Title :
Dielectric relaxation and DC conductivity of transformer pressboard and XLPE cable insulation
Author :
Hegerberg, R. ; Lundgaard, L. ; Ildstad, E.
Author_Institution :
Norwegian Electr. Power Res. Inst., Trondheim, Norway
Abstract :
The authors present results from preliminary laboratory measurements of return voltage made on samples of oil-impregnated transformer pressboard and XLPE (cross-linked polyethylene) cable insulation. The effects of temperature and water content have been examined. Particular attention has been paid to the dielectric response of water-tree-aged cable insulation. The qualitatively different effects of water on XLPE and impregnated paper observed in these preliminary investigations may indicate that, while interfacial polarization is a dominant effect in the paper-oil system, electron (or hole) trapping in sites in the tree regions is an effective charge storage mechanism in XLPE. The fact that the presence of water apparently reduces the trapped charge mobility in XLPE objects containing trees is difficult to explain, but again it must be related to the trapping mechanism(s) being modified by water
Keywords :
cable insulation; composite insulating materials; dielectric polarisation; dielectric relaxation; electric breakdown of solids; electron traps; hole traps; insulating oils; organic insulating materials; paper; polymers; power cables; space charge; transformer insulation; DC conductivity; XLPE cable insulation; charge storage mechanism; dielectric relaxation; effects of temperature; electron trapping; hole trapping; interfacial polarization; oil-impregnated transformer pressboard; paper-oil system; return voltage; tree regions; water content; water trees; Cable insulation; Conductivity; Dielectric measurements; Electron traps; Oil insulation; Polyethylene; Power transformer insulation; Temperature; Voltage measurement; Water storage;
Conference_Titel :
Conduction and Breakdown in Solid Dielectrics, 1992., Proceedings of the 4th International Conference on
Conference_Location :
Sestri Levante
Print_ISBN :
0-7803-0129-3
DOI :
10.1109/ICSD.1992.224958