Cable Response Research Articles

Recovery voltage response of XLPE cables based on polarisation and depolarisation current measurements

Recovery voltage measurement (RVM) is one of the common diagnostic techniques for the condition assessment of electrical insulation. The method has been used to examine the dielectric response, especially deterioration or depolymerisation of the polymeric insulation under ageing condition. In this study, a mathematical model of the RVM measurement based on the Debye equivalent circuit is elucidated. The methodology for determining the modelling parameters from the polarisation and depolarisation currents (PDCs) is described. For the experiments, two short-sections of service-aged 11-kV cross-linked polyethylene insulated (XLPE) cable are used, and the PDC of these test specimens are measured. Here, the model adapted comprises three R-C relaxation branches, where each branch represents a polarisation type. From the derived model, the peak of the RV can be predicted and are constructed over a wide range of charging time. Bode plots of the test objects are also presented with the magnitude and phase response which assist in understanding the RVM response.

A Compressive Sampling-Based Channel Estimation Method for Network Visibility Instrumentation

This article proposes a novel method to estimate the frequency response of cables for applications of physical layer testing and network visibility. By exploiting compressive sampling, the method allows using analog-to-digital converters with a sampling frequency much lower than the symbol rate of the transmitted bit stream. Moreover, it does not need a properly generated signal, as it happens in time-domain reflectometry; however, any signal having a pulse-amplitude modulation, orthogonal frequency-division multiplexing (OFDM), or spread spectrum modulation can be used. Therefore, the transceiver actually used for data transmission can also be used to generate test signals for the channel estimation and the measurement instrument can be integrated into the data communication equipment without requiring additional generators. The mathematical formulation of the method is presented, together with its evaluation by numerical simulations and experimental tests. The results show the capability of the method of properly estimating the frequency response of the channel, even with a sampling frequency much lower than the symbol frequency.

Modeling of High-Temperature Superconducting Cable via Time Domain Reflectometry and General Regression Neural Network

When a fault occurs in the high-temperature superconducting (HTS) cable, a fault current consisting of extremely high frequency components is generated and propagated based on the transient response of the HTS cable. Therefore, a simulation model based on high frequency characteristic of the HTS cable is essential to obtain accurate simulation results in the transient fault analysis. In this paper, the result of time domain reflectometry is used to design the model of the HTS cable. To determine model parameters, a general regression neural network based on the kernel density estimation is utilized. After the modeling procedure, the accuracy of the model is evaluated by time-frequency domain reflectometry, whose response depends on the high frequency characteristic of the cable. It is expected that the proposed modeling method can be applied to various application area of HTS cable, such as fault analysis, protection, and diagnostics in the future.

Analysis of the Thermomechanical Response of Structural Cables Subject to Fire

Cable-supported structures such as bridges and stadia are critical for the surrounding community and the consequences arising from a major fire event can be substantial. Previous computational studies into the thermal response of cables often employed simplistic heat transfer models that assumed lump capacitance or cross-sectional homogeneity without proof of validity. This paper proposes a methodology for calculating the thermal response of a cable cross-section allowing for heat transfer by conduction through each strand contact surface and radiation across inter-strand cavities. The methodology has been validated against two experiments of cables subjected to radiant heating and an input sensitivity analysis has been undertaken for the heat transfer and material parameters. The approach is compared against simple heat transfer lumped methods for a parallel-strand cable where it is shown that these lumped models are not always conservative. The model is then coupled with a two-dimensional generalised plain strain model to study the likely effect of the cross-sectional temperature gradients on the mechanical response. The study considers three qualitatively different hydrocarbon jet fire scenarios, both with and without external insulation for fire protection. It is shown that the proposed methodology can reproduce realistic cross-sectional temperature distributions with up to 50% temperature difference at the cable external surface and can capture the phenomenon of load shedding in a gradually heated cable. It is also shown that assuming a lumped thermal mass neglects the possibility of moment-inducing temperature gradients which are not considered in the ambient design of cables that is driven by tensile capacities. The proposed model and its predictions contribute towards an improved understanding and a more informed structural design of cable-supported structures in fire.

