Cable Loss Research Articles

Offshore Electrical Grid Layout Optimization for Floating Wind—A Review

Electrical grid layout optimization should consider the placements of turbines and substations and include effects such as wake losses, power losses in cables, availability of different cable types, reliability-based power losses and operational/decommissioning cost besides the initial investment cost. Hence, optimizing the levelized cost of energy is beneficial capturing long-term effects. The main contribution of this review paper is to identify the current works and trends on electrical layout optimization for offshore wind farms as well as to analyze the applicability of the found optimization approaches to commercial-scale floating wind farms which have hardly been investigated so far. Considering multiple subproblems (i.e., micrositing and cabling), simultaneous or nested approaches are advantageous as they avoid sequential optimization of the individual problems. To cope with this combinatorial problem, metaheuristics seems to offer optimal or at least close-to-optimal results while being computationally much less expensive than deterministic methods. It is found that floating wind brings new challenges which have not (or only insufficiently) been considered in present optimization works. This will also be reflected in a higher complexity and thus influence the suitability of applicable optimization techniques. New aspects include the mobility of structures, the configurations and interactions of dynamic cables and station-keeping systems, the increased likelihood of prevailing heterogeneous seabeds introducing priority zones regarding anchor and riser installation, the increased importance of reliability and maintainability due to stricter weather limits, and new floating specific wind farm control methods to reduce power losses. All these facets are crucial to consider when thoroughly optimizing the levelized cost of energy of commercial-scale floating offshore wind farms.

Why Does the PV Solar Power Plant Operate Ineffectively?

Quality, reliability, and durability are the key features of photovoltaic (PV) solar system design, production, and operation. They are considered when manufacturing every cell and designing the entire system. Achieving these key features ensures that the PV solar system performs satisfactorily and offers years of trouble-free operation, even in adverse conditions. In each cell, the quality of the raw material should meet the quality standards. The fulfillment of the quality management system requires every part that goes into the PV solar system to undergo extensive testing in laboratories and environments to ensure it meets expectations. Hence, every MWh of electricity generated by the PV solar system is counted, the losses should be examined, and the PV system’s returns should be maximized. There are many types of losses in the PV solar system; these losses are identified and quantified based on knowledge and experience. They can be classified into two major blocks: optical and electrical losses. The optical losses include, but are not limited to, partial shading losses, far shading losses, near shading losses, incident angle modifier (IAM) losses, soiling losses, potential induced degradation (PID) losses, temperature losses, light-induced degradation (LID) losses, PV yearly degradation losses, array mismatch losses, and module quality losses. In addition, there are cable losses inside the PV solar power system, inverter losses, transformer losses, and transmission line losses. Thus, this work reviews the losses in the PV solar system in general and the 103 MWp grid-tied Al Quweira PV power plant/Aqaba, mainly using PVsyst software. The annual performance ratio (PR) is 79.5%, and the efficiency (η) under standard test conditions (STC) is 16.49%. The normalized production is 4.64 kWh/kWp/day, the array loss is 1.69 kWh/kWp/day, and the system loss is 0.18 kWh/kWp/day. Understanding factors that impact the PV system production losses is the key to obtaining an accurate production estimation. It enhances the annual energy and yield generated from the power plant. This review benefits investors, energy professionals, manufacturers, installers, and project developers by allowing them to maximize energy generation from PV solar systems and increase the number of solar irradiation incidents on PV modules.

Studying the Cable Loss Effect on the Seismic Behavior of Cable-Stayed Bridge

As the demand and construction of cable-stayed bridges have increased, research on the safety of cable-stayed bridges in the event of natural disasters such as fires and explosions is actively being conducted. If a cable-stayed bridge is damaged by an unexpected natural disaster or accident, it can cause serious traffic congestion and huge economic losses. This study evaluates the usability of the cable-stayed bridge in the event of cable damage. Additionally, seismic performance and the impact of the damage are evaluated by numerical analysis. To achieve this goal, the cable-stayed bridge is modeled using 3D BEAM elements and two-node cable elements. Then, the impact of the damage was evaluated by gradually damaging the cable. The deflection, axial force of the girder, and cable stress changes under far-field ground motion (El-Centro earthquake) were reviewed. A representative dynamic analysis program LS-DYNA was utilized for the numerical analyses. The results show that the loss of a small number of cables does not affect the usability of the bridge. However, if five or more cables are continuously lost, or if an earthquake occurs when cables are already lost, excessive deflections and changes in the girders’ axial forces can cause usability problems.

