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Recent Developments in Theories, Technologies and Applications of HVDC Insulation Systems

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A special issue of Energies (ISSN 1996-1073). This special issue belongs to the section "F6: High Voltage".

Deadline for manuscript submissions: closed (28 March 2024) | Viewed by 16008

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Special Issue Editors

Dr. Jiaming Yang

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Guest Editor

Key Laboratory of Engineering Dielectrics and Its Application, Ministry of Education, Harbin University of Science and Technology, Harbin 150080, China
Interests: high voltage cable insulation; space charge; environmentally friendly insulating materials

Dr. Shihang Wang

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Guest Editor

School of Electrical engineering, Xi’an Jiaotong University, 28 West Xianning Road, Xi’an 710049, China
Interests: high voltage cable insulation, nanocomposite insulating materials, Insulation damage under complex voltage waveform

Dr. Yalin Wang

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Guest Editor

1. Department of Electrical Engineering, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China
2. Key Laboratory of Control of Power Transmission and Conversion (SJTU), Ministry of Education, Shanghai 200240, China
Interests: charge transport of insulating materials; state detection and intelligent diagnosis of power equipment; insulation design and condition monitoring of electric aircraft propulsion motor; insulation; reliability of power electronics package
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Special Issue Information

Dear Colleagues,

With the large-scale development and utilization of renewable energy, high-voltage direct current (HVDC)transmission technology has developed rapidly. The development of HVDC power systems puts forward more requirements on the insulation system. Under the high DC electric field, space charge accumulates in the bulk or on the surface of the insulator, leading to distortion in the electric field and insulation aging. Especially when the operating voltage inverses or with the presence of a large temperature gradient, the insulation system is more likely to fail prematurely. Therefore, the suppression of the electric field distortion, improving the anti-aging performance, and prolonging the insulation lifetime are the key issues of the HVDC insulation system. In recent years, environmentally friendly insulating materials have attracted widespread attention. Before they can be applied in HVDC insulation systems, a synergistic optimization of heat resistance properties, mechanical properties, and dielectric properties needs to be achieved, as well as endurance under extreme electrical and thermal shocks such as overvoltage and short-circuit faults. This Special Issue aims to jointly discuss new theories, new technologies, and new applications of HVDC insulation systems, and promote the development of insulation technology. This Special Issue plans to set up the following columns and sincerely invites scholars, researchers, and professionals who are engaged in related technical research to contribute.

Topics of interest for publication include (but are not limited to) the following:

New HVDC insulating materials, including nanocomposite insulating materials, functional molecular-modified insulating materials, graded insulating materials, nonlinear insulating materials, and environmentally friendly insulating materials;
Charge transport characteristics in HVDC insulating materials, including carrier transport model and numerical calculation method, space charge characteristics under coupling electric and thermal fields, electric conduction characteristics, etc.;
Flashover behavior of gas-insulated switchgear and outdoor insulation;
Aging behavior of HVDC insulating materials;
Design of new HVDC insulation system and insulation structure;
The regulation and optimization of the design of the electric field in the HVDC insulation system;
Monitoring and diagnosis of the insulation status of HVDC power equipment;
New characterization technology of structure and performance of HVDC insulation.

Dr. Jiaming Yang
Dr. Shihang Wang
Dr. Yalin Wang
Guest Editors

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Keywords

HVDC insulation system
new materials
DC dielectric characteristics
aging
design
monitoring and diagnosis
new characterization technology

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Published Papers (9 papers)

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Research

14 pages, 4260 KiB

Open AccessArticle

Blending Modification Technology of Insulation Materials for Deep Sea Optoelectronic Composite Cables

by Shuhong Xie, Zhenzhen Chen, Zhiyu Yan, Xingyu Qiu, Ming Hu, Chunfei Gu, Xindong Zhao and Kai Wang

