Journal articles: 'HVDC insulation'

1

Jörgens, Christoph, and Markus Clemens. "A Review about the Modeling and Simulation of Electro-Quasistatic Fields in HVDC Cable Systems." Energies 13, no. 19 (October 5, 2020): 5189. http://dx.doi.org/10.3390/en13195189.

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In comparison to high-voltage alternating current (HVAC) cable systems, high-voltage direct current (HVDC) systems have several advantages, e.g., the transmitted power or long-distance transmission. The insulating materials feature a non-linear dependency on the electric field and the temperature. Applying a constant voltage, space charges accumulate in the insulation and yield a slowly time-varying electric field. As a complement to measurements, numerical simulations are used to obtain the electric field distribution inside the insulation. The simulation results can be used to design HVDC cable components such that possible failure can be avoided. This work is a review about the simulation of the time-varying electric field in HVDC cable components, using conductivity-based cable models. The effective mechanisms and descriptions of charge movement result in different conductivity models. The corresponding simulation results of the models are compared against measurements and analytic approximations. Different numerical techniques show variations of the accuracy and the computation time that are compared. Coupled electro-thermal field simulations are applied to consider the environment and its effect on the resulting electric field distribution. A special case of an electro-quasistatic field describes the drying process of soil, resulting from the temperature and electric field. The effect of electro-osmosis at HVDC ground electrodes is considered within this model.

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Bang, Seungmin, Ho-Seung Kim, Jae-Hong Koo, and Bang-Wook Lee. "Consideration of the Insulation Design Method on a ±200 kV Converter Valve Unit in an HVDC Converter Hall." Energies 14, no. 8 (April 19, 2021): 2296. http://dx.doi.org/10.3390/en14082296.

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A converter valve unit, which converts Alternating Current (AC) to Directing Current (DC) and DC to AC, is one of the key elements of high voltage direct current (HVDC) transmission. The insulation design of a converter valve unit should be considered for air clearance according to the DC superimposed overvoltage and the insulator that maintains the insulation performance and the corona shield to suppress DC corona discharge. There is no prescribed standard for the insulation design of a converter valve unit. Moreover, insulation performance under an applied DC voltage has not yet been thoroughly investigated. Therefore, it is necessary to study the insulation design method of the converter valve unit. In this paper, consideration of the insulation design method on a ±200 kV converter valve unit in an HVDC converter hall is performed. The finite element method (FEM) is used to simulate the 3D model. Additionally, the safety factor (SF) is applied in accordance with the dielectric test in IEC 62271-1. As a result, an insulation design process on the converter valve unit is proposed and the insulation design is carried through the design factors. It is confirmed that design factors on the air clearance, insulator and corona shield have a significant effect on a highly reliable insulation design.

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Jörgens, Christoph, and Markus Clemens. "Modeling the electric field at interfaces and surfaces in high-voltage cable systems." COMPEL - The international journal for computation and mathematics in electrical and electronic engineering 39, no. 5 (May 8, 2020): 1099–111. http://dx.doi.org/10.1108/compel-01-2020-0041.

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Purpose In high-voltage direct current (HVDC) cable systems, space charges accumulate because of the constant applied voltage and the nonlinear electric conductivity of the insulating material. The change in the charge distribution results in a slowly time-varying electric field. Space charges accumulate within the insulation bulk and at interfaces. With an operation time of several years of HVDC systems, typically the stationary electric field is of interest. The purpose of this study is to investigate the influence of interfaces on the stationary electric field stress and space charge density. Design/methodology/approach An analytic description of the stationary electric field inside cable insulation is developed and numerical simulations of a cable joint geometry are applied, considering spatial variations of the conductivity in the vicinity of the electrodes and interfaces. Findings With increasing conductivity values toward the electrodes, the resulting field stress decreases, whereas a decreasing conductivity results in an increasing electric field. The increased electric field may cause partial discharge, resulting in accelerated aging of the insulation material. Thus, interfaces and surfaces are characterized as critical areas for the reliability of HVDC cable systems. Research limitations/implications This study is restricted to stationary electric field and temperature distributions. The electric field variations during a polarity reversal or a time-varying temperature may result in an increased electric conductivity and electric field at interfaces and surfaces. Originality/value An analytical description of the electric field, considering surface effects, is developed. The used conductivity model is applicable for cable and cable-joint insulations, where homo- and hetero-charge effects are simulated. These simulations compare well against measurements.

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Schneider, H. M., J. F. Allaire, H. P. Lips, E. V. Olavarria, T. L. Ong, F. Richens, I. Vancers, R. J. Wehling, and C. T. Wu. "Insulation of HVDC converter stations." IEEE Transactions on Power Delivery 14, no. 2 (April 1999): 387–92. http://dx.doi.org/10.1109/61.754078.

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Azizian Fard, Mehrtash, Mohamed Emad Farrag, Alistair Reid, and Faris Al-Naemi. "Electrical Treeing in Power Cable Insulation under Harmonics Superimposed on Unfiltered HVDC Voltages." Energies 12, no. 16 (August 14, 2019): 3113. http://dx.doi.org/10.3390/en12163113.

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Insulation degradation is an irreversible phenomenon that can potentially lead to failure of power cable systems. This paper describes the results of an experimental investigation into the influence of direct current (DC) superimposed with harmonic voltages on both partial discharge (PD) activity and electrical tree (ET) phenomena within polymeric insulations. The test samples were prepared from a high voltage direct current (HVDC) cross linked polyethylene (XLPE) power cable. A double electrode arrangement was employed to produce divergent electric fields within the test samples that could possibly result in formation of electrical trees. The developed ETs were observed via an optical method and, at the same time, the emanating PD pulses were measured using conventional techniques. The results show a tenable relation between ETs, PD activities, and the level of harmonic voltages. An increase in harmonic levels has a marked effect on development of electrical trees as the firing angle increases, which also leads to higher activity of partial discharges. This study of the influencing operational parameters of HVDC converters on power cable insulation is predicted to contribute to enhancements in cable design and progressive advancement in condition monitoring and insulation diagnostic techniques that can lead to more effective asset management in HVDC systems.

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Jörgens, Christoph, and Markus Clemens. "Electric Field and Temperature Simulations of High-Voltage Direct Current Cables Considering the Soil Environment." Energies 14, no. 16 (August 11, 2021): 4910. http://dx.doi.org/10.3390/en14164910.