APPLICATION OF STATIC SYNCHRONOUS COMPENSATOR (STATCOM) AS REACTIVE POWER CONTROL IN DFIG WIND FARM AND GRID INTERCONNECTION SYSTEMS

The most difficult aspect of optimizing a wind farm is creating an accurate wind farm model, especially if the farm is connected to the grid. The inconsistency and unpredictability of wind speeds exacerbates this issue. When dealing with wind farms, it is possible that the reactive power addition capabilities of individual wind turbines are insufficient to meet network requirements. This is due to cable losses and line losses between the wind farm and PCC. This study employs a doubly fed induction generator (DFIG) and a Static Synchronous Compensator (STATCOM) compensator to keep the output voltage amplitude more constant. Using two PI controller loops, the STATCOM will generate reactive (capacitive) power if the DFIG voltage is lower. The STATCOM will then absorb reactive (inductive) electricity if the DFIG system voltage is greater. STATCOM's ability to regulate the flow of reactive power can increase the network's stability. By optimizing the network's reactive power, the power factor is increased and stabilized up to 0.99. In addition, the system's harmonics never exceed the 5% limit specified by the IEEE 519-1992 standard.

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.

A new damage indicator based on homogeneity and wireless accelerometers for evaluating the structural condition of a cable-stayed bridge

Structural health monitoring is crucial to avoid devastating human and economic losses, mainly for large and high-demanding structures as the case of vehicular bridges. In this regard, a methodology to identify a cable loss in a cable-stayed bridge from the analysis of vibration signals, which are provided by a set of wireless accelerometers installed on the bridge, is here presented. Regarding the method, the damage detection is carried out by a new proposed damage indicator, which is calculated from the homogeneity values of the vibration signals. The homogeneity values are also employed as inputs in a multilayer perceptron neural network to determine the damage location when a damage condition is identified. The usefulness of the proposal is tested on the vibrational responses obtained in experimental manner from the Rio Papaloapan Bridge located in Veracruz, Mexico, resulting in 93.33% of effectiveness to detect and locate the cable loss.

Electromagnetic analysis and AC losses of triaxial cables with multiple 2G-HTS layers per phase

Electromagnetic analysis and AC losses of triaxial cables with multiple 2G-HTS layers per phase

Experimental study on flame spread and extinction over horizontal power cables under longitudinal ventilation in a utility tunnel

Flame spread and extinction over horizontal power cables (polyethylene (PE) sheathed and cross-linked polyethylene (XLPE) insulated power cable) under longitudinal ventilation in a utility tunnel was experimentally studied. Power cables (1.35 mm/8.5 mm in core diameter/cable diameter) of five components (sheath: PE, wrapping: Non-woven fabric, filling: PP, insulation: XLPE, copper: Cu) are used as samples. Flame geometrical characteristics (average flame height Hf, U∞, average flame width Wf, average pyrolysis length Lp) are analyzed. A prediction model of Hf, U∞ based on three main characteristic length scales (the length scale lD, the flow momentum-buoyancy length scale lM and the characteristic length scale of a purely buoyant plume lQ) that control flame dynamics, there is a good agreement between experimental and prediction results. The increasing wind speed and number of cables lead to the increasing mass loss and mass loss rate (MLR), and the reason for the delay in cable mass loss is revealed. The flame spread rate (FSR) prediction model considering the exposed copper wire length in the combustion zone based on Hf, U∞, Wf, flame inclination angle (β) and Lp was optimized. FSR increases with wind speed and the number of cables increase. The study contributes to a better knowledge of the cable's fire risk in utility tunnels.