Energies 2024, 17(4), 820; https://doi.org/10.3390/en17040820 - 8 Feb 2024

Cited by 1 | Viewed by 965

Abstract

The insulation layer of deep-sea optoelectronic composite cables in direct contact with high-pressure and highly corrosive seawater is required for excellent water resistance, environmental stress cracking resistance (ESCR), and the ability to withstand high DC voltage. Although high-density polyethylene (HDPE) displays remarkable water resistance, it lacks sufficient resistance to environmental stress cracking (ESCR). This article is based on a blend modification approach to mixing HDPE with different vinyl copolymer materials (cPE-A and cPE-B). The processing performance and mechanical properties of the materials are evaluated through rheological and mechanical testing. The materials’ durability in working environments is assessed through ESCR tests and water resistance experiments. Ultimately, the direct current electrical performance of the materials is evaluated through tests measuring space charge distribution, direct current resistivity, and direct current breakdown strength. The results indicate that, in the polyethylene blend system, the rheological properties and ESCR characteristics of HDPE/cPE-A composite materials did not show significant improvement. Further incorporation of high melt index linear low-density polyethylene (LLDPE) material not only meets the requirements of extrusion processing but also exhibits a notable enhancement in ESCR performance. Meanwhile, copolymerized polyethylene cPE-B, with a more complex structure, proves effective in toughening HDPE materials. The material’s hardness significantly decreases, and when incorporating cPE-B at a level exceeding 20 phr, the composite materials achieve excellent ESCR performance. In a simulated seawater environment at 50 MPa, the water permeability of all co-modified composite materials remained below 0.16% after 120 h. The spatial charge distribution and direct current resistivity characteristics of the HDPE, cPE-A, and LLDPE composite systems surpassed those of the HDPE/cPE-B materials. However, the HDPE/cPE-B composite system exhibited superior dielectric strength. The application of composite materials in deep-sea electro–optical composite cables is highly promising. Full article

(This article belongs to the Special Issue Recent Developments in Theories, Technologies and Applications of HVDC Insulation Systems)

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18 pages, 7308 KiB

Open AccessArticle

Improved Isothermal Relaxation Current Measurement Based on Isolated Circuit for Nondestructive Evaluation of High-Voltage Cable Insulation

by Huangjing Gu, Yongkang Zhang, Bin Shen, Ziqi Liu, Yunjie Zhou, Xiaodi Wang, Xinyang Zhu and Yalin Wang

Energies 2023, 16(23), 7892; https://doi.org/10.3390/en16237892 - 3 Dec 2023

Cited by 1 | Viewed by 1291

Abstract

The Isothermal Relaxation Current (IRC) method, as a non-destructive condition evaluation method based on insulation dielectric response, has been applied in the maintenance of power cables. However, the relaxation current is usually conducted through the outer shield of the high-voltage wire, which will introduce the extra depolarization current into the test circuit, affecting the accuracy of the test results. Furthermore, most IRC cable measurements are single-phase, which means depolarization currents are measured for each cable separately. In order to improve the measurement accuracy and efficiency of the IRC test, this paper proposes an improved IRC measurement method based on an isolated circuit, which discharges the interference current from the high-voltage insulated wire back to the earth and reduces the measurement error of depolarization current. At the same time, a three-phase IRC simultaneous test system is designed, and the control software is developed. Furthermore, by verifying the accuracy of the test system, the independence of the single-phase circuit and the consistency of the three-phase circuit is achieved. The effect of depolarization time and temperature on the relaxation current is then explored to determine the suitable parameter of the IRC test. Finally, the IRC system is used to evaluate the aging state of 10 kV cables with various aging conditions in the air and water for the longest 12 months. Critical parameters such as aging factor and time constants are compared to investigate the aging characteristics of tested cables with various aging conditions in the air and water. The proposed method and research conclusions can provide helpful references for the non-destructive condition evaluation for high-voltage cable insulation. Full article

(This article belongs to the Special Issue Recent Developments in Theories, Technologies and Applications of HVDC Insulation Systems)

