Article
Engineering, Electrical & Electronic
Jiefeng Liu, Boshu Song, Enze Zhang, Heng Zhang, Yiyi Zhang, Hui Hwang Goh
Summary: This work proposes a two-stage residual lifespan prediction model for insulating paper based on methanol and furfural indicators. The changes in the contents of methanol and furfural in the oil are examined to determine two demarcation points for dividing the insulation's life into different aging stages. By coupling with the second-order aging kinetic equation, the two-stage residual lifespan model is obtained. The proposed model is proven to be valid with a mean absolute percentage error of 5.6% for insulating paper's residual lifespan when compared to the conventional method of using a single indicator.
IEEE TRANSACTIONS ON POWER DELIVERY
(2023)
Article
Engineering, Electrical & Electronic
Lijun Zhou, Wei Liao, Dongyang Wang, Yi Cui, Lujia Wang, Liqing Zhang, Lei Guo
Summary: This study investigates the effects of traction loads on the thermal aging of oil-paper insulation in traction transformers through accelerated aging experiments and data analysis, revealing the relationship between traction load and insulation aging.
IEEE TRANSACTIONS ON POWER DELIVERY
(2021)
Article
Engineering, Electrical & Electronic
Tao Zhao, Yixin Tong, Yameng Zheng, Zhongyuan Zhang, Yunpeng Liu, Nijie Chao
Summary: This article studies the bubble effect of oil-paper insulation in natural ester. Experimental results show that bubbles aggregate in the gap between paper layers before entering the oil and the Initial Temperature of Bubble Escape (ITBE) is influenced by the number of winding insulation paper layers and the temperature rise rate. With the thermal aging of pressboard, ITBE increases.
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
(2022)
Article
Engineering, Electrical & Electronic
Hyungjin Yoon, George Chen, Ian L. Hosier
Summary: Mineral oil is commonly used as a dielectric liquid in HVDC converter transformers due to its excellent electrical insulation and cooling properties. However, the low biodegradability and high fire risk of mineral oil have sparked interest in natural ester oil as a potential alternative. This article investigates the impact of thermal aging on the space charge characteristics of natural ester oil-impregnated paper compared to mineral oil-impregnated paper. The results show that although natural ester oil leads to increased charge accumulation, it exhibits a higher dc breakdown voltage compared to mineral oil.
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
(2023)
Article
Engineering, Electrical & Electronic
Yusuf Cilliyuz, Yunus Bicen, Faruk Aras, Guzide Aydugan
Summary: The use of natural esters as an insulating liquid has become popular since the early 2000s. While studies emphasize their environmental friendliness and safety, there is still a need for further experimental verification regarding their effectiveness in delaying the aging of cellulosic insulation material.
INTERNATIONAL JOURNAL OF ELECTRICAL POWER & ENERGY SYSTEMS
(2021)
Article
Engineering, Electrical & Electronic
U. Mohan Rao, Issouf Fofana, Pawel Rozga, Patrick Picher, Dilip K. Sarkar, Rajan Karthikeyan
Summary: The focus of this study is on the oxidation aspects (gelling) of natural esters and its impact on the performance of transformer insulation systems. Even though natural esters are not suitable for breathing units, the scenario considered simulates a defect in the sealing system, allowing direct contact with atmospheric air. Commercially available natural ester liquids are thermally degraded under controlled aging conditions to observe the formation of sol and gel. The influence of sol and gel on the insulation is analyzed through physicochemical and electrical characterizations.
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
(2023)
Article
Engineering, Electrical & Electronic
Chuhan Geng, Jiefeng Liu, Heng Zhang, Chuying Liu, Yiwen Luo, Yiyi Zhang
Summary: The study demonstrates that increased moisture content in the paper accelerates the diffusion of furfural from paper to oil, and enhances the van der Waals force between oil and furfural.
