Relevant bibliographies by topics / HVDC insulation

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  1. Journal articles
  2. Dissertations / Theses
  3. Books
  4. Book chapters
  5. Conference papers

Academic literature on the topic 'HVDC insulation'

Author: Grafiati
Published: 4 June 2021
Last updated: 16 February 2022

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Journal articles on the topic "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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Dissertations / Theses on the topic "HVDC insulation"

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Bruce, Graham Philip. "Ageing of Outdoor Polymeric Insulation under HVDC." Thesis, University of Manchester, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.505489.

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Nartey, Emmanuel Akuffo. "Oil/ Paper Insulation for HVDC: Conductivity of Oil." Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for elkraftteknikk, 2011. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-13264.

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The work begins with a theoretical description of conductivity and the importance of this material property in the electrical power industry. The various theories describing high voltage conduction in highly insulating dielectric liquids are analysed to ascertain their propensity to explain the exponential rise in the conductivity of the insulating liquid at high fields.The work goes further to analyse the various methods and standards that are presently utilised in the measurement of conductivity of highly insulating oils. The short-comings of the present methods particularly the IEC 61620 and 60247 are identified. The physics behind the peculiar behaviour of the conductivity when stressed under high electric fields is described and analysed.Measurements carries out according to a standard, may not lead to useful results. Therefore, it is preferable to determine the conductivity under practical aspects and also to measure the different parameters on which the conductivity depends (1). A new method of carrying out conductivity measurements based on the use of triangular and sinusoidal input high voltage is used in this work.Conductivity analysis is carried out based on this method while time dependency, frequency dependency and field dependencies are studied.The results of the various results show a strong dependency of the resistance of the oil on the input electric field up to two powers of ten; when the electric field is varied from zero to 10 kV/mm for all frequencies. The frequency of input voltage has a minimum effect of the results of the conductivity up to 0.1 Hz; the only observable change is the increasing values of the capacitive current component of the measured total current.The time dependency of the resistance values shows a very remarkable variation of conductivity. There is an average of 3 times in the conductivity when the oil is stressed over a 24 hour period.Finally Comsol Multiphysics simulation is carried out to compare to the results of the experimental results obtained in the laboratory. The results of the current as well as the resistance values obtained using the comsol simulation bears great similarity to that of the laboratory experiments.
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Limbo, Beulah Sepo. "Insulator aging tests with HVAC and HVDC excitation using the tracking wheel tester." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/2529.

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Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009.
ENGLISH ABSTRACT: Limited research results are available on the aging impacts of surface discharges for High Voltage Direct Current (HVDC) excitation on practical insulators using the Tracking Wheel Tester (TWT) methodology. This thesis gives details of an experimental investigation to compare the aging performance of insulator samples using the TWT for High Voltage Alternating Current (HVAC) and positive and negative polarity HVDC excitation. Two series of tests were performed. The first series of tests evaluated the aging of six insulator rods, namely three Room Temperature Vulcanized Silicone Rubber (RTV SR) coated glass samples and three uncoated glass samples. Three creepage distances were used for each of the test materials, namely 277 mm, 346 mm and 433 mm. The tests were conducted with HVAC excitation and the test methodology described in the IEC 61302 standard. The second series of tests involved the testing of actual insulator samples. The test voltage and conductivity of the salt water solution were also adapted. Six insulators from different manufacturers, representing different materials and specific creepage distances, were tested with HVAC and positive and negative polarity HVDC excitation. The test samples consisted of Ethylene Propylene Diene Monomer (EPDM), High Temperature Vulcanized Silicone Rubber (HTV SR), porcelain and SR coated porcelain insulators. The aging performance of the different test samples for the three types of excitation are compared in terms of peak leakage current, visual observations of surface degradation and hydrophobicity properties. The leakage current data for HVAC excitation shows that the insulators from the different manufacturers perform differently, even for the same type of material. The results also indicate differences in the way the surfaces degrade, as well as the rate of degradation. For insulators representing the same specific creepage distance, but different materials, it has been shown that the material does influence the aging performance. Comparison of the leakage current data for the HTV SR insulators from the same manufacturer, but with different specific creepage distances, shows that the specific creepage distance affect the aging performance significantly. In general, the test insulators showed higher peak leakage currents with HVDC excitation compared to HVAC excitation. The results for positive polarity HVDC excitation show that the dry band arcing, as well as the discharges, has the same form for all six insulators. The colour of the dry band discharges ranged from a blue-ish orange to a dark yellow, depending on the intensity of the leakage currents. The hydrophobic insulators, namely the HTV SR, EPDM and RTV SR coated porcelain insulators, had lost hydrophobicity within the first week of testing. The results for negative polarity HVDC excitation show severe surface degradation compared to the results for HVAC excitation. The effect of positive polarity HVDC excitation, however, seems to be more severe in terms of leakage currents and aging compared to negative polarity HVDC excitation.
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Ghorbani, Hossein. "Characterization of Conduction and Polarization Properties of HVDC Cable XLPE Insulation Materials." Licentiate thesis, KTH, Elektroteknisk teori och konstruktion, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-180809.

