Cable Applications Research Articles

Phase Field Modeling on By-Product Migration in Crosslinking Polymers for HVDC Cable Insulation Applications

Cross-linking by-products has been considered as one of the crucial factors for dielectric properties of cross-linked polyethylene, which plays an important role in the insulation performance of high voltage direct current (HVDC) cables. It migrates across cable insulation incorporating space charge effect, temperature variation of conductivity, etc., which makes it a long-standing puzzle of manipulating the electric field distribution for HVDC cable insulation, especially with the increasing voltage level. Nevertheless, there still lacks a theoretical model describing the migration of the by-products, especially for cable insulation with sizeable dimensions. In this article, a phase field model is established to simulate the migration of acetophenone (i.e., one of the by-products) through calculating the free energy landscape considering the competition between the diffusion driven by concentration gradient and the uphill diffusion caused by by-product aggregation. The results show that the time-dependence migration during degassing leads to an uneven distribution of acetophenone across the cable insulation, which is in good coincidence with the measured results for a full-size cable. Accordingly, the distortion of the electric field in HVDC cable insulation due to the radial distribution variation of acetophenone has been estimated regarding the relationship between by-product content and conductivity, and a method of manipulating the distribution of acetophenone is proposed to optimize the distribution of the electric field in cable insulation. Our work provides a numerical approach for the simulation of by-product migration in crosslinked polymers for insulation applications.

Analysis of Multi-Tendon Friction-Based Composite Anchorage Device for CFRP Cables and Its Anchorage Mechanism

Carbon fiber-reinforced polymer (CFRP) cables are anticipated to be employed in larger, longer, and more durable structures in the engineering field. However, its anchorage devices and mechanism should be appropriately developed and improved. At present, mainly relying on the adhesive force, most anchorage devices may lose their efficiency because of adhesive aging and failure or the slip of an individual tendon. A friction-based composite anchorage device with an integrated bearing of inner cone filler (i.e., load transfer media (LTM)) bonding and a single extruding anchor is proposed, and the anchorage mechanism is examined for Φ7 CFRP cables of strength 2400 MPa. Firstly, sufficient conditions for anti-slip failure of CFRP tendons in the anchorage zone are derived by assuming uniform LTM bonding. The obtained results reveal that the smaller inner pore size of the barrel leads to higher efficiency. Additionally, the maximum efficiency depends on the friction coefficient of the contact surface, the inner cone angle of the barrel, and the diameter and quantity of the CFRP tendons. The necessary conditions for the safety of the CFRP tendon anchorage zone are carefully obtained based on the Tsai–Wu failure criterion. It is concluded that the compressive stress of CFRP tendons in the anchorage zone should gradually increase from the load-bearing end to the no-loading end. Additionally, the relations among the anchorage efficiency coefficient and the CFRP tendon diameter d, the anchorage length l, the dip angle of LTM external conical surface α, and the friction angle β are derived based on the equivalent failure principle. The CFRP cables of four specifications (i.e., with Φ12, Φ19, Φ37, and Φ121 tendons) are designed under theoretical guidance, and eight static tests are carried out for more verification studies. The test results indicate that the anchorage efficiency coefficient of designed anchorage devices can be over 90%, and even up to 96.8%. Further, the failure modes are divergent destruction, which verifies the reliability of friction-based anchorage devices and provides a solid theoretical foundation for the design and engineering applications of CFRP cables.

Tuneable conductivity at extreme electric fields in ZnO tetrapod-silicone composites for high-voltage power cable insulation

Resistive Field Grading Materials (RFGM) are used in critical regions in the electrical insulation system of high-voltage direct-current cable systems. Here, we describe a novel type of RFGM, based on a percolated network of zinc oxide (ZnO) tetrapods in a rubber matrix. The electrical conductivity of the composite increases by a factor of 108 for electric fields > 1 kV mm−1, as a result of the highly anisotropic shape of the tetrapods and their significant bandgap (3.37 eV). We demonstrate that charge transport at fields < 1 kV mm−1 is dominated by thermally activated hopping of charge carriers across spatially, as well as energetically, localized states at the ZnO–polymer interface. At higher electric fields (> 1 kV mm−1) band transport in the semiconductive tetrapods triggers a large increase in conductivity. These geometrically enhanced ZnO semiconductors outperform standard additives such as SiC particles and ZnO micro varistors, providing a new class of additives to achieve variable conductivity in high-voltage cable system applications.

