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1. Research on Short-Circuit Withstand Capability of Transformer Considering the Mechanical Accumulation Characteristics of Insulation Materials

Author

Liao, Zhihao, Li, Zhongxiang, Ma, Zhiqin, Zhou, Dan, Shu, Xiang, Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Li, Yong, Series Editor, Liang, Qilian, Series Editor, Martín, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Oneto, Luca, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zamboni, Walter, Series Editor, Tan, Kay Chen, Series Editor, Yang, Qingxin, editor, Li, Zewen, editor, and Luo, An, editor

Published
2024
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2. Calculation and Analysis of Temperature Field Characteristics of Power Transformers in Oil During Short Circuit Processes

Author

Cai, Linglong, Tai, Bin, Ma, Zhiqin, Jin, Yuhui, Jiang, Shuo, Li, Zhongxiang, Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Li, Yong, Series Editor, Liang, Qilian, Series Editor, Martín, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Oneto, Luca, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zamboni, Walter, Series Editor, Tan, Kay Chen, Series Editor, Yang, Qingxin, editor, Li, Zewen, editor, and Luo, An, editor

Published
2024
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3. Refinement of Short-Circuit Withstand Capability Calculation for Power Transformers and Application in Fault Analysis

Author

Jin, Yuhui, Yang, Xian, Ma, Zhiqin, Lin, Chunyao, Liu, Jiangnan, Li, Zhongxiang, Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Li, Yong, Series Editor, Liang, Qilian, Series Editor, Martín, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Oneto, Luca, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zamboni, Walter, Series Editor, Tan, Kay Chen, Series Editor, Yang, Qingxin, editor, Li, Zewen, editor, and Luo, An, editor

Published
2024
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4. Simulation of Mechanical Characteristics of Contact Group During the Switching Process of On-Load Tap Changer

Author

Ma, Zhiqin, Jiang, Danyu, Zhou, Dan, Cai, Linglong, Hong, Ziyang, Liao, Zihao, Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Li, Yong, Series Editor, Liang, Qilian, Series Editor, Martín, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Oneto, Luca, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zamboni, Walter, Series Editor, Zhang, Junjie James, Series Editor, Tan, Kay Chen, Series Editor, Dong, Xuzhu, editor, and Cai, Li Cai, editor

Published
2024
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7. Design and Application of Non-contact Voltage Acquisition Module for Dry Air Core Reactor

Author

Ma, Zhiqin, Wang, Gang, Jiang, Danyu, Yang, Xian, Shu, Xiang, Jiang, Shuo, Angrisani, Leopoldo, Series Editor, Arteaga, Marco, Series Editor, Chakraborty, Samarjit, Series Editor, Chen, Jiming, Series Editor, Chen, Shanben, Series Editor, Chen, Tan Kay, Series Editor, Dillmann, Rüdiger, Series Editor, Duan, Haibin, Series Editor, Ferrari, Gianluigi, Series Editor, Ferre, Manuel, Series Editor, Jabbari, Faryar, Series Editor, Jia, Limin, Series Editor, Kacprzyk, Janusz, Series Editor, Khamis, Alaa, Series Editor, Kroeger, Torsten, Series Editor, Li, Yong, Series Editor, Liang, Qilian, Series Editor, Martín, Ferran, Series Editor, Ming, Tan Cher, Series Editor, Minker, Wolfgang, Series Editor, Misra, Pradeep, Series Editor, Mukhopadhyay, Subhas, Series Editor, Ning, Cun-Zheng, Series Editor, Nishida, Toyoaki, Series Editor, Oneto, Luca, Series Editor, Panigrahi, Bijaya Ketan, Series Editor, Pascucci, Federica, Series Editor, Qin, Yong, Series Editor, Seng, Gan Woon, Series Editor, Speidel, Joachim, Series Editor, Veiga, Germano, Series Editor, Wu, Haitao, Series Editor, Zamboni, Walter, Series Editor, Zhang, Junjie James, Series Editor, Tan, Kay Chen, Series Editor, Dong, Xuzhu, editor, Yang, Qingxin, editor, and Ma, Weiming, editor

Published
2023
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11. Analysis of interturn short circuit in regulating winding of power transformer based on field-circuit coupling.