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Since its first introduction in 1998, extruded direct current (DC) cable technology has been growing rapidly leading to many cable system installations with operation voltages up to 320 kV. Cable manufacturers invest heavily on technology development in this field and today extruded DC cable systems for operation voltages as high as 525 kV are commercially available. The electrical field distribution in electrical insulation under DC voltage is mainly determined by the conduction physics, therefore a good understanding of the DC conduction is necessary. In case of Cross-linked Polyethylene (XLPE) insulation, the presence of the peroxide decomposition products (PDP) is believed to influence its electrical properties. The PDP are volatile and therefore they may diffuse out of the samples during sample preparation and testing. Besides, the morphology of the XLPE is known to evolve over time even at moderate temperatures. Since the material may change during preparation, storage and even measurement, the procedure during all stages of the study should be chosen carefully. In this work, the physics of the dielectric response and conduction in XLPE is briefly discussed. The existing measurement techniques relevant to characterization of DC conduction in XLPE insulation materials are reviewed. The procedure for high field DC conductivity measurement is evaluated and recommendations for obtaining reproducible results are listed. Two types of samples are studied, i.e. thick press molded samples and thick plaque samples obtained from the insulation of in-factory extruded cables. For press molded samples, the influence of the press film used during press molding and the effect of heat-treatment on the electrical properties of XLPE and LDPE are studied. High field DC conductivity of XLPE plaque samples is measured with a dynamic electrode temperature to simulate the standard thermal cycles. Investigations show that using PET film during press molding leads to higher apparent DC conductivity and dielectric losses when compared to using aluminum foil. The influence of heat-treatment is different depending on the press film. High field DC conductivity measurements and chemical composition measurement of samples obtained from the cable insulation are in good agreement with the results obtained from the full scale measurements. Finally a non-monotonic dependence of apparent DC conductivity to temperature of some samples pressed with PET film is discovered which to the author’s best of knowledge has not been previously reported in the literature.
Sedan det första införandet i 1998 har extruderad likspänning (DC) kabeltekniken vuxit snabbt och har lett till många existerande kabelsysteminstallationer med driftspänningar upp till 320 kV. Kabeltillverkare investerar kraftigt i teknikutveckling inom detta område och idag finns extruderade DC kabelsystemen tillgängliga för driftspänningar så höga som 525 kV. Elektrisk fältfördelning i isolationsmaterial under hög DC spänning, beror framförallt på materialets elektriska ledningsfysik, därför är en bra förståelse av DC ledningsförmåga nödvändig. Isolationsmaterial av tvärbunden polyeten (PEX) innehåller tvärbindningsrestgaser som tros påverka materialets elektriska egenskaper. Restgaserna är flyktiga och kan diffundera bort från proven under preparering och mätning, även under måttliga temperaturer. PEX materialets morfologi ändras även med tiden. Med tanke på att materialet kan ändras under provpreparering, lagring och även vid mätning, så måste samtliga steg ovan väljas mycket försiktigt. I detta arbete diskuteras grundläggande fysik för dielektrisk polarisering och ledningsförmåga i PEX-isolation tillsammans med granskning av existerande mätteknik relevant för karakterisering av ledningsförmåga i PEX. Procedurer för mätning av DC ledningsförmåga under höga elektriska fält är undersökta och rekommendationer för reproducerbar mätningar är framtagna. Två typer av prover är studerade, tjocka pressade plattor och tjocka plattor som ursvarvats från kommersiell tillverkade högspänningskablar. För pressade plattor, studerades effekten utav press-filmens påverkan på de elektriska egenskaperna hos PEX och LDPE. Påverkan av värmebehandling på DC ledningsförmåga av PEX plattor studerades också. Slutligen studerades DC ledningsförmåga av PEX och LDPE plattor under höga DC fält och med dynamisk temperatur på elektroderna med syftet att efterlikna standardvärmecyklingar. Undersökningarna visade att användningen av PET filmer under pressning av plattor ledde till högre DC ledningsförmåga och högre dielektriska förluster i proven i jämförelse med användning av aluminiumfolie. Påverkan utav värmebehandling är olika beroende på typ av film som används pressningen. Det finns en stark korrelation mellan resultaten från DC konduktivitet och kemisk komposition mätningar från plattor skaffat från kabelisolation och resultaten från fullskaliga kabelmätningar. Slutligen, upptäcktes ett icke monotont beroende av DC konduktivitet hos PEX och LDPE plattor på temperatur som tidigare inte rapporterats i litteraturen.

