Abstract
In this study, the space charge behavior in ethylene propylene rubber (EPR) under a 50-Hz AC field is studied based on the variation of space charge response, FTIR spectra and impurity contents inside EPR with thermal treatment. The space charge was detected with the pulsed electroacoustic (PEA) method and the phase shift of detecting pulse under 50 Hz AC field was realized according to the automatic equal phase shift (AEPS) principle. The results show three main types of impurities in untreated EPR. Three distinct regions of space charge distribution are seen in untreated EPR under a 50-Hz AC field. The mean phase density of space charge ρ θ is increased with the enhancement of the applied field from 15 to 61 kV/mm. The maximum electric field distortion rate of untreated EPR tends to rise first and then decrease, ranging from 6.65% to 31.87%. The impurity content and the ρ θ decreased significantly for EPR thermal treated at 150 °C for 18 h. Corresponding, the maximum electric field distortion rate is effectively reduced to 0.66%. Finally, the space charge source and migration process are speculated based on the diffusion trend of the space charge isodensity line and the migration direction of various charges under the electric field.
Highlights
Ethylene propylene rubber (EPR) is one of the main insulators at medium and high voltage scales and accounts for 15% of total sales on the market, being second only to cross-linking polyethylene (XLPE) which accounts for 40%
SPACE CHARGE BEHAVIOR Space charge behavior from 0◦ to 360◦ are shown in Figure 2 for untreated samples polarized under a 50-Hz AC field
The induced charges caused by the applied field at the interface between the electrode and EPR are removed to clearly observe the space charge accumulation inside EPR
Summary
Ethylene propylene rubber (EPR) is one of the main insulators at medium and high voltage scales and accounts for 15% of total sales on the market, being second only to cross-linking polyethylene (XLPE) which accounts for 40%. It plays a dominant role in several important fields, such as coal mining, oil production and submarine cable manufacture, due to its excellent corona resistance, water tree resistance, flexibility and high temperature performance [1]–[4]. The aging and failure mechanisms of EPR have been researched extensively. It has been shown that both the average discharge power and the average discharge current
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