Author

Fei, Liangchang, Ma, Zhiqin, Cai, Linglong, Zhou, Dan, Shu, Xiang, Liao, Zihao, Lin, Chunyao, and Li, Xianqiang

Subjects
SHORT circuits, ELECTROMAGNETIC fields, POWER transformers, ELECTROMAGNETIC forces, WIND power, MAGNETIC flux density, ELECTRIC transients
Abstract

The interturn short circuit fault is one of the common faults in power transformers. At present, research on interturn short circuit faults focuses on high, medium, and low voltage windings, while there is relatively little research on interturn short circuit in regulating windings. Specifically, there is a lack of reported studies on the transient electromagnetic processes, magnetic field distribution, and electromagnetic force characteristics of interturn short circuits in regulating windings unconnected to the circuit. This study presents an actual fault scenario involving interturn short circuits occurring in the untapped portion of the regulating windings of a specific power transformer. A field-circuit coupled model was established to analyze the transient electromagnetic processes during the fault, and the model's effectiveness was validated by comparing its results with actual fault recording data. Additionally, the magnetic field distribution and electromagnetic force characteristics during the fault were analyzed, and discussions were carried out regarding various ratios of short-circuit turns in the regulating windings. The results indicate that even when an interturn short circuit occurs in the portion of the regulating winding that is not connected to the circuit, the current in the short-circuited turns can reach several tens of times the rated value. Additionally, the leakage magnetic field and the electromagnetic force experienced by the short-circuited ring also increase significantly. The short-circuit ratio has a significant impact on the current of the short-circuited ring, leakage magnetic field intensity, and electromagnetic force. This study contributes to a better understanding of the impact of interturn shortcircuit faults in the untapped portion of the regulating windings, offering crucial technical support for fault diagnosis and prevention of power transformers. [ABSTRACT FROM AUTHOR]

Published
2024
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16. A Method for Identifying External Short-Circuit Faults in Power Transformers Based on Support Vector Machines.

Author

Du, Hao, Cai, Linglong, Ma, Zhiqin, Rao, Zhangquan, Shu, Xiang, Jiang, Shuo, Li, Zhongxiang, and Li, Xianqiang

Subjects
SUPPORT vector machines, POWER transformers, ELECTRIC power, POWER resources, MAGNETIC flux leakage, KERNEL functions
Abstract

Being a vital component of electrical power systems, transformers significantly influence the system stability and reliability of power supplies. Damage to transformers may lead to significant economic losses. The efficient identification of transformer faults holds paramount importance for the stability and security of power grids. The existing methods for identifying transformer faults include oil chromatography analysis, temperature assessment, frequency response analysis, vibration characteristic examination, and leakage magnetic field analysis. These methods suffer from limitations such as limited sensitivity, complexity in operation, and a high demand for specialized skills. In this paper, we propose a method to identify external short-circuit faults of power transformers based on fault recording data on short-circuit currents. It involves analyzing the current signals of various windings during faults, extracting appropriate features, and utilizing a classification algorithm based on a support vector machine (SVM) to determine fault types and locations. The influence of different kernel functions on the classification accuracy of SVM is discussed. The results indicate that this method can proficiently identify the type and location of external short-circuit faults in transformers, achieving an accuracy rate of 98.3%. [ABSTRACT FROM AUTHOR]

Published
2024
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26. Field Experiences on Oil Ageing Characteristics of Transformer On-Load Tap Changers

Author

Jiang Shuo, Xian Yang, Jiang Danyu, Zhou Dan, and Ma Zhiqin

Subjects
Leak, Materials science, Petroleum engineering, 010405 organic chemistry, Group composition, 010402 general chemistry, 01 natural sciences, Tap changer, 0104 chemical sciences, law.invention, Field experience, law, Breakdown voltage, Research Object, Transformer, Water content
Abstract

