Cable Insulation Materials Research Articles

Recyclable Polymeric Cable Insulation Materials: A Comprehensive Review

Recyclable Polymeric Cable Insulation Materials: A Comprehensive Review

Surface Microstructure Study on Corona Discharge-Treated Polyethylene Using Positron Annihilation Spectroscopy.

The microstructure and chemical properties of the corona discharge process could provide an effective method for predicting the performance of high-voltage cable insulation materials. In this work, the depth profile of the microstructure and chemical characteristics of corona discharge-treated PE were extensively investigated using Doppler broadening of position annihilation spectroscopy accompanied with positron annihilation lifetime spectroscopy, attenuated total reflectance Fourier transform infrared spectra, Raman spectra and contact angle measurement. By increasing corona discharge duration, the oxygen-containing polar groups, including hydroxyl, carbonyl and ester groups, strongly contribute to the deterioration of hydrophobicity and the enhancement of hydrophilicity. And the mean free volume size, with a broadening distribution, decreases slightly. The line shape S parameter decreases because of the decrease in free volume elements and the appearance of oxygen-containing groups. Also, the thickness of the degradation layer, determined from the S parameter with positron injection depth, increases and diffuses into the PE matrix. A linear S-W plot within the degradation layer of different corona treatment duration samples indicates the defect type does not change. The S parameter decreases and the W parameter increases with an increasing corona duration. Using a slow positron beam, the nondestructive probe can be used to profile the microstructure and chemical environment across the corona discharge damage depth, which is beneficial for investigating the surface and interfacial insulation materials.

Temperature Evaluation Considering Gradient Distribution for MV Cable XLPE Insulation Based on Wave Velocity

Temperature is an important factor for the service life of cable insulation. To ensure safety, the operating temperature of cables must be monitored. Since optical fiber temperature measurement technology is difficult to be used widely in medium voltage (MV) cables due to cost, this paper proposes a temperature evaluation method based on wave velocity. Firstly, the dielectric constant of cross-linked polyethylene (XLPE) cable insulation under different temperature is obtained through experiment. Based on the result, the relationship curve between wave velocity and temperature is established. The asymmetry effect due to temperature gradient in the cable insulation is discussed via finite element simulation. The effectiveness of obtaining the average insulation temperature of the cable based on wave velocity is validated. In addition, the mechanism of the temperature influence on the cable insulation material’s dielectric constant is analyzed by molecular dynamics simulation, which further deepens understanding of the characteristics of cable insulation materials.

Designing the Extruding Process of LLDPE/HDPE-Alumina Blends using Two-Level Factorial Method for Conductivity Level Optimizing HVDC Cable Insulation Material

Designing the Extruding Process of LLDPE/HDPE-Alumina Blends using Two-Level Factorial Method for Conductivity Level Optimizing HVDC Cable Insulation Material

Extra-Low Frequency Dielectric Relaxation in HVDC Cable Insulation Material Caused by Cross-Linking Byproduct

Extra-Low Frequency Dielectric Relaxation in HVDC Cable Insulation Material Caused by Cross-Linking Byproduct

Effect of Ethylene-Propylene-Diene Monomer Blending on the Dielectric Properties of Polypropylene for Power Cable Insulation

Thermoplastic materials such as polypropylene (PP) are ideal candidates to be used as power cable insulation materials. However, the mechanical properties of PP, which is brittle and stiff, need to be modified to meet the requirements of power cable insulation applications. To overcome this, ethylene-propylene-diene monomer (EPDM) can be melt blended with PP to improve PP’s mechanical properties. In the current work, the effect of blending different contents of EPDM with PP was investigated in terms of the morphology, chemical structure, dielectric response, electrical, and mechanical properties. The results show that the EPDM blended well with the PP as the EPDM dispersed in the PP structure. Meanwhile, the chemical structure and dielectric response of the EPDM and PP blend became slightly different with high contents of EPDM, which subsequently affected the breakdown strength and mechanical properties. Nevertheless, it is worth noting that PP blended with low contents of EPDM has the potential to be used as recyclable power cable insulation materials.