Influence of organic additives with electron‐withdrawing and electron‐donating groups on insulation properties of cross‐linked polyethylene at high temperatures for HVDC cable applications

AbstractThis paper investigated the influence of three aromatic voltage stabilizers (4‐n‐propylbenzoic acid, 2‐methoxyphenylboronic acid, and 3‐aminobenzoylmethylamide) on insulating properties of cross‐linked polyethylene (XLPE) at high temperatures for high voltage direct current (HVDC) applications. The XLPE blends containing 1 wt% voltage stabilizers were prepared through a solution‐blending method. The addition of voltage stabilizers suppressed the space charge inside the XLPE at high temperatures. The DC conductivity of XLPE and its blends increased with temperature. The DC conductivity of the XLPE blended with the 4‐n‐propylbenzoic acid was lowest at the different temperatures and electric fields. The DC breakdown strength of the tested materials continually decreased as the temperature increased. Notably, the DC breakdown strength of XLPE with the addition of 4‐n‐propylbenzoic acid and 3‐aminobenzoylmethylamide was higher than the reference XLPE at high temperatures. Moreover, the thermal stability of the XLPE remained unaffected after the voltage stabilizer's addition, whereas the thermal conductivity was improved. Quantum chemical calculations showed that the addition of voltage stabilizers with lower LUMO could effectively buffer the high‐energy electrons and improve the DC breakdown strength of the XLPE. A buffering mechanism of high‐energy electrons demonstrated the effect of the voltage stabilizers on the DC breakdown strength in the XLPE.

Effect of Polyolefin Elastomers’ Characteristics and Natural Magnesium Hydroxide Content on the Properties of Halogen-Free Flame-Retardant Polyolefin Composites

This study examines the preparation of several composites that are based on natural magnesium hydroxide (n-MDH) and various poly(ethylene-co-octene) polyolefin elastomers (POEs). Design of experiment (DoE) principles have been applied in order to optimize the mechanical, rheological, and flame-retardant properties of the final composites. DoE allows one to evaluate the influence of each variable on an experiment’s final properties. By increasing the density and crystallinity of the POE, a higher elastic modulus was obtained, which resulted in greater tensile strength and lower elongation at break. Improved flame retardant properties (as measured by the limiting oxygen index (LOI) and vertical burning tests) were obtained by increasing the amount of filler within the composite up to 65% and using a polymer with high crystallinity. More specifically, the best balance between mechanical, rheological, and flame retardant properties was provided by DoE using 63.75% n-MDH filler. The agreement between the predicted performance and the final properties of the composites has enabled the innovative use of DoE to provide reliable predictions about the final mechanical and flame retardant properties of the compounds that are used for low voltage electrical cable applications.

Analisis Perpindahan Besar Akibat Gaya Non-Konservatif

Structural applications based on large displacement analysis are widespread in various fields, such as the application of aircraft structures, membranes, cables, pipelines and risers. In this study, the author reviews the structural responses based on large displacement theory and non-conservative load models, assuming linear sections and materials. The parameters reviewed are the variation of the load factor and the variation of the slope angle of the load P at the end of the span. Solving non-linear differential equations with non-conservative force, using numerical integration method. The simulation results with the variation of the load factor with the angle of inclination, vertical and horizontal displacements are obtained, where the final orientation of the acting force corresponds to the deformation of the structure, and the maximum deformation occurs at a load angle of 90o, the deformation decreases for the angle orientation is getting smaller.

Effect of gamma irradiation on titanium dioxide-filled polymer composites in cable insulation applications

Effect of gamma irradiation on titanium dioxide-filled polymer composites in cable insulation applications

