Robust measurements of electric conductivity in polyethylene based materials: measurement setup, data processing and impact of sample preparation

Xu, Xiangdong; Karlsson, Mattias; Gąska, Karolina; Gubanski, Stanislaw; Hillborg, Henrik; Gedde, Ulf W.

doi:10.5324/nordis.v0i25.2370

Cited by 6 publications

(7 citation statements)

References 7 publications

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“…The observed bulk morphologies for the studied sample preparation methods are very consistent for specimens prepared at KTH and CTH (presented by Xu et al [10] at NORDIS 2017). In literature where the morphology of LDPE specimens for HVDC cable applications have been studied, no banded spherulites are seen in the extruded samples [5].…”

Section: Resultsmentioning

confidence: 48%

“…A finer surface structure is obtained by using PET film, whereas clear lamellar structures are shown when using Al foil. The influence of protective film on the DC conductivity is presented by Xu et al [10] at NORDIS 2017. Figure 5 shows the results from DC conductivity measurements at 22 ¡C and 3.3 kV mm -1 for the above mentioned sample preparation procedures at KTH and CTH.…”

Section: Resultsmentioning

confidence: 99%

“…Also the influence of protective films (PET or Al foil) during compression moulding has been investigated. Conductivity measurements of the prepared samples is presented by Xu et al [10] at NORDIS 2017.…”

Section: Introductionmentioning

confidence: 99%

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DC Conductivity Measurements of LDPE: Influence of Specimen Preparation Method and Polymer Morphology

Karlsson¹,

Xu²,

Gąska³

et al. 2017

NORD-IS

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DC conductivity measurements are important for gaining fundamental understanding of conduction mechanisms of insulation materials, as well as in the development of HVDC power system components, such as extruded cable systems. In this study, the influence of sample processing on the morphology and DC conductivity of low-density polyethylene (LDPE) has been studied. Direct compression moulding of LDPE pellets is commonly used in research laboratories for obtaining plaque samples, whereas extrusion is an additional commonly used technique for dispersion of particles in nanocomposites prior to the compression moulding process. In this study LDPE plaques have been obtained by either compression moulding directly from pellets, or by extrusion followed by compression moulding. The morphology obtained in the first case consisted of banded spherulites, whereas the latter method yielded a morphology of small axialites. The difference in sample processing had also an impact on the DC conductivity. The DC conductivity at 22 ¡C and 3.3 kV mm -1 was of the order of 4x10 Ð18 S m -1 for the plaques obtained by extrusion and compression moulding whereas the plaques obtained by direct compression moulding exhibited a conductivity of 1x10 Ð16 S m -1 . In addition, the reproducibility of the performed DC conductivity measurements was also verified in a round robin test performed between the Royal Institute of Technology and Chalmers Technical University.

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Section: Resultsmentioning

confidence: 48%

Section: Resultsmentioning

confidence: 99%

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DC Conductivity Measurements of LDPE: Influence of Specimen Preparation Method and Polymer Morphology

Karlsson¹,

Xu²,

Gąska³

et al. 2017

NORD-IS

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“…However, as the noise reduction rate of the filtered conduction current has not been quantitatively considered, it is difficult to determine whether the change in the conduction current of aged XLPE samples after using the filter is within the range of intrinsic characteristics [8]. The software filters of the conduction current has been discussed; however, the noise reduction rate has not been focused [11]. The software filter was applied statistically, and the original data lost its intrinsic characteristics as the number of uses and data acquired increased [11].…”

Section: Polymeric Materials Have Been Continuously Developed As High-voltagementioning

confidence: 99%

Reliability Evaluation of Software Filters Applied to Conduction Current in HVDC Power Cables

et al. 2021

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For design and operation, the conduction current of insulation must be obtained in high-voltage direct current (HVDC) power cables. The measured noise from the environment and equipment can have a significant impact on the reliability of the conduction current. To obtain an accurate conduction current, software filters of the moving average filter (MAF) and moving median filter (MMF) are employed. This study aimed to develop an evaluation method that can quantify the noise reduction of the conduction current measured in HVDC power cables. In addition, we proposed a new software filter with excellent performance. The conduction current was measured at various temperatures using an applied electric field, and the noise reduction rate of the filtered conduction current was evaluated using a statistical method. The experimental results showed that the maximum noise reduction rate of the software filters is 94 %, and the newly proposed filter is up to 26 % more effective in reducing noise than MAF and MMF. This demonstrates the development of a reliable new software filter and evaluation method.INDEX TERMS Moving average filter (MAF), moving median filter (MMF), high voltage direct current (HVDC)

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“…In order to achieve better noise rejection and effective data handling, a dynamic averaging method, referred as "smart averaging", has been used to enable simultaneous processing and recording of the data. Detail discussion about the averaging algorithm, the measuring setup and data processing can be found in [34,35]. The following experimental procedure was used for conductivity measurements.…”

Section: Conductivity Measurementsmentioning

confidence: 99%

Electrical Characterization of a New Crosslinked Copolymer Blend for DC Cable Insulation

Kumara

Hammarström

et al. 2020

Energies

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To design reliable high voltage cables, clean materials with superior insulating properties capable of operating at high electric field levels at elevated temperatures are required. This study aims at the electrical characterization of a byproduct-free crosslinked copolymer blend, which is seen as a promising alternative to conventional peroxide crosslinked polyethylene currently used for high voltage direct current cable insulation. The characterization entails direct current (DC) conductivity, dielectric response and surface potential decay measurements at different temperatures and electric field levels. In order to quantify the insulating performance of the new material, the electrical properties of the copolymer blend are compared with those of two reference materials; i.e., low-density polyethylene (LDPE) and peroxide crosslinked polyethylene (XLPE). It is found that, for electric fields of 10–50 kV/mm and temperatures varying from 30 °C to 70 °C, the DC conductivity of the copolymer blend is in the range of 10−17–10−13 S/m, which is close to the conductivity of crosslinked polyethylene. Furthermore, the loss tangent of the copolymer blend is about three to four times lower than that of crosslinked polyethylene and its magnitude is on the level of 0.01 at 50 °C and 0.12 at 70 °C (measured at 0.1 mHz and 6.66 kV/mm). The apparent conductivity and trap density distributions deduced from surface potential decay measurements also confirmed that the new material has electrical properties at least as good as currently used insulation materials based on XLPE (not byproduct-free). Thus, the proposed byproduct-free crosslinked copolymer blend has a high potential as a prospective insulation medium for extruded high voltage DC cables.

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Robust measurements of electric conductivity in polyethylene based materials: measurement setup, data processing and impact of sample preparation

Cited by 6 publications

References 7 publications

DC Conductivity Measurements of LDPE: Influence of Specimen Preparation Method and Polymer Morphology

DC Conductivity Measurements of LDPE: Influence of Specimen Preparation Method and Polymer Morphology

Reliability Evaluation of Software Filters Applied to Conduction Current in HVDC Power Cables

Electrical Characterization of a New Crosslinked Copolymer Blend for DC Cable Insulation

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