Cable Applications Research Articles

Opportunities to Improve Marine Power Cable Ratings with Ocean Bottom Temperature Models

Determining reliable cable ampacities for marine High Voltage Cables is currently the subject of significant industry and academic reassessment in order to optimize (maximizing load while maintaining safe operating temperatures) design and reduce costs. Ampacity models can be elaborate, and inaccuracies are increasingly predicated on the uncertainty in environmental inputs. A stark example is the role of ambient temperature at cable depth, which, due to the scale of cables and the inaccessibility of the seafloor, is commonly estimated at 15 °C. Oceanographic models incorporating ocean bottom temperature are increasingly available, and they achieve coverage and spatiotemporal resolutions for cable applications without the requirement for project specific measurements. Here, a rudimental validation of the AMM15 and AMM7 mean monthly ocean bottom temperature models for the NW European Shelf indicates encouraging accuracies (MBE ≤ 1.48 °C; RMSE ≤ 2.2 °C). A series of cable case studies are used to demonstrate that cable ratings can change between −4.1% and +7.8% relative to ratings based on a common static (15 °C) ambient temperature value. Consideration of such variations can result in both significant ratings (and hence capital expenditure and operating costs) gains and/or the avoidance of cable overheating. Consequently, validated modelled ocean bottom temperatures are deemed sufficiently accurate, providing incomparable coverage and spatiotemporal resolutions of the whole annual temperature signal, thereby facilitating much more robust ambient temperatures and drastically improving ampacity estimates.

Cable Temperature Prediction Based on RF-GPR for Digital Twin Applications

With the wide application of power cables in the field of transmission and distribution and the increasing emphasis of power departments on the reliability, safety and stability of power cable operation, how to more accurately and quickly analyze the temperature distribution of power cables and how to evaluate the running state of power cables have become research hotspots. Through the combination of finite element calculation and the artificial intelligence method, an innovative method of digital twin cable temperature prediction based on RF-GPR is proposed in this paper. Firstly, the finite element method is used to calculate the coupling of the electromagnetic field and temperature field of a 10 kV AC cable laid in the cable trench, and a certain amount of basic data are provided through the finite element calculation results. Then, using the basic principle of the random forest (RF) variable importance score, the RF-GPR cable temperature prediction model is constructed using the series hybrid model and Gaussian process regression (GPR), the model prediction results are compared and analyzed, and the calculation time is improved by about 1500 times. Finally, a digital twinning platform for cable temperature calculation based on RF-GPR is designed, which provides technical support for the application of digital twinning.

Methods for multi-segment continuous cable analysis

Cables are invaluable members for some applications of engineering. The specialty is due to its behavior under transverse loads. Having almost no rigidity in transverse direction makes cables different from other structural elements. In most applications, cables are assumed to be two force members. However, not only its weight but also its application with roller supports makes them different structural elements. Generally, cables are assembled as single-segmented cables (SSC) where they are fixed at their ends. However, in most of the SSC applications, cables have intermediate supports which can be rollers or sliders. These type of cable applications are called as multi-segment continuous cables (MSCC). In MSCC systems, the cable fixed at its ends and supported by a number of intermediate rollers. Total length of cable is constant, and the intermediate supports are assumed to be frictionless and stationary. In this problem, the critical issue is to find the distribution of the cable length among the segments in the final equilibrium state, so reactions at all supports can be found. Two methods are proposed for the segment length adjustment based on the stress continuity among the cable. These methods are named as direct stiffness method and tension distribution method (relaxation method). Results calculated from the proposed methods are verified by both the reference benchmark problems and commercial finite element program.

Full Anchor Cable Support Mechanism and Application of Roadway with Thick Soft Rock Mass Immediate Roof

The focus of this paper is the thick soft rock mass roof of the track roadway in the No. 3606 panel of the Chaili Coal Mine. Due to its substantial thickness, the soft rock mass roof of the roadway is susceptible to damage and deformation during the mining process. In order to preserve the integrity of the roadway roof, a full anchor cable support scheme is proposed after studying the mechanism of bolt-anchor cable support. The supporting parameters and feasibility of the scheme were determined through support experience and numerical simulation analyses in the field. Moreover, on-site monitoring and data analysis were conducted, revealing that the anchor cables and anchor bolts played a stable role in supporting the roadway. The displacement of the roadway’s roof and floor was minimal, as was the displacement of the two ribs. The overall deformation of the roadway was minor. Practice demonstrated that the full anchor cable support method was effective in supporting the immediate roof of thick soft rock.