A Power Cable Reference Frame dqn Model for Fundamental Frequency Analysis

This paper proposes an underground power cable dqn model that can be used for both electric machines analysis and control at or around the fundamental rated power frequencies (50Hz or 60Hz). The model can be used as an observer to estimate the cable output states. This makes the far end measurements available through estimations for long cable applications such as electrical submersible pumps and wind generations. The model can be used also in simulation analysis with accelerated simulation time. Advantages include fast computation, decoupled network, and ability to work under unbalanced supply or network conditions without requiring an interface stage, such as the Eigen vectors calculation, between the cable and electric machine models. Detailed model derivations and analyses, including balanced, unbalanced, and transient conditions, are provided. Verifying using MATLAB SIMULINK, the model has a higher accuracy in balanced and unbalanced conditions when compared to the per-phase shifted frequency analysis (SFA) model in simulations, along with one of the shortest computation times among all simulated models. For the experiment, the researchers design a test consisting of a 20 ft cable operating at 6 kHz used to emulate an equivalent 2,000 ft cable with the proposed cable model as an observer., the results prove to be accurate, with the maximum error between the measured cable output and the model output estimation at 0.12%. Therefore, the model is verified by the experiments in the same given conditions as the simulations, and it can be considered as a reference in the future.

Cooling System Equipped with Turbo-Brayton Refrigerator for HTS Cable

The Turbo-Brayton refrigerator is needed to keep the sub-cooled state of liquid nitrogen in a cooling system for the High Temperature Superconducting (HTS) Cable. Our developed Turbo-Brayton refrigerator were applied in two HTS Cable applications of electric power and railway feeder. In this paper, the specifications and performance test results of Turbo-Brayton refrigerators aimed for electric power and railway feeder applications are described. Further, this Turbo-Brayton refrigerator had been proven reliable in the HTS Cable demonstration Project at Yokohama. These test results of the cooling system, including the Turbo-Brayton refrigerator, are also introduced.

Stability Analysis of Rock Slope with Multilayer Weak Interlayer

The existence of the weak interlayer of the rock slope changes its mechanical characteristics. To ensure the safety of the slope, it is necessary to analyze the overall stability of the slope. Taking the double-layer weak interlayer rock slope beside 318 National Road in Qiyue Mountain, Hubei Province, as an example, a slope model with a weak interlayer was established through GTS software, and the model was imported into FLAC3D for calculation, and the deformation of the slope by the double-layer soft interlayer was studied. The influence of characteristics and safety factors reveals the controlling effect of the double-layer weak interlayer on the stability of the slope and its failure mode. The potential sliding surface of the slope is determined to be the lower weak interlayer, and the weak interlayer after the anchor cable reinforcement is carried out. Numerical analysis shows that the reasonable application of anchor cables significantly improves slope stability. The research results can provide reference significance for slope stability analysis of similar projects.

Electrical conductivity of intermetallic and nanocomposites: A comparative experimental and theoretical study

• Four series of intermetallic and metal nanocomposites were synthesized. • The influence of heat treatment, coinage metal, and ferromagnetic material was investigated. • Electrical conductivity increases with heat treatment temperature and sub-zero temperature. • The electrical conductivity of nanocomposites was higher than IMCs and coinage metals. • Experimental finding was supported by the theoretical (computational) study. In an attempt to find room-temperature superconductors, the electrical conductivity of intermetallic and nanocomposites needs to be explored at room and subzero temperatures by different experimental and theoretical methods. For the same, the intermetallic compounds (IMCs) and nanocomposites (NCs) of ZnO, TiO 2 , Al 2 O 3 , and CuO were synthesized by high-temperature reactive synthesis and Sol-gel techniques, respectively. NCs were annealed at 100, 200, 300, and 400 °C. The NCs were characterized by FESEM, XRD, UV visible, and FTIR methods. The theoretical study (DMol3, CASTEP, Forcite, Reflex, and VAMP) were performed to study the electronic and optical properties of metal nanoparticles. The effect of annealing, the coinage metals, and ferromagnetic material, and decrease in temperature on the electrical conductivity of IMCs and NCs were meticulously investigated. The electrical conductivity of NCs increases with heat treatment temperature (400 °C), and with the decrease in temperature (−70 °C). The addition of α-Fe 2 O 3, and coinage metals does not have a significant effect on the increase in electrical conductivity of NCs. The conductivity of NCs was found higher than IMCs and coinage metals. The synthesized NCs can have a large number of applications in nanowires, nano cables, and quantum dots.

