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26. Moisture Assessment of Oil-Immersed Paper Based on Dynamic Characteristics of Frequency Domain Spectroscopy

Author

Qingchuan Xu, Shengkang Wang, Fuchang Lin, and Hua Li

Subjects
oil-immersed paper, Frequency domain spectroscopy (FDS), General Computer Science, General Engineering, moisture assessment, General Materials Science, oil-paper insulation, dynamic characteristic, Electrical engineering. Electronics. Nuclear engineering, TK1-9971
Abstract

In on-site measurement, as the transformer’s structure is often unknown, the application of frequency domain spectroscopy (FDS) is greatly limited in moisture assessment of transformer. This paper proposes a moisture assessment method for oil-immersed paper based on the dynamic characteristic frequency even for an unknown transformer structure. FDS tests are performed on the oil-paper insulation, corresponding oil-immersed paper, and mineral oil under different moisture conditions. The moisture criterion of oil-immersed paper and the influence of the structural parameters on the calculated frequency spectroscopy at different frequencies are discussed. It is concluded that the moisture criterion’s effectiveness, which indicates the sensitivity of assessed moisture content to the error of the tan $\delta $ , changes at different frequencies. Moreover, there are some frequencies at which tan $\delta $ is not influenced by structural parameters and is close to the measured value, which are regarded as “characteristic frequencies.” Based on the characteristic frequency, the moisture content of oil-immersed paper is assessed according to the frequency spectroscopy of oil-paper insulation without the structural parameters. The result shows that the assessing frequency changes under different moisture conditions, and the error of the assessed moisture content is less than 0.1%.

Published
2022

45. Influence of Aging on Creepage Discharge Characteristics of Oil-Paper Insulation Under AC-DC Combined Voltage

Author

Liang Bin, Zhou Yuanxiang, and Jin Fubao

Subjects
Aging, Materials science, General Computer Science, 020209 energy, 02 engineering and technology, 01 natural sciences, law.invention, Dc voltage, law, 0103 physical sciences, 0202 electrical engineering, electronic engineering, information engineering, Arc flash, creepage discharge, General Materials Science, Composite material, Transformer, 010302 applied physics, AC-DC combined voltage, General Engineering, inception voltage, Electrode, oil-paper insulation, lcsh:Electrical engineering. Electronics. Nuclear engineering, Stage (hydrology), DC voltage component, lcsh:TK1-9971, Voltage
Abstract

There is a relative lack of research on the development of creepage discharge in aged oil-paper insulation subjected to AC-DC combined voltage in converter transformers. In this study, based on the physical and chemical properties of oil-paper, we propose a sphere-plate electrode model to study the creepage discharge parameters and characteristic spectra of aged oil-paper subjected to AC-DC combined voltage. The results show that the creepage discharge inception voltage of aged oil-paper is related to the AC voltage component of the AC-DC combined voltage. However, when the DC voltage component is 60 kV, the flashover phenomenon was found to occur in one of the severely aged samples before the AC voltage was applied. Despite being subjected to the same DC voltage, the flashover phenomenon did not occur in three other samples aged to different degrees. Large-amplitude discharges were found to appear earlier in the severely aged samples. At the same creepage discharge stage, as the aging time of the oil-paper increased, the number of large-amplitude discharges was found to rapidly increase, and the time interval between adjacent discharges was found to gradually decrease. At each stage of the creepage discharge, the small-amplitude discharge has a “hump” shaped distribution. The larger the DC voltage component, the shorter the endurance time of aged oil-paper, and the more severe the damage to the oil-paper. The DC voltage component was found to have an accelerating effect on the development of creepage discharge in aged oil-paper insulation.

Published
2021

46. A Comprehensive Evaluation of Metadata-Based Features to Classify Research Paper’s Topics

Author

Ghulam Mustafa, Muhammad Usman, Muhammad Tanvir Afzal, Abdul Shahid, and Anis Koubaa

Subjects
Word2Vector (W2V), decision tree (DT), association of computing machinery (ACM), metadata, Electrical engineering. Electronics. Nuclear engineering, k-nearest neighbor’s (KNN), Research paper classification, TK1-9971
Abstract

The existing plethora of document classification techniques exploits different data sources either from the content or metadata of research articles. Various journal publishers like Springer, Elsevier, IEEE, etc., do not provide open access to the content of research articles, whereas metadata is freely available there. Metadata like title, keyword, and abstract can serve as a better alternative to the content in various scenarios. In the current literature, researchers have assessed the role of some of the metadata individually. We believe that the collective contribution of metadata parameters can play a significant role in classifying research papers. This paper presents a comprehensive evaluation of the role of metadata, individually as well as in combinations to achieve the objective of research paper classification. Moreover, we have classified the research articles into ACM hierarchy root categories (e.g. general literature, hardware, software, etc.). In this comprehensive evaluation, we have assessed all the possible combinations of metadata features against different classifiers such as Random Forest, K Nearest Neighbor, and Decision Tree. The results of this research reveal that the title & keywords combination outperforms other combinations with an F-measure score of 0.88.

Published
2021