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.

Preparation and physical properties of fluorosilicone rubber/polypropylene thermoplastic vulcanizates

ABSTRACT A new thermoplastic vulcanizate (TPVs) composed of polypropylene and fluorosilicone rubber was successfully prepared via dynamic vulcanization focusing on undersea cable and automobile applications. Phase morphology confirms the dispersed rubber particles in a continuous thermoplastic phase. The influence of vulcanization and post-curing time on the mechanical and dynamic properties of TPVs was investigated. Notably, the tensile strength decreased, and the compression set increased with an increase in vulcanization time. Overall, the fabricated TPVs possessed good tensile strength, elastic behavior, and thermal stability. The post-curing time effect on TPVs exhibited a good compression set and lower hardness, but tensile properties deteriorated.

A Novel Smart CFRP Cable Based on Optical Electrical Co-Sensing for Full-Process Prestress Monitoring of Structures.

Carbon-fiber-reinforced polymer (CFRP) is a type of composite material with many superior performances, such as high tensile strength, light weight, corrosion resistance, good fatigue, and creep performance. As a result, CFRP cables have great potential to replace steel cables in prestressed concrete structures. However, the technology to monitor the stress state in real-time throughout the entire life cycle is very important in the application of CFRP cables. Therefore, an optical-electrical co-sensing CFRP cable (OECSCFRP cable) was designed and manufactured in this paper. Firstly, a brief description is outlined for the production technology of the CFRP-DOFS bar, CFRP-CCFPI bar, and CFRP cable anchorage technology. Subsequently, the sensing and mechanical properties of the OECS-CFRP cable were characterized by serious experiments. Finally, the OECS-CFRP cable was used for the prestress monitoring of an unbonded prestressed RC beam to verify the feasibility of the actual structure. The results show that the main static performance indexes of DOFS and CCFPI meet the requirements of civil engineering. In the loading test of the prestressed beam, the OECS-CFRP cable can effectively monitor the cable force and the midspan defection of the beam so as to obtain the stiffness degradation of the prestressed beam under different loads.

Digital Predistortion Linearization of a GaN HEMT Push-Pull Power Amplifier for Cable Applications With High Fractional Bandwidth

This paper presents two linearization strategies for a custom-designed wideband push-pull (PP) power amplifier (PA) for wired communication applications such as, for example, cable TV. Two digital predistortion (DPD) behavioral models are proposed to meet the in-band and out-of-band linearity requirements when efficiently amplifying wideband DOCSIS signals with high fractional bandwidth (FBW). A radiofrequency (RF) DPD linearizer based on a band-pass generalized memory polynomial (BP-GMP) behavioral model and a baseband (BB) I-Q DPD linearizer based on a harmonic distortion GMP (HD-GMP) behavioral model are proposed. Both DPD models take into account the harmonic distortion typical of high FBW amplification. Experimental results will show high efficient and linear amplification of a 4 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\times$</tex-math> </inline-formula> 192 MHz composite DOCSIS signal by properly combining a crest factor reduction (CFR) technique and the proposed DPD strategies.

Dow driving decarbonization with cable insulation compounds and collaborating with New Energy Blue to develop plastic from corn residue

On June 1, 2023, Dow (NSYE: DOW) introduced ENDURANCE™ HFDD-4201 SC Compound for Cable Systems to the North America market, the company's novel cross-linked polyethylene (XLPE) solution. XLPE insulation reportedly is the leading technology for high-voltage transmission cable applications but currently requires degassing periods of up to a few weeks to reduce cross-linking byproducts. ENDURANCE™ HFDD-4201 is claimed to transform the cable manufacturing process by significantly reducing cable degassing times, which should result in lower CO2 emissions during the manufacturing phase, while keeping the same high quality.

Static tensile mechanical properties and engineering application of constant resistance and large deformation anchor cable

