Abstract
The PEA technique is used to measure the distribution of space charge in an epoxy resin after polarisation for one week at an applied field of 7.14 kV/mm over a range of temperatures. The decay of the space charge is followed for times up to 114 h after removal of the voltage and analysed in terms of a number of alternative decay mechanisms. It is shown that the rate-determining stage of the decay mechanism is that of a thermally activated process that has been associated with charge de-trapping. At times greater than 102 s the de-trapping process behaves as though the space charge field does not exist and the retention time of the space charge depends only upon the depth of the deepest occupied traps and the temperature
Highlights
The generation of space charge in insulators under voltage alters the field distribution from that that would apply in its absence
The base resin is essentially composed by Diglycidyl Ether-Bisphenol A (DGEBA) and Iso-Octyl Glycidyl Ether (IOGE) whereas the hardener is a mixture of Triethylene Tetra Amine (TETA) and Polyoxypropylene as major components
Given sufficient stressing time space charge can be injected into epoxy resins at fields as low as 7.14kV/mm
Summary
The generation of space charge in insulators under voltage alters the field distribution from that that would apply in its absence. In [5] simultaneous measurement of space charge by the thermal pulse method and the external current showed that the decay of space charge in an anti-static doped highdensity polyethylene (HDPE) following short-circuit was governed by the injection of negative charge This injection neutralised positive heterocharge (charge of opposite polarity to the electrode) that had formed next to the cathode. The experiments reported in [7] could not distinguish between a transport mechanism controlled by field-assisted thermally activated hopping between neutral sites or a Poole-Frenkel process [6] It was shown in [9] that the decay of space charge in an epoxy resin was controlled by the time dependent de-trapping of the injected charge from trap sites whose trap depths uniformly covered a range of energies. This approach is intended to provide a means of analysing data in order to both identify the decay mechanism and to extract pertinent parameter values
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