Power Cable Applications Research Articles

Novel dual‐resonance damped alternating current testing system for offline partial discharge measurement of power cables

AbstractTo accurately detect the early deterioration of electrical insulation in power cables, an energizing system is required for offline partial discharge (PD) measurements. The damped alternating current (DAC) testing system has emerged as an effective tool for inducing PD events. However, the existing systems often suffer from limitations such as signal interference, low sensitivity, and high costs. To address these issues, this study proposes a novel dual‐resonance DAC testing system that is simple in structure and cost‐effective. The prototype was built for testing 10‐kV distribution cables, and its effectiveness was validated through experimental tests on a cable sample. The results show that this approach significantly improves PD detection sensitivity and successfully completes PD localization. This research contributes to the development of more efficient and affordable DAC generation technology for power cable testing applications.

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.

Application of suspended inter-array power cables in floating offshore wind farms

The aim of the present study is to propose an engineering approach of designing suspended inter-array power cable configuration for offshore wind farms. To achieve this, a spar type and a semi-submersible type floating offshore wind turbines (FOWTs) are modeled in the dynamic analysis software OrcaFlex. The accuracy of these models is validated against reference studies. Several different cable configurations connecting two spar FOWTs are assessed based on Fitness Factors using static and dynamic analyses. The non-linear bending behavior and the marine growth effects are considered in the analyses. The number of buoys is found to be the main parameter affecting the maximum effective tension and the minimum bending radii of the cables. The buoy spacing determines whether the cable touches the seabed, floats fully submerged, or floats at the sea surface. The influence of the cable length and the marine growth on the observed cable tensions and curvatures is small for the investigated configurations. The optimum cable configuration found for the two spar FOWTs is employed to connect two semi-submersible FOWTs. The influence of the floater type on the suspended power cable tension and curvature is found to be negligible. Analysis of power cable behavior in an offshore wind farm layout shows that a two-turbine setup with different environmental load directions can be used as a representative case for the suspended power cables design of the entire wind farm.

Nonlinear solutions applied to parameter estimation of overhead transmission lines and submarine cables in offshore facilities

AbstractThis paper proposes a nonlinear analysis of the parameter estimation problem in overhead and submarine power cable applications. The proposed methodology is able to estimate both positive and zero sequence parameters. Also, the measurement model incorporates random uncertainty in a rigorous manner, addressing the issue of noise propagation after applying symmetrical components. Three nonlinear estimation methods were studied to address the nonlinear least squares problems. Several noise levels and sample sizes were considered to demonstrate the robustness of the proposed approach. Finally, the methods were validated using both a simplified 2‐bus system and the IEEE 14‐bus system. The results obtained demonstrated significantly better performance compared to similar results found in the technical literature.

Polypropylene nanocomposites doped with carbon nanohorns for high-voltage power cable insulation applications

Polypropylene nanocomposites doped with carbon nanohorns for high-voltage power cable insulation applications

Effects of Installing Different Types of Cooling Fins on the Cold Side of a Thermoelectric Power Generation Device on the Thermal Efficiency and Exergy Efficiency of Power Cable Surface Waste Heat Recovery.

This study investigates the thermal efficiency and exergy efficiency of a thermoelectric power generation device for recovering power cable surface waste heat. Numerical simulations are conducted to analyze the impact of different types of cooling fins on the system's performance. The results demonstrate that the installation of cooling fins improves heat transfer efficiency and enhances the thermoelectric power generation device's output power. Among the various fin designs, the system equipped with cooling fins with 17 teeth exhibits the highest performance. These findings highlight the importance of fin design in optimizing the system's thermal efficiency and exergy efficiency. This study provides valuable insights for the development and improvement of thermoelectric power generation systems for power cable surface waste heat recovery applications.