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For long distance electric power transport, high-voltage direct current (HVDC) cable systems are a commonly used solution. Space charges accumulate in the HVDC cable insulations due to the applied voltage and the nonlinear electric conductivity of the insulation material. The resulting electric field depends on the material parameters of the surrounding soil environment that may differ locally and have an influence on the temperature distribution in the cable and the environment. To use the radial symmetry of the cable geometry, typical electric field simulations neglect the influence of the surrounding soil, due to different dimensions of the cable and the environment and the resulting high computational effort. Here, the environment and its effect on the resulting electric field is considered and the assumption of a possible radial symmetric temperature within the insulation is analyzed. To reduce the computation time, weakly coupled simulations are performed to compute the temperature and the electric field inside the cable insulation, neglecting insulation losses. The results of a weakly coupled simulation are compared against those of a full transient simulation, considering the insulation losses for two common cable insulations with different maximum operation temperatures. Due to the buried depth of HV cables, an approximately radial symmetric temperature distribution within the insulation is obtained for a single cable and cable pairs when, considering a metallic sheath. Furthermore, the simulations show a temperature increase of the earth–air interface above the buried cable that needs to be considered when computing the cable conductor temperature, using the IEC standards.

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Diban, Bassel, and Giovanni Mazzanti. "The Effect of Insulation Characteristics on Thermal Instability in HVDC Extruded Cables." Energies 14, no. 3 (January 21, 2021): 550. http://dx.doi.org/10.3390/en14030550.

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This paper aims at studying the effect of cable characteristics on the thermal instability of 320 kV and 500 kV Cross-Linked Polyethylene XLPE-insulated high voltage direct-current (HVDC) cables buried in soil for different values of the applied voltages, by the means of sensitivity analysis of the insulation losses to the electrical conductivity coefficients of temperature and electric field, a and b. It also finds the value of dielectric loss coefficient βd for DC cables, which allows an analytical calculation of the temperature rise as a function of insulation losses and thermal resistances. A Matlab code is used to iteratively solve Maxwell’s equations and find the electric field distribution, the insulation losses and the temperature rise inside the insulation due to insulation losses of the cable subjected to load cycles according to CIGRÉ Technical Brochure 496. Thermal stability diagrams are found to study the thermal instability and its relationship with the cable ampacity. The results show high dependency of the thermal stability on the electrical conductivity of cable insulating material, as expressed via the conductivity coefficients of temperature and electric field. The effect of insulation thickness on both the insulation losses and the thermal stability is also investigated.

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Oh, Dong-Hun, Ho-Seung Kim, and Bang-Wook Lee. "A Novel Diagnosis Method for Void Defects in HVDC Mass-Impregnated PPLP Cable Based on Partial Discharge Measurement." Energies 14, no. 8 (April 7, 2021): 2052. http://dx.doi.org/10.3390/en14082052.

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Mass Impregnated PPLP cable, which is applied to various high-voltage direct current (HVDC) projects due to its excellent dielectric and temperature properties, has a problem wherein voids are formed inside the butt-gap due to cavitation. However, there has been no previous research into technology for void defect identification and insulation diagnosis on HVDC MI-PPLP cables. In this paper, to propose an insulation diagnosis method for void defects in HVDC MI-PPLP cable, the direct current (DC) void discharge patterns were analyzed according to the specimen temperature and the magnitude of applied voltage using the pulse sequence analysis method. In addition, to confirm the pre-symptoms of dielectric breakdown in MI-PPLP cable due to DC void discharge, partial discharge patterns were analyzed continuously until dielectric breakdown occurred. From the experimental results, DC void discharge patterns of the same shape were obtained regardless of the specimen temperature and the magnitude of applied voltage. In addition, it was confirmed that new insulation aging patterns were generated as electrical and thermal aging occurred due to the continuous DC void discharge. Therefore, it is demonstrated that identification and insulation diagnosis of void defects in HVDC MI-PPLP cable is possible through the obtained DC void discharge and insulation aging patterns.

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Fard, Mehrtash, Mohamed Farrag, Scott McMeekin, and Alistair Reid. "Electrical Treeing in Cable Insulation under Different HVDC Operational Conditions." Energies 11, no. 9 (September 12, 2018): 2406. http://dx.doi.org/10.3390/en11092406.

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Electrical treeing (ET) can irreversibly deteriorate the insulation of polymeric power cables leading to a complete failure. This paper presents the results of an experimental investigation into the effects of unipolar and polarity reversing DC voltages on electrical tree (ET) and partial discharge (PD) behavior within high voltage direct current (HVDC) cross linked polyethylene (XLPE) cable insulation. A double needle configuration was adopted to produce non-uniform electric fields within the insulation samples, potentially leading to electrical trees. The development of trees was monitored through an optical method and the associated partial discharge signals were measured through an electrical detection technique, simultaneously. The analysis of the results shows reasonable relation between the formation of ETs and the type of the applied voltages. The polarity reversing attribute of the test voltages has a pronounced effect on formation and growth of electrical trees. This implicates an interaction between the space charges that accumulate within polymeric materials and the operational polarity reversing electric fields, which causes insulation degradation. Therefore, study of influencing HVDC operational parameters on insulation degradations can contribute to improvements in cable design and advancement in insulation diagnostic strategies applicable in HVDC systems leading to more effective asset management.

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Liu, Shili, Wei Wei, Tao Liu, Zhaoyu Hui, Yuhua Hang, Huan Zheng, Changyou Suo, and Zhonghua Li. "Conductivity Characterization of Insulation and Its Effects on the Calculation of the Electric Field Distribution in HVDC Cables." Mathematical Problems in Engineering 2021 (February 17, 2021): 1–13. http://dx.doi.org/10.1155/2021/6647731.