Deep engineering is faced with mechanical phenomena, such as substantial soft rock deformation and in situ stresses, that results in frequent disasters because the energy of the surrounding rock cannot be released normally after excavation. Traditional support materials have low elongation and safety reserves, cannot adapt to large deformations of the surrounding rock, and cannot apply high preload, making it difficult to absorb energy. This study introduces a new type of constant resistance and large deformation (CRLD) cable through static tensile experiments, and compared the results of which with those of ordinary high-strength (HS) cables. Our results showed that the CRLD cable had an obvious constant resistance stage, with a constant resistance value of approximately 415 kN and an elongation rate as high as 25%, which is 3.9 times that of the HS cable. Furthermore, the energy absorption of the CRLD cable was 3.5 times that of the HS cable. Before the first steel strand broke, the temperature of the entire cable was approximately 33 °C, and the energy was absorbed evenly without obvious energy concentration. After breaking, the standard deviation of the segmental elongation of the steel strand was 4.16 mm, with a small degree of dispersion. The deformation of each section of the steel strand was uniform lengthwise and the necking rate of the fracture was 8.5%, indicating that there was no obvious necking. On this basis, a comprehensive mechanical performance evaluation index of the cable, that is, the static toughness UT, was proposed, reflecting the strength, elongation, and energy absorption density of the cable. Compared with the HS cable and another widely used He cable with excellent energy absorption characteristics, the UT of the CRLD cable was 117% higher than that of the HS cable and 38.1% higher than that of the He cable. This study also proposes a support and design principle for the CRLD cable and applies a CRLD cable to a roadway with a buried depth of 1050 m. Our results show that, owing to the high-strength reserve of the CRLD cable, the applicable preload can reach more than 85% of the breaking load of the cable, which is 2.3 times that of the HS cable. After this new support was adopted, the maximum deformation of the surrounding rock of the roadway was 180 mm, which is 36% of that of the traditional support. The deformation of the roadway was controlled and the surrounding rock was stable.

Application and Practice of Variable Axial Force Cable in Powerhouse Truss Reinforcement System

Long-span steel structure trusses are widely used in factory buildings. However, with the increase in service time and dynamic load fatigue, transverse cracks at the bottom of the middle span and oblique deformation of the abdomen during the operation process may appear in a considerable part of long-span trusses with dynamic load. The U-shaped cracks at the bottom and belly, as well as the mid-span down deflection of the main truss, can also reduce the functionality of the factory building truss structure and limit the original crane load, thus affecting the normal safety and durability of the structure. Therefore, the principle of variable axial force cable system in the long-span factory building truss structure and 3D3S software modelling were applied. Analysing and studying the reinforcement method of large-span powerhouse trusses can provide practical experience for subsequent similar projects. In view of the above phenomenon, the large-span powerhouse trusses of Hongcheng Powerhouse No. 1 and No. 2, located in Tonglu, Zhejiang Province, were used as the research objects, and the variable axial force cable method was proposed to strengthen and lift the load. Considering the span of the powerhouse truss, a cable system with 22 m and a controlling force of 400 kN was proposed for Powerhouse 1, and a cable system with a variable axial force of 24 m was proposed for Powerhouse 2. The force model of large-span trusses was established by using the finite element method, which is commonly used to analyse the force of the truss. The influence of the reinforcement effect was analysed under two working conditions and compared from three aspects: stiffness, bearing capacity and stability. Furthermore, the phenomenon of uneven stress distribution was analysed. The stress distribution characteristics of each node were understood by simulating the most disadvantageous node plates with the greatest internal force before and after reinforcement.

Mechanical behavior of soft rock roadway reinforced with NPR cables: A physical model test and case study

Deep soft rock roadways are prone to large deformations and failure when reinforced with traditional rockbolts owing to the stiffness mismatch between soft rocks and rockbolts. Thus, a novel rockbolt named “negative Poisson’s ratio (NPR) bolt/cable” that maintains a constant support force during loading is used to reinforce deep soft rock roadways to prevent large deformations. In this study, a large-scale physical model test was conducted to reveal the mechanical performance of NPR cables in soft rocks and obtain the mechanical properties of reinforced rock masses. The test results show that the rock mass reinforced with the NPR cable underwent progressive failure and exhibited the characteristics of a constant-resistance yielding-pressure under external loading, suggesting that NPR cables operate well with soft rock masses. Moreover, on-site investigations confirmed that the effective control of NPR cable supports slow and large deformations of soft rock roadways. An analytical model was developed to verify the physical model test results. The study findings can serve as a reference for theoretical model studies and field applications of NPR cables to prevent large deformations.