Novel Electrical Insulation Coatings for HTS Cables

To develop epoxy based electrical insulation for HTS power cable and other device applications, the suitability of two cryogenic rated commercial epoxies, (MASTERBOND EP29-LPSP and EP37-3FLFAO) were evaluated. Characterization of their electrical breakdown characteristics, mechanical strength, and the interfacial shear strength of the interface with HTS tapes were conducted at room temperature and 77 K. The epoxy materials are ductile at cryogenic temperatures to support their use as electrical insulation of HTS power devices.

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.

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.

Polystyrene: A Self-Dispersing, Ultralow Loading Additive for Improving the Breakdown Strength of Polypropylene for High Voltage Power Cable Applications

Voltage stabilizers (VSs) with benzene derivatives have received great interest as high-performance additives for improving the electrical durability of polypropylene (PP)-based insulation materials for high voltage (HV) power cable applications. In this work, atactic polystyrene (aPS) was first used as a thermoplastic VS (TVS) to efficiently dope the benzene units into isotactic PP (iPP). The aPS TVS was incorporated in the iPP matrix through melt-mixing, and the domain size of immiscible aPS decreased with the decrease of aPS content. The smaller amount of aPS doping increased the direct current (DC) breakdown strength (BDS) of iPP, even at ultralow loading levels below 0.01 phr. The enhancement ratio of the BDS value of iPP with 0.001 phr of aPS was higher compared to the results obtained for other types of additives reported in the previous literature.

Influence of phosphorus-based flame retardants on polypropylene insulation for high-voltage power cable applications

For high voltage (HV) power cable applications, various studies have been performed to improve the mechanical and electrical properties of polypropylene (PP)-based insulation materials to replace crosslinked polyethylene. However, studies on the effect of additives to yield additional PP properties are still lacking. Herein, we prepared PP blends by melt-mixing widely used commercial flame retardants for PP with isotactic PP (iPP) and investigated their electrical breakdown, flame retardancy behaviors, and UV stability. Among the five kinds of flame retardants employed, aluminum hypophosphite (AHP), aluminum diethyl phosphinate, melamine pyrophosphate, ammonium polyphosphate (APP), and APP treated with silane, AHP was very effective in minimizing the decrease of the direct current breakdown strength of iPP at both 25 °C and 110 °C in the range of 5–20 phr. Particularly, only AHP afforded V-2 grade flame retardancy to iPP, and the flame retardancy was maintained even when the content was reduced to 3 phr. Furthermore, upon exposure to ultraviolet (UV) rays for 5 d, the tensile strength of pristine iPP decreased by approximately 44%, while that of a blend with 3 phr AHP decreased by only 10%. The study results will contribute to the optimization of power cable products through the use of appropriate flame retardants in the design of high-performance PP-based HV insulation materials.

Performance evaluation of thermally aged ATH and BN co‐doped silicone rubber nano‐micro composites for power cable applications

AbstractPower cables are intended to operate at high temperatures over a long period which may change the performance of silicone rubber insulation used in high voltage cable accessories. Therefore, in the current study, to enhance the properties of silicone rubber, alumina try‐hydrate (ATH) and boron nitride (BN) micro and nanoparticles were added to the silicone rubber matrix. The synthesized undoped silicone rubber, silicone rubber with 40 wt% micro ATH, 7 wt% nano BN, and 10 wt% micro ATH + 5 wt% nano BN composites were thermally aged for 600 h at 180ºC. The composite properties were analyzed through electrical, thermal, and physicochemical techniques. To assess the electrical characteristics, water droplet‐initiated corona discharge studies as per IEC 60112 were conducted and leakage current, corona inception voltage, and erosion resistance were evaluated. A deep learning technique also was employed for the prediction of erosion resistance of the samples. Further, to examine the surface texture and chemical changes on the surface of the material, 3‐D microscopy and Fourier transform infrared spectroscopy (FTIR) was adopted. Finally, thermal distribution analysis was performed for all the composites by infrared thermography. The results demonstrated the suitability of nano‐micro co‐doped composites over nanocomposites and micro composites for power cable applications.