QC 20160125

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Lau, Wai Shyan. "Simultaneous space charge and current measurements in polyethylene insulation under HVDC conditions." Thesis, University of Southampton, 2003. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.416497.

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Bilock, Alexander. "Probabilistic Approach to InsulationCoordination." Thesis, Uppsala universitet, Elektricitetslära, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-296483.

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The present work was performed at HVDC ABB as an initial study on how to adopt probabilistic concepts into the VCSHVDC insulation coordination. Due to large voltage levels in HVDC applications the corresponding insulation need to be properly addressed to ensure a safe, economical and reliable operation. Traditionally, only the maximum overvoltage is considered, where no adoption to the shape of the overvoltage distribution is regarded. Use of probabilistic concepts in the insulation coordination procedure can ideally reduce insulation margins with a maintained low risk of flashover. Analysis and understanding of probabilistic concepts of AC systems is needed in order to implement the concepts into VSC-HVDC. With use of advanced VSC-HVDC models, faults are simulated with varied fault insertion time in PSCAD. The resulting overvoltages from the simulation is gathered using different statistical methods in order to obtain the approximated overvoltage distribution. It was found from the simulation results that use of a Gaussian distribution is inappropriate due to shape variety in the overvoltage distributions. Instead, Kernel Density Estimate can serve as a flexible tool to approximate overvoltage distributions with a variety in number of modes and shape. The retrieved approximated overvoltage distributions are compared with the insulation strength in order to calculate the risk of flashover. The comparison shows that the insulation can be tuned in order to match set requirements. The thesis work should be seen as pilot study, where key problems have been pointed out and recommended further studies are proposed.
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Oldervoll, Frøydis. "Electrical and Thermal Ageing of Extruded Low Density Polyethylene Insulation Under HVDC Conditions." Doctoral thesis, Norwegian University of Science and Technology, Department of Electrical Power Engineering, 2000. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-208.