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12 pages, 3604 KiB

Open AccessArticle

Study on Nonlinear Dielectric Properties of Micro Silica

by Yucui Xue, Wenmin Guo, Yunlong Sun, Zhonghua Li, Yongsen Han and Hongxu Jia

Energies 2023, 16(5), 2479; https://doi.org/10.3390/en16052479 - 5 Mar 2023

Cited by 1 | Viewed by 1835

Abstract

Inorganic insulating powder can potentially be used in nuclear power plant cables, fire-resistant cables, and so on due to its high heat resistance and radiation resistance. It is of great academic and engineering value to study the dielectric properties of inorganic insulating powder. In this paper, we aim to study the nonlinear dielectric properties via the measurement of the time-domain polarization current spectrum under the application of a DC electric field. Three kinds of silica powders are measured by a measurement system with adjustable pressure. The effects of powder shape, particle size, and packing pressure and temperature on the dependence of relaxation polarization and electrical conductivity on the applied electric field are studied. The experimental results show that the relationship between electrical conductivity and the electric field of inorganic insulating powder presents two different characteristics, i.e., field-induced enhancement and field-induced weakening. The relationship between conductance and temperature shows an increase with temperature. That is, the electrical conductivity increases or decreases with the increase in temperature. The inorganic powder insulation can be regarded as a composite, which is composed of inorganic powder particles and air gaps. The interface between the powder particles and air gaps contributes a lot to the polarization of inorganic insulating powder. The phenomena (including the field-induced weakening characteristic between relaxation polarization and electric field and the decrease characteristic of polarization with increasing temperature) can be explained by a simplified interface polarization mechanism. Full article

(This article belongs to the Special Issue Recent Developments in Theories, Technologies and Applications of HVDC Insulation Systems)

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15 pages, 7758 KiB

Open AccessArticle

Effect of Shear Action on Structural and Electrical Insulation Properties of Polypropylene

by Dianyu Wang, Jiaming Yang, Lu Li, Xuan Wang, Xu Yang, Xindong Zhao, Hong Zhao, Lin Li and Heqian Liu

Energies 2023, 16(3), 1421; https://doi.org/10.3390/en16031421 - 1 Feb 2023

Cited by 1 | Viewed by 1556

Abstract

Polypropylene undergoes permanent alterations during the processing and manufacture of cables due to shear effects, which in turn affect all of its qualities. There are currently few research papers on the modulation of material structure and many performance parameters by the shear stress field. In this study, we examined the impact of various shear levels on the structural, mechanical, and electrical properties of polypropylene, as well as their relationships. The results indicated that shear strength decreased the material’s viscosity and oxidation resistance. As shear duration increased, crystallinity began to diminish. In the meantime, the crystallinity improved as the shear temperature rose. The thermal elongations of the sheared samples were all about 5%. Short-term shearing boosted the material’s toughness, but as the degree of shear continued to increase, the material’s toughness and rigidity steadily decreased. The storage modulus of the material decreased with increasing shear, the loss peak initially increased and subsequently decreased, the peak position shifted from low to high temperature, and the loss factor was relatively small. In samples sheared for brief periods, an accumulation of space charge and an increase in its nonlinear threshold field strength were observed. With increasing shear time, the material’s space charge accumulation was repressed, the current density initially grew and then reduced, and the nonlinear threshold field strength initially fell and then increased. Under shearing, the electrical strength of the material increased by approximately 2%. In addition, the presence of an antioxidant improved all of the aforementioned features. Full article

(This article belongs to the Special Issue Recent Developments in Theories, Technologies and Applications of HVDC Insulation Systems)