Simulation of Dynamic Resistance and Total Loss of HTS CORC Cables

In some high temperature superconducting (HTS) applications, HTS coated conductors carry DC current under external AC magnetic fields. Dynamic resistance occurs when the amplitude of the magnetic field is greater than the threshold magnetic field of the coated conductors. The resulting AC loss, termed as total loss, consists of dynamic loss due to dynamic resistance and magnetization loss due to the shielding currents caused by the AC magnetic field. Conductor on round core (CORC) cables wound with HTS coated conductors have attracted broad attention due to their large current-carrying capability and mechanical flexibility for coil applications. However, there has been no report on dynamic resistance and total loss in CORC cables. In this work, we present 3D FEM simulation results on the dynamic resistance and total loss of a spiral tape and three CORC cables, based on the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${\boldsymbol{T-A}}$ </tex-math></inline-formula> formulation. The number of layers of the CORC cables, the amplitude of the AC magnetic field and transport DC current levels have been varied to study the impact of those parameters on dynamic resistance and total loss of the three CORC cables. The simulation results show that magnetization loss without current in a spiral tape can be analytically estimated by Brandt and Indenbom’s theoretical equation for a superconducting strip under perpendicular AC magnetic field with a geometric coefficient 2/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula> . Furthermore, dynamic resistance of the spiral tape and each tape in a single-layer cable can be predicted by the analytical equation for a strip carrying DC current under perpendicular AC magnetic field, also taking into account the geometric coefficient 2/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula> . The simulation results also show that the difference of total loss values in the three CORC cables depends on the shielding effect: the more layers of CORC cables, the lower each loss component. The two-layer Cable with each tape in the outer layer sitting on top of the tape in the inner layer has the lowest loss and the highest threshold magnetic field.

Effects of pylon configuration on the response of cable-stayed bridge to sudden cable loss

This paper presents a finite-element (FE) investigation into the effects of pylon configuration on the general response of cable-stayed bridges (CSBs) in the event of sudden cable loss. An example CSB is proposed and analysed using a three-dimensional FE model for H-shaped pylon (HSP) and A-shaped pylon (ASP) configurations; the effects of p–δ (large stress) and geometric non-linearities are accounted for. The FE study was conducted for two scenarios of cable loss – the simultaneous sudden loss of the longest two adjacent cables in the mid span or the side span. The results showed that the general responses of the main-span deck structural elements due to breakage of the longest two main-span cables were comparable for both HSP and ASP configurations, but the responses due to breakage of the longest two side-span cables differed. From a practical viewpoint, the loss of side-span cables may cause notable rotation of the main-span deck for a CSB with HSPs, but not for a CSB with ASPs. The results of this study may be useful for designing a situation of accidental cable loss.

Magnetization loss of CORC cables under axial tensile loading

As a highly flexible and fully isotropic cable structure, CORC (Conductor on Round Core) cable wound with high-temperature superconducting (HTS) tapes has promise for giant magnets, including fusion magnets, high-energy accelerator magnets, and nuclear magnetic resonance. CORC cables are subjected to mechanical, thermal, and electromagnetic loadings during preparation and operation. Axial tension is one of the basic deformation modes of CORC cables. To investigate the impact of axial tension loads on the electromagnetic performance of CORC cables, a mechanical-electromagnetic model is created in this study. A comparison of numerical simulations and experiments was first performed for single straight tape and single-layer CORC cables to verify the model's reliability, with particular attention to the critical current reduction and the variation of magnetization loss during axial tension. The model developed in this paper may evaluate electromagnetic performance under applied AC magnetic fields with small amplitudes and mechanical response to axial tension loads. On this basis, the strain distribution of CORC cables under axial tension and their magnetization loss characteristics under various strain states are presented. The effects of different cable design parameters on the critical current and magnetization loss are discussed. The results show that the strain affects the magnetization loss of CORC cable significantly, especially for ones with larger winding angles. The magnetization loss can be reduced by choosing a narrower tape, a smaller winding angle, or a cable core material with a higher Poisson ratio. This study can provide a theoretical basis for the structure optimization design and practical application of CORC cables.

Critical Current and AC Ripple Loss Analysis of a Global Self-Shielding HTS DC Cable Made of Filament REBCO Tapes

For the high-temperature superconducting dc cable with the same current orientation in every layer, the maximum magnetic field generally arises in the outermost layer. When the cable transmits a large current, the generated strong magnetic field will make the utilization rate of tapes extraordinarily low. The current direction of two neighboring layers in the self-shielding sandwich cable is inverse, which can whittle the magnetic field interaction of each layer, so as to minish the critical current attenuation of REBCO tape. The previous global self-shielding dc cable adjusts the current distribution between layers to homogenize the magnetic field. However, this article proposes a new global self-shielding dc cable made of filament REBCO tapes, which adjusts the current distribution in each layer. The uniformity of magnetic field can be improved further by using filament tapes to wind the cable. In this article, <bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><i>T-A</i></b> formulation is adopted to study the critical current and ac ripple loss of global self-shielding sandwich cables made of filament REBCO tapes in detail. The simulation results demonstrate that the structure made of filament tapes has better performance than the previous global self-shielding structure.