Study on the pyrolysis characteristics of styrene-grafted polypropylene cable insulation material

Polypropylene (PP) has garnered significant attention as a cable insulation material due to its exceptional electrical performance and recyclability. Styrene-grafted polypropylene (PP-g) emerges as a promising alternative in this context. This study employs thermogravimetric-gas chromatography experiments and reactive molecular dynamics simulations to compare the pyrolysis process and decomposition products of pure PP and PP-g as cable insulation materials. Results indicate that while both materials produce similar pyrolysis products, PP-g exhibits greater resistance to decomposition than PP. The predominant hydrocarbons in the decomposition products include methane (CH4), ethylene (C2H4), propylene (C3H6), and ethane (C2H6). The relative proportion of hydrocarbons decreases with increasing temperature, with a shift toward increased C2H6 production. The ratio of C2H6 to (CH4 + C2H4) molecular weights in thermal decomposition products rises with temperature, suggesting enhanced stability. Graft modification alters the decomposition pathway, specifically increasing the generation of C2H6. This study lays a theoretical foundation for cable aging monitoring and life assessment.

Comparative study on matrix resins in two low‐density polyethylene based cable insulation materials with different voltage grades

AbstractIn industry, crosslinked polyethylene (XLPE) cable insulation is usually produced from crosslinkable compounds consisting of low‐density polyethylene (LDPE) and additives, which known as “cable materials”. Considering that in addition to additives, the structure of matrix resin is a key factor in determining the property of XLPE, it is worthy to study the structure requirements of matrix resin for the development of cable materials with different voltage grades. In this work, the structure of matrix resins of a high voltage grade and an extra high voltage grade cable material were comparatively investigated. Interestingly, it was found that the matrix resins have no significant difference in chain structure parameters including molecular weight and its distribution and vinyl content between two samples, and their crystalline structure as well as the melt rheology and melting crystallization behavior are also very similar. These results suggest that these matrix resins may not substantially differ. Our work shows that cable materials with different voltage grades are not necessarily diverge in terms of matrix resin structure, and it could be possible to develop higher grade cable materials using the same matrix resin as lower grade counterparts.

On the issue of applying the dynamic thermal rating in electric power distribution system

The article considers separate studies and review articles on dynamic thermal rating system in power transmission lines and electrical equipment. Available researches of foreign authors are mainly devoted to forecasting algorithms, model-ing methodologies and implementation of dynamic thermal rating in order to increase the capacity of power transmis-sion lines. It is shown that for the tasks of planning and management of the electric power system in Russia, the need to study and coordinate domestic and foreign developments on the assessment of the capacity of power transmission lines and power distribution is currently relevant. The expansion of residential areas increases the load on electric distribution network due to the shift of maximum power consumption. The currently dynamically changing conditions of electricity consumption direct attention to the development of new technological concepts and the applicability of the existing approaches to assessing the capacity of electricity transmission lines to distribution networks. Available research on dynamic thermal rating in electric distribution networks has focused much attention on both the potential problems and benefits of its implementation in the integration of distributed generation based on the renewable energy sources, in particular wind generation. The ambiguous impact of dynamic thermal rating systems on the reliability of the electric distribution network and the need for their reasonable use, as well as a significant lack of research in relation to cable distribution networks and consistency in assessing their capacity depending on the cable insulation material are being not-ed. Few studies have verified the adaptation of the state-of-the-art approach of dynamic thermal rating of overhead transmission lines to cable lines for predicting parameters corresponding to operational objectives. The research results can be useful in the development and modernization of metering systems, in which new functions of power loss moni-toring and automated determination of distribution network reliability indicators are implemented, which will allow, within the framework of “smart grids”, to ensure the required level of reliability of power supply to consumers.