Effect of geometrical irregularities on fatigue of lead sheathing for submarine high voltage power cable applications

High voltage subsea power cables are typically composed of several layers, including: a conductive core, a dielectric layer, a ductile metallic watertight barrier and a series of radial and axial armours and polymer layers. The watertight barrier serves the purpose of preventing water permeating to the dielectric due to the outer layers' polymer hygroscopicity. Water impregnation may cause dielectric breakdown, with fatal consequences on the integrity of the power cable. The watertight barrier is made of extruded lead alloy and is subjected, during the installation and operational life of the component, to axial and radial displacement-controlled fatigue which might lead to cracking, thus to a loss of its isolating properties. Lead, due to the low melting temperature, is characterized by creep deformation and damage even at room temperature. A steel tape is winded around the polyethylene sheathing surrounding the lead barrier, which is deformed, and a helical ridge is generated. This irregularity causes a local concentration of strain which might potentially lead to early failure of the lead sheathing. In this work the results of displacement-controlled fatigue testing at different strain rates of sheathing material including the irregularity is presented and compared to the results in equivalent conditions, but in the absence of the irregularity. The strain concentration caused by the defect is analysed with the implementation of a creep material model calibrated on the cyclic properties of the alloy and the notch sensitivity of the material for the class of defects, temperature and frequency in exam is obtained. The results are applied to the modelling of the stress-strain field in the component with and without irregularity and conclusions are drawn on the danger that such irregularities pose on the structural integrity on the power cable.

Research on live detection technology of cable joint defects based on high-speed light sensing and pressure wave method

With the widespread application of stable high-voltage power cables, cable failures have gradually become the main source of major accidents in the process of power transmission. The most easily damaged part is the cable joint. Since the cable joints are made on site, it is easy to introduce high-voltage cable defects and cause insulation failures. Therefore, the defect detection of high-voltage voltage joints is particularly important. In order to promote the process of urbanization, ensure people’s life quality and personal safety, the popularization of high-voltage cables is an inevitable trend. However, difficulties will be encountered in the detection of cable joint faults. To improve the detection efficiency, relatively extensive research has been carried out on the detection of high-voltage cable joints at home and abroad. Based on the high-speed light sensing and pressure wave method, the online detection method of cable joint defects proposed in this paper has accurate, fast, convenient and non-contact online detection features.

Insulative ethylene-propylene copolymer-nanostructured polypropylene for high-voltage cable insulation applications

Worldwide, various efforts to replace crosslinked-polyethylene (XLPE) as an insulation layer in the cable industry, is becoming increasingly popular for improved recycling of polymer waste. Polypropylene (PP) has been proposed as a representative candidate because of its excellent thermomechanical and electrical performances. However, overcoming the mechanical limitations of intrinsic rigidity is required for cable applications. Herein, PP-based insulating materials were prepared via melt-blending with rubbery ethylene-1-octene copolymer (EOC), followed by mixing an ethylene-propylene random copolymer (rPP) as a surfactant for high-voltage power cable applications. Simple melt-blending of rPP formed a core-shell nanostructure composed of EOC/rPP and a fine dispersion of macron-sized EOC domains. The nanostructured PP ternary blends exhibited multiple advantages in terms of thermal stability, mechanical properties, dielectric performances, and long-term stability compared to the existing XLPE. This study provides a straightforward, rational design of environmental insulation materials for high voltage power cable applications.

Material progress toward recyclable insulation of power cables. Part 1: Polyethylene-based thermoplastic materials: Dedicated to the 80th birthday of professor Toshikatsu Tanaka

New catalyst, copolymerization, blending, nanotechnology, and additives have been used to improve the electrical properties of thermoplastic polyethylene for power cable insulation applications.

