Title :
Polarization and dielectric behavior of ac-aged polyethylene
Author :
Das-Gupta, D.K. ; Scarpa, P.C.N.
Author_Institution :
Sch. of Electron. Eng. & Comput. Syst., Univ. of Wales, Bangor, UK
fDate :
6/1/1996 12:00:00 AM
Abstract :
High field polarization and dielectric relaxation behavior have been used to study the aging mechanisms of crosslinked polyethylene (XLPE) and low density polyethylene (LDPE) aged at constant alternating electrical field stress in a humid environment at room temperature. For this study, the dielectric spectroscopy data in the frequency range of 10-5 to 106 Hz and their comparative analysis, have been used to provide electrical analog models of the aging. The dielectric data in the frequency range of 10-5 to 5×10 -2 Hz were calculated from the desorption current, whereas bridge measurements provide the data in the frequency range of 10 Hz to 106 Hz. In addition, thermal transient current and thermally stimulated discharge current measurements have been carried out in order to determine the polarization and space charge accumulation in ac aged polyethylene. A correlation has been observed in the behavior of polarization and dielectric relaxation in the present work. The dielectric behavior of the XLPE cable samples and of the LDPE flat samples show a presence of both the inter-cluster (low frequency) charge exchange and the intra-cluster (high frequency) charge motion, the former mechanism becoming more dominant as the aging progresses. For the XLPE cable samples ac aged in a humid environment at room temperature, relaxation peaks obeying the fractional power law have been observed in addition to a quasi-dc process
Keywords :
XLPE insulation; ageing; dielectric polarisation; dielectric relaxation; polyethylene insulation; space charge; thermally stimulated currents; 1E-5 to 1E6 Hz; AC aging; LDPE flat sample; XLPE cable sample; bridge measurements; crosslinked polyethylene; desorption current; dielectric relaxation; dielectric spectroscopy; electrical analog model; high field polarization; humid environment; inter-cluster charge exchange; intra-cluster charge motion; low density polyethylene; space charge; thermal transient current; thermally stimulated discharge current; Aging; Bridges; Current measurement; Dielectrics; Electrochemical impedance spectroscopy; Frequency; Polarization; Polyethylene; Stress; Temperature;
Journal_Title :
Dielectrics and Electrical Insulation, IEEE Transactions on