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After extensive research during the last decades extruded polymeric insulation is now becoming an alternative to the traditional oil-paper systems for high voltage DC (HVDC) cables. Durability is of great importance for power cables, and the main purpose of this work has been to increase the knowledge of factors controlling the endurance of an extruded polymeric insulation under HVDC conditions. The effect of electrical and thermal ageing on electrical properties like space change accumulation, DC breakdown strength and electrical tree initiation has been investigated and related to changes in morphology, oxidation level and antioxidant concentration.

Low density polyethylene (LDPE) with and without an antioxidant additive was selected as insulating material. Test objects with plane electrodes or needle-plane electrodes were prepared by pressure moulding and equipped with aluminium electrodes. Iron particles with a diameter of 45 – 55 μm were introduced to simulate conducting contaminations in the insulation. The test objects were subjected to thermal ageing of 70°C and 90°C and the applied electrical field during ageing ranged from zero to 150 kV/mm. ageing was conducted both with constant DC polarity and with polarity reversals. The ageing period ranged from 4 weeks to 5 months.

Thermal oxidation was observed in LDPE without antioxidant and this clearly affected the electrical properties. The DC breakdown voltage was reduced by 40% and this was explained by enhanced high-field conduction and increased joule heating due to the oxidation products. It was found that oxidation was prohibited when the thickness of the aluminium electrodes increased.

Introduction of iron particles reduced the short term DC strength by 20 – 30%, but during long term ageing with constant DC voltage no difference was observed between test objects with and without particles. This was probably caused by screening of the particles by accumulated space charge.

The experiments showed that abrupt grounding or polarity reversal initiated electrical trees from the needle-electrodes. The longest trees were observed when the test objects had first been subjected to thermal and electrical ageing. The tree formation was caused by the high electrical field arising when the accumulated homocharge around the needle was converted to heterocharge at polarity or grounding,

The following main conclusions were made from the work:

*Oxidation is detrimental and must be avoided in HVDC insulation.

* The antioxidant additive can have a negative influence on the electrical properties under HVDC stress.

*Polarity reversal or abrupt grounding can initiate electrical trees from protrusions present at the electrode-insulation interface of a HVDC insulation system.

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Hägerbrand, Jonathan. "Measurements of resistivity in transformer insulation liquids." Thesis, Uppsala universitet, Institutionen för elektroteknik, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-413804.

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This thesis focuses on measuring techniques and results of resistivity in four commercially available insulating transformer oils: mineral oil, ester oil and two isoparaffin oils. Two measuring techniques, the industrially used diagnostic system for electrical insulation IDA and the Labview implemented Triangular Method, are used for resistivity measurements and the techniques are compared, a correction algorithm to the triangular method is suggested. Dielectric properties of mineral & ester and isoparaffin A&B mixtures are investigated, it is experimentally shown that the transformer oils that show high resistivity also show low loss factor. The effect moisture has on resistivity in mineral and ester oil are shown both in terms of relative humidity and actual water content in parts per million. A previous measurement cell is redesigned, the cell is manufactured in copper and gold. It is found that the material choice of the cell significantly affects the resistivity measurements. The electrical double layer and contact resistance between the oil and cell are investigated as a way to explain the difference in measured resistivity. These experiments are limited to the mineral oil and isoparaffin oil A, it is found that contact resistance is a plausible explanation. The electrical double layer is fairly constant for both oils and the Debye length of the double layer is negligible compared to the total distance between the electrodes of the cell. Lastly, the field of insulating transformer oils and its future is discussed, from data obtained regarding the dielectric properties and environmental aspects of the four transformer oils used in this study. A positive trend which combines the high insulating properties with good biodegradability qualities is found. Suggesting a positive future in the field of insulating transformer oils. The results found in this thesis can be used as a basis for future theses regarding transformer oils used for HVDC applications.
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Pallon, Love. "Polyethylene/metal oxide nanocomposites for electrical insulation in future HVDC-cables : probing properties from nano to macro." Doctoral thesis, KTH, Polymera material, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-193591.