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The calculation of an electric field distribution provides the basis for the structural design of the insulation, and an accurate characterization of conductivity as a function of temperature and electric field forms an important basis for the simulation of the electric field distribution in HVDC (high-voltage direct current) cables. However, the conductivity functions that describe the insulating materials used for HVDC cables in different studies are different, and very little has been reported regarding how to choose the most accurate function. In this work, the conductivity of insulating materials used for HVDC cables is characterized, and the effects of the conductivity characterization on the simulation of the electric field in HVDC cables are studied. First, eight common conductivity functions are compared qualitatively. Then, the conductivities of XLPE for different temperatures and electric fields are measured, and a data fitting technique is used to analyze the coincidence degree between different functions and the test results. Finally, the steady-state electric field distributions of HVDC cables for different temperature gradients are simulated in COMSOL Multiphysics. The results show that the sum of the square of the relative errors of the fitting when using the original functions is larger than that achieved when using the logarithmic form of the functions. The deviations in the electric field caused by taking the logarithm of different functions are smaller.

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11

He, Jinliang, and George Chen. "Insulation materials for HVDC polymeric cables." IEEE Transactions on Dielectrics and Electrical Insulation 24, no. 3 (June 2017): 1307. http://dx.doi.org/10.1109/tdei.2017.006721.

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12

Du, Boxue, and Ghunem Refat. "Editorial: Polymeric materials for HVDC insulation." IEEE Transactions on Dielectrics and Electrical Insulation 26, no. 3 (June 2019): 673. http://dx.doi.org/10.1109/tdei.2019.008148.

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Du, Boxue, and Ghunem Refat. "Editorial: Polymeric materials for HVDC insulation." IEEE Transactions on Dielectrics and Electrical Insulation 26, no. 3 (June 2019): 673. http://dx.doi.org/10.1109/tdei.2019.8726010.

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Zebouchi, Nabila, and Manu A. Haddad. "A Review on Real-Size Epoxy Cast Resin Insulators for Compact High Voltage Direct Current Gas Insulated Switchgears (GIS) and Gas Insulated Transmission Lines (GIL)—Current Achievements and Envisaged Research and Development." Energies 13, no. 23 (December 4, 2020): 6416. http://dx.doi.org/10.3390/en13236416.

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Due to the ever-increasing demand for electricity in the one hand and the environmental constraints to use clean energy on the other hand, the global production of energy from remote renewable sources, particularly from large hydropower plants and offshore wind farms and their connection to the grid are expected to grow significantly in the future. Consequently, the demand to carry this electric power by high voltage direct current (HVDC) technology will increase too. The most suitable HVDC power transmission technology to deliver large amounts of power, exceeding a capacity of 5 GW per bipolar system over long distances with lower losses is by using compact HVDC gas insulated transmission lines (DC GIL) and gas insulated switchgears (DC GIS) with rated voltage (maximum continuous operating voltage) of ±550 kV and 5000 A which are presently under development worldwide. Among the critical challenges for the development of these HVDC gas insulated systems, there are the epoxy cast resin insulators that are used to separate gas compartments also called spacers. Indeed, thorough research studies have been and still being carried out to well understand and clarify the electrical insulation characteristics of HVDC spacers using mainly cylindrical samples and small insulator models, where useful results have been obtained and proposed for implementation in real compact gas insulated systems. However, few practical investigations have been undertaken on real size spacers (product scale) to verify such research outcomes and validate the reliability of the spacers to collect experiences or for commercial use. This paper reviews the current achievements of real size HVDC spacers development. It describes the basic electric field calculation and spacers design, the verification of the insulation performance and validation testing. It gives today’s commercially available compact HVDC GIS/GIL and finally it presents the envisaged future research and development.

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Zhou, Yifan, Wei Wang, and Tailong Guo. "Space Charge Accumulation Characteristics in HVDC Cable under Temperature Gradient." Energies 13, no. 21 (October 24, 2020): 5571. http://dx.doi.org/10.3390/en13215571.

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One of the main issues that affect the development of high-voltage direct-current (HVDC) cable insulation is the accumulation of space charge. The load operation of an HVDC cable leads to the formation of a radially distributed temperature gradient (TG) across the insulation. In this study, the space charge accumulation in a cross-linked polyethylene (XLPE) cable is measured under a DC electric field and TG using the pulsed electro-acoustic (PEA) method, and the effect of the TG on the space charge behavior is investigated. In addition, the bipolar charge transport (BCT) model and the conductivity model based on an improved cylindrical geometry are used to simulate the charge behavior in the HVDC XLPE cable under TG, and the experimental and simulated results are compared. The results show that the higher temperature of the cable conductor promotes the accumulation of homocharge near the side of high temperature. Additionally, with the increase of the TG, not only does more heterocharge accumulates adjacent to the side of low temperature, but more space charge also extends into the bulk of the cable insulation. More attention should be paid to the conductor shield layer and the insulation shield layer in HVDC cables. Moreover, the BCT model can more accurately describe the experimental results than the conductivity model.

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Vu, Thi Thu Nga, Gilbert Teyssedre, and Séverine Le Roy. "Electric Field Distribution in HVDC Cable Joint in Non-Stationary Conditions." Energies 14, no. 17 (August 30, 2021): 5401. http://dx.doi.org/10.3390/en14175401.

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Accessories such as joints and terminations represent weak points in HVDC cable systems. The DC field distribution is intimately dependent on the thermal conditions of the accessory and on material properties. Moreover, there is no available method to probe charge distribution in these conditions. In this work, the field distribution in non-stationary conditions, both thermally and electrically, is computed considering crosslinked polyethylene (XLPE) as cable insulation and different insulating materials (silicone, rubber, XLPE) for a 200 kV joint assembled in a same geometry. In the conditions used, i.e., temperatures up to 70 °C, and with the material properties considered, the dielectric time constant appears of the same order or longer than the thermal one and is of several hours. This indicates that both physical phenomena need to be considered for modelling the electric field distribution. Both the radial and the tangential field distributions are analysed, and focus is given on the field distribution under the stress cone on the ground side and near the central deflector on the high voltage side of the joint. We show that the position of the maximum field varies in time in a way that is not easy to anticipate. Under the cone, the smallest tangential field is obtained with the joint insulating material having the highest electrical conductivity. This results from a shift of the field towards the cable insulation in which the geometrical features produce a weaker axial component of the field. At the level of the central deflector, it is clear that the tangential field is higher when the mismatch between the conductivity of the two insulations is larger. In addition, the field grows as a function of time under stress. This work shows the need of precise data on materials conductivity and the need of probing field distribution in 3D.

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Chen, Yuan Feng. "Research Progress and Obstacles in Development of HVDC." Advanced Materials Research 1030-1032 (September 2014): 1327–30. http://dx.doi.org/10.4028/www.scientific.net/amr.1030-1032.1327.