On-Ioad tap changer (OLTC), extinguishing arc with oil, is one of the important components of transformer. Combined many years of field experience, physicochemical properties and electrical properties of oil deteriorate under the combined action of electric, thermal and mechanical agitation. Taking the oil for OLTC in 110kV transformers as research object, ageing characteristics of oil in different operation periods, such as water content, breakdown voltage and oil group composition, were studied comparatively. The results show that the decrease of breakdown voltage is determined by the water content in oil, operation time and operation times of OLTC. Furthermore, the low content of aromatic carbon in the oil is also cause the breakdown voltage to decrease obviously, but the change of water content is small. The water content undulates during operation. The leak of sealed for OLTC is the main factor that makes the breakdown voltage and the water content greatly change.

Published
2020

27. Research on Fault Diagnosis of Oil-Paper Insulated Bushing Based on Frequency Domain Dielectric Spectrum

Author

Xian Yang, Jiang Danyu, Ma Zhiqin, Jin Yuhui, Cai Linglong, and Shu Xiang

Subjects
Materials science, Dielectric spectrum, law, Bushing, Electrical equipment, Frequency domain, Acoustics, Fault (power engineering), Transformer, humanities, Radio spectrum, Dielectric spectroscopy, law.invention
Abstract

As an important component of power transformer, transformer bushing cause thirty percent of transformer accidents. It is difficult to find defects in transformer bushing in advance because of the lack of on-site inspection methods. Frequency domain dielectric spectroscopy is widely used in the field of insulation evaluation of electrical equipment because of its frequency bandwidth and rich information. However, the frequency domain dielectric spectroscopy in the inspection of oil-paper insulated transformer bushing is affected by lacking substation test case and diagnostic criteria. In this paper, a dielectric response model of the transformer bushing is established to reveal the different defect types corresponding to the test curves in different frequency bands. In the low frequency band which is less than 0.0lHz, it is reflecting the water content of bushing. In the middle frequency band which is between 0.0lHz to 100Hz, it is reflecting the aging of bushing. Several cases of substation bushing defects detected by frequency domain dielectric spectroscopy have verified the above results. It is difficult to propose uniform fault diagnosis criteria for the frequency domain dielectric spectrum of transformer bushing which is affected by the structure and type. Based on a large number of substation case studies, a defect diagnosis criterion based on Frechet similarity method is proposed in this paper, which is universal for different structures and different types of bushing.

Published
2020

29. Experience Gained in Fault Diagnosis and Tear-down Analysis of Transformer Bushings

Author

Cai Linglong, Zhou Dan, Lin Chunyao, Ma Zhiqin, Ouyang Xudong, Ou Xiaobo, and Xian Yang

Subjects
Computer science, law, Frequency domain spectroscopy, Bushing, Dissolved gas analysis, Partial discharge, Diagnostic test, Key features, Transformer, Reliability engineering, law.invention
Abstract

As an essential component of power transformer, transformer bushing’s reliable operation does not only impact the safety of transformer itself but also other equipment located nearby. To prevent bushing failures, it is therefore important to routinely assess bushing insulation and pin-point the potential problem as early as possible. In this paper, fault diagnosis and tear-down analysis of five 500kV oil-impregnated paper (OIP) transformer bushings are presented. Results of different field and laboratory diagnostic tests are discussed and compared. Key features of partial discharge-led defect with x-wax deposits are analysed. The effectiveness of adopting frequency domain spectroscopy (FDS) in combination with dissolved gas analysis (DGA) as supplementary field diagnostic test is then demonstrated.