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Nanocomposites of polyethylene and metal oxide nanoparticles have shown to be a feasible approachto the next generation of insulation in high voltage direct current cables. In order to reach an operationvoltage of 1 MV new insulation materials with reduced conductivity and increased breakdown strengthas compared to modern low-density polyethylene (LDPE) is needed.In this work polyethylene MgO nanocomposites for electrical insulation has been produced andcharacterized both from an electrical and material perspective. The MgO nanoparticles weresynthesized into polycrystalline nanoparticles with a large specific surface area (167 m2 g–1). Meltprocessing by extrusion resulted in evenly dispersed MgO nanoparticles in LDPE for the silane surfacemodified MgO as compared to the unmodified MgO. All systems showed a reduction in conductivityby up to two orders of magnitude at low loading levels (1–3 wt.%), but where the surface modifiedsystems were able to retain reduced conductivity even at loading levels of 9 wt.%. A maximuminteraction radius to influence the conductivity of the MgO nanoparticles was theoretically determinedto ca. 800 nm. The interaction radius was in turn experimentally observed around Al2O3 nanoparticlesembedded in LDPE using Intermodulation electrostatic force microscopy. By applying a voltage on theAFM-tip charge injection and extraction around the Al2O3 nanoparticles was observed, visualizing theexistence of additional localized energy states on, and around, the nanoparticles. Ptychography wasused to reveal nanometre features in 3D of electrical trees formed under DC-conditions. Thevisualization showed that the electrical tree grows by pre-step voids in front of the propagatingchannels, facilitating further growth, much in analogy to mechanical crack propagation (Griffithconcept). An electromechanical effect was attributed as possible mechanism for the formation of the voids.
Nanokompositer av polyeten och metalloxidpartiklar anses vara möjliga material att använda i morgondagens isolationshölje till högspänningskablar för likström. För att nå en transmissionsspänning på 1 MV behövs isolationsmaterial som i jämförelse med dagens polyeten har lägre elektrisk ledningsförmåga, högre styrka mot elektriskt genomslag och som kan kontrollera ansamling av rymdladdningar. De senaste årens forskning har visat att kompositer av polyeten med nanopartiklar av metalloxider har potential att nå dessa egenskaper. I det här arbetet har kompositer av polyeten och nanopartiklar av MgO för elektrisk isolation producerats och karaktäriserats. Nanopartiklar av MgO har framställts från en vattenbaserad utfällning med efterföljande calcinering, vilket resulterade i polykristallina partiklar med en mycket stor specifik ytarea (167m2 g-1). MgO-nanopartiklarna ytmodifierades i n-heptan genom att kovalent binda oktyl(trietoxi)silan och oktadekyl(trimetoxi)silan till partiklarna för att skapa en hydrofob och skyddande yta. Extrudering av de ytmodifierade MgO nanopartiklarna tillsammans med polyeten resulterade i en utmärkt dispergering med jämnt fördelad partiklar i hela kompositen, vilket ska jämföras med de omodifierade partiklarna som till stor utsträckning bildade agglomerat i polymeren. Alla kompositer med låg fyllnadsgrad (1–3 vikt% MgO) visade upp till 100 gånger lägre elektrisk konduktivitet jämfört med värdet för ofylld polyeten. Vid högre koncentrationer av omodifierade MgO förbättrades inte de isolerande egenskaperna på grund av för stor andel agglomerat, medan kompositerna med de ytmodifierade fyllmedlen som var väl dispergerade behöll en kraftig reducerad elektrisk konduktivitet upp till 9 vikt% fyllnadshalt. Den minsta interaktionsradien för MgO-nanopartiklarna för att minska den elektriska konduktiviten i kompositerna fastställdes med bildanalys och simuleringar till ca 800 nm. Den teoretiskt beräknade interaktionsradien kompletterades med observation av en experimentell interaktionsradie genom att mäta laddningsfördelningen över en Al2O3-nanopartikle i en polyetenfilm med intermodulation (frekvens-mixning) elektrostatisk kraftmikroskop (ImEFM), vilket är en ny AFM-metod för att mäta ytpotentialer. Genom att lägga på en spänning på AFM-kantilevern kunde det visualiseras hur laddningar, både injicerades och extraherades, från nanopartiklarna men inte från polyeten. Det tolkades som att extra energinivåer skapades på och runt nanopartiklarna som fungerar för att fånga in laddningar, ekvivalent med den gängse tolkningen att nanopartiklar introducera extra elektronfällor i den polymera matrisen i nanokompositer. Nanotomografi användes för att avbilda elektriska träd i tre dimensioner. Avbildningen av det elektriska trädet visade att tillväxten av trädet hade skett genom bildning av håligheter framför den framväxande trädstrukturen. Håligheterna leder till försvagning av materialet framför det propagerande trädet och förenklar på det sättet fortsatt tillväxt. Bildningen av håligheter framför trädstrukturen uppvisar en analogi till propagering av sprickor vid mekanisk belastning, i enlighet med Griffiths koncept.