Aging and life control of cross-linked polyethylene as cable insulation material

Cross-linked polyethylene (XLPE) has been widely used in the field of power cables due to its excellent mechanical properties and insulating properties. However, during the manufacturing of high voltage cables, XLPE will inevitably be affected by electrical aging, thermal aging and electro-thermal combined aging, which makes the resistance and life of the material decline. Therefore, it is necessary to enhance the aging resistance of XLPE without affecting its mechanical properties and insulating properties, so as to extend its service life. In this work, the structural characteristics and cross-linking mechanism of XLPE are introduced, the aging process and influencing mechanism are systematically analyzed, and the life decay problems of XLPE due to aging are explored by using methods such as the temperature Arrhenius equation and the inverse power law of voltage. The improvement strategies such as grafting, blending, and nanoparticle modification can be used to enhance the thermal stability, antioxidant properties, and thermal aging resistance of XLPE, thereby extending its service life. Finally, the strategies of adjusting and controlling the service life of XLPE cable insulation materials in the future are discussed, which provide theoretical guidance for further improving long-term stable operation of XLPE cable insulation materials.

Обоснование безопасного расстояния между размещенными в одной пожарной зоне кабелями каналов безопасности атомных электростанций с водо-водяными реакторами

Currently, there are no methods of mathematical modeling of the operability of power and signal cables used at the nuclear power plants in real and standard fire conditions, including the use of intumescent flame retardants. The purpose of the article is a theoretical assessment of the safe distance between the cables of the safety channels of nuclear power plants with pressurized water reactors located in the same fire zone. To achieve it, the time of occurrence of a short circuit in the cables of the channels of safety systems from the beginning of a real fire and depending on the distance between adjacent cable lines was estimated. An integral method of mathematical modeling of the development of a fire in a room is used. To determine the temperature distribution inside the cable insulation, the thermal conductivity equation is solved. The analysis of the obtained results is carried out. The calculation results made it possible to formulate the requirements for the swelling temperature of fire retardant compounds for treating the outer surfaces of SB cables: the above temperature should be no more than 150 °C for the flame retardant cables, and 180 °C for the non-flame retardant cables, as well as at distances between open cables of two safety systems smaller than 2, the outer surfaces of the safety cables must be treated with a fire retardant compound with a fire retardant efficiency of at least 120 minutes. The conducted theoretical assessment of the safe distance between the cables of the safety channels of nuclear power plants with pressurized water reactors located in the same fire zone, using the proposed mathematical model, showed that in a real fire, in order to prevent a short circuit in the cables of the safety systems, as well as ignition of the insulation of adjacent cables, it is required to justify safe distances between the adjacent cables of the safety system of nuclear power plants, taking into account the specific dimensions of the premises and the properties of the cable insulation material and the fire-retardant coatings used.

Electrical aging of fluoropolymer cable insulation materials induced by partial discharge

Electrical aging of fluoropolymer cable insulation materials induced by partial discharge

High throughput synthesis of SiO2 microspheres enhancing dielectric properties of quartz fibers insulation composites for high temperature resistant communication cable

The development of the digital society has led to an urgent demand for high-temperature-resistant, low-dielectric cable insulation materials. In order to meet the stable high temperature service performance, it is necessary to use inorganic materials instead of the traditional organic insulating materials as the cable insulation layer. Silicon dioxide (SiO2) as a widely used inorganic dielectric material has great potential for application, and quartz fiber is another wave-transparent material with good dielectric properties. The combination of SiO2 and quartz fiber can provide a feasible path for pure inorganic composite insulation materials. In this work, the high-throughput (>50 g) synthesis of SiO2 was investigated to explore the factors affecting the dielectric properties. The effects of different quartz fiber composite amounts and sintering temperatures on the dielectric properties of the composites were investigated by testing the dielectric properties of the composite powders after pressing. The composite powders doped with 20 wt% quartz fibers at 600 °C sintering temperature were found to have better dielectric properties with dielectric constant of 2.48 and dielectric loss of 0.0109 at 20 M Hz. Furthermore, the composite powders were filled into the cables and measured for electrical properties by a network analyzer. And dielectric properties of the cables preliminarily meet the performance requirements for the applications of high temperature (900 °C) radio frequency (RF) communication cables with dielectric constant of 1.731 and insertion loss of 2.02 dB at 18 G Hz. Therefore, this inorganic composite material can be used as the insulation layer for RF high-temperature-resistant communication cables for aerospace, nuclear power plants and energy fields.

Improved Electrical Properties of Organic Modified Thermoplastic Insulation Material for Direct Current Cable Application.

