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4 pages, 508 KiB

Open AccessEditorial

High-Voltage Engineering and Applications in Our Modern Society

by Issouf Fofana and Bo Zhang

Energies 2022, 15(22), 8341; https://doi.org/10.3390/en15228341 - 8 Nov 2022

Viewed by 1289

Abstract

Electrical energy is polymorphic, with voltage levels varying between a few volts to MVs and frequencies from a few Hz to MHz [...] Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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Research

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11 pages, 3207 KiB

Open AccessArticle

Optical Diagnostic Characterization of the Local Arc on Contaminated Insulation Surface at Low Pressure

by Hao Yang, Haotian Zhang, Wen Cao, Xuanxiang Zhao, Ran Wen, Junping Zhao, Shengwu Tan and Pengchao Wang

Energies 2021, 14(19), 6116; https://doi.org/10.3390/en14196116 - 26 Sep 2021

Cited by 2 | Viewed by 1522

Abstract

Flashover of contaminated insulators is a major problem for power systems at high altitude. Laboratory experiments have shown that the optical diagnostic method can provide extensive information on the physical process of contamination flashover. In this paper, a study of the local arc [...] Read more.

Flashover of contaminated insulators is a major problem for power systems at high altitude. Laboratory experiments have shown that the optical diagnostic method can provide extensive information on the physical process of contamination flashover. In this paper, a study of the local arc on a wet polluted surface under low pressure by using the optical diagnostic method is presented. The thickness of the continuous spectrum, spectral line intensity and the spectral composition varies significantly in different stages of the local arc development. Thermodynamic parameters of the local arc (including electron temperature, electron density and conductivity) are obtained by analyzing the spectra. Both the electron temperature and the conductivity increase with the increase in leakage current and air pressure. Although the electron density does not change significantly with an increase in leakage current, it increases significantly with an increase in air pressure. The findings of this work could be used as supplementary information for the investigation of local arc parameters, thus providing a reliable reference for the calculation of contamination flashover at high altitude. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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16 pages, 5351 KiB

Open AccessArticle

Research on Mechanical Defect Detection and Diagnosis Method for GIS Equipment Based on Vibration Signal

by Liang He, Jie Yang, Ziwei Zhang, Zongwu Li, Dengwei Ding, Minghu Yuan, Rong Li and Mao Chen

Energies 2021, 14(17), 5507; https://doi.org/10.3390/en14175507 - 3 Sep 2021

Cited by 10 | Viewed by 1921

Abstract

Gas insulated switchgear equipment (GIS) is widely used in power system, and more attention has been paid to discharge defects than mechanical defects. However, since mechanical defects are a major cause of the failure in GIS, it is of great significance to carry [...] Read more.

Gas insulated switchgear equipment (GIS) is widely used in power system, and more attention has been paid to discharge defects than mechanical defects. However, since mechanical defects are a major cause of the failure in GIS, it is of great significance to carry out relevant research on mechanical defects. Detection and diagnosis methods of mechanical defects based on vibration signal are studied in this paper. Firstly, vibration mechanisms of GIS are analyzed. Due to structural differences between single phase insulated type GIS and three phase insulated type GIS, there are big differences in vibration mechanisms between the two types of GISs. Secondly, experimental research on mechanical defects is carried out based on a 110 kV GIS equipment and a self-developed vibration detection system; results show that mechanical defects can be diagnosed by analyzing signal amplitude, frequency spectrum and waveform distortion rate, and a large current is more beneficial for diagnosing mechanical defects. Lastly, field application has been carried out on 220 kV GIS equipment, and a poor contact defect is found, demonstrating that abnormal diagnosis can be realized by method proposed in this paper. Experimental research and field application demonstrate the feasibility and effectiveness of detection and diagnosis method for mechanical defects based on vibration signal and provide experience for subsequent engineering application. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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16 pages, 12733 KiB

Open AccessArticle

Study on Evaluation Method of Impulse Dispersion Performance of Grounding Device Using X-ray Imagining System

by Xiaoyan Han, Donghui Luo, Xin Zhang, Yongxing Cao, Yu Zhang and Gege Ban

Energies 2021, 14(16), 5124; https://doi.org/10.3390/en14165124 - 19 Aug 2021

Viewed by 1318

Abstract

When the lightning current enters the ground through the grounding system, the impulse dispersion performance can be observed by the phenomenon of soil spark discharge, which is fundamentally determined by the nearby soil. At present, engineers use an empirical formula to convert the [...] Read more.