QC 20161006

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Shifidi, S. K. "Modelling and performance evaluation of an HV impulse test arrangement with HVDC bias." Thesis, Stellenbosch : University of Stellenbosch, 2009. http://hdl.handle.net/10019.1/2722.

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Thesis (MScEng (Electrical and Electronic Engineering))--University of Stellenbosch, 2009.
ENGLISH ABSTRACT: From a systems operation and design perspective, it is important to understand the behaviour of HVDC system insulation when presented with high voltage transients, such as induced by lightning and switching operations. Therefore, this thesis investigates the design, operation and performance of a circuit arrangement that can be used in high voltage laboratories to generate impulse voltage waveforms superimposed on a dc bias voltage. The circuit arrangement consists of an impulse generator and a dc source that supplies continuous dc voltage to stress the test object, which can be any type of insulator, i.e. composite, porcelain, glass, gap arrangements, etc. The composite waveform obtained from the test arrangement is used experimentally to investigate the impulse flashover of insulators. For modelling and analysis purposes, the test circuit was transformed to a Laplace equivalent in order to derive the applicable nodal voltage equations. After substitution of circuit parameter values, the voltage equations are then transformed to time domain equations that predict the time-domain behaviour of the circuit. To validate this mathematical approach, the voltage waveforms obtained with this mathematical model is compared with the waveforms measured under laboratory conditions and also with waveforms simulated with HSPICE software. These comparisons are performed using graphical representations. Good correlation was obtained and the results are presented in this thesis. The final stage of this thesis discusses the application of the designed test arrangement for flashover and withstands tests on a silicon rubber insulator. The determination of the flashover values is done by using the existing statistical methods. The insulator was tested under dry conditions and also under polluted wet conditions for both positive and negative impulses compared to the DC bias voltage polarity. The results show that the dc bias voltage does not affect the total voltage flashover of the insulator significantly. It was also observed that wetting affects the flashover for negative impulse more severely, while the influence of wetting is minimal with positive impulse voltages
AFRIKAANSE OPSOMMING: Vanuit ‘n stelselbedryf en ontwerp perspektief, is dit is belangrik om die gedrag van HSGS stelsels te verstaan wanneer dit onderwerp word aan hoogspanning oorgangsverskynsels soos veroorsaak deur weerlig en skakeloperasies. Daarom ondersoek hierdie tesis die ontwerp, werking en werkverrigting van ‘n stroombaanopstelling wat gebruik kan word in hoogspanningslaboratoriums om impulsspannings gesuperponeer op gelykspanning voorspannings op te wek. Die stroombaan bestaan uit ’n impulsgenerator en ‘n gs-bron wat die langdurige gs-spanning voorsien aan die toetsvoorwerp, wat enige tipe isolator kan wees. bv. porselein, glas, gapings, ens. Die saamgestelde golfvorm wat met die toetsopstelling verkry word, is eksperimenteel gebruik om die impulsoorvonking van isolators te ondersoek. Vir die doel van modellering and analise, is die stroombaan na ‘n Laplace ekwivalent getransformeer om die toepaslike knooppunt spanningsvergelykings af te lei. Na substitusie van die stroombaan parameter waardes, word die spanningsvergelykings getransformeer na die tydgebied vergelykings wat die tydgebied gedrag van die stroombaan voorspel. Om die wiskundige benadering te toets, word die spanningsgolfvorms wat met die wiskundige model voorspel word, vergelyk met golfvorms wat onder laboratorium toestande gemeet is en ook met golfvorms wat met HSPICE programmatuur gesimuleer is. Hierdie vergelykings word gedoen met behulp van grafiese voorstellings. Goeie korrelasie is verkry en die resultate word in die tesis gegee. Die finale stadium van hierdie tesis bespreek die toepassing van die ontwerpte toetsopstelling vir oorvonk- en weerstaantoetse op ‘n silikonrubber isolator. Die bepaling van die oorvonkwaardes word gedoen deur bestaande statistiese metodes te gebruik. Die isolator is onder droë en nat besoedelde toestande gedoen, vir beide positiewe sowel as negatiewe impulse met verwysing na die GS voorspan spanning. Die resultate toon dat die gsvoorspanning nie die oorvonkspanning van die isolator beïnvloed nie. Dit is ook waargeneem dat die benatting die oorvonking neer beïnvloed met ‘n negatiewe impuls terwyl die invloed minimaal is met positiewe impulsspannings.
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Books on the topic "HVDC insulation"

