Decay of space charge in a glassy epoxy resin following voltage removal

Abstract

This is the unspecified version of the paper.This version of the publication may differ from the final published version. Permanent repository link ABSTRACTThe 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 7.14kV/mm over a range of temperatures. The decay of the space charge is followed for times up to 114 hours 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 10 2 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.

An improved model to estimate trapping parameters in polymeric materials and its application on normal and aged low-density polyethylenes

“…As mentioned, previous modelling works 13,15 to estimate trapping parameters are confined to space charge dynamics of depolarization measurements. Also, after the removal of the external voltage, observed space charges are assumed to be trapped charges only and any free charges escaped from traps were thought to be flowing away from electrodes instantly.…”

“…In recent years, many approaches have been developed on determination or estimation of these trapping parameters for various insulation materials, especially polyethylene [13][14][15][16][17][18] . Chen proposed a trapping-detrapping model based on two energy levels.…”

“…It has been revealed that physical and chemical modifications brought by irradiation process is reflected on the changes in trapping parameters. In the case of epoxy resin, Dissado et al proposed a model considering charge detrapping process within three steps 15 . Futhermore, with such model, trapping parameters of different-time aged cross-linked polyethylene (XLPE) cable peelings 16 were evaluated.…”

“…data from polarization test were not exploited; (iii) Observed charge decay after switching off power supply was thought to be caused by detrapping process, or in other words, any charges escaped from the trap sites were presumed to flow away instantly. (iv) Both studies tried to separate traps with a range of energy levels into two equivalent levels 13 or ranges 15 . And it is noteworthy in works based on Chen's model 13,14,19 , the two energy levels, i.e.…”

Trapping parameters comparison between cable sections from different service conditions by a new trapping-detrapping model

“…where is the trapped charge density, is temperature (300K used in the present paper), is the Boltzmann constant (~1.38 × 10 m kg), and 0 is the attempt to escape frequency (~2 × 10 Hz at room temperature [7]). However, our model is applied to the condition when the applied electric field is removed.…”