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12 pages, 10978 KiB

Open AccessArticle

Influence of Bismaleimide HVA-2 Grafting on the Direct Current Dielectric Properties of XLPE

by Chengcheng Zhang, Sen Wang, Hong Zhao and Xuan Wang

Energies 2023, 16(1), 302; https://doi.org/10.3390/en16010302 - 27 Dec 2022

Cited by 2 | Viewed by 1942

Abstract

In this paper, N, N’-m-phenylene dimaleimide (HVA-2) grafted crosslinked polyethylene (XLPE) insulation materials with different HVA-2 contents were prepared. The grafting, crosslinking, and crystalline structure were characterized by Fourier-transform infrared spectroscopy (FTIR), Soxhlet extraction, and differential scanning calorimetry (DSC), respectively. The space charge distribution, direct current (DC) breakdown strength, and DC conduction current density were tested and the electronic structure was calculated from first-principles. HVA-2 grafting modification can significantly reduce the accumulation of space charges and the conduction current density of XLPE, but have a negative effect on DC breakdown strength. The polar groups of the grafted HVA-2 anchored on XLPE by the grafting reaction can introduce deep traps densely and evenly in XLPE, which would capture and scatter charge carriers, thus reducing the carrier concentration and mobility and further improving the space charge distribution and reducing conduction current density. However, the grafting of HVA-2 can increase the crosslinking extent of XLPE to make the crystallinity decrease and the crystallization inhomogeous, leading to a certain decrease in the breakdown strength of the grafted XLPE. Full article

(This article belongs to the Special Issue Recent Developments in Theories, Technologies and Applications of HVDC Insulation Systems)

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17 pages, 13126 KiB

Open AccessArticle

Comparative Analysis of XLPE and Thermoplastic Insulation-Based HVDC Power Cables

by Jae-In Lee, Woo-Hee Jeong, Minh-Chau Dinh, In-Keun Yu and Minwon Park

Energies 2023, 16(1), 167; https://doi.org/10.3390/en16010167 - 23 Dec 2022

Cited by 4 | Viewed by 2878

Abstract

The application of cross-linked polyethylene (XLPE) cables to voltage sourced converter (VSC)-based high voltage direct current (HVDC) systems has already been technically verified and has become common, and thermoplastic (TP) is attracting attention as an insulation material for next-generation cables due to the recent development of material-related technologies. However, studies related to TP cables are mainly focused on improving material properties, and studies related to cable systems are insufficient. In this paper, XLPE and TP cables were designed for application to VSC-based HVDC systems, and major characteristics such as electric field distribution and thermal stability were compared and analyzed through overvoltage simulation. The insulation design method of HVDC cable was presented, and the design was performed using XLPE and TP insulation materials. The temperature and electric field profiles of the cables were also analyzed through a finite element method simulation. To analyze the performance of the designed cable, it was simulated with the PSCAD/EMTDC program. Based on the simulation results, the major characteristics of XLPE and TP cables were compared and analyzed. Results showed that in the case of TP cables, insulation properties were excellent, but thermal conductivity was relatively low; therefore, countermeasures are needed. Full article

(This article belongs to the Special Issue Recent Developments in Theories, Technologies and Applications of HVDC Insulation Systems)

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10 pages, 2401 KiB

Open AccessArticle

Effect of Aged Nonlinear Resistive Field Grading Material on Electric Field Distribution of DC Cone Spacer

by Yongsen Han, Feng Yang and Chenguang Zhao

Energies 2022, 15(22), 8361; https://doi.org/10.3390/en15228361 - 9 Nov 2022

Cited by 2 | Viewed by 1632

Abstract

Nonlinear resistive field grading materials are widely used in the electrical and electronic applications, and are usually researched based on the initial nonlinear conductivity characteristics of synthetic materials. However, the long-term stability of these materials are rarely reported. In this paper, the effects of thermal ageing on nonlinear resistive field grading material and the electric field distribution of DC cone spacers are studied. The 30 wt.% SiC/epoxy micro-composites are prepared and are thermally aged at 180 °C for 1080 h. The infrared spectroscopy, dielectric properties, breakdown strength and nonlinear conductivity are measured, respectively. In addition, a simulation model for a cone spacer is built, and the electric field and power dissipation density are calculated. With the increasing thermal ageing time, the relative permittivity and loss tangent increase, and the breakdown strength decreases. Besides, the nonlinear coefficient of nonlinear conductivity almost increases, and the switching electric field of nonlinear conductivity decreases. Simulation results show that the aged micro-composites can homogenize the electric field in the cone spacer, but the thermal ageing causes the increase in power dissipation density and threatens the safe operation of the cone spacer. Full article