Assessment of the effect on the plasticizer diffusion of inorganic fillers in plasticized poly(vinyl chloride) composite films for cable sheath applications

AbstractIn cable sheath applications, plasticizer migration is important as it causes reduction in mechanical properties, deterioration, and pollution in transported environments. This study focuses on the effect of inorganic fillers on the diffusion of plasticizers from plasticized‐PVC cable films. Plastisols were prepared by mixing plasticizer, thermal stabilizers, and inorganic fillers (boric acid, boron clay, sintered calcined boron waste clay, talc, and zircon oxide) into the PVC resin. Plastigel films were cured and thermally aged at 100, 130, and 160°C. Oxidation index were determined by Fourier transform infrared spectroscopy. The diffusion coefficient and activation energies were calculated from mass loss. Thermogravimetric analysis analyses were performed to obtain weight loss. Fillers were characterized for their zeta potential, particle size distribution, polydispersion. Morphology of the fillers was also conducted using scanning electron microscopy. Their mechanical and rheological analyses were evaluated with the tensile and melt flow index test. The order of diffusivity was determined as the films having boric acid &gt; undoped &gt; talc = sintered boron clay &gt; zircon &gt; boron clay. The result of this evaluations is the addition of inorganic filler increases the mechanical and thermal applicability and reduces the plasticizer diffusion. It is thought that the results, will contribute to the studies on the plasticizer transition in cable applications.

Lightweight Copper–Carbon Nanotube Core–Shell Composite Fiber for Power Cable Application

The substitution of traditional copper power transmission cables with lightweight copper–carbon nanotube (Cu–CNT) composite fibers is critical for reducing the weight, fuel consumption, and CO2 emissions of automobiles and aircrafts. Such a replacement will also allow for lowering the transmission power loss in copper cables resulting in a decrease in coal and gas consumption, and ultimately diminishing the carbon footprint. In this work, we created a lightweight Cu–CNT composite fiber through a multistep scalable process, including spinning, densification, functionalization, and double-layer copper deposition. The characterization and testing of the fabricated fiber included surface morphology, electrical conductivity, mechanical strength, crystallinity, and ampacity (current density). The electrical conductivity of the resultant composite fiber was measured to be 0.5 × 106 S/m with an ampacity of 0.18 × 105 A/cm2. The copper-coated CNT fibers were 16 times lighter and 2.7 times stronger than copper wire, as they revealed a gravimetric density of 0.4 g/cm3 and a mechanical strength of 0.68 GPa, suggesting a great potential in future applications as lightweight power transmission cables.

Laboratory Model Test and Field In Situ Test of Distributed Optical Fiber Monitoring of Seepage in a Karst Depression Reservoir Basin

Karst depressions are ideal places for building reservoirs and stacking wastes, but karst depressions are mostly located in areas with strong karst development, and there is a problem of karst leakage. The study of karst depression monitoring methods can provide technical support for the construction of reservoirs in karst depressions, and leakage monitoring technology based on distributed temperature sensing (DTS) has the clear advantages of a large measurement range, high precision, continuity, wide distribution, large area, etc. In this paper, a temperature-sensing optical cable is first used to conduct leakage monitoring tests in different soil media, and the temperature change curve in different media is obtained, which verifies the feasibility of the heatable temperature-sensing optical cable to identify leakage in soil media with different moisture contents. Then, for the heatable distributed temperature-sensing optical cable, the variation law of the temperature eigenvalues of the sensing optical cable under different seepage velocities is studied using the layout method wrapped with saturated medium-coarse sand, and the relationship between the seepage rate and the temperature eigenvalues was analyzed. A regression formula for quantitative analysis of leakage velocity was established; finally, the manganese slag silo project in Songtao County in Guizhou Province, China, was used to simulate different leakage conditions on site for testing, and the data were compared and analyzed to obtain the route under different conditions. The temperature distribution law of the seepage section verifies the feasibility of the application of heatable temperature-sensing optical cables in the seepage monitoring of karst depressions.

Research on 3D Shape Monitoring System of Submarine Cable

Submarine cables have been used for more than one hundred years, while they have been widely used in recent decades. Safety has always been an issue with submarine cable applications because of their fast expansion. Submarine cables are more susceptible to operational risks and failure than terrestrial cables. Once the submarine cable malfunctions, it will bring huge inconvenience to production and life, which will cause huge economic losses. Therefore, it is very necessary to quickly locate the fault point of the cable and complete the emergency repair work. This article provides a 3D monitoring method for submarine cables, with a simulation monitoring system built in the laboratory to verify the method’s feasibility.