Published
2019

30. Internal Oil Flow of Transformer Based on Multiphysics Coupling Characteristic Analysis

Author

Ma Zhiqin, Jiang Danyu, Xian Yang, Zhou Dan, and Jingli Dou

Subjects
Computer simulation, Computer science, business.industry, Inner core, Mechanical engineering, Gas protection, Multiphysics coupling, Magnetic field, law.invention, Electric power system, Software, law, Transformer, business
Abstract

The misoperation of gas protection in transformer out-of-zone faults will seriously affect the security and stability level of power system. In this paper, the oil flow characteristics in transformer under different operating conditions are analyzed by multi-physical field coupling simulation. The principle of common gas protection relays and their causes of misoperation are analyzed. A numerical simulation model of multi-physical field inside transformer is established. The inner core and winding of transformer are modeled and simulated by ANSYS Maxwell 3D and ANSYS Fluent software. The variation of multiphysical field in normal operation, out-of-zone fault and in-zone fault of transformer is obtained. The changes of magnetic field and electromagnetic stress, oil flow and outlet pressure of inner winding and core of transformer are analyzed. This study provides a new basis for formulating measures to improve the reliability of gas protection operation.

Published
2019

37. Investigation of characteristic parameters for condition evaluation of transformer oil-paper insulation using frequency domain spectroscopy.

Author

Wang, Youyuan, Gao, Jun, Liao, Ruijin, Zhang, Yiyi, Hao, Jian, Liu, Jiefeng, and Ma, Zhiqin

Subjects
FREQUENCY-domain analysis, INSULATING materials, POWER transformers, DIELECTRIC materials, MOISTURE
Abstract

Frequency domain spectroscopy (FDS) is employed to evaluate the moisture content and aging state of oil-paper insulation in power transformers. Oil-paper insulation samples with different moisture content and aging states were primarily prepared in the laboratory. A method was proposed based on a study of the influence of the aging state and moisture content on the frequency domain dielectric property of oil-paper insulation. This method distinguishes the influence of moisture content and aging state on FDS through the imaginary part of complex relative permittivity ( εr″). Relevant characteristic parameters that characterize the moisture content and aging state of oil-impregnated pressboards were also extracted. Results reveal that the extracted characteristic parameters are sensitive to moisture content in the range of 10−1 Hz to 101 Hz and in the range of 10−3 Hz to 10−1 Hz for the aging state. An obvious exponential relationship exists between the maximum values of the characteristic parameters in the given frequency ranges and degree of polymerization and moisture content. The new method can be utilized for a non-destructive condition assessment of oil-paper insulation of transformers. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Published
2015
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39. Quantitative analysis ageing status of natural ester-paper insulation and mineral oil-paper insulation by polarization/depolarization current.

Author

Hao, Jian, Liao, Ruijin, Chen, George, Ma, Zhiqin, and Yang, Lijun

Subjects
QUANTITATIVE research, ESTERS, ELECTRIC insulators & insulation, MINERAL oils, POLARIZATION (Electricity), ELECTRIC currents, PHYSICS experiments, TEMPERATURE effect
Abstract

Polarization and Depolarization Current (PDC) technique is an effective tool to assess the condition of oil-paper insulation system in power transformers. So far the PDC behaviors of mineral oil-paper insulation have been widely investigated. However, with the increasing number of transformer choosing natural ester as its insulation oil, it is important to investigate the PDC characteristics of natural ester-paper insulation to see whether the PDC technique can also be used to assess the condition of new insulation system using natural ester in transformers accurately. In this research, natural esterpaper insulation sample and mineral oil-paper insulation sample were subjected to thermally accelerated ageing experiment at 110°C for 120 days. The PDC characteristics of natural ester-paper insulation sample and mineral oil-paper insulation sample were compared over the ageing process. A new method for assessing the ageing condition of the oil-paper insulation in terms of the depolarization charge quantity was proposed. Results show that the polarization/depolarization current of natural ester-paper insulation sample is higher than that of mineral oil-paper insulation sample with the same ageing intervals. The depolarization charge quantity of both kinds of oil-paper insulation sample is very sensitive to their ageing conditions. There is an exponential relation between the stable depolarization charge quantity of both kinds of oil-paper insulation sample and the degree of polymerization (DP) of paper. The depolarization charge quantity can be used to predict the ageing condition of oil-paper insulation providing the measurement temperature is kept the same. [ABSTRACT FROM PUBLISHER]

Published
2012
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40. [Clinical analysis of patients with cardiopulmonary resuscitation in emergency department and establishment of prediction model of restoration of spontaneous circulation in hospital].