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Du, Boxue, ed. Polymer Insulation Applied for HVDC Transmission. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-15-9731-2.

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Book chapters on the topic "HVDC insulation"

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Zha, Jun-Wei, Ming-Sheng Zheng, Wei-Kang Li, George Chen, and Zhi-Min Dang. "Polypropylene Insulation Materials for HVDC Cables." In Polymer Insulation Applied for HVDC Transmission, 77–96. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-9731-2_4.

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Li, Chuanyang, Chuanjie Lin, and Tohid Shahsavarian. "HVDC Spacers by Adaptively Controlling Surface Charges." In Polymer Insulation Applied for HVDC Transmission, 347–63. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-9731-2_14.

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Chen, Chi, Xia Wang, Kai Wu, and Chuanhui Cheng. "Space Charge Characteristics of Coaxial Cable Insulation." In Polymer Insulation Applied for HVDC Transmission, 151–72. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-9731-2_7.

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Zhang, Boya, and Guixin Zhang. "Surface Charge Accumulation on Insulators in HVDC Gas-Insulated Systems: Measurement, Characteristics, and Suppression." In Polymer Insulation Applied for HVDC Transmission, 365–95. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-9731-2_15.

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Cheng, Sang, and Qi Li. "Polymer Dielectrics for Film Capacitors Applied in HVDC Transmission." In Polymer Insulation Applied for HVDC Transmission, 607–26. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-9731-2_24.

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Wang, Shihang. "DC Insulation Performance of Crosslinked Polyethylene for HVDC Cables." In Polymer Insulation Applied for HVDC Transmission, 3–22. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-9731-2_1.

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Yang, Zhuoran, Zhonglei Li, Honghua Xu, Hao Wang, Wei Chen, and Zihe Yang. "Charge Properties of SiC/SiR Composites with Nonlinear Conductivity at Different Temperatures." In Polymer Insulation Applied for HVDC Transmission, 243–70. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-9731-2_10.

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Su, Jingang, Boxue Du, Tao Han, Zhonglei Li, Liqiang Wei, and Peng Zhang. "Effect of Temperature and Mechanical Stress on Charge Transport and Ageing Properties of EPDM for Cable Accessories." In Polymer Insulation Applied for HVDC Transmission, 271–92. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-9731-2_11.