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
(2022)
Article
Chemistry, Analytical
Ruimin Song, Weigen Chen, Ziyi Wang, Zhixian Zhang, Yingzhou Huang, Jianxin Wang
Summary: This study presents a novel approach using dual-enhanced Raman spectroscopy for sensing liquid components. The method employs a centrifugal extractor for selective enhancement of targeted components, and utilizes a liquid-core fiber to optimize laser transmission and Raman signal collection efficiency. The system demonstrates fast, stable, and adaptable performance, suitable for the detection of a wide range of liquid ingredients.
ANALYTICAL CHEMISTRY
(2023)
Article
Engineering, Electrical & Electronic
Jose E. Contreras, Josue Rodriguez, Carlos Gaytan
Summary: Currently, the use of new biodegradable dielectric liquids as an alternative to conventional mineral oil in transformers is being considered. However, the higher viscosity of ester liquids compared to mineral oil requires modifications in the impregnation process of insulation materials.
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
(2022)
Article
Engineering, Electrical & Electronic
Dongxin He, Haoxin Guo, Wenjie Gong, Zhe Xu, Qingquan Li, Shijie Xie
Summary: In this study, a test pulse matching circuit was developed to accurately match the test pulse with the polarity reversal polarization voltage and perform a multi-point rapid test of the space charge transient characteristics during polarity reversal. The influence of polarity reversal time on the charge residence characteristics of oil-paper insulation was compared and analyzed. The study of the charge residence characteristics and the dynamic charge behavior during the polarity inversion process has important guiding significance for clarifying the deterioration mechanism of the converter transformer oil-paper insulation under polarity-reversal electric field.
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
(2023)
Article
Computer Science, Information Systems
Xianhao Fan, Huan Zhao, Tengyue Sun, Jiefeng Liu, Yiyi Zhang, Yubo Zhang
Summary: The study used molecular dynamics simulations to investigate the diffusion mechanism of methanol molecules in paper-oil insulation system, revealing that the diffusion of methanol is faster in cellulose insulation compared to insulating oil. The presence of hydrogen bonds affects the diffusion rate of methanol molecules in cellulose insulation and insulating oil.
Article
Engineering, Electrical & Electronic
Qingchuan Xu, Shengkang Wang, Fuchang Lin, Hua Li
Summary: This article proposes a method for extracting the frequency spectroscopy of oil-immersed paper from the oil-paper insulation without the known insulation structure. By measuring the frequency spectroscopy of the oil-immersed paper under different conditions and constructing a transformer insulation model, accurate extraction of the frequency spectroscopy of oil-immersed paper can be achieved.
IEEE TRANSACTIONS ON INSTRUMENTATION AND MEASUREMENT
(2022)
Article
Polymer Science
Andres Montero, Belen Garcia, Carlos Lopez
Summary: The use of alternative insulating liquids in transformers is increasing worldwide due to their superior fire resistance and their ability to extend equipment lifespan. This study examined the aging process of Kraft paper retrofilled with a natural ester in the laboratory, revealing that retrofilling can slow down the degradation rate of solid insulation in transformers.
Article
Engineering, Electrical & Electronic
Qingguo Chen, Chunpeng Li, Song Cheng, Wei Sun, Minghe Chi, He Zhang
Summary: This article addresses the shortcomings in the assessment of the aging state of transformer cellulose insulation paper and proposes a basic model and a modified model. The accuracy and feasibility of the models are validated through verification experiments.
IEEE TRANSACTIONS ON DIELECTRICS AND ELECTRICAL INSULATION
(2022)
Article
Materials Science, Multidisciplinary
Chuan Luo, Chuan Li, Xiaorong Wan, Zhengang Zhao
Summary: Insulation paper is the main material for insulation in transformer windings, and its impact on natural heat dissipation is significant. This study analyzed the heat transfer characteristics of the insulation paper-oil contact surface and established a characteristic number equation with a roughness correction factor. An experimental apparatus based on similarity principle and modeling theory was designed to determine the convective heat transfer coefficient. The results have important implications for modeling the transformer space thermal circuit and solving hot-spot temperature issues.