Study on temperature rise characteristics of 110 kV XLPE cable under different service years considering dielectric loss

This paper studies temperature rise characteristics of 110 kV XLPE cable under different service years. When the load is 900 A, the maximum temperature of the cable under 0, 15 and 30 service years is 335.5 K, 372.96 K and 393.88 K respectively. Compared with the data obtained from non-aged cable, the temperature increase for samples operating for 15 and 30 years is 111.15% and 117.4% higher. For these samples, the proportion of heating due to cable dielectric loss is 2.77%, 25.45% and 34.78%. The research content of this paper provides a basis for the research on the optimal current carrying capacity of cables with different service years, provides a reference for the actual application of cables, and has guiding significance for the research on prolonging the service life of cables and improving the utilization rate of cable resources.

Effect of winding methods: transport AC losses in CORC coils

AC losses undoubtedly increase the burden on the cooling system and affect the overall performance of high-temperature superconducting (HTS) cables. Therefore, AC losses in HTS cables are important design factors for large-scale HTS equipments. Extensive research has been conducted on straight, densely wound conductors. However, AC losses of bending/circular HTS cable conductors have not been sufficiently studied. In this article, the transport AC losses in a circular HTS conductor coil bended by a conductor on round core (CORC) type cable were investigated using experiments and numerical simulations. The effect of different winding methods was also studied. First, the modeling method of the three-dimensional simulation and the experimental procedures were presented. The simulation results of the straight densely wound conductor (SDWC) and circular densely wound coil (CDWC) were compared with the corresponding experimental results. Finally, the winding method for the CDWC was optimized using both the simulation and experimental approaches. Both the experiments and simulations showed that reducing the tape-to-tape frontal area was able to decrease the transport AC loss, and the results show that the optimum winding angle of the HTS CORC coil was 24.15°. Overall, the modeling and experiments provide useful optimization strategies for designing winding structures of high-performance CORC coils/magnets.

The Virtual Inertia Control of MMC-HVDC Considering the Effect of Active Power Loss of DC Line

Modular multi-level converter based high-voltage Direct-Current (MMC-HVDC) grid integration is an effective measure to achieve offshore wind power grid integration of large-scale and long-distance. As the offshore wind farms get farther and farther offshore, the active power loss of their submarine DC cables has become a non-negligible part of offshore wind power's participation in frequency regulation. In this paper, on the basis of simulating the inertia of synchronous generator with DC capacitor energy, a virtual inertial control strategy considering the influence of active power loss of DC cable is derived. And, the influence on the frequency stability of the system after considering the active power loss of the DC cable is also analyzed at the same time. Finally, a model of offshore wind power grid-connected through MMC-HVDC is built on MATLAB/Simulink. The simulation results show that the virtual inertia control strategy considering the active power loss of the DC line can effectively improve the frequency stability of the power system.

Fully Coupled Computation of Losses in Metallic Sheaths and Armor of AC Submarine Cables

The problem of computing in an efficient and accurate way the armor losses in three-core AC submarine cables has been of great interest to the offshore cable community for some years. Indeed, efficiency of the computation method is crucial to allow comprehensive parametric analysis as might be needed in the design study. In (Giussani <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">et al.</i> 2021), an algorithm based on integral equations for performing such calculations with an accuracy comparable (within acceptable tolerances) to state-of-the-art Finite Element Method (FEM) approaches was presented. In the present study, we extend the above mentioned algorithm to account for the mutual inductive coupling between armor wires and metallic screens, which are often present in actual cables structure. We show that the most notable properties of the original algorithm are preserved in this coupled formulation. In particular we discuss how exploiting the cable structure periodicity and symmetry leads to huge computational cost reductions. The new extended simulation tool is applied to a parametric study to assess how geometry and material properties influence losses and to assess in particular the impact of the metallic sheaths.

