Cable Parameters Research Articles

Free vibration of two taut cables interconnected by a damper

Connecting cables together to form a cable net could mitigate cable vibration. However, because most of the studies and practices use secondary cables as cross-ties, little attention has been paid on the connection by dampers. In this paper, a system of two parallel taut cables with an interconnected damper is proposed to mitigate cable vibration. The characteristic equation of the system is derived by applying the transfer matrix method. The analytical special limit solutions, which are corresponding to special kinds of vibration mode, are given for the case when the parameter of the system tends to specific limiting values. Analytical solutions to twin taut cable system, two taut cables with different mass–tension ratios, whereas other cable parameters are the same were also discussed. Parameter studies were further addressed to study effects of cable length ratio and frequency ratio on the third and fourth mode behaviors for two cables system. Different solution regimes with different kinds of modes are discussed as damper interconnected at arbitrary point of cables. Multimode damping optimization method was proposed with the concept of maximizing the average of damping ratio while minimizing the variation for the considered multimodes. The case study for two length cables of a harp system was carried out. It was found that connecting two cables with a properly designed damper could significantly increase multimode damping ratio while slightly increase vibration frequency.

Stability analysis of slopes reinforced with anchor cables and optimal design of anchor cable parameters

Pre-stressed anchor cables are widely used in slope engineering for effectively improving slope stability as a reinforcement measure. Based on assumptions of stresses on a slip surface, this work proposes a new limit equilibrium (LE) method to analyse the stability of slopes reinforced with anchor cables. Meanwhile, the nonlinear Mohr–Coulomb (M–C) strength criterion has been adopted to describe the slope sliding for shear failure of the slip surface. Then, after comparison and analysis of several examples, the feasibility of the proposed method is verified. Compared with the traditional LE methods, the proposed method has a simple calculation process without iterative loop calculation of the slope factor of safety, and a reasonable solution can also be obtained. Furthermore, the slope reinforced by anchor cables with more than a row can be simplified into a slope with a row to analyse its stability because the same stability would be obtained for the reinforced slope with different reinforcement patterns under an equivalent reinforcement relation. Thereafter, to facilitate the engineering application and optimize the design of anchor cable parameters, the stability charts of the reinforced slope under the linear M–C strength criterion are drawn.

Design optimization and evaluation of the 3 kA MgB2 cable at 4.3 K for the superconducting link project at CERN

High-current superconducting links (SC links) are being developed at CERN for powering the superconducting magnets of the High-Luminosity Large Hadron Collider upgrade. The links contain MgB2 cables, each about 100 m long, rated at currents of up to 18 kA. The assembly of the cables is carried out with reacted wires; cable geometry and cabling processes take into account the mechanical properties of the reacted MgB2 conductor. The production of the cables as well as their final installation requires good mechanical stability, flexibility and electrical performance. The superconductor should have good mechanical strength in view of the stresses during cabling (tension and bending), operation at cryogenic temperatures (Lorentz forces and thermal contraction) and handling installation (tension and bending) at room temperature. Moreover, the electrical integrity of the MgB2 wire (IC degradation ≤5%) should be ensured after the cabling process for the SC links. Therefore, the study of the mechanical properties of the MgB2 wire and the definition of the cable design parameters are crucial for the project. In the present work we report on the optimization and validation of the design of the 18-strand, 3 kA MgB2 cable by assessing the electromechanical behaviour of 3 kA MgB2 superconducting cables produced with different cabling parameters. The critical current (IC) of the MgB2 wires was measured after triple bending and axial tensile load, and strands extracted from the cables were tested to quantify the critical current degradation. Electrical measurements of two, 2 m long, 18-strand MgB2 cables were carried out in the FRESCA test facility at CERN and no degradation was observed. Cabling parameters such as the bending radius and the twist pitch were evaluated, and the most appropriate geometries for the MgB2 18-strand cables have been selected. Numerical simulations were performed to allow a detailed study of the strains developed in the MgB2 strands due to the mechanical loading. The present results have been successfully transferred to industry for the first industrial production in the framework of the SC Link project.