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Li, Jin, Chenlei Han, Boxue Du, and Tatsuo Takada. "Theoretical Model and Suppressing Method of Interface Charge Accumulation in HVDC Cable Accessory: A Review." In Polymer Insulation Applied for HVDC Transmission, 293–308. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-9731-2_12.

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Zhao, Yushun, Kerong Yang, Song Zhang, Bin Du, Xuepei Wang, and Yuanhan He. "Epoxy Resin Insulating Composites for Vacuum Cast Electrical Insulators of GIS." In Polymer Insulation Applied for HVDC Transmission, 311–46. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-9731-2_13.

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Conference papers on the topic "HVDC insulation"

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Zhang, Chong, Zhaoliang Xing, Pengfei Wu, Xiying Dai, Zhiyun Han, Xuwei Huang, Ziwei Dong, Zian Ding, and Yujin Guo. "Study on the high frequency insulation strength of disiloxane modified polyimide film." In 2020 4th International Conference on HVDC (HVDC). IEEE, 2020. http://dx.doi.org/10.1109/hvdc50696.2020.9292671.

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Zheng, Jiankang, Qiming Gong, Hai Nan, Xiaoting Su, Cheng Duan, and Mingyang Xu. "Research on XLPE Insulation Failure Characteristics of DC Cables in Fire Environmet." In 2020 4th International Conference on HVDC (HVDC). IEEE, 2020. http://dx.doi.org/10.1109/hvdc50696.2020.9292857.

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Weiwang, Wang, He Jiefeng, Wang Xin, Liu Ying, and Li Shengtao. "Analysis of Electric Field Stress and Dielectric Loss in Insulation of Magnetic Component for Cascaded Power Electronic Transformer." In 2020 4th International Conference on HVDC (HVDC). IEEE, 2020. http://dx.doi.org/10.1109/hvdc50696.2020.9292863.

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Christen, Thomas. "Characterization and robustness of HVDC insulation." In 2013 IEEE International Conference on Solid Dielectrics (ICSD). IEEE, 2013. http://dx.doi.org/10.1109/icsd.2013.6619804.

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Jiang, Shan, Peter Kuffel, and Ram Adapa. "Live Work Insulation Considerations on HVDC lines." In 2020 IEEE Electric Power and Energy Conference (EPEC). IEEE, 2020. http://dx.doi.org/10.1109/epec48502.2020.9320070.

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Kohalmy, S. "Polyolefins as candidates for HVDC cable insulation materials." In 11th International Symposium on High-Voltage Engineering (ISH 99). IEE, 1999. http://dx.doi.org/10.1049/cp:19990832.

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Stevens, G. C., N. A. Freebody, A. Hyde, F. Perrot, I. Szkoda-Giannaki, A. S. Vaughan, S. Virtanen, et al. "Balanced nanocomposite thermosetting materials for HVDC and AC applications." In 2015 IEEE Electrical Insulation Conference. IEEE, 2015. http://dx.doi.org/10.1109/icacact.2014.7223516.

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Huang, Z. Y., J. A. Pilgrim, P. L. Lewin, and S. G. Swingler. "Real-time electric field estimation for HVDC cable dielectrics." In 2015 IEEE Electrical Insulation Conference. IEEE, 2015. http://dx.doi.org/10.1109/icacact.2014.7223560.

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Huang, Z. Y., J. A. Pilgrim, P. L. Lewin, S. G. Swingler, and D. Payne. "Current rating methodology for mass impregnated HVDC cables." In 2013 IEEE Electrical Insulation Conference (EIC). IEEE, 2013. http://dx.doi.org/10.1109/eic.2013.6554301.

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Huang, Z. Y., J. A. Pilgrim, P. L. Lewin, S. G. Swingler, and G. Tzemis. "Numerical thermo-mechanical stress analysis for HVDC cables." In 2014 IEEE Electrical Insulation Conference (EIC). IEEE, 2014. http://dx.doi.org/10.1109/eic.2014.6869415.

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