Author

Liu J, Duan X, Ma Z, Fu H, Wu B, and Wang Q

Subjects
Humans, Retrospective Studies, Case-Control Studies, Emergency Service, Hospital, Hospitals, Albumins, Cardiopulmonary Resuscitation methods, Heart Arrest therapy
Abstract

Objective: To screen the independent influencing factors of restoration of spontaneous circulation (ROSC) in patients after cardiopulmonary resuscitation (CPR) and establish a predictive model, and explore its clinical value., Methods: A retrospective case control study was conducted. The clinical data of cardiac arrest patients admitted to the emergency department of Tangdu Hospital of Air Force Military Medical University and received CPR from January to July 2023 were analyzed, including general information, blood biochemical indicators, main cause of cardiac arrest, whether it was defibrillation rhythm, duration from admission to CPR, and whether ROSC was achieved. The clinical data between the patients whether achieved ROSC or not were compared. The binary multivariate Logistic regression analysis was used to screen the independent influencing factors of ROSC in in-hospital CPR patients. According to the above influencing factors, the ROSC prediction model was established, and the receiver operator characteristic curve (ROC curve) was drawn to evaluate the predictive value of the model for ROSC., Results: A total of 235 patients who received CPR in the emergency department were enrolled, including 153 cases (65.11%) of in-hospital CPR and 82 cases (34.89%) of out-of-hospital CPR. The ROSC ratio was 30.21% (71/235). Among all patients, the majority were aged 61-80 years [40.43% (95/235)], and cardiogenic disease was the main cause of cardiac arrest [32.77% (77/235)]. Among 153 patients with in-hospital CPR, 89 were non-ROSC and 64 were ROSC with ROSC rate of 41.83%. Compared with the non-ROSC group, the patients in the ROSC group had lower blood lactic acid (Lac), N-terminal pro-brain natriuretic peptide (NT-proBNP), Lac/albumin (Alb) ratio (LAR), and ratio of non-defibrillation rhythm [Lac (mmol/L): 5.50 (2.33, 9.65) vs. 7.10 (3.50, 13.35), NT-proBNP (μg/L): 0.87 (0.20, 8.68) vs. 3.00 (0.58, 20.17), LAR: 0.14 (0.07, 0.29) vs. 0.19 (0.10, 0.43), non-defibrillation rhythm ratio: 68.75% (44/64) vs. 93.26% (83/89)], higher actual base excess (ABE) and Alb [ABE (mmol/L): -3.95 (-12.75, 0.23) vs. -7.50 (-13.50, -3.35), Alb (g/L): 38.13±7.03 vs. 34.09±7.81], and shorter duration from admission to CPR [hours: 3.25 (1.00, 14.00) vs. 8.00 (2.00, 27.50)], the differences were statistically significant (all P < 0.05). Binary multivariate Logistic regression analysis showed that LAR [odds ratio (OR) = 0.037, 95% confidence interval (95%CI) was 0.005-0.287], non-defibrillation rhythm (OR = 0.145, 95%CI was 0.049-0.426), and duration from admission to CPR (OR = 0.984, 95%CI was 0.972-0.997) were independent influencing factors for ROSC in hospitalized CPR patients (all P < 0.05). Based on the above influencing factors, a ROSC prediction model was constructed through regression analysis results. The ROC curve analysis showed that the area under the ROC curve (AUC) for predicting ROSC in in-hospital CPR patients was 0.757 (95%CI was 0.680-0.834), Yoden index was 0.429, sensitivity was 76.6%, and specificity was 66.3., Conclusions: LAR, non-defibrillation rhythm and duration from admission to CPR were independent influencing factors for ROSC in patients with in-hospital CPR. The ROSC prediction model established based on the above influencing factors has a good predictive value for ROSC of CPR patients in hospital, and can guide clinicians to evaluate the prognosis of patients through relevant indicators as early as possible.

Published
2024
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