Application of FEA to image-based models of electrical trees with uniform conductivity

Abstract

X-ray computed tomography and serial block-face SEM have provided detailed threedimensional reconstructions of electrical trees for the first time. The application of finite element analysis (FEA) to the analysis of electrical fields in an epoxy block containing a tree is considered. Illustrations are provided by way of a number of case studies. It is shown that the limitations of FEA do not arise from the discrete nature of the meshing: rather uncertainties are more concerned with material properties in high fields on the micrometer scale, the limitations imposed by the pixel size of the imaging technique, and the discrete nature of the image reconstruction technique. For a dynamic model of tree growth space charge dynamics on the same physical scale need also to be modelled. A meshing strategy is used, calibrated against the charge simulation method, to ensure accurate but manageable computations in critical parts of a tree such as branch tips. Examples of field values are given using geometric constructs and low-field material characteristics as illustrative values. The field variation around a conducting tree structure, including the maximum field direction as a branch starts to bifurcate, is determined as an example. These yield values in excess of those expected if space charge movement was considered, but consistent with analytical calculations. Index Terms -XCT, x-ray computed tomography, SBFSEM, Serial block-face SEM, FEA, finite element analysis, electrical tree, field, model, charge simulation method, CSM, image-based modeling. This work is licensed under a Creative Commons Attribution 3.0 License. For more information, see http://creativecommons.org/licenses/by/3.0/ Qi Li (aka Steven) was born in Hunan Province, China, in September 1984. He completed the B.Eng. degree in electrical and electronics engineering at

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“…These PDs make the air voids to be electrically conductive in the shape of cracks. These formed cracks lead finally to the complete propagation of ET [2,[11][12][13][14].…”

“…As the non-uniform electric fields play a vital role in the ET inception and growth, the researchers seek seriously to the accurate calculation and distribution of these fields. They realised the complexity of the calculation of these fields by using the traditional methods so the numerical methods are the best approaches to be used [1,2,[13][14][15][16].…”

A review on deterministic and stochastic models for electrical treeing initiation and propagation in solid insulation systems from the perspective of prediction assessment techniques

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