Damping effects of nonlinear dampers on a shallow cable

This study investigates the damping performance of nonlinear dampers on a shallow cable for vibration control. For this purpose, a method is presented to appreciate the system damping based on periodically forced vibration analysis. Furthermore, the reduced-order model for cable-damper systems in the literature is improved to analyze the near-resonant responses of the system and to consider two dampers installed respectively near the two cable ends. The method is then verified based on a cable attached with linear dampers and further applied to a shallow cable with one and two nonlinear viscous dampers. By grouping the damper and cable parameters appropriately, the damping curves of linear cable-damper systems are extended to shallow cables with nonlinear dampers, which are useful for damper design in practice. Extensive numerical studies are subsequently conducted for shallow cables of varying sag-extensibility parameter attached respectively with one viscous damper and two viscous dampers of different nonlinearity near cable ends, focusing on the sag affected vibration modes. The numerical results suggest that when the sag-extensibility parameter is small, a nonlinear damper is superior to a linear damper in terms of maximal damping effect for these modes, owing to the nonlinearity induced energy bleeding effect. Interestingly, in a particular range of the sag-extensibility parameter, the maximal damping of these modes achieved by a nonlinear damper is smaller than that by an optimal linear damper. It is also suggested that when two dampers are installed symmetrically near the cable ends, the damping effect for a symmetric mode is considerably different from the summation of the optimal damping achieved by each damper alone, and the optimal damper coefficient varies as well. The difference depends on the sag-extensibility parameter and the damper nonlinearity.

A FRACTAL MODEL OF PERMEABILITY FOR THE LIQUID HELIUM FLOW IN CABLE-IN-CONDUIT CONDUCTORS

The heat removal capability and the coolant pumping costs in the design of cable-in-conduit conductors are depend on the thermo-hydraulics of the liquid helium flow. Therefore, the accurate knowledge of the thermo-hydraulics of the flow is significant for the design of the cables, especially for permeability. In this paper, the fractal method is proposed to describe the cable cross-section and an approximate expression is derived. Then, a fractal permeability model for helium flow in CICCs is presented based on a porous medium analogy. The feasibility and validity of this model is verified by the comparison of the predicted values and the experimental values. The fractal model indicates that permeability of cables is determined by the cable geometric parameters, such as the effective porosity, the average cabling angle, the average diameter of strands and the pore area fractal dimension of the cable cross-section. This model does not contain any empirical constants or fitting constants and can be used to explain the mechanism and to predict the permeability of the helium flow in CICCs. Furthermore, the effects of cable geometric characteristics on the presented fractal permeability model are also analyzed and simulated. The results imply that permeability of cables decreases with increasing the cabling angle, increases with the effective porosity, the pore fractal dimension and the average diameter of the strands increase. These results are consistent with the physical situations.

Research on characteristic function for cable inverse analysis based on dynamic stiffness theory and its application

Parameter identification of cables in the operation period is a significant issue related to the state of serviceability and safety evaluation of cables. A generalized characteristic function is established based on the dynamic stiffness theory to identify cable parameters in the study. The characteristic function exhibits an analytical form. The function relatively fits actual engineering cables due to comprehensively considering cable bending stiffness, sag, inclination, etc., and thus it is a relatively accurate inverse-analysis model of cable parameters. The variation of bending stiffness and cable force with different geometric parameters and the influence of geometric parameters on the identification accuracy of the two parameters are investigated based on numerical analysis. And a parameter identification method based on the H-I ridges of inverse-analysis characteristic function is proposed. The proposed method identifies cable parameters using the multi-order frequencies of cables simultaneously, and the order of modal frequencies and the fundamental or lower-order frequency are not required in the application of the proposed method. Finally, the results of tension tests on two real cables with lengths of 20 m and 168 m verify the applicability of the inverse-analysis characteristic function and the parameter identification method proposed in the study.

Frequency-domain modeling of unshielded multiconductor power cables for periodic excitation with new experimental protocol for wide band parameter identification

A complete modeling technique for unshielded power cables is proposed. The focus is on applications where the resonance phenomena take place in electrically long cables and is originated from periodic excitation, such as power converters. The resonance problems caused by switching converters tend to become more common with the advent of wide band gap semiconductors. This paper includes a new experimental protocol specific for unshielded power cable parameter identification in a wide frequency band, from DC up to medium frequencies (tens of MHz), with an impedance analyzer. It also introduces a frequency-domain simulation tool with conversion to the time domain, via the Fourier series. This frequency-domain modeling is straightforward, and its accuracy depends only on the accuracy of the cable parameter identification.