Application of dehumidification as anti-corrosion technology on suspension bridges: A review

• Dehumidification is a proactive corrosion protection for suspension bridges’ main cable. • A review on different dehumidification systems on suspension bridges. • Discussion on limitations and adaptations for main cable anti-corrosion application. • Identifying future scenarios and challenges of dehumidification on suspension bridges. The moisture from residual droplets during construction and infiltration of wet air during operation can cause metal corrosion of main cables on suspension bridges. Main cable dehumidification, emerged as a prospective corrosion protection approach, which provides an internal environment of relative humidity below 60%, would significantly mitigate the corrosion. This paper presents a state-of-the-art listicle review of existing dehumidification systems implemented on 47 suspension bridges (e.g., the Akashi Kaikyo Bridge, the Runyang Yangtze River Bridge). Dehumidification methods adopted in suspension bridges, including solid desiccant dehumidification, condensing dehumidification and integrated dehumidification, are elaborated. Based on that, crucial limitations and adaptations of various systems for main cable applications are discussed. Then, technical suggestions concerning the moisture load matching, sensor configurations, full-bridge sealings, dehumidification equipment placement and system division, are given to realize system sustainability and energy efficiency. Finally, this paper examined one potential development of a multi-stage dehumidification system that uses condensing dehumidification and solid desiccant dehumidification, which facilitates cascade utilization of the waste energy and enhances the system efficiency.

High density polyethylene and metal oxides based nanocomposites for high voltage cable application

AbstractThe current research aims to study the influence of loading of aluminum oxide (Al2O3) and titanium dioxide (TiO2) nanoparticles on the mechanical, electrical, dielectric, thermal and dielectric breakdown strength properties of high density polyethylene (HDPE) specially used for the main insulation in power cables. The HDPE/Al2O3and HDPE/TiO2nanocomposites were prepared by melt blending technique with different ratios of nanoparticles. A modifier was used to reduce the agglomeration of TiO2and Al2O3nanoparticles inside the HDPE matrix. There are improvement in tensile strength (35% and 47.2%), tensile modulus (37.9% and 40.8%), flexural strength (18.8% and 23.1%), flexural modulus (11.2% and 12.4%), impact strength (11.8% and 13.9%), electrical conductivity (102and 104), dielectric constant (80% and 224%), dielectric breakdown strength (35% and 41%), thermal stability (43°C and 34°C), melting point (5.5°C and 5.9°C), hardness (7.3% and 9.4%), and crystallization temperature (3.3°C and 4.2°C) of HDPE/Al2O3and HDPE/TiO2nanocomposites, respectively, after certain loading of both fillers compared to neat HDPE. The elongation at break and crystallinity were reduced after the addition of both nanofillers within the HDPE matrix. Except thermal stability, the titania based nanocomposites exhibited good performance compared to alumina based nanocomposites. Overall, this substantial improvement in results showed that both composites can be used for high voltage cable application.

Synthesis of a Cyclophosphazene Derivative Containing Multiple Cyano Groups for Electron-Beam Irradiated Flame-Retardant Materials

A cyclophosphazene derivative containing multiple cyano groups, denoted as hexa(4-cyanophenoxy)cyclotriphosphazene (CN-CP), was synthesized by a one-step nucleophilic substitution reaction for a phosphorus-nitrogen flame retardant. To meet the strict requirement of safe and environment-protective insulation materials, a series of composites based on low-density polyethylene-poly(ethylene-co-vinyl acetate) containing CN-CP/Mg(OH)2/Al(OH)3 organic-inorganic synergistic flame retardants was fabricated. High-energy electron beam irradiation was subsequently applied to obtain a halogen-free flame-retardant crosslinked system. The relationship between crosslinking degree and irradiation dose was studied, and crosslinking degrees ranging within 63–85% were obtained under 100–190 kGy. Furthermore, the effects of CN-CP filler and irradiation dose on the properties of the composites were carefully investigated. The maximum tensile stress and limiting oxygen index values of most composites irradiated by EB were more than 15 MPa and 28%. Results revealed that the obtained materials had excellent thermal and mechanical, flame-retardant, and insulation properties, thereby suggesting their promising prospects for wire and cable applications.