When the lightning current enters the ground through the grounding system, the impulse dispersion performance can be observed by the phenomenon of soil spark discharge, which is fundamentally determined by the nearby soil. At present, engineers use an empirical formula to convert the soil spark discharge to the impulse coefficient of impulse grounding resistance. Therefore, there is no available quantitative analysis method to evaluate soil impulse dispersion performance. To solve this problem, this paper proposes an evaluation method for the impulse discharge efficiency of soil by using X-ray images, define V_I as the parameter, which is the ratio of the volume of the discharge area to the peak current. Then, the rationality and validity of the method are verified. Finally, the variation rules of impulse discharge efficiency are analyzed in different soils. Results show that the V_I can reflect the change rules of impulse dispersion performance more clearly under different soil conditions, and this parameter provides a new idea for enhancing the impulse dispersion performance of soil near the grounding electrode. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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11 pages, 7882 KiB

Open AccessArticle

Transient Voltage UWB Online Monitoring System for Insulation Failure Analysis and Fault Location of GIL

by Ziwei Zhang, Dengwei Ding, Liang He, Weidong Liu, Cuifen Bai and Junjun Liu

Energies 2021, 14(16), 4863; https://doi.org/10.3390/en14164863 - 9 Aug 2021

Cited by 4 | Viewed by 1671

Abstract

Transient voltage generated in ultra-high voltage (UHV) transmission system has a severe impact on the insulation state of gas-insulated transmission lines (GIL). In order to monitor the transient voltage process occurring in UHV GIL during operation, this paper constructs a transient voltage ultra-wideband [...] Read more.

Transient voltage generated in ultra-high voltage (UHV) transmission system has a severe impact on the insulation state of gas-insulated transmission lines (GIL). In order to monitor the transient voltage process occurring in UHV GIL during operation, this paper constructs a transient voltage ultra-wideband (UWB) online monitoring system based on capacitive voltage division. This system has been applied in an 1100 kilovolt (kV) GIL utility tunnel project. It can be used to analyze the characteristics of the recorded transient voltage waveforms for distinguishing different types of insulation failure. In this paper, through the case studies in time domain and time–frequency domain, the case of SF₆ gap breakdown and that of post insulator flashover have differentiated characteristics in instantaneous frequency. Additionally, a case of secondary discharge is successfully estimated through the time–frequency distribution of the transient voltage. In order to find the malfunctioning chamber of GIL rapidly, a two-terminal TW-based fault location method based on this monitoring system is developed in this paper. The case study validates the locating accuracy which directly support for shortening the maintenance time of GIL. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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14 pages, 11163 KiB

Open AccessArticle

Research on the Influence of Typical Soil Parameters on Critical Breakdown Field Strength and Residual Resistivity Based on Discharge Topography

by Donghui Luo, Jialun Li, Yongxing Cao, Bo Tan, Wei Li and Hanyu Wang

Energies 2021, 14(16), 4810; https://doi.org/10.3390/en14164810 - 6 Aug 2021

Viewed by 1285

Abstract

Partial discharge of soil occurs when a lightning current enters the ground, and the strength of partial discharge is closely related to the magnitude of its critical breakdown field strength. Therefore, how to accurately obtain the variation law of the typical soil critical [...] Read more.