Dynamic analysis of submarine cable during the process of laying back to the seabed

ABSTRACTIn the actual process of the submarine cable laying, there are problems of excessive cost and long time spent on the project. Therefore, it is necessary to predict the process to improve the safety and economic performance of the project. Based on the lumped mass method, the submarine cable is discretized into a lumped mass model. In consideration of the specific parameters of a certain submarine cable, combined with the specific process of laying back to the seabed, by necessary simplification, the equivalent finite element simulation model for the dynamic analysis of submarine cable during the process of laying back to the seabed has been established. The results of the theoretical analysis and the finite element simulation are compared and analyzed, and the correctness of the simulation model is verified. The effects of different hanging length, accelerations and velocities of the engineering vessel at different stages on the safety of the submarine cable are discussed. With the basis of the maximum effective tension and the minimum bending radius of the cable, some results have been given, which are useful for the submarine cable laying. The conclusion has certain guiding significance in the practical engineering.

Effects of cable insulations’ physical and geometrical parameters on sheath transients and insulation losses

This paper investigates the influence of insulations’ physical and geometrical parameters on cable sheath transients and insulation losses considering power cables for high voltage alternating current (HVAC) applications. The study is based on theoretical analysis, Electromagnetic Transient Program (EMTP) simulations, and finite element (FE) simulations. Special attention is paid to the effects of the insulations’ relative permittivities and the protective jacket thickness on cable capacitance, transient voltages, and dielectric losses for different possible conditions including the variations in insulation permittivity and ground resistivity. The cable model used in this work is a single core (SC) underground coaxial cable with an AC voltage supply of 220 kV and 60 Hz frequency. A method for calculating the dielectric losses in cable insulations due to transient voltages was developed. The proposed method is based on the numerical calculations of the flowing electric currents through insulations using FE model. In addition, the relation of the dielectric loss and the maximum sheath overvoltage as a function of permittivites and as a function of protective jacket thickness was explored to obtain an optimum protective jacket relative permittivity from the viewpoint of both the overvoltage and the loss. For given cable system parameters, the transient voltage waveforms within a time period of t = 0–2 ms obtained on the core and the sheath produced dielectric losses 34.362 [W/m] and 3.365 [W/m] at insulation and protective jacket, respectively.Results and conclusion provide a useful background for the ongoing power cable design process and application studies.

Comparison of Current Limiting Effect of an HTS DC Cable Under Different Short-Circuit Conditions

Power transmission with HTS dc cables has the characteristics of high capacity, high efficiency, more compact size, and environmental friendly. It has become an alternative and revolutionary upgrade of the traditional dc power transmission. The self-acting limit function during its quenching for fault current is unique to HTS dc cables. Fault-current-limiting capability of the HTS DC cable in a line-commutated converter (LCC) HVDC system is therefore analyzed with HTS current-limiting features in different short-circuit situations to identify the HTS dc transmission system design and operation features and verification achieved with the HTS dc cable characteristics and parameters, especially the peak value of the fault currents in the LCC HVDC systems.

Comparing frequency‐dependent and distributed parameter with lumped losses power cable line models for cable insulation coordination against overvoltages

Simulations of transients are an obliged step for the insulation coordination of cable lines. Although a frequency-dependent power cable line model better takes into account real conditions since resistive and inductive parameters vary with frequency, a distributed parameter with lumped losses power cable models can be useful to simplify and give higher flexibility to the insulation coordination study. In such a case, a dilemma rises up when a frequency shall be selected for the determination of the cable parameters. In this study, a comparative analysis between the two models has been performed considering a typical configuration layout, i.e. an overvoltage coming from an overhead line and stressing the cable line terminated on a transformer. The overvoltages stressing both cable insulation wall and cable thermoplastic jacket are evaluated using the same system configuration with both frequency-dependent and distributed parameter with lumped losses power cable line models, in the latter case sweeping different frequency values for the determination of the cable parameters. A frequency range that minimise the differences between the overvoltage estimation using the two models is suggested.