To achieve exceptional recyclable DC cable insulation material using thermoplastic polypropylene (PP), we have introduced the organic polar molecule styrene-maleic anhydride copolymer (SMA) into PP-based insulation materials following the principles of deep trap modification. PP, PP/SMA, PP/ethylene-octene copolymer (POE), and PP/POE/SMA insulating samples were prepared, and their meso-morphology, crystalline morphology, and molecular structure were comprehensively characterized. The results indicate that SMA can be uniformly dispersed in PP with minimal impact on the crystalline morphology of PP. The DC electrical properties of the materials were tested at temperatures of 30, 50, and 70 °C. The findings demonstrate that the introduction of SMA can improve the DC properties of the material in both PP and PP/POE. The thermal stimulated depolarization current results reveal that SMA can introduce deep traps into the material, thereby improving its DC properties, which is in agreement with the quantum chemical calculation results. Subsequently, a bipolar carrier transport model was employed for coaxial cables to simulate the space charge distribution in the insulation layer of the four sets of insulation samples as well as the actual cable in service. The results highlight that SMA can significantly suppress space charge in PP and PP/POE systems, and it exhibits excellent electric field distortion resistance. In summary, the results illustrate that SMA is expected to be used as an organic deep trap modifier in PP-based cable insulation materials.

Polymer Composites With High Thermal Conductivity for HVDC Cable Insulation: A Review

With the development of high voltage direct current (HVDC) transmission technology, the voltage level and transmission capacity of power cable need to be further improved. Joule heat originating from the current in the cable conductor brings a great challenge to extruded cable insulation because of the low thermal conductivity of polymer insulation materials. This paper reviews the harms caused by heat accumulation in cable insulation and methods for improving the thermal conductivity of polymer materials. First, the effects of heat on cable insulation are summarized. Second, the mechanism, influencing factors, and structure design of filler-based polymer composites with high thermal conductivity are introduced. Subsequently, investigations on cable insulation materials with enhanced thermal conductivity are reviewed. At last, some problems with the design of thermal conductive networks in semi-crystalline polymer materials are discussed, and our suggestions for future work are proposed.

Defect detection of composite materials for cable insulation layer based on terahertz

Hidden defects can seriously affect the insulation performance of cables and pose safety hazards. In this article, a novel Non-Destructive evaluation technique for insulation materials based on terahertz time-domain spectroscopy technology is proposed. Firstly, terahertz time-domain spectroscopy technology was used to perform reflective scanning on insulation materials. Various imaging algorithms were used to image terahertz defects. The results showed that the maximum imaging and peak to peak time imaging were effective. At the same time, bilateral filtering was used to process terahertz defect images. The results showed that bilateral filtering not only filtered out noise in terahertz images, but also retained edge details. Terahertz time-domain spectroscopy technology offers a fresh approach for detecting cable insulation material defects non-destructively, and finds application in various electrical environment inspections.

Thermal properties and mechanical behavior of functionalized carbon nanotube-filled polypropylene composites using molecular dynamics simulation

Polypropylene (PP) is widely recognized as an environmentally friendly material for cable insulation due to its good insulation performance and environmental friendliness. One common method for enhancing the overall performance of PP is the addition of nanoparticles. To analyze the influence of different functionalized multi-walled carbon nanotubes (MWCNT) fillers on the properties of PP/MWCNT composite materials from a microscale perspective, molecular dynamics is used to construct pure PP models and models filled with untreated carbon nanotubes (UFCNT), amino-functionalized carbon nanotubes (AFCNT), carboxyl-functionalized carbon nanotubes (CFCNT), and hydroxyl-functionalized carbon nanotubes (HFCNT) (functionalized MWCNT with 4 or 8 functional groups grafted onto them). The simulation results indicate that the doping of nanotubes can effectively enhance the thermodynamic properties of PP. Among them, PP/CFCNT-8 exhibits the most significant improvement in melting temperature and mechanical properties, with an increase in melting temperature of 88.85 K and a 184.52 % increase in Young's modulus. The melting temperature of PP/HFCNT-8 is second only to PP/CFCNT-8, with an increase of 82.59 K. The results indicate that the thermodynamic properties of PP nanocomposites filled with functionalized MWCNT are improved with the grafting rate. The filling of functionalized MWCNT alters the microscale properties of PP composites, with a significant decrease in root mean square displacement (RMSD), and improvement in free volume fraction (FFV) as well as interfacial binding energy, which can better maintain the electrical properties of PP insulation materials. Applying functionalized carbon nanotubes to filled PP can significantly increase the electrical insulation properties of PP cable materials, which provides meaningful guidance for adopting polypropylene cable insulation materials.