Simulation of oscillation wave test system for partial discharge detection of three-core cables in wind power plants

Wind power plants include wind power generation systems, which contain machinery, electrical appliances and their control equipment. Each equipment requires a corresponding cable to connect. In the current application of power cables, the cables used are three single-core conductors or one three-core conductor. Moreover, the wind energy cable must be able to rotate in the forward and reverse directions with the wind turbine. Therefore, the cable must have a soft structure, sufficient tensile strength and bending resistance, and oil and low temperature resistance for the insulating sheath. Due to the harsh environment of wind power generation, the fan has a long service life, and the cable rotates with the fan, which requires high performance of the cable. At this time, the insulation detection of the cable is particularly important. For the current power cable oscillation wave test system, most of the literature only introduces the simple principle of the detection system, and studies based on single-core cable. Based on the three-core cable, this paper performs oscillating wave detection on the three-core cable, and designs the simulation system and studies the influence of insulation defects in different parts. From the experiment results, the proposed system is able to successfully simulate the working procedure of the oscillation wave test system, and to collect the effective partial discharge signals, which validates the effectiveness of the simulation system.

Space charge suppression of polyethylene induced by blending with ethylene-butyl acrylate copolymer

High-voltage direct current (HVDC) power cables have been paid more attention due to the big issue concerning the main insulation materials. The residues in the industrial production process will cause space charge generation and accumulation in the materials, which has become one bottleneck to limit the development of power cables up to higher voltage levels. In this paper, the LDPE matrix was modified by three types of ethylene-butyl acrylate (EBA) copolymers (1.0 wt%) with different polarities (BA content) via melt blending to optimize the space charge behavior of the LDPE insulation. The micromorphology and structure of the blends are examined by polarized light microscope and differential scanning calorimetry. The space charge distribution is tested by the pulsed electroacoustic method. The trap level is studied by the thermally stimulated current. The results show that EBA introduces more deep traps and decreases the shallow traps. The medium-polar EBA (16% BA content) can effectively suppress charge accumulation, and have the same suppressed effect on XLPE/EBA blends. This study will provide important insights into the design and development of advanced HVDC power cable applications.

Electron-phonon scattering and Joule heating in copper at extreme cold temperatures

A quantum mechanical model has been used to calculate the full electron-phonon scattering rates in pure copper at extreme cold temperatures. The proposed model uses Fermi’s Golden rule, specific to each scattering mechanism and wave vector state, providing more accuracy and more details than the widely used empirical third power rule for scattering rates. The empirical third power rule is actually only valid in the low-temperature limit. The results are in good agreement with existing experimental data and theoretical calculations with the assumption that the wave vector of a phonon is much larger than the wave vector of an electron (q ≫ k) and three-dimensional density of states converted to one-dimensional density of states to reduce calculation burden by orders of magnitude. The energy generated by Joule heating is calculated using the proposed model and compared with the experimental data from the literatures. Although the results presented are specific to copper, the method is directly applicable to other metals. In addition, the proposed model can be used to study the thermal properties of copper wires in high temperature superconductor power cable applications.

Effects of HTS Tape Arrangements on AC Loss in Self-Shielding DC HTS Cable With AC Ripple Current

Critical current and ac loss of high-temperature superconducting (HTS) tapes are two important factors for the application of ac HTS power cables. Generally, the current in the dc HTS cable is a combination of main dc current and ac ripple current due to the use of rectifier. The ac ripple current distribution without proper adjusting would be nonuniform in each layer especially when the dc HTS cable layer increases; it may lead to high ac loss and poor transmission capacity. In order to understand the ac ripple current sharing among dc HTS cable layers, the inductance matrix of the cable layers was deduced based on the geometry configuration of a self-shielding dc HTS cable. In this paper, in addition to the uniform current design principle, a self-shielding dc HTS cable is also designed with the HTS tape arrangements of each layer optimized by taking the ratios of ac ripple current amplitude to critical current in each layer as equal for minimizing the ac loss. According to the design configuration and deduced inductance matrix, current in each layer and ac loss are calculated. The results show that it is necessary to use the optimized design in the dc HTS cable design and the equal ratio design is better than the uniform current design.