioning. In the electrically aged LDPE there is a decrease of conductivity and the broad peak of the non-isothermal spectra shows a slight shift towards higher temperatures when compared with the data found in the thermally aged polymer.
Lanca, M. C., E. R. Neagu, R. M. Neagu, C. J. Dias, J. N. Marat-Mendes, and D. K. Das-Gupta,
"Space charge studies in LDPE using combined isothermal and non-isothermal current measurements",
Ieee Transactions on Dielectrics and Electrical Insulation, vol. 11, no. 1, pp. 25-34, 2004.
AbstractUsing a recently developed procedure combining isothermal and non-isothermal current measurements space charge trapping and transport in LDPE was successfully studied. Unaged, thermally and electrically aged samples were investigated. The samples were conditioned before each measurement in order to obtain reproducible results. In the non-isothermal measurements appeared a broad peak (40degreesC to 50degreesC) that was possible to decompose into two or three peaks (35, 45 and 65degreesC). At even higher temperature another peak was sometimes present (85degreesC) depending on the prior sample conditioning. The space charge is trapped near the surface in deep traps (maximum depth of approximate to 15 mum). Relaxation times, mobilities and activation energies have been calculated for different charging/discharging conditions. For unaged samples the reproducibility of the results was poor while for the aged polyethylene it was quite good, meaning that aging helps conditioning. In the electrically aged LDPE there is a decrease of conductivity and the broad peak of the non-isothermal spectra shows a slight shift towards higher temperatures when compared with the data found in the thermally aged polymer.
Neagu, E. R., C. J. Dias, M. C. Lança, and J. N. Marat-Mendes,
The study of molecular movements in dielectrics using isothermal and non- isotehermal current measurements,
, vol. 183, pp. –-, Jan, 2009.
Abstractn/a