A flexible MRI coil based on a cable conductor and applied to knee imaging

Flexible radiofrequency coils for magnetic resonance imaging (MRI) have garnered attention in research and industrial communities because they provide improved accessibility and performance and can accommodate a range of anatomic postures. Most recent flexible coil developments involve customized conductors or substrate materials and/or target applications at 3 T or above. In contrast, we set out to design a flexible coil based on an off-the-shelf conductor that is suitable for operation at 0.55 T (23.55 MHz). Signal-to-noise ratio (SNR) degradation can occur in such an environment because the resistance of the coil conductor can be significant with respect to the sample. We found that resonating a commercially available RG-223 coaxial cable shield with a lumped capacitor while the inner conductor remained electrically floating gave rise to a highly effective “cable coil.” A 10-cm diameter cable coil was flexible enough to wrap around the knee, an application that can benefit from flexible coils, and had similar conductor loss and SNR as a standard-of-reference rigid copper coil. A two-channel cable coil array also provided good SNR robustness against geometric variability, outperforming a two-channel coaxial coil array by 26 and 16% when the elements were overlapped by 20–40% or gapped by 30–50%, respectively. A 6-channel cable coil array was constructed for 0.55 T knee imaging. Incidental cartilage and bone pathologies were clearly delineated in T1- and T2-weighted turbo spin echo images acquired in 3–4 min with the proposed coil, suggesting that clinical quality knee imaging is feasible in an acceptable examination timeframe. Correcting for T1, the SNR measured with the cable coil was approximately threefold lower than that measured with a 1.5 T state-of-the-art 18-channel coil, which is expected given the threefold difference in main magnetic field strength. This result suggests that the 0.55 T cable coil conductor loss does not deleteriously impact SNR, which might be anticipated at low field.

Modelling Thermal Performance of Unloaded Spiral Strand and Locked Coil Cables Subject to Pool Fires

Structural cables are used to design critical bridge structures. These are not typically redundant; a loss or compromise of a few cables can lead to the progressive collapse. Previous experimental research has shown that the degradation of material properties and thermal expansion of structural cables is more onerous than the standard carbon prestressing steel. Despite its importance for design no well-validated methodology exists to aid in the thermal performance of structural cables in the event of a fire, particularly for spiral and locked-coil cables which inherently are complex due to their cross-sectional geometry. A state-of-the-art methodology for modelling structural cables' thermal response is presented. The methodology will enable the development of an understanding of the temperature distribution and thermal deformation in a cable cross-section and allow estimation of post-fire resilience. Validation is performed against experiments of locked-coil and spiral cables, subjected to realistic pool fires. The cables range from 22 to 100 mm in diameter and are constructed of galvanized or stainless steel. The cables are modelled undergoing non-linear thermal analysis in LS-DYNA. 2D models are found to provide conservative estimates for critical values such as peak temperature with 90% accuracy, while 3D models provide slightly more conservative estimates.

Discussion on cable-strut systems of the suspen-dome structures

According to the architectural requirements, the roof structure of a large-span gymnasium adopts the suspen-dome structure. In the scheme selection stage of the pre-stressed cable-strut system at the bottom part of the suspen-dome structure, a Levy-type scheme and a Loop-free scheme are established. The finite element models are established, and the static analysis under the design loads, the whole process analysis of load-displacement, and the dynamic response analysis after accidental cable break are carried out. The architectural expression of the two schemes are discussed. The component material consumption, the structural stiffness, the tension distribution characteristics, and the static bearing capacity of the two schemes are discussed. The failure mode and the progressive collapse resistance of the two schemes after accidental cable break are also discussed. The results show that the Loop-free scheme requires significantly less in terms of component material consumption than the Levy-type scheme. The static failure mode of the two schemes is strength failure, but the Loop-free scheme has greater bearing capacity. The Loop-free scheme has greater structural stiffness, lower cable forces, and uniformly distributed cable forces in each layer, and lower stress on the top reticulated shell members. Neither of the two schemes experience progressive collapse after accidental cable break. Due to the rupture in the loop cable of the Levy-type scheme, the rigidity of the rear region decreases greatly, and the cable force loss is large. On the contrary, internal force redistribution occurs in the Loop-free cable scheme and the cable force loss is not obvious, hence the progressive collapse resistance is better than that of the Levy-type scheme.

2.9 K VCSEL demonstrates 100 Gbps PAM-4 optical data transmission

A cryogenic packaged vertical-cavity-surface-emitting laser (VCSEL) with microwave input and coupled with OM4 fiber for optical output was developed and demonstrated laser operation from 295 to 2.9 K. Record 2.9 K optical data links of 100 Gbps pulsed amplitude modulation 4-level have been demonstrated with an energy per bit ∼153.4 fJ/bit when TDECQ = 3.79 dB. The energy/bit is limited by the link path bandwidth resulted from the input cable loss to 2.9 K VCSEL and can be further improved. Thus, the VCSEL optical data link is proven to be a viable solution for cryogenic communication and computing.