(This article belongs to the Special Issue Recent Developments in Theories, Technologies and Applications of HVDC Insulation Systems)

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11 pages, 5730 KiB

Open AccessArticle

Abnormal Time-Domain Current Spectrum of Inorganic Insulating Powder under DC Voltage

by Yucui Xue, Wenmin Guo, Yunlong Sun, Zhonghua Li and Yongsen Han

Energies 2022, 15(21), 8227; https://doi.org/10.3390/en15218227 - 4 Nov 2022

Cited by 1 | Viewed by 1272

Abstract

The total current of dielectrics under DC voltage consists of relaxation current and conduction current, which contains the information about the relaxation polarization and conduction. The time-domain spectrum (TDS) is an effective method to study the dielectric properties of insulating dielectrics. In this paper, the TDS method is also used to study the dielectric properties of the compressed inorganic hexagonal boron nitride (BN) and magnesium oxide (MgO) insulating powders. It is interestingly found that these inorganic insulating powders shows an abnormal TDS, where the current decreases monotonically to a certain level at first and then increases with time while in normal TDS the current decreases monotonically with time and finally reaches a steady value which is conduction current. The experiments verify that the abnormal phenomenon is attributed to the moisture absorption of powders during the testing process, which causes an increase in conductivity and leads to the increasing current at the end of testing time. The insulating powder cannot be regarded as a time-invariant system during the measurement, and the time-varying characteristic is mainly manifested in conduction. A time-domain least squares fitting method is presented and is effective to eliminate the deviation from normal TDS. The results of this paper provide a reference for dealing with abnormal TDS. Full article

(This article belongs to the Special Issue Recent Developments in Theories, Technologies and Applications of HVDC Insulation Systems)

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15 pages, 3493 KiB

Open AccessArticle

Nonlinear Surface Conductivity Characteristics of Epoxy Resin-Based Micro-Nano Structured Composites

by Ning Guo, Jiaming Sun, Yunlei Li, Xiaoyu Lv, Junguo Gao, Mingpeng He and Yue Zhang

Energies 2022, 15(15), 5374; https://doi.org/10.3390/en15155374 - 25 Jul 2022

Cited by 3 | Viewed by 1466

Abstract

Nonlinear composite materials serve to homogenize electric fields and can effectively improve the local concentration of the electric field in power systems. In order to study the nonlinear surface conductivity properties of micro-nano epoxy composites, two types of epoxy micro-nano composite specimens were prepared in the laboratory using the co-blending method. The surface conductivity of the composites was tested under different conditions using a high-voltage DC surface conductivity test system. The results show that the surface conductivity of micro-nano structured composites increases and then decreases with the rise of nanofiller doping concentration. The nonlinear coefficient was 1.781 at 4 wt% of doped nanostructured SiC, which was the most significant nonlinear coefficient compared to other doping contents. For the same doping concentration, the micro-nano structured composites doped with nanostructured SiC have more significant surface conductivity at the same test temperature with a nonlinear coefficient of 1.635. As the temperature increases, the surface conductivity of the micro-nano structured composite increases significantly, and the threshold field strength moves towards the high electric field. Along with the increase in temperature, the nonlinear coefficients of micro-nano composites after doping with nanostructured SiC showed a gradually decreasing trend. The temperature has little effect on the nonlinear coefficients of the micro-nano structured composites after doping with O-MMT. Full article

(This article belongs to the Special Issue Recent Developments in Theories, Technologies and Applications of HVDC Insulation Systems)

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