Nuclear magnetic resonance imaging of electrical trees in PE

Weigand, F.; Spiess, Hans Wolfgang; Blümich, Bernhard; Salge, G.; Möller, Klaus

doi:10.1109/94.598283

“…Nuclear magnetic resonance is a spectroscopy which employs radio frequency radiation in magnetic fields to examine properties of the atomic nuclei [47]. It is a non-invasive Table 1.…”

Section: Nuclear Magnetic Resonancementioning

confidence: 99%

Imaging and analysis techniques for electrical trees using X-ray computed tomography

Schurch

¹

,

Rowland

²

,

Bradley

³

et al. 2014

IEEE Trans. Dielect. Electr. Insul.

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Electrical treeing is one of the main mechanisms of degradation in polymeric high voltage insulation, a precursor of power equipment failure. Electrical trees have been previously imaged mostly using two-dimensional imaging techniques; thereby loosing valuable information. Here we review the techniques that have been previously used and present the novel application of X-ray computed tomography (XCT) for electrical tree imaging. This non-destructive technique is able to reveal electrical trees, providing a threedimensional (3-D) view and therefore, a more complete representation of the phenomenon can be achieved. Moreover, taking virtual slices through the replica so created brings the possibility of internal exploration of the electrical tree, without the destruction of the specimen. Here, laboratory created electrical trees have been scanned using XCT with phase contrast enhancement, and 3-D virtual replicas created through which the trees are analyzed. Serial Block-Face scanning electron microscopy (SBFSEM) is shown to be a successful complementary technique. Computed tomography enables quantification of electrical tree characteristics that previously were not available. Characteristics such as the diameter and tortuosity of tree channels, as well as the overall tree volume can be calculated. Through the cross-section analysis, the progression of the number of tree channels and the area covered by them can be investigated. Using this approach it is expected that a better understanding of electrical treeing phenomenon will be developed.

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“…In attempts to visualize electrical trees using nuclear magnetic resonance, the technique was used to analyze morphological changes in polyethylene. Again, only generally affected areas (areas of treeing) can be detected, rather than any detail, and the reported spatial resolution was around 0.7 mm [47,48].…”

Section: Nuclear Magnetic Resonancementioning

confidence: 97%

Imaging and analysis techniques for electrical trees using X-ray computed tomography

Schurch

¹

,

Rowland

²

,

Bradley

³

et al. 2014

IEEE Trans. Dielect. Electr. Insul.

View full text Add to dashboard Cite

Electrical treeing is one of the main mechanisms of degradation in polymeric high voltage insulation, a precursor of power equipment failure. Electrical trees have been previously imaged mostly using two-dimensional imaging techniques; thereby loosing valuable information. Here we review the techniques that have been previously used and present the novel application of X-ray computed tomography (XCT) for electrical tree imaging. This non-destructive technique is able to reveal electrical trees, providing a threedimensional (3-D) view and therefore, a more complete representation of the phenomenon can be achieved. Moreover, taking virtual slices through the replica so created brings the possibility of internal exploration of the electrical tree, without the destruction of the specimen. Here, laboratory created electrical trees have been scanned using XCT with phase contrast enhancement, and 3-D virtual replicas created through which the trees are analyzed. Serial Block-Face scanning electron microscopy (SBFSEM) is shown to be a successful complementary technique. Computed tomography enables quantification of electrical tree characteristics that previously were not available. Characteristics such as the diameter and tortuosity of tree channels, as well as the overall tree volume can be calculated. Through the cross-section analysis, the progression of the number of tree channels and the area covered by them can be investigated. Using this approach it is expected that a better understanding of electrical treeing phenomenon will be developed.

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“…It was found that the short and long components of T 2 indicated the existence of different environmental states in the water. Later, partial discharge and electrical treeing experiments were carried out on samples of low‐density polyethylene [22, 23]. Proton NMR techniques were employed which focused on identifying morphological changes [25, 26], the results showed that only 10% natural deuterium determined by deuterium spectra and a short and long components of T 2 indicated the existence of different environmental states for the water.…”

Section: Overview Of Nmrmentioning

confidence: 99%

“…Amongst commonly used techniques, we cite thermal analysis techniques such as differential scanning calorimetry [9], the X-ray diffraction technique to analyse the structural changes of thermally aged XLPE, spectroscopy techniques such as Fourier-transform infrared spectroscopy method, nuclear magnetic resonance (NMR) spectroscopy and dielectric spectroscopy [10][11][12][13][14], and mechanical strength testing techniques such as elongation at break and elasticity measurements [15]. Some researchers who used NMR techniques to investigate ageing and degradation have mainly focused on thermal ageing [15][16][17][18][19][20], and ageing due to partial discharge, electrical treeing, and water treeing [21][22][23]. Studies investigating erosion and tracking on SiR insulation and erosion due to surface discharge on XLPE insulation are very limited.…”

Section: Introductionmentioning

confidence: 99%

¹ H NMR tests on damaged and undamaged XLPE and SiR samples

Gkoura

¹

,

Wang

²

,

Αναστασίου

³

et al. 2019

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Cross-linked polyethylene (XLPE) and silicone rubber (SiR) samples were subjected to a high-voltage AC stress plane-plane configuration and inclined plane test, respectively. The voltage was applied such that discharge was observed across the surface of the XLPE test sample for several hours and for visible damage to occur on SiR samples also after several hours. Selected stressed samples together with virgin samples from the same manufactured batch were tested using nuclear magnetic resonance (NMR) spectroscopy. Specifically, 1 H NMR spin-lattice (T 1) and spin-spin (T 2) relaxation time measurements were employed to examine potential changes in the chemical bonding of undamaged and damaged XLPE and SiR samples. Preliminary results show that there may be a moderate increase in the T 1 and T 2 values of the damaged samples in comparison with the undamaged ones. This raises the possibility that NMR can be a useful additional experimental tool in characterising material degradation.

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Nuclear magnetic resonance imaging of electrical trees in PE

Cited by 12 publications

References 20 publications

Imaging and analysis techniques for electrical trees using X-ray computed tomography

Imaging and analysis techniques for electrical trees using X-ray computed tomography

Imaging and analysis techniques for electrical trees using X-ray computed tomography

¹ H NMR tests on damaged and undamaged XLPE and SiR samples

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Nuclear magnetic resonance imaging of electrical trees in PE

Cited by 12 publications

References 20 publications

Imaging and analysis techniques for electrical trees using X-ray computed tomography

Imaging and analysis techniques for electrical trees using X-ray computed tomography

Imaging and analysis techniques for electrical trees using X-ray computed tomography

1 H NMR tests on damaged and undamaged XLPE and SiR samples

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¹ H NMR tests on damaged and undamaged XLPE and SiR samples