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The merits of HVDC,such as long-distance power transmission, less line lose,ability to transmit high-power and so on,were introduced. The obstacles in development of HVDC,including failure of commutation,hazards of higher harmonics,limitations of transmission direction, problems of insulation and so on,were analyzed. The research progress both at home and abroad in development of HVDC were summarized.At last,research and application prospects of HVDC were prospected briefly.

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Gu, Yi Lei, Xiao Ming Huang, Peng Qiu, Wen Hua, Zhe Ren Zhang, and Zheng Xu. "Study of Overvoltage Protection and Insulation Coordination for MMC Based HVDC." Applied Mechanics and Materials 347-350 (August 2013): 1812–17. http://dx.doi.org/10.4028/www.scientific.net/amm.347-350.1812.

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This paper focus on overvoltage protection and insulation coordination in Modular Multilevel Converter based HVDC system planning. An overvoltage protection scheme, which bases on the topology used inTransbay project by Siemens, is proposed in this paper. Thescheme draws fromthe characteristics of MMC-HVDC systems and the research results in classic HVDC systems, byplacing arresters at some key locations in the MMC-HVDC converter station.With this scheme, the overvoltage at those key pointscan be limitedto an acceptable range and hence protect the key equipment concerned. Since all the DC lines of the project are undersea cables, no lighting overvoltage is considered and 14 faults which could happen are carefully selected to serve as the verification conditions for the insulation design. Based on the PSCAD/EMTDC simulations and the deterministic method, the specified withstand voltage levels of the critical equipment in the converter station is calculated.

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Mazzanti, Giovanni. "Issues and Challenges for HVDC Extruded Cable Systems." Energies 14, no. 15 (July 26, 2021): 4504. http://dx.doi.org/10.3390/en14154504.

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The improved features of AC/DC converters, the need to enhance cross-country interconnections, the will to make massive remote renewable energy sources available, and the fear of populations about overhead lines have fostered HVDC cable transmission all over the world, leading in the last two decades to an exponential increase of commissioned HVDC cable projects, particularly of the extruded insulation type. Comprehensive surveys of the issues to be faced by HVDC extruded cable systems appeared in the literature some years ago, but they are not so up-to-date, as HVDC extruded cable technology is developing fast. Therefore, the contribution this paper aims at giving is a systematic, comprehensive and updated summary of the main present and future issues and challenges that HVDC cable systems have to face to further improve their performance and competitiveness, so as to meet the growing quest for clean and available energy worldwide. The topics covered in this review–treated in alphabetical order for the reader’s convenience–are accessories, higher voltage and power, laying environment (submarine and underground cables), modeling, multiterminal HVDC, operation and diagnostics, recyclable insulation, space charge behavior, testing, thermal stability, transient voltages.

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Adnan, Muhammad, Zulkurnain Abdul‐Malek, Kwan Yiew Lau, and Muhammad Tahir. "Polypropylene‐based nanocomposites for HVDC cable insulation." IET Nanodielectrics 4, no. 3 (April 5, 2021): 84–97. http://dx.doi.org/10.1049/nde2.12018.

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Yang, Hongda, Qingguo Chen, Xinyu Wang, Minghe Chi, and Jinfeng Zhang. "Dielectric and Thermal Conductivity Characteristics of Epoxy Resin-Impregnated H-BN/CNF-Modified Insulating Paper." Polymers 12, no. 9 (September 13, 2020): 2080. http://dx.doi.org/10.3390/polym12092080.

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High-voltage direct-current (HVDC) dry bushing capacitor-core insulation is composed of epoxy resin-impregnated insulating paper (RIP). To improve the thermal conductivity, breakdown strength, and space charge characteristics of RIP, 0.1 wt % nano-cellulose fiber (CNF)-modified RIP (CNF/RIP), 2.5–30 wt % hexagonal boron nitride (h-BN)-modified RIP (h-BN/RIP), and 2.5–30 wt % h-BN + 0.1 wt % CNF-modified RIP (h-BN + 0.1 wt % CNF/RIP) were prepared. Scanning electron microscopy (SEM) was implemented; the thermal conductivity, DC conductivity, DC breakdown strength, and space charge characteristics were tested. The maximum thermal conductivity of h-BN + 0.1 wt % CNF/RIP was 0.376 W/m.K with a h-BN content of 30 wt %. The thermal conductivity was 85.2% higher than that of unmodified RIP. The breakdown strength and charge suppression were the best in the case of 10 wt % h-BN + 0.1 wt % CNF/RIP. The maximum breakdown strength was 11.2% higher than that of unmodified RIP. These results can play a significant role in the research and development of insulation materials for HVDC dry bushing.

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Rafiq, Muhammad, Yuzhen Lv, and Chengrong Li. "A Review on Properties, Opportunities, and Challenges of Transformer Oil-Based Nanofluids." Journal of Nanomaterials 2016 (2016): 1–23. http://dx.doi.org/10.1155/2016/8371560.

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The mineral oil or synthetic oil in conjunction with paper is mainly being applied as dielectric medium in many of the high voltage apparatus. However, the advent of high voltage levels such high voltage alternating current (HVAC) and high voltage direct current (HVDC) has prompted researchers to direct their focus onto an insulation system which can bear the rising high voltage levels. The modern insulating liquid material development is guided by various factors such as high electrical insulation requirements and other safety and economic considerations. Therefore transformer manufacturer companies have to design transformers with these new specific requirements. The transformer oil-based nanofluids with improved dielectric and thermal properties have the potential to replace mineral oil base products in the market place. They are favorable because they function more superior than mineral oil and they contribute definite insulating and thermal gains. This paper reviews recent status of nanofluids use as transformer oils. The nanofluids used as transformer oils are presented and their advantages are described in comparison with mineral oil. The multiple experimental works carried out by different researchers are described, providing an overview of the current research conducted on nanofluids. In addition scope and challenges being confronted in this area of research are clearly presented.

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Karlsson, M. E., A. Calamida, D. Forchheimer, H. Hillborg, V. Ström, J. M. Gardner, M. S. Hedenqvist, and R. T. Olsson. "The effect of ZnO particle lattice termination on the DC conductivity of LDPE nanocomposites." Materials Advances 1, no. 6 (2020): 1653–64. http://dx.doi.org/10.1039/d0ma00390e.

