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The impact of air gaps between needle and polymer on electrical treeing in needle-plane samples.
- Source :
-
IEEE Transactions on Dielectrics & Electrical Insulation . Jun2020, Vol. 27 Issue 3, p739-747. 9p. - Publication Year :
- 2020
-
Abstract
- Electrical trees are widely grown in laboratories from metallic needle electrodes to enable the degradation process to proceed rapidly at voltages of ∼10 kV AC. Here it is shown that cone-shaped air gaps may form at a needle tip, even when they are not visible optically. Using X-ray imaging techniques, samples with and without air gaps up to 55 μm long have been characterized. The presence of air gaps led to partial discharge (PD) patterns resembling void-discharges. Prior to tree initiation, discharge characteristics evolved with increased voltage increments and increased phase lag behind the applied voltage. These changes to PD characteristics reflect a change in the physical state of the air gap. Although samples with air gaps generally initiated trees quicker than those with no gap, PD activities did not appear to play a decisive role in tree initiation times. However, initial voids were found to have major impact on the subsequent tree growth. In samples with persistent pre-tree air-gap PDs, trees grew larger branchy structures with higher PD magnitudes. In addition, the PDs became more asymmetric between positive and negative half-cycles than occurred in samples with no air gaps. It is shown that understanding the interface between the needle and polymer at a micron scale is critical to interpretation of laboratory tree growth experiments. [ABSTRACT FROM AUTHOR]
Details
- Language :
- English
- ISSN :
- 10709878
- Volume :
- 27
- Issue :
- 3
- Database :
- Academic Search Index
- Journal :
- IEEE Transactions on Dielectrics & Electrical Insulation
- Publication Type :
- Academic Journal
- Accession number :
- 143495479
- Full Text :
- https://doi.org/10.1109/TDEI.2019.008538