Three dimensional imaging of electrical trees in multiple stages

Electrical trees are degraded paths in polymeric insulation and are the mechanism of electrical failure of high voltage insulation systems. Previous studies have confirmed the application of X-ray Computed Tomography (XCT) imaging of electrical trees using phase contrast enhancement. This work evaluates the feasibility of X-ray imaging of electrical trees to measure growth at several stages of growth in the same treeing sample. The impact of x-ray dose on the epoxy resin studied is determined experimentally. An example of multi-stage tree imaging using laboratory micro-XCT and reconstructed renderings is provided. Based on the three-dimensional tree models, characteristics such as the degraded volume and surface area can be quantified. Furthermore, a comparison between two stages is presented to show the growth of the electrical tree in a fixed period of time. Insight into the treeing characteristics is also discussed

Lessons from Three-Dimensional Imaging of Electrical Trees

Electrical trees are artifacts resulting from aging of polymeric insulation in high electrical fields. Whilst there is some debate concerning the mechanism by which they grow, there is no doubt that their growth can lead to the ultimate failure of the host insulation. Studying electrical trees is mainly confined to measurement of associated partial discharges and observing the physical growth of the tree structure optically. This paper reviews developments in observations of the growth of trees in the laboratory. In particular, consideration is given to the benefits of generating three-dimensional replicas of real trees from X-ray computer tomography (XCT) and serial block face scanning electron microscopy (SBFSEM), and how these can facilitate better understanding of tree development mechanisms. It is concluded that both two- and three-dimensional imaging are required, and these need correlating with partial discharge measurements to develop models of tree growth and effective asset management tools

Mathematical modeling of the reaction of metal oxides with methane

Methane reduction has attracted substantial interest in recent years because an abundant amount of natural gas has been found and methane possesses a strong reduction ability.</p

A model and simulation of fast space charge pulses in polymers

The transport of space charge packets across polyethylene and epoxy resin in high electric fields has been characterized as fast or slow depending on packet mobility. Several explanations for the formation and transport of slow space charge packets have been proposed, but the origins of fast space charge pulses, with mobilities above 10-11 m2V-1s-1, are unclear. In one suggested model, it is assumed that the formation of fast charge pulses is due to discontinuous electromechanical compression and charge injection at the electrode-insulation interface, and their transport is related to corresponding relaxation processes. In that model, charges travel as a pulse because of group polarization. This paper provides an alternative model based on the reduction of charge carrier activation energy due to charge density triggered polymer chain movement and subsequent chain relaxation times. The generation and transport of fast charge pulses are readily simulated by a bipolar charge transport model with three additional parameters: reduced activation energy, charge density threshold, and chain relaxation time. Such a model is shown to reproduce key features of fast space charge pulses including speed, duration, repetition rate and pulse size. This model provides the basis for a deep understanding of the physical origins of fast space charge pulses in polymers.<br/

The Dynamic Character of Partial Discharge in Epoxy Resin at Different Stages of Treeing

Simultaneous imaging of electrical tree growth and partial discharge measurement have allowed 5 stages of tree growth to be identified. Partial discharge (PD) characteristics have been collected from tree growth in needle-plane epoxy resin samples under 15 kV peak AC voltage, and have been shown to behave differently at different stages of tree growth. Initial slow growth is accompanied by large discharges (about 10 pC). Thereafter, growth of fine channels is associated with smaller PDs (about 0.3 pC). It was observed that the tree propagation is further driven by even smaller PDs below the equipment sensitivity. However, when the tree approaches the counter electrode, the PD magnitude increases again and a more substantial tree grows with a low propagation rate. Reverse tree channels then occur from the planar electrode towards the needle, together with higher magnitude PDs characterized by thick and dark branches before breakdown

Data analysis accuracy of Urban and rural economic forecast based on neural network algorithm

Abstract Economic forecasting is affected by many factors. The analysis of economic data needs an intuitive and operable algorithm model. Therefore, based on this, this paper designs an urban and rural economic forecasting system based on neural network algorithm, and conducts a system test. First of all, in the data processing module, this paper adopts an efficient BP neural network algorithm based on error back propagation. This algorithm can effectively improve the accuracy of data recognition. At the same time, in order to solve the identification error caused by the complexity of urban and rural economic data during data input, the data processing layer of the system can preprocess the input data and normalize the multiple linear regression algorithm. Finally, in order to further prove the availability of the neural network algorithm used in this paper, by comparing the results of the original data and the predicted data, it is concluded that the data prediction results obtained by using the model algorithm in this paper have high accuracy and are basically consistent with the target value. Finally, through the analysis of the urban and rural economic development data, the degree of coordination of urban and rural economic development is analyzed, and the urban and rural development model is constructed. This paper also further analyzes the factors that restrict the coordinated development of urban and rural economy through indicators such as population structure, economic development, residents' life, social services and ecological construction, so as to achieve a more comprehensive urban and rural economic forecast, and provide a basis for improving the development of urban and rural economy in the regional economy.</jats:p