Enabling High-Performance Polypropylene Nanocomposites With Interfacial Deep Traps

Polymer nanocomposites are the material of choice for dc insulation. The emerging demand for high-capacity high voltage direct current (HVdc) power transmission requires polymer nanocomposites capable of safe and stable operation at high temperatures. However, the high-temperature electrical properties of current polymer nanocomposites are still unsatisfactory. Here, we report that the modulation of polymer/nanoparticle interfaces can greatly improve the high-temperature insulation properties of polypropylene (PP)-based nanocomposite for recyclable HVdc cable insulation application. The nanoparticles are surface-modified with PP-graft-maleic anhydride (PP- <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${g}$ </tex-math></inline-formula> -mah), which is not only well miscible with PP but also contains polar groups to act as interfacial deep traps. We demonstrate that the interfacial deep traps can improve the dc breakdown strength and the electrical resistivity of polymer nanocomposite by inhibiting the charge injection. This work deepens the understanding of interfacial effects in polymer nanocomposites and provides new opportunities for designing high-performance recyclable insulation materials for HVdc cables.

Optimal Content Selection of Voltage Stabilizers Using TOPSIS Method to Achieve Enhanced Material Properties for HVDC Cable Insulation Applications

Three different contents (1, 3, and 5 wt%) of 4-n-propylbenzoic acid as the voltage stabilizer are added to cross-linked polyethylene (XLPE), whereas electrical, mechanical, and thermal properties of XLPE/stabilizer blends are measured. The obtained results show that the voltage stabilizer addition facilitates a reduction in accumulated space charges and conduction current and improves the life exponent and thermal conductivity of the XLPE but negatively affects the degree of cross-linking. The optimal content of the voltage stabilizer to attain the balanced overall properties is selected by the technique for order of preference by similarity to ideal solution (TOPSIS) method. The electric field distortion rate, conduction current, and temperature sensitivity of electrical conductivity under 40 kV/mm, dc breakdown strength, thermal conductivity, gel content, elongation at break, tensile strength, crystallinity, and temperature at a maximum decomposition rate of the samples are selected as evaluation indices for the TOPSIS method, which yields the 1 wt% of 4-n-propylbenzoic acid as the optimal content. The calculated life exponent is maximum for the XLPE-1, suggesting that the high voltage direct current (HVDC) cable having XLPE insulation with the optimal content of the voltage stabilizer will have a longer service life.

Insulation Properties and Interfacial Quantum Chemical Analysis of Cross-Linked Polyethylene Under Different Degassing Time for HVDC Cable Factory Joint Applications

Degassing treatment is critical to remove cross-linking by-products in cross-linked polyethylene (XLPE) cable factory joints and prevent early insulation deterioration. In this article, 500-kV high-voltage direct-current (HVDC) cable factory joint samples were prepared, and the physicochemical and temperature-dependent electrical properties of the samples under different degassing times were investigated. The results show that prolonged degassing treatment increases the crystallinity and reduces the tensile properties of the XLPE samples. The samples without degassing have visible micropores near the interface, and these micropores can be eliminated after a longer degassing time. In addition, degassing treatment can reduce the current density, increase the threshold field strength, and enhance the breakdown strength of the samples. A significant negative charge accumulation appears at the interface of the sample without degassing, which dramatically distorts the electric field. Long-term degassing treatment can improve this phenomenon, and the accumulated charge at the interface at elevated temperatures is significantly reduced. Furthermore, a model of the molecular chain microstructure at the interface before and after degassing is proposed. The molecular chain’s energy band structure and electron cloud distribution at the interface are analyzed based on quantum chemical calculation. It is found that cable makers can improve the insulation properties of cable factory joints by appropriately extending the degassing time to avoid interface deterioration.

Study on high-temperature and high-voltage insulation characteristics of polypropylene blend with highly packed elastomeric domains for power cable applications

In this paper, we report the high-temperature and high-voltage (HV) insulation characteristics of the polypropylene (PP) blend with highly packed elastomeric domains that showed excellent mechanical toughness in our previous study to find its suitability as insulation material for power cable applications. The main focus lies on tensile properties with thermal aging, thermomechanical behavior corresponding to the thermal transition, high-temperature volume resistivity and DC dielectric strength, and space charge accumulation behavior of the PP blend in comparison to the crosslinked polyethylene (XLPE). Our PP blend having low elastic modulus of approximately 266.9 MPa exhibited high tensile strength and elongation at break, and high-temperature stability as well. Using this PP blend, not only good HV insulating performances in volume resistivity and DC breakdown strength (BDS) were obtained similar to XLPE, but also adequate values were obtained at high temperature, even at 110 °C, which was not possible with XLPE. However, there was space charge accumulation and electric field distortion in the PP blend like XLPE, which needs to be suppressed. Therefore, our PP blend is expected to have the potential to replace existing XLPE as insulation materials for future HV power cables.