Design and manufacture of a 100 kA coaxial pulsed power cable for plasma generator and PPS in ETC guns

Based on our previous pulsed current and internal overvoltage test data and the experience of common commercial high power cables, a 100 kA coaxial pulsed power cable is designed and manufactured to adapt the coaxial electric energy breech transmission between the plasma generator and the pulsed power supply (PPS) in electrothermal-chemical (ETC) guns. The index parameters are analyzed and determined. Semi-conductor layers and a shield stiffener are introduced to prevent the deformation and burst of the pulsed power cable structurally. The semi-conductor layer can eliminate the air gap and balance the electric field in the cable. The shield stiffener can multiply the mechanical strength to restrain the strong electrodynamic force produced by the core dislocation of the outer conductor. The multi-coupling of electromagnetic field, stress field and thermal field analysis are established to assist in aided design of electrical strength, mechanical strength and temperature rise characteristics. Both a DC voltage withstand test and pulsed discharge tests are introduced to verify and inspect the performance and dynamic response of the pulsed power cable. The 25 kV/5min DC voltage withstand test result shows that the sample leakage current is nearly 3 μA and no abnormal phenomena of the pulsed power cable sample occurred. The pulsed discharge tests show that the sample can sustain the 100 kA peak current. Furthermore, this 100 kA coaxial pulsed power cable can satisfy the ETC test requirements.

Mitigation mechanism of longitudinal ribs on rain-wind induced vibrations of stay cables

For cable stayed bridges rain-wind induced vibrations of stay cables are probably one of the most widespread phenomenon. Aerodynamic countermeasures have been implemented to tackle such vibrations, but there is still not sufficient insight on the inherent mitigation mechanisms. To this goal, a numerical model, based on lubrication theory, was employed in order to study the coupled cable vibration response, aerodynamic forces, and formation and oscillation of rivulets for stay cables equipped with longitudinal ribs. Coupled equations governing the synchronous cable motion and water film evolution were established in order to understand the effects of several key parameters associated with the vibration mitigation performance of the ribs. Such parameters include the cable inclination angle, the wind yaw angle, the number and the height of the ribs. Computed results were successfully validated against experimental data. For the various studied cases, it was apparent that the ribs did not stop the formation of rivulets, but they could affect both their position and oscillation ranges. Through such a control action they could further affect the oscillation range and frequency content of aerodynamic forces, mitigating or not cable vibrations.

Experimental investigation on aerodynamic interference of two kinds of suspension bridge hangers

In order to study the aerodynamic interference between cables of suspension bridge hangers, two types of cable test models with smooth and rough surfaces, which respectively correspond to parallel wire strand (PWS) and wire rope (WR) hangers, were manufactured. The comparisons between the features of wake-induced vibration of the PWS and WR hangers were carefully investigated by means of wind tunnel tests. First, a series of force measurement tests for the two types of hangers were carried out to measure the mean aerodynamic coefficients of the downstream cable within spatial region of 3 ≤X≤11 and -4≤Y≤4 with an interval of ΔX =ΔY=0.25. The results of the force measurement tests show that obvious differences between the force coefficients of the downstream PWS and WR hangers are found. It seems that the variation amplitude of the force coefficient of the PWS hanger is significantly larger than that of the WR hanger. Moreover, the mean drag and lift coefficients of the downstream PWS hanger for U=15m∕s are obviously different from those for U=10m∕s, which indicates that the wake-induced vibration of the hanger might be strongly related to wind velocity (i.e., Reynolds Number). Second, a series of vibration measurement wind tunnel tests for the PWS and WR hangers were carried out to measure the responses of the downstream cables within the spatial region of 2.5≤X≤11 and 0≤Y≤4 with an interval of ΔX=ΔY=0.25. The results show that obvious wake-induced vibrations are both observed for the PWS and WR hangers. However, it appears that the unstable region of the WR hanger is significantly less than that of the PWS hanger, which indicates that the WR cable seems to be more suitable than the PWS cable to be used as the hanger of suspension bridge. Parametric studies show that the wake-induced vibration of the PWS hanger is not divergent because the amplitude of the downstream cable stop increasing with the increase of the wind velocity, whereas the oscillation amplitude of the WR hanger keeps increasing with the increase of the wind velocity (up to 18 m/s in the wind tunnel). Moreover, it seems that the structural damping ratio have no significant influence on the critical wind velocity of the wake-induced vibration of the hanger of the suspension bridge.

Research on lightning