Sensitivity Analysis of Cable Parameters on Tension of a Suspended Cable under Combination Resonances

This paper studies the vibration of a suspended cable with small sag excited by a second excitation (normal) mode causing combination resonance in the three modes, i.e. tangent, normal and bi-normal modes. The displacement response spectra in the time domain and phase portraits are provided as evidence of the transition from the unstable steady-state motion to the stable one for nonlinear cable oscillation. A nondimensional equation for the cable tension is established with its variation evaluated for the unstable zone. The half-normalized sensitivity analysis of cable parameters, such as damping coefficient, excitation amplitude, arc length parameter and initial conditions, for their influence on cable tension is conducted in the time domain by a direct integration method. Also, the characteristics of the dynamic sensitivity of cable tension to the parameters are discussed. As a result, a sensitivity ranking chart is prepared based on the sensitivity analyses for the parameters considered. It is clearly revealed that cable tension is very sensitive to tangent and normal initial displacements in spite of their small values, whereas the same is not true for the arc length parameter and bi-normal damping coefficient. To verify the sensitivity analysis algorithm, a forced Rayleigh oscillator is introduced. A feasibility study using the oscillator shows that the numerical results obtained are in good qualitative agreement with the analytical predictions, implying that the associated algorithm works well.

Comparative Study of Short-Circuit Fault Characteristics for VSC-Based DC Distribution Networks With Different Distributed Generators

Distributed power generation integration can effectively improve the reliability and economy of dc distribution network operation. However, it is difficult to evaluate the fault behaviors caused by the diversification of distributed generation, which might render preexisting protection schemes invalid and even cause damage to power electronic equipment. When different distributed generators access a voltage source converter (VSC)-based dc system, an in-depth study of fault characteristics is of great significance to design relay protection. This paper investigated the short-circuit fault characteristics of VSC-based dc distribution networks containing distributed generation systems. The fault responses of different fault stages for three kinds of distributed generators (photovoltaic power system, supercapacitor energy storage system, and wind power generation system) were investigated to provide an intuitive comparison of fault behaviors. The effects of these distributed generators on the magnitude and peak time of fault current were analyzed. It was found that the dc cable parameters and these distributed power generators’ dc-link capacitors have great impacts on the fault behaviors of dc distribution networks. Detailed analyses based on MATLAB calculations are presented, and simulation results based on power systems computer aided design/electromagnetic transients including dc verified the effectiveness of the proposed transient fault models.

Dynamic Rating of Three-Core XLPE Submarine Cables for Offshore Wind Farms

This article aims to determine the most suitable cross-sectional area for a high voltage alternating current (HVAC) submarine cable in the design phase of new projects. A thermal ladder network method (LNM) was used to analyse the thermal behaviour in the centre of the conductor as the hottest spot of the cable. On the basis of the calculated cable parameters and a thermal cable analysis of transient conditions applied by a step function with a time duration greater than 1 h, this article proposes a method for a dynamic rating of submarine cables. The dynamic rating is accomplished through an iterative process. The method was tested with a MATLAB simulation and validated in comparison with a finite element method (FEM)-based approach.

Integrate Method to alleviate the High Frequency PWM Pulse Voltage on SMES Magnet

The SMES system generally adopts the power conditioning system (PCS), which is made of high frequency power electronics switching devices. The superconducting magnet withstands high frequency PWM pulse voltage, which will induce insulation deterioration, even induce the insulation breakdown. This paper proposes the integrate method to alleviate the PWM pulse voltage. Based on the voltage distribution characteristic of SMES magnet, the influence factors of the pulse overvoltage on SMES magnet are analyzed. Then, considering the interaction between different components of SMES, the factors including PCS control, power cable parameters, filter type, and magnet parameters are designed comprehensively. Finally, the proposed method is implemented in a SMES model to evaluate its effectiveness.

Resonance regions due to interaction of forced and parametric vibration of a parabolic cable