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Freebody, Nicola, Gary Stevens, Alun Vaughan, Fabrice Perrot, and Andrew Hyde. "New HVDC nano-composite electrical insulation for improved MV and HVAC performance." CIRED - Open Access Proceedings Journal 2017, no. 1 (October 1, 2017): 359–62. http://dx.doi.org/10.1049/oap-cired.2017.0912.

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Mauri, Massimiliano, Anna Peterson, Ayça Senol, Khalid Elamin, Antonis Gitsas, Thomas Hjertberg, Aleksandar Matic, Thomas Gkourmpis, Oscar Prieto, and Christian Müller. "Byproduct-free curing of a highly insulating polyethylene copolymer blend: an alternative to peroxide crosslinking." Journal of Materials Chemistry C 6, no. 42 (2018): 11292–302. http://dx.doi.org/10.1039/c8tc04494e.

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Zhang, Peng, Yongqi Zhang, Xuan Wang, Jiaming Yang, and Wenbin Han. "Effect of Acetylated SEBS/PP for Potential HVDC Cable Insulation." Materials 14, no. 7 (March 25, 2021): 1596. http://dx.doi.org/10.3390/ma14071596.

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Blending thermoplastic elastomers into polypropylene (PP) can make it have great potential for high-voltage direct current (HVDC) cable insulation by improving its toughness. However, when a large amount of thermoplastic elastomer is blended, the electrical strength of PP will be decreased consequently, which cannot meet the electrical requirements of HVDC cables. To solve this problem, in this paper, the inherent structure of thermoplastic elastomer SEBS was used to construct acetophenone structural units on its benzene ring through Friedel–Crafts acylation, making it a voltage stabilizer that can enhance the electrical strength of the polymer. The DC electrical insulation properties and mechanical properties of acetylated SEBS (Ac-SEBS)/PP were investigated in this paper. The results showed that by doping 30% Ac-SEBS into PP, the acetophenone structural unit on Ac-SEBS remarkably increased the DC breakdown field strength of SEBS/PP by absorbing high-energy electrons. When the degree of acetylation reached 4.6%, the DC breakdown field strength of Ac-SEBS/ PP increased by 22.4% and was a little higher than that of PP. Ac-SEBS, with high electron affinity, is also able to reduce carrier mobility through electron capture, resulting in lower conductivity currents in SEBS/PP and suppressing space charge accumulation to a certain extent, which enhances the insulation properties. Besides, the highly flexible Ac-SEBS can maintain the toughening effect of SEBS, resulting in a remarkable increase in the tensile strength and elongation at the break of PP. Therefore, Ac-SEBS/PP blends possess excellent insulation properties and mechanical properties simultaneously, which are promising as insulation materials for HVDC cables.

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Baek, Seung-Myeong, Hae-Jong Kim, Jeon-Wook Cho, and Hee-Seok Ryoo. "Cryogenic Electrical Insulation Characteristics of Solid Insulator for the HVDC HTS Cable." IEEE Transactions on Applied Superconductivity 28, no. 4 (June 2018): 1–4. http://dx.doi.org/10.1109/tasc.2018.2824337.

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Rizzo, Giuseppe, Pietro Romano, Antonino Imburgia, Fabio Viola, and Guido Ala. "The Effect of the Axial Heat Transfer on Space Charge Accumulation Phenomena in HVDC Cables." Energies 13, no. 18 (September 15, 2020): 4827. http://dx.doi.org/10.3390/en13184827.

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To date, it has been widespread accepted that the presence of space charge within the dielectric of high voltage direct current (HVDC) cables is one of the most relevant issues that limits the growing diffusion of this technology and its use at higher voltages. One of the reasons that leads to the establishment of space charge within the insulation of cables is the temperature dependence of its conductivity. Many researchers have demonstrated that high temperature drop over the insulation layer can lead to the reversal of the electric field profile. In certain conditions, this can over-stress the insulation during polarity reversal (PR) and transient over voltages (TOV) events accelerating the ageing of the dielectric material. However, the reference standards for the thermal rating of cables are mainly thought for alternating current (AC) cables and do not adequately take into account the effects related to high thermal drops over the insulation. In particular, the difference in temperature between the inner and the outer surfaces of the dielectric can be amplified during load transients or near sections with axially varying external thermal conditions. For the reasons above, this research aims to demonstrate how much the existence of “hot points” in terms of temperature drop can weaken the tightness of an HVDC transmission line. In order to investigate these phenomena, a two-dimensional numerical model has been implemented in time domain. The results obtained for some case studies demonstrate that the maximum electric field within the dielectric of an HVDC cable can be significantly increased in correspondence with variations along the axis of the external heat exchange conditions and/or during load transients. This study can be further developed in order to take into account the combined effect of the described phenomena with other sources of introduction, forming, and accumulation of space charge inside the dielectric layer of HVDC cables.

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Christen, Thomas. "HVDC insulation boundary conditions for modeling and simulation." IEEE Transactions on Dielectrics and Electrical Insulation 22, no. 1 (February 2015): 35–44. http://dx.doi.org/10.1109/tdei.2014.004559.

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Zhan, Yunpeng, George Chen, and Miao Hao. "Space charge modelling in HVDC extruded cable insulation." IEEE Transactions on Dielectrics and Electrical Insulation 26, no. 1 (February 2019): 43–50. http://dx.doi.org/10.1109/tdei.2018.007413.

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Xu, Ruoyu, Mingyu Zhou, Zhengyi Han, Yi Luo, Haitian Wang, Yuzhen Zhou, and Tong Yang. "Development of Cable Accessories with SiR Insulation for 320kV HVDC Cables." E3S Web of Conferences 115 (2019): 01004. http://dx.doi.org/10.1051/e3sconf/201911501004.

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HVDC cable accessories with environment-friendly insulating material and flexible compatibility other than ethylene propylene diene monomer (EPDM) are demanded in the global market. In this paper, the authors present their newly developed silicone rubber (SiR) insulated cable joints and terminations as a potential answer to that call. Simulation models were built in computer programs. Three most venerable spots in the insulator were identified. SiR insulated accessories with optimised conductivity were produced and tested according to Cigre TB 496 and IEC 62895:2017. The test objects passed the type test with good success. It proved that with proper design, manufacturing and installation, SiR insulated cable accessories are able to provide good service in the power system networks.