Evaluation of graphene/crosslinked polyethylene for potential high voltage direct current cable insulation applications

This paper evaluates the potential usage of graphene/crosslinked polyethylene (graphene/XLPE) as the insulating material for high voltage direct current (HVDC) cables. Thermal, mechanical and electrical properties of blends with/without graphene were evaluated by differential scanning calorimetry (DSC), tensile strength, DC conductivity, space charge measurements and water tree aging test. The results indicate that 0.007–0.008% weight amount of graphene can improve the mechanical and electrical insulation properties of XLPE blends, namely higher tensile/yield strength, improved space charge distribution, and shorter/fewer water tree branches. The improvements mainly attribute to the high stiffness of graphene, deep traps introduced by the interaction zones of graphene and XLPE, and the blockage effect of graphene within XLPE. For thermal performance of XLPE blends, graphene nano-fillers have but limited improvement. The crystallinity of the blends barely changes with the addition of graphene. However, the crosslinking degree increases as the additive-like amounts of graphene doped. The above findings provide a guide for tailoring lightweight XLPE materials with excellent mechanical and electrical performances by doping them with a small amount of graphene.

Cable Force Measurement Technology and Engineering Application

With the continuous development of prestressing technology, cables have been widely used in structural engineering. A special concern in practical engineering is selecting the appropriate cable force measurement technology. This paper analyzes and introduces the principle of cable force measurement technology commonly used in current engineering from three aspects, namely, strain, vibration and wave fluctuation, and force balance. Combined with an actual project, the selection and arrangement of measuring points in the cable pre-tension measurement and other issues are discussed. The engineering example shows that the cable force measurement method based on FBG sensor presented in this paper can capture the action of each construction tensioning operations in real time and accurately. Monitoring the tension of the structure in real time is convenient for engineers and technician. The process is suitable for cable force monitoring during the construction tensioning stage. Furthermore, the EM sensor has good stability and durability and is suitable for long-term cable force monitoring.

High-temperature electrical conductivity and thermal stability of FeCl3 doping in carbon nanotube tapes

We report on the development of high-conductivity carbon nanotube (CNT) tapes with high stability at elevated temperatures (220 °C) by a two-step FeCl3-doping process at ambient pressure. Raman spectroscopy, electron microcopy, and thermogravimetric analysis reveal that this robust behavior is ascribed to the retentiveness of the dopants in the CNTs. These results advance the development of CNT tapes for practical cable applications under harsh conditions.

Optimization of the Mechanical Properties of Polyolefin Composites Loaded with Mineral Fillers for Flame Retardant Cables

Formulations based on mineral fillers and polymeric matrices of different nature were studied to obtain halogen-free flame retardant compounds (HFFR) for cable applications. The work was carried out by comparing fire-retardant mineral fillers of natural origin with synthetic mineral ones available on the market. As a reference, a formulation based on micronized natural magnesium hydroxide (n-MDH, obtained from brucite) and an ethylene-vinyl acetate copolymer with 28% by weight (11% by moles) of vinyl acetate were selected, and the mechanical and flame retardant properties compared with formulations based on secondary polymers combined with EVA, metal hydroxides, and carbonates. Notably, we found a synergistic effect in the mechanical, rheological and flame retardant properties for the composite containing a mixture of n-MDH and boehmite in a 3:1 weight ratio. Overall, the present work provided a complete and optimized recipe for the formulation of polymer composites characterized by the required flame retardant and mechanical features in electric cables applications.

SUSPEN DOME: AN EVALUATION WITH CFRP CABLES

This study investigated the feasibility of using CFRP cable as tension cables in suspen domes in view of the fact that suspen domes have been made with steel cables as its cable-strut system for centuries due to its availability. Indisputably, CFRP cables have become the material of choice in the 21st century for its efficiency and innovative design in bridge works. However, the application of CFRP cables to other cable structures has been limited. The need for its application to other cable structures is required in order to acquire more knowledge about its behavioral patterns. This paper gives preliminary findings of a successfully designed and constructed suspen dome prototype which comprehensively deepens the understanding of CFRP cable performance as a cable-strut system in a suspen dome. Results show that with its high stiffness, low weight and high strength, CFRP has proven to be a technically efficient and adequately strengthening material for structurally improving the adequacy of a suspen dome.

Research on application of tower sharing in overhead transmission line in China

As a social public infrastructure, overhead transmission lines were mainly used to transmit high load electrical energy and communication information. It was an important lifeline project, and had the characteristics of extensive spatial distribution, large number, and safe operation and so on. Transmission lines had a certain technical reserve and good feasibility in shared tower technology, in line with the communication and sensing industry of shared application and development. The results demonstrated that shared transmission line can support the application of different OPGW cables, acre station and micro base station for multiple vendors, and different sensing devices. It was showed very good economic benefit and social benefit in different shared application scenarios.