Taut cables such as those used in cable-stayed bridges are prone to exert a large amplitude response due to support motion. Support motion generally involve longitudinal and transverse components with respect to the cord. Such motions induce parametric and external excitation of the cable. For a certain excitation frequency, multimodal interaction due to simultaneous parametric and primary resonance can be expected. Previous studies have focused on changes in the boundary curves of the primary region of the parametric resonance affected by forced vibrations due to primary resonance. The hysteresis regions have not been determined; they have only been analyzed using the frequency-amplitude curves of the response. Moreover, the influence of the longitudinal and transverse displacement ratio has not been discussed thus far. This paper presents a complete formulation of the continuum equations of a cable model that is excited by support motion. A nonlinear discretized model that includes quadratic and cubic nonlinearities is obtained using the Galerkin method. Further, the analytical solution is determined using the method of multiple scales (MMS). By obtaining the expressions for the amplitudes and phases, the mathematical conditions are set for the amplitude of the parametric and primary resonance from which analytical expressions for the boundary curves of the interaction resonance region are derived. Local stability analysis is conducted for the steady-state response, and direct numerical integration is used for validating the frequency-amplitude curves obtained using the MMS. The solutions are verified using two independent numerical models. It is shown that the ratio of the transverse and longitudinal components of support motion significantly affects the resonance region, and several different response solutions can be obtained. It is also shown that different values of the mechanical cable parameters affect the resonance region and vibration amplitude.

Improved Speed Sensorless Vector Control Algorithm of Induction Motor Based on Long Cable

In many applications, especially electrical submersible pump required remote operation of inverter via a long motor cable. The conventional control algorithm of induction motor (IM) didn’t operate effectively, which ignored the influence of the cable length, and didn’t consider the effect of long cable distribution parameters. A speed sensor technique was also difficult to achieve. In this paper, an improved speed sensorless vector control algorithm (ISSVCA) for IM based on long cable was proposed. Based on the analysis of long cable motor drive system of the inverter, the two-port π network model of the long cable was established. The functional relationship between the voltage/current parameters of the two ports of the long cable and the cable distribution parameters was deduced. The function expression was transformed to the α − β stationary reference frame, the accurate motor terminal voltage/current was calculated, so that the flux model was constructed to realize the observation of the flux, accurate velocity identification, and closed-loop control of the torque, flux and current. Simulation and experimental results showed that the proposed ISSVCA based on long cable increased the starting electromagnetic torque, decreased speed dip and speed recovery time caused by sudden loads, reduced the DC current harmonics, and had good dynamic and static characteristics.

Adaptive Observer-based Control Strategy for Maximum Power Point Tracking of Uncertain Photovoltaic Systems

This work presents an adaptive observer-based control strategy for maximum power point tracking (MPPT) of uncertain photovoltaic (PV) systems. On the one hand, the PVG output voltage and/or current measurements are needed for MPPT techniques and controllers design and, on the other hand, the PV arrays have to be installed in a site that profits from good daily sunshine. This obviously leads to difficulty of PVG output current and voltage measurement if ever such a site is at great distance from the converter. Furthermore, the MPPT control accuracy could be significantly affected due to the cable parameters if only voltage and current measurements on the converter side of the cable are instead used. To overcome this issues, an adaptive extended Kalman–like observer providing estimates of PVG output current and voltage regardless of cable resistance and inductance deviations, is first designed. Afterwords, a backstepping controller is synthesized to ensure the MPPT objective. The designed adaptive observer-based MPPT control convergence is formally analyzed and its effectiveness in compensating for cable parameters uncertainties on the MPPT accuracy is validated through numerical simulations.

Research of the Electrical Parameters of the Telephone Cable in the Frequency Range Up To 30 MHz

The work is devoted to the research of the electrical parameters of the domestic telephone cables in the frequency range from 1 to 30 MHz. The paper presents the results of the experimental determination of the frequency characteristics of the transmission parameters and the crosstalk of the TPPep 10х2х0,4 and TPPepZ 10х2х0,4 types telephone cables produced by ODESKABEL PJSC. The conformity of the domestic production cables with the requirements for digital subscriber line cables for VDSL2 technology services is determined. According to the results of the measurements, approximation formulas for the frequency dependence of the own attenuation, near end crosstalk and equal level far end crosstalk, which are proposed to be used in the modelling of the transmission systems using VDSL2 technology on the domestic broadband access networks based on these cables, are determined.

Flexible cable strength with regard to tribological interaction of its elements

This paper considers certain issues of tribological interaction between flexible cable elements. It proposes a new approach for determining frictional forces of cable elements while taking into account cable parameters. This study is the first to derive formulas of mechanical stresses in the zone of contacting elements for assessing the cable strength. The paper demonstrates how the derived formulas for cables can be used in practice for design purposes. The influence of geometric parameters of cable design on its strength has been analyzed.