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Dang, Bin, Jinliang He, Jun Hu, and Yao Zhou. "Tailored sPP/Silica Nanocomposite for Ecofriendly Insulation of Extruded HVDC Cable." Journal of Nanomaterials 2015 (2015): 1–9. http://dx.doi.org/10.1155/2015/686248.

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Cross-linked polyethylene (XLPE) is a thermosetting material that cannot be recycled at the end of its lifetime. This study investigated the potential of syndiotactic polypropylene (sPP)/silica as an ecofriendly extruded insulation system for HVDC cables. We investigated the morphology, Fourier transform infrared, and thermal, thermomechanical, and electrical behaviors of sPP modified with 0.5–3% nanosilica. We found that the silica/sPP nanocomposite without cross-linking offered a suitable mechanical modulus at room temperature and sufficient intensity at high temperatures, and adding nanosilica modified by a silane coupling agent to the sPP resulted in significant DC resistivity and space charge improvement. The optimal nanosilica content in the sPP was determined by balancing the mechanical and thermomechanical characteristics and the DC resistivity. The sPP/silica nanocomposite reported here shows great potential as a candidate insulation material for future ecofriendly extruded HVDC cables.

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Fabiani, Davide, Gian Montanari, and Leonard Dissado. "Measuring a possible HVDC insulation killer: fast charge pulses." IEEE Transactions on Dielectrics and Electrical Insulation 22, no. 1 (February 2015): 45–51. http://dx.doi.org/10.1109/tdei.2014.004597.

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Florkowski, Marek, Maciej Kuniewski, and Pawel Zydron. "Partial Discharges in HVDC Insulation with Superimposed AC Harmonics." IEEE Transactions on Dielectrics and Electrical Insulation 27, no. 6 (December 2020): 1906–14. http://dx.doi.org/10.1109/tdei.2020.008966.

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35

Nakane, Ryuichi, Hitoshi Okubo, and Katsumi Kato. "HVDC electrical insulation performance based on charge activity in oil-pressboard composite insulation structures." IEEE Transactions on Dielectrics and Electrical Insulation 26, no. 2 (April 2019): 576–83. http://dx.doi.org/10.1109/tdei.2019.007682.

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36

Cao, Liang, Lisheng Zhong, Yinge Li, Kai Zhang, Jinghui Gao, and George Chen. "Enhanced High-Temperature DC Dielectric Performance of Crosslinked Polyethylene with a Polystyrene Pinning Structure." Materials 12, no. 8 (April 15, 2019): 1234. http://dx.doi.org/10.3390/ma12081234.

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In this paper, we propose a method on improving direct current (DC) dielectric performance by designing a polystyrene (PS) pinning crosslinked polyethylene (XLPE) for the application of insulation materials on high voltage direct current (HVDC) extruded cable. Electrical experimental results show that the addition of PS (1–5 phr, parts per hundreds of resin) can significantly reduce DC conductivity and increase DC breakdown strength of XLPE in the test temperature range of 30–90 °C. Microstructure investigation shows PS distributed as particles could participate in the formation of a crosslinking network with the help of a crosslinking agent, thus forming a polymer pinning structure at the interface between XLPE and PS. It is believed that such a special design strengthens the structure of XLPE, which leads to the improved DC dielectric performance at elevated temperatures. Our findings may contribute a new solution for developing HVDC cable insulation materials.

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37

Nilsson, Douglas Jutsell, Stanislaw M. Gubanski, and Yuriy V. Serdyuk. "Electrical Detection of Degradation in Specimens of HVDC Cable Insulation." Energies 13, no. 15 (August 1, 2020): 3963. http://dx.doi.org/10.3390/en13153963.

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One of the challenges in laboratory investigation of degradation and ageing of HVDC cable insulation is related to securing, or in other words, imitating the real service environment of the material specimens. So far, the published data refer to experiments conducted in thermo-oxidative conditions, which is not the case during normal cable operation. In service, the cable insulation is protected by a metallic barrier that blocks the transfer of any substances in and out of the construction. By-products from the cross-linking reactions cannot diffuse out and any foreign substances are blocked from entering the insulation. Thus, in order to generate results that are valid, these conditions must be replicated in laboratory experiments. This contribution presents a methodology elaborated for performing ageing experiments in a hermetically sealed environment. Degradation of the material is evaluated through changes in the electrical tree inception voltage and test object capacitance over time. Securing the environmental isolation is accomplished with an isolation system consisting of a glass enclosure with attached metallic electrodes. Indium is used to create a glass-to-metal seal between the glass and the electrodes. The electrode geometry is of needle–plane type and the needle injection process is semi-automated to ensure specimen repeatability.

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Jörgens, Christoph, and Markus Clemens. "Empirical Conductivity Equation for the Simulation of the Stationary Space Charge Distribution in Polymeric HVDC Cable Insulations." Energies 12, no. 15 (August 5, 2019): 3018. http://dx.doi.org/10.3390/en12153018.

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Many processes are involved in the accumulation of space charges within the insulation materials of high voltage direct current (HVDC) cables, e.g., the local electric field, a conductivity gradient inside the insulation, and the injection of charges at both electrodes. An accurate description of the time dependent charge distribution needs to include these effects. Furthermore, using an explicit Euler method for the time integration of a suitably formulated transient model, low time steps are used to resolve fast charge dynamics and to satisfy the Courant–Friedrichs–Lewy (CFL) stability condition. The long lifetime of power cables makes the use of a final stationary charge distribution necessary to assess the reliability of the cable insulations. For an accurate description of the stationary space charge and electric field distribution, an empirical conductivity equation is developed. The bulk conductivity, found in literature, is extended with two sigmoid functions to represent a conductivity gradient near the electrodes. With this extended conductivity equation, accumulated bulk space charges and hetero charges are simulated. New introduced constants to specify the sigmoid functions are determined by space charge measurements, taken from the literature. The measurements indicate accumulated hetero charges in about one quarter of the insulation thickness in the vicinity of both electrodes. The simulation results conform well to published measurements and show an improvement to previously published models, i.e., the developed model shows a good approximation to simulate the stationary bulk and hetero charge distribution.