Partial discharge of soil occurs when a lightning current enters the ground, and the strength of partial discharge is closely related to the magnitude of its critical breakdown field strength. Therefore, how to accurately obtain the variation law of the typical soil critical breakdown field strength and residual resistivity is the key to realizing the safe operation of the grounding devices and cables in the ground. This paper first selects a variety of typical soils to study the influence of various factors on the morphology of the discharge channel, and then studies the calculation methods of the soil critical breakdown field strength and residual resistivity under the introduction of different discharge channel morphologies and structures, and further discusses the reason why typical soil media factors have a small impact on the critical breakdown field. The experimental results show that under the same conditions, the critical breakdown field strengths of different soils from small to large are sand soil, loam soil and Yellow cinnamon soil. The largest ratio of residual resistivity to initial resistivity of the three soils is sand soil. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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13 pages, 3280 KiB

Open AccessArticle

Numerical Simulation on Charge Transport and DC Breakdown in Polyethylene-Based Micro-h-BN/Nano-SiO₂ with Filler Orientation Dependent Trap Energy

by Xuri Xu, Yu Gao, Jing Li, Zheng Song, Huicun Zhao and Tao Han

Energies 2021, 14(15), 4645; https://doi.org/10.3390/en14154645 - 30 Jul 2021

Cited by 4 | Viewed by 2159

Abstract

In order to improve the thermal conductivity and the insulation properties of polyethylene (PE) used as cable insulation under DC stress, hexagonal boron nitride (h-BN) and inorganic particles have been considered as micro-filler and nano-filler, respectively. As a 2D material, the orientation of [...] Read more.

In order to improve the thermal conductivity and the insulation properties of polyethylene (PE) used as cable insulation under DC stress, hexagonal boron nitride (h-BN) and inorganic particles have been considered as micro-filler and nano-filler, respectively. As a 2D material, the orientation of h-BN possibly affects the insulation properties of the polymer. It is important to understand the influence of the filler orientation on the insulation performance of the polymer. In this work, a numerical simulation has been performed to investigate the effect of orientation of micro-h-BN on charge transport and DC breakdown of PE-based micro/nano-composites and a comparison between the simulation result and previous literature data has been conducted. The h-BN was designated to be parallel, perpendicular to the normal sample surface vector (the direction of electric field in this work) or randomly distributed in the matrix, and the charge transport behavior and DC breakdown strength in the samples were discussed by using the bipolar charge transport (BCT) model. The results indicated that when the h-BN was perpendicular to the normal vector, the density of trapped charge was the largest and the DC breakdown strength was the highest among the three cases studied. It is suggested that the charge trapping/de-trapping processes and the electric field in the sample vary with the orientation of h-BN through tailoring the trap characteristics of the material. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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15 pages, 5576 KiB

Open AccessArticle

Autonomous Analysis of Infrared Images for Condition Diagnosis of HV Cable Accessories

by Lixiao Mu, Xiaobing Xu, Zhanran Xia, Bin Yang, Haoran Guo, Wenjun Zhou and Chengke Zhou

Energies 2021, 14(14), 4316; https://doi.org/10.3390/en14144316 - 17 Jul 2021

Cited by 5 | Viewed by 1983

Abstract

Infrared thermography has been used as a key means for the identification of overheating defects in power cable accessories. At present, analysis of thermal imaging pictures relies on human visual inspections, which is time-consuming and laborious and requires engineering expertise. In order to [...] Read more.

Infrared thermography has been used as a key means for the identification of overheating defects in power cable accessories. At present, analysis of thermal imaging pictures relies on human visual inspections, which is time-consuming and laborious and requires engineering expertise. In order to realize intelligent, autonomous recognition of infrared images taken from electrical equipment, previous studies reported preliminary work in preprocessing of infrared images and in the extraction of key feature parameters, which were then used to train neural networks. However, the key features required manual selection, and previous reports showed no practical implementations. In this contribution, an autonomous diagnosis method, which is based on the Faster RCNN network and the Mean-Shift algorithm, is proposed. Firstly, the Faster RCNN network is trained to implement the autonomous identification and positioning of the objects to be diagnosed in the infrared images. Then, the Mean-Shift algorithm is used for image segmentation to extract the area of overheating. Next, the parameters determining the temperature of the overheating parts of cable accessories are calculated, based on which the diagnosis are then made by following the relevant cable condition assessment criteria. Case studies are carried out in the paper, and results show that the cable accessories and their overheating regions can be located and assessed at different camera angles and under various background conditions via the autonomous processing and diagnosis methods proposed in the paper. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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12 pages, 5481 KiB