Insulation aging diagnosis and defect location of crosslinked polyethylene cable in the distribution network based on radio frequency identification

With the expansion of power grid construction, the regulatory requirements of various equipment are increasing. Further, the safe and stable operation of the distribution network plays a crucial role in the entire power system. In particular, the cables in DNs are prone to aging during long-term operation due to various factors, such as electricity and heat. Therefore, the effective diagnosis of their operating status is necessary. Crosslinked polyethylene (XLPE) is widely used as the main insulation material for cables in power systems. In this study, the microscale and macroscale performance of the molding process of XLPE cables were compared. Wireless radio frequency identification (RFID) technology was used to diagnose the aging and locate the defects of XLPE cables in the DN. The experiment noted the average insulation crosslinking degree of 88.93% and 87.98% for the suspension chain- and tower-type XLPE cables, respectively. The insulation-melting and crystallization temperatures of the suspension chain-type XLPE cable were approximately 110 °C and 92 °C, respectively, and the crystallinity was approximately 36.5%. The insulation-melting and crystallization temperatures of the tower-type XLPE cable were approximately 105 °C and 88 °C, respectively, and the crystallinity was approximately 34%. Using the wireless RFID technology, the precise positioning of the local aging and insulation damage defects in XLPE cables can be achieved. The error in locating the cable defects using the high-frequency phase spectrum of the cable was less than 0.5 m. Therefore, the study on the manufacture of XLPE cables has significant impact on the physical and chemical properties of their insulation layer. Further, the cable inspection using the wireless RFID technology provides a guarantee on the safe operation of the power system.

Comprehensive Properties of Grafted Polypropylene Insulation Materials for AC/DC Distribution Power Cables

Polypropylene (PP) exhibits excellent insulation properties, high thermo-stability, and recyclable nature, thus expected to be the next-generation insulation material for HV cable application. Chemical grafting modification is an effective technology to improve the electrical properties of polypropylene. In this paper, we develop and report a new-type grafted PP insulation material by water-phase grafting technology. The comprehensive properties including electrical, thermal, and mechanical of it are tested and compared with traditional cable insulation material—crosslinked polyethylene (XLPE). The results show that the grafted PP holds superior thermal properties and enough mechanical flexibility. The electrical properties are of significant advantages, including resistivity enhanced by nearly two degrees of magnitudes, AC/DC breakdown strength raised by over 20%, and obviously suppressed space charge accumulation. These results indicate that grafted PP is very suitable for application in HV cable systems, either AC or DC. This research lays a foundation for the research and development of the next-generation recyclable polypropylene cables at higher voltage levels.

Effect of zinc oxide nanoparticle size on the dielectric properties of polypropylene‐based nanocomposites

AbstractTo develop new environmentally friendly and recyclable high‐voltage cable insulation materials, the effects of the particle size of zinc oxide (ZnO) on the mechanical and electrical properties of nanocomposites were investigated based on a feasibility study of polypropylene (PP) as a high‐performance cable insulation material. The small particle size of ZnO can synergistically toughen PP with a polyolefin elastomer (POE), but the large particle size of ZnO leads to lower elongation at break. Adding ZnO nanoparticles can improve the bulk resistivity of the composites and suppress space charge injection. 0.5ZnO200 has the highest direct current and alternating current breakdown field strengths, 36.6% and 14.7% higher than PP/POE, respectively. This improvement may be due to the ability of 200 nm ZnO to introduce more deep traps. However, as the nanoparticle content rises and the particle size decreases, the agglomeration becomes more frequent, leading to the overlap of inter‐nano interfaces and reducing the modification effect of the nanoparticles. This study on the effect law of nano‐ZnO with different particle sizes on the microstructure, mechanical properties, and electrical properties of PP can provide a reference for developing new recyclable high‐voltage insulated cable materials.