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Jutsell Nilsson, Douglas, and Stanislaw Gubanski. "Electrical detection of degradation in specimens of HVDC cable insulation." Proceedings of the Nordic Insulation Symposium, no. 26 (August 7, 2019): 43–46. http://dx.doi.org/10.5324/nordis.v0i26.3276.

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One of the challenges in laboratory investigation of degradation and ageing of HVDC cable insulation is related to securing, or in other words, imitating the real service environment of the material specimens. So far, the published data refer to experiments conducted in thermo-oxidative conditions, which is not the case during normal cable operation. In reality the cable insulation is protected by a metallic barrier that blocks the transfer of any substances in and out of the construction. By-products from the cross-linking reactions cannot diffuse out and any foreign substances, such as oxygen and water, are blocked from entering into the insulation. Thus, in order to generate results that are valid, these conditions must be replicated in laboratory experiments.This contribution presents a methodology elaborated for performing ageing experiments in a hermetically sealed environment. Degradation of the material is evaluated through measurements of changes in the electrical tree inception voltage and test object capacitance over time. Securing the environmental isolation is primarily accomplished with an isolation system consisting of a glass enclosure with attached metallic electrodes. Indium is used to create a glass-to-metal seal between the glass and the electrodes. The electrode geometry is of needle-plane type and the needle injection process is semi-automated to secure a large degree of repeatability in specimen preparation.

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Wei, Yanhui, Mingyue Liu, Jiaxing Wang, Guochang Li, Chuncheng Hao, and Qingquan Lei. "Effect of Semi-Conductive Layer Modified by Magnetic Particle SrFe12O19 on Charge Injection Characteristics of HVDC Cable." Polymers 11, no. 8 (August 5, 2019): 1309. http://dx.doi.org/10.3390/polym11081309.

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For high voltage direct current (HVDC) cable, a semi-conductive layer lies between the conductor and the insulation layer; as the charge migrates the path from the conductor to the insulation material, it will affect space charge injection. In this work, the research idea of changing the injection path of moving charges within semi-conductive layer by magnetic particles was proposed. Semi-conductive composites with different SrFe12O19 contents of 1 wt.%, 5 wt.%, 10 wt.%, 20 wt.%, and 30 wt.% were prepared, and the amount of injected charges in the insulation sample was characterized by space charge distribution, polarization current, and thermally-stimulated depolarization current. The experimental results show that a small amount of SrFe12O19 can significantly reduce charge injection in the insulation sample, owing to the deflection of the charge migration path, and only part of the electrons can enter the insulation sample. When the content is 5 wt.%, the insulation sample has the smallest charge amount, 0.89 × 10−7 C, decreasing by 37%, and the steady-state current is 6.01 × 10−10 A, decreasing by 22%. When SrFe12O19 content exceeds 10 wt.%, the charge suppression effect is not obvious and even leads to the increase of charge amount in the insulation sample, owing to the secondary injection of charges. Most moving charges will deflect towards the horizontal direction and cannot direct access to the insulation sample, resulting in a large number of charges accumulation in the semi-conductive layer. These charges will seriously enhance the interface electric field near the insulation sample, leading to the secondary injection of charges, which are easier to inject into the insulation sample.

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41

He, Huiwen, Lei Wang, Peihong Zhou, and Fei Yan. "Overvoltage and Insulation Coordination of Overhead Lines in Multiple-Terminal MMC-HVDC Link for Wind Power Delivery." International Journal of Rotating Machinery 2017 (2017): 1–7. http://dx.doi.org/10.1155/2017/4849262.

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The voltage-sourced converter-based HVDC link, including the modular multilevel converter (MMC) configuration, is suitable for wind power, photovoltaic energy, and other kinds of new energy delivery and grid-connection. Current studies are focused on the MMC principles and controls and few studies have been done on the overvoltage of transmission line for the MMC-HVDC link. The main reason is that environmental factors have little effect on DC cables and the single-phase/pole fault rate is low. But if the cables were replaced by the overhead lines, although the construction cost of the project would be greatly reduced, the single-pole ground fault rate would be much higher. This paper analyzed the main overvoltage types in multiple-terminal MMC-HVDC network which transmit electric power by overhead lines. Based on ±500 kV multiple-terminal MMC-HVDC for wind power delivery project, the transient simulation model was built and the overvoltage types mentioned above were studied. The results showed that the most serious overvoltage was on the healthy adjacent line of the faulty line caused by the fault clearing of DC breaker. Then the insulation coordination for overhead lines was conducted according to the overvoltage level. The recommended clearance values were given.

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42

Zhang, Zhijin, Xinhan Qiao, Shenghuan Yang, and Xingliang Jiang. "Non-Uniform Distribution of Contamination on Composite Insulators in HVDC Transmission Lines." Applied Sciences 8, no. 10 (October 17, 2018): 1962. http://dx.doi.org/10.3390/app8101962.

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In recent years, the air particulate pollutants formed by the combustion of fossil fuels and the emission of industrial waste gases have constantly been produced, and the polluted particles deposit also seriously affects social production and people’s lives. For instance, pollution-induced flashover is seriously threatening the safe operation of the power system, while insulator pollution non-uniformity has great influence on the flashover voltage of insulators. Therefore, in this paper both field contamination experiments of HVDC (High Voltage Direct Current) transmission lines and wind tunnel contamination simulation tests were conducted, and pollution non-uniformity coefficient KT/B, KW/L and KH/M were proposed and obtained. The results showed that the degree of contamination on top surface and leeward side is heavier than that on bottom surface and windward side. Thus, in the DC energized condition, contamination along the string is also non-uniform, and serious pollution occurs mainly in the high voltage terminal. In order to explain the uneven distribution phenomenon along the string, the coupling-physics model of composite insulator string was established and using the finite element method, the electric field around the insulator was simulated. Furthermore, basing on the field charging theory, the value of electric field force on particles around the insulator surface was calculated and the mechanism of non-uniformity along the insulator sting was then explained. The results are very important for guiding insulation design and field anti-pollution works.

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43

Lee, Seung-Won, Hae-Jong Kim, Ik-Su Kwon, and Jang-Seob Lim. "Evaluation of Electrical Performance and Life Estimation of PPs for HVDC Power Cable." Energies 14, no. 18 (September 9, 2021): 5673. http://dx.doi.org/10.3390/en14185673.