Open AccessArticle

DC Aging Mechanism of Co₂O₃-Doped ZnO Varistors

by Xia Zhao, Haibin Shen, Men Guo, Ziming He, Yupeng Li and Ran Wen

Energies 2021, 14(13), 4011; https://doi.org/10.3390/en14134011 - 3 Jul 2021

Cited by 5 | Viewed by 1830

Abstract

Lowered power loss and asymmetrically electrical parameters are reported in the DC aging of Co₂O₃-doped ZnO varistors in this paper. Based on the frequency domain dielectric responses of the pristine and degraded samples, the present study explores the roles [...] Read more.

Lowered power loss and asymmetrically electrical parameters are reported in the DC aging of Co₂O₃-doped ZnO varistors in this paper. Based on the frequency domain dielectric responses of the pristine and degraded samples, the present study explores the roles of point defects in the aging process via dielectric relaxations and their parameters. It is found that breakdown field increased more in the positive direction than the negative direction. Nonlinearity increased in the positive direction, whereas it decreased in the negative direction, and leakage current density increased more in the negative direction than the positive direction. Given the lowest migration energy of Zinc interstitial (Zn_i, 0.57 eV) and high oxygen ion conductivity in Bi₂O₃-rich phase, it is speculated that Zni and adsorbed oxygen (O_ad) migrate under DC bias, and then change the defect structure and the double Schottky barrier (DSB) at grain boundaries. As a result, the forward-biased barrier height gradually decreases more than the reverse-biased one. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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15 pages, 4467 KiB

Open AccessArticle

Research on the Non-Contact Pollution Monitoring Method of Composite Insulator Based on Space Electric Field

by Dongdong Zhang, Hong Xu, Jin Liu, Chengshun Yang, Xiaoning Huang, Zhijin Zhang and Xingliang Jiang

Energies 2021, 14(8), 2116; https://doi.org/10.3390/en14082116 - 10 Apr 2021

Cited by 12 | Viewed by 3223

Abstract

Through spatial electric field monitoring, it is expected to realize insulator pollution condition monitoring and contamination flashover warning in a non-contact way. Therefore, in this paper, the spatial electric field distribution characteristics of 110 kV composite insulators are simulated, where the effects of [...] Read more.

Through spatial electric field monitoring, it is expected to realize insulator pollution condition monitoring and contamination flashover warning in a non-contact way. Therefore, in this paper, the spatial electric field distribution characteristics of 110 kV composite insulators are simulated, where the effects of different surface states and their discharge levels on the spatial electric field of insulators are analyzed. On this basis, a non-contact monitoring method for composite insulator pollution based on the spatial electric field is proposed. The results show that there are significant differences in the spatial electric field of the composite insulator among three conditions, namely cleaning, pollution layer wetting, and dry band arcing. Increases of pollution layer wetting and dry band arcing would lead to an increase of the amplitude of the spatial electric field of the insulator. Verification experiments well indicated that it is feasible to identify the degree of pollution layer wetting as well as dry band arcing of the insulator string by fixed-point monitoring, the spatial electric field signal at the cross-strand of d = 0.5 m and directly opposite the last three positions. Research results can provide references for the online monitoring of overhead line polluted insulators and its flashover warning. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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15 pages, 19182 KiB

Open AccessArticle

Research on the Time-Domain Dielectric Response of Multiple Impulse Voltage Aging Oil-Film Dielectrics

by Chenmeng Zhang, Kailin Zhao, Shijun Xie, Can Hu, Yu Zhang and Nanxi Jiang

Energies 2021, 14(7), 1948; https://doi.org/10.3390/en14071948 - 1 Apr 2021

Viewed by 1662

Abstract

Power capacitors suffer multiple impulse voltages during their lifetime. With the multiple impulse voltage aging, the internal insulation, oil-film dielectric may deteriorate and even fail in the early stage, which is called accumulative effect. Hence, the time-domain dielectric response of oil-film dielectric with [...] Read more.

Power capacitors suffer multiple impulse voltages during their lifetime. With the multiple impulse voltage aging, the internal insulation, oil-film dielectric may deteriorate and even fail in the early stage, which is called accumulative effect. Hence, the time-domain dielectric response of oil-film dielectric with multiple impulse voltage aging is studied in this paper. At first, the procedure of the preparation of the tested samples were introduced. Secondly, an aging platform, impulse voltage generator was built to test the accumulative effect of capacitor under multiple impulse voltage. Then, a device was used to test the time-domain dielectric response (polarization depolarization current, PDC) of oil-film dielectric in different aging states. And finally, according to the PDC data, extended Debye model and characteristic parameters were obtained by matrix pencil algorithm identification. The results indicated that with the increase of impulse voltage times, the time-domain dielectric response of oil-film dielectric changed accordingly. The polarization current curve moved up gradually, the insulation resistance decreased when subjected to the repeated impulses. In frequency domain, the frequency spectrum of tan δ changed along with the impulse accumulation aging, especially at low frequency. At last, combined with the aging mechanism of oil-film dielectric under multiple impulse voltage, the test results were discussed. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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13 pages, 3548 KiB

Open AccessArticle

Three-Dimensional Electro-Thermal Analysis of a New Type Current Transformer Design for Power Distribution Networks

by Bingbing Dong, Yu Gu, Changsheng Gao, Zhu Zhang, Tao Wen and Kejie Li

Energies 2021, 14(6), 1792; https://doi.org/10.3390/en14061792 - 23 Mar 2021

Cited by 8 | Viewed by 2274

Abstract

In recent years, the new type design of current transformer with bushing structure has been widely used in the distribution network system due to its advantages of miniaturization, high mechanical strength, maintenance-free, safety and environmental protection. The internal temperature field distribution is an [...] Read more.

In recent years, the new type design of current transformer with bushing structure has been widely used in the distribution network system due to its advantages of miniaturization, high mechanical strength, maintenance-free, safety and environmental protection. The internal temperature field distribution is an important characteristic parameter to characterize the thermal insulation and aging performance of the transformer, and the internal temperature field distribution is mainly derived from the joule heat generated by the primary side guide rod after flowing through the current. Since the electric environment is a transient field and the thermal environment changes slowly with time as a steady field under the actual conditions, it is more complex and necessary to study the electrothermal coupling field of current transformer (CT). In this paper, a 3D simulation model of a new type design of current transformer for distribution network based on electric-thermal coupling is established by using finite element method (FEM) software. Considering that the actual thermal conduction process of CT is mainly by conduction, convection and radiation, three different kinds of boundary conditions such as solid heat transfer boundary condition, heat convection boundary condition and surface radiation boundary condition are applied to the CT. Through the model created above, the temperature rise process and the distribution characteristics of temperature gradient of the inner conductor under different current, different ambient temperatures and different core diameters conditions are studied. Meanwhile, the hottest temperature and the maximum temperature gradient difference are calculated. According to this, the position of weak insulation of the transformer is determined. The research results can provide a reference for the factory production of new type design of current transformer. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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15 pages, 4060 KiB

Open AccessArticle

Dielectric and AC Breakdown Properties of SiO₂/MMT/LDPE Micro–Nano Composites

by Hongtao Jiang, Xiaohong Zhang, Junguo Gao and Ning Guo

Energies 2021, 14(5), 1235; https://doi.org/10.3390/en14051235 - 24 Feb 2021

Cited by 9 | Viewed by 1976

Abstract

Low-density polyethylene (LDPE) is an important thermoplastic material which can be made into films, containers, wires, cables, etc. It is highly valued in the fields of packaging, medicine, and health, as well as cables. The method of improving the dielectric property of materials [...] Read more.

Low-density polyethylene (LDPE) is an important thermoplastic material which can be made into films, containers, wires, cables, etc. It is highly valued in the fields of packaging, medicine, and health, as well as cables. The method of improving the dielectric property of materials by blending LDPE with inorganic particles as filler has been paid much attention by researchers. In this paper, low-density polyethylene is used as the matrix, and montmorillonite (MMT) particles and silica (SiO₂) particles are selected as micro and nano fillers, respectively. In changing the order of adding two kinds of particles, a total of five composite materials were prepared. The crystallization behavior and crystallinity of five kinds of composites were observed, the ε_r and tanδ changes of each material were investigated with frequency and temperature, and the power frequency (50 Hz) AC breakdown performance of materials were measured. The differential scanning calorimetry (DSC) and X-ray diffraction (XRD) results show that the crystallinity of the composites is higher than that of LDPE. Experimental data of dielectric frequency spectra show that the dielectric constants of micro–nano composites and composites with added MMT particles are lower than LDPE, the dielectric loss of composites can be improved by adding MMT particles. The experimental data of dielectric temperature spectra show that the permittivity of SiO₂-MMT/LDPE is still at a low level under the condition of 20~100 °C. In terms of breakdown field strength, the SiO₂/LDPE composite material increased by about 17% compared with the matrix LDPE, and the breakdown field strength of the materials SiO₂-MMT/LDPE and MMT-SiO₂/LDPE increased by about 6.8% and 4.6%, respectively. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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19 pages, 6656 KiB

Open AccessArticle

A Novel Fault Location Method for Power Cables Based on an Unsupervised Learning Algorithm

by Mingzhen Li, Jialong Bu, Yupeng Song, Zhongyi Pu, Yuli Wang and Cheng Xie

Energies 2021, 14(4), 1164; https://doi.org/10.3390/en14041164 - 22 Feb 2021

Cited by 6 | Viewed by 1964

Abstract

In order to locate the short-circuit fault in power cable systems accurately and in a timely manner, a novel fault location method based on traveling waves is proposed, which has been improved by unsupervised learning algorithms. There are three main steps of the [...] Read more.

In order to locate the short-circuit fault in power cable systems accurately and in a timely manner, a novel fault location method based on traveling waves is proposed, which has been improved by unsupervised learning algorithms. There are three main steps of the method: (1) build a matrix of the traveling waves associated with the sheath currents of the cables; (2) cluster the data in the matrix according to its density level and the stability, using Hierarchical Density-Based Spatial Clustering of Applications with Noise (HDBSCAN); (3) search for the characteristic cluster point(s) of the two branch clusters with the smallest density level to identify the arrival time of the traveling wave. The main improvement is that high-dimensional data can be directly used for the clustering, making the method more effective and accurate. A Power System Computer Aided Design (PSCAD) simulation has been carried out for typical power cable circuits. The results indicate that the hierarchical structure of the condensed cluster tree corresponds exactly to the location relationship between the fault point and the monitoring point. The proposed method can be used for the identification of the arrival time of the traveling wave. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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17 pages, 7073 KiB

Open AccessArticle

Study on Structural Parameters and Analysis Method of Soil Successive Impulse Discharge Channel

by Donghui Luo, Yongxing Cao, Yu Zhang, Shijun Xie, Chenmeng Zhang and Shuping Cao

Energies 2021, 14(4), 877; https://doi.org/10.3390/en14040877 - 8 Feb 2021

Cited by 6 | Viewed by 1956

Abstract

The transient analysis model of grounding systems is an important tool to analyze the lightning characteristics of grounding devices. When lightning enters the soil through the grounding device, there is a centralized discharge channel. The spatial structure of the discharge channel in the [...] Read more.

The transient analysis model of grounding systems is an important tool to analyze the lightning characteristics of grounding devices. When lightning enters the soil through the grounding device, there is a centralized discharge channel. The spatial structure of the discharge channel in the soil has a great effect on the accuracy of the transient analysis model of the soil impulse discharge. In this paper, based on the gray information analysis method, the volume of successive impulse discharge channels in the ground under various currents and soil conditions is calculated, and the changing law with time interval is analyzed. According to the experimental results, an analysis method of the model considering the discharge channel structure is proposed, and an example is analyzed. The results show that the time interval has an effect on the volume of the discharge channel. In a certain range, the volume of the channel increases with the time interval of successive impulse discharges. Taking the critical breakdown electric field strength as the judgment condition and the residual resistivity as the variable, the development process of the discharge channel can be simulated. The calculated results of the model are close to the experimental results. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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12 pages, 3620 KiB

Open AccessArticle

Pattern Recognition of Development Stage of Creepage Discharge of Oil–Paper Insulation under AC–DC Combined Voltage Based on OS-ELM

by Fubao Jin, Shanjun Zhang and Yuanxiang Zhou

Energies 2021, 14(3), 552; https://doi.org/10.3390/en14030552 - 21 Jan 2021

Viewed by 1585

Abstract

The recognition of the creepage discharge development process of oil–paper insulation under AC–DC combined voltage is the basis for fault monitoring and diagnosis of converter transformers; however, only a few related studies are available. In this study, the AC–DC combined voltage with a [...] Read more.

The recognition of the creepage discharge development process of oil–paper insulation under AC–DC combined voltage is the basis for fault monitoring and diagnosis of converter transformers; however, only a few related studies are available. In this study, the AC–DC combined voltage with a ratio of 1:1 was used to develop a recognition method for the creepage discharge development process of an oil–paper insulation under a cylinder–plate electrode structure. First, the pulse current method was used to collect the discharge signals in the creepage discharge development process. Then, 24 characteristic parameters were extracted from four types of creepage discharge characteristic spectra after dimensionality reduction. Finally, based on the online sequential extreme learning machine (OS-ELM) algorithm, these characteristic parameters were used to recognize the development stage of the creepage discharge of the oil–paper insulation. The results showed that when the size of the sample training set used in the OS-ELM algorithm is close to the number of hidden layer neurons, a high recognition accuracy can be obtained, and the type of activation function has little influence on the recognition accuracy. Four stages of the creepage discharge development process were recognized using the OS-ELM algorithm; the trend was the same as that of the characteristic parameters of the entire creepage discharge development process. The recognition accuracy was 91.4%. The algorithm has a high computing speed and high accuracy and can train data in batches. Therefore, it can be widely used in the field of online monitoring and evaluation of electrical equipment status. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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Review

Jump to: Editorial, Research

12 pages, 1452 KiB

Open AccessReview

Recent Development of Two Alternative Gases to SF₆ for High Voltage Electrical Power Applications

by John Owens, Ang Xiao, Jason Bonk, Michael DeLorme and Agnes Zhang

Energies 2021, 14(16), 5051; https://doi.org/10.3390/en14165051 - 17 Aug 2021

Cited by 38 | Viewed by 5155

Abstract

For many years, SF₆ has been the preferred dielectric medium in electrical power applications, particularly in high voltage gas-insulated equipment. However, with the recognition that SF₆ has an extremely long atmospheric lifetime and very high global warming potential, governments have pursued [...] Read more.

For many years, SF₆ has been the preferred dielectric medium in electrical power applications, particularly in high voltage gas-insulated equipment. However, with the recognition that SF₆ has an extremely long atmospheric lifetime and very high global warming potential, governments have pursued emission reductions from gas-filled equipment. The electrical power industry has responded to this environmental challenge applying SF₆-free technologies to an expanding range of applications which have traditionally used SF₆, including gas-insulated switchgear, gas-insulated circuit breakers and gas-insulated lines or bus bars. Some of these SF₆-free solutions include gas mixtures containing fluorinated compounds that have low climate impact, among them, a fluoronitrile and a fluoroketone developed as 3M™ Novec™ 4710 Insulating Gas and 3M™ Novec™ 5110 Insulating Gas, respectively. Both fluoronitrile and fluoroketone mixtures are successfully used in gas-insulated equipment currently operating on the grid where they reduce greenhouse gas emissions by more than 99% versus SF₆. This paper reviews these leading components of alternative-gas mixtures with updates on the performance, safety and environmental profiles in electrical power applications. Full article

(This article belongs to the Special Issue Selected Papers from 2020 IEEE International Conference on High Voltage Engineering (ICHVE 2020))

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