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Demand and need for the application of high voltage direct current (HVDC) are increasing because of high capacity and long-distance transmission. Research on polypropylene (PP) that can increase the operation temperature compared to existing insulation is constantly being considered. This study aimed to evaluate the electrical performance and estimate the life of HVDC application of PP. In this study, a DC V-t characteristic tests were conducted on three types of PP sheets at a temperature of 110 °C. In addition, a life estimation formula based on the electrical stress was derived and the electrical performances were evaluated. The experimental results show that the life exponent of material mixed with block copolymer, homo polymer and high density polyethylene (HDPE) was 23 and the electrical performance was 17% better than block copolymer, thereby demonstrating the reliability and electrical performance for application of HVDC.

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44

Jung, Chae-Kyun, Hung-Sok Park, and Ji-Won Kang. "Insulation Design and Reliability Evaluation of ±80kV HVDC XLPE Cables." Journal of Electrical Engineering and Technology 9, no. 3 (May 1, 2014): 1002–8. http://dx.doi.org/10.5370/jeet.2014.9.3.1002.

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45

Syatirah, M. N., N. A. Muhamad, Khairul Anwar A. Halim, M. Z. Zakariya, M. N. K. Anuar, and A. A. H. Zaidi. "A Review: Polymer-based Insulation Material for HVDC Cable Application." IOP Conference Series: Materials Science and Engineering 932 (December 18, 2020): 012064. http://dx.doi.org/10.1088/1757-899x/932/1/012064.

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46

Zhao, Xuefeng, Lu Pu, Zhiqiang Xu, George Chen, Wei Duan, Haofei Sun, and Zeli Ju. "Interfacial space charge characteristic of PPLP insulation for HVDC cables." High Voltage 5, no. 5 (October 1, 2020): 628–35. http://dx.doi.org/10.1049/hve.2019.0395.

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47

Chao, Yang, Li Jianliang, Li Zili, Zhang Shouxin, Dai Long, and Zhang Chengbin. "Study on interference and protection of pipeline due to high-voltage direct current electrode." Corrosion Reviews 37, no. 3 (June 26, 2019): 273–81. http://dx.doi.org/10.1515/corrrev-2018-0089.

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AbstractTo study the rules of interference and protective measures on buried pipelines of high-voltage direct current (HVDC), the influence of different factors, including current into soil, soil resistance, damaged rate of coatings, and electrode-to-pipe distance, on pipe-to-soil potential deviation were simulated. Based on the simulated results, the fitted equations and interference judgment pattern were also obtained. The protective measures of insulation and cathodic protection can be performed for buried pipelines to prevent the interference, but the cathodic protection in the isolated area may become the stray current source of the other pipe section. This study can provide suggestions for the evaluation of interference and protective measures of pipelines of HVDC.

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48

Wei, Yanhui, Mingyue Liu, Wang Han, Guochang Li, Chuncheng Hao, and Qingquan Lei. "Charge Injection Characteristics of Semi-Conductive Composites with Carbon Black-Polymer for HVDC Cable." Polymers 11, no. 7 (July 3, 2019): 1134. http://dx.doi.org/10.3390/polym11071134.

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Semi-conductive composites composed of carbon black-polymer play an important role in uniform electric field in high voltage direct current (HVDC) cable. They also affect space charge behaviors in the insulation material. However, the charge injection characteristics of semi-conductive composites are not detailed. In this work, the electrode structure of ‘Semi-conductive composites- Insulation material- Metal bottom’ (S-I-M) is proposed, and the currents formed by injected charges from semi-conductive composites are characterized by the thermally stimulated depolarization current (TSDC) method. Further, the experimental results based on the structure of S-I-M are compared with the traditional electrode structure of M-I-M (Metal upper electrode- Insulation material- Metal bottom electrode) and the simplified cable electrode structure of MS-I-M (Metal upper electrode-Semi-conductive electrode- Insulation material- Metal bottom electrode), respectively. The experimental results show that the semi-conductive composite plays an important role in the charge injection process and it presents a different tendency under different compound modes of temperature and electric field. For the low electric field (E ≤ 5 kV/mm) and the low temperature (T ≤ 50 °C), the current caused by the accumulated charges follows the rule, IS > IMS > IM. For the low electric field and high temperature (T > 50 °C), the current caused by the injected charges follows the rule, IMS > IM > IS. This phenomenon is closely related to the interface characterization and contact barrier.

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Wang, Guoming, Han Hu, Min Tang, Jinlong Gong, Yifan Wang, Hong-Keun Ji, and Gyung-Suk Kil. "De-noising of partial discharge signal using wavelet transform for GIS under HVDC." Journal of Electrical Engineering 71, no. 4 (August 1, 2020): 254–61. http://dx.doi.org/10.2478/jee-2020-0034.

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AbstractDetection and analysis of partial discharge (PD) have been regard as the most effective method for condition monitoring and asset management of gas-insulated structures (GIS) in the power system. However, PD detection sensitivity and accuracy are greatly influenced by on-site noise and interference, resulting in failures in PD severity assessment, defect identification or localization. Although de-noising of PD signal under AC was well studied, related investigations under DC have not been carried out. With the rapid development of HVDC technology, it is a new challenge to eliminate noise from PD signal under DC for diagnosis of related power facilities. Therefore, this paper dealt with the discrimination of PD signal based on wavelet transform (WT) techniques for HVDC GIS, aiming to improve the sensitivity and accuracy of insulation diagnosis. Experimental setup was configured to generate PD signal under DC and four types of artificial defects were fabricated to simulate typical insulation defects in GIS. The WT techniques were used to discriminate PD pulse sequences from background noise, amplitude modulation radio interference, non-sinusoidal noise, and switching impulse and the effectiveness was compared with a high-pass filter.

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Tanabe, S., T. Hasegawa, K. Yamaji, and H. Irokawa. "INSULATION CHARACTERISTICS OF 500KV WATER-COOLED THYRISTOR VALVE FOR HVDC TRANSMISSION." IEEJ Transactions on Power and Energy 117, no. 6 (1997): 791–97. http://dx.doi.org/10.1541/ieejpes1990.117.6_791.

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Journal articles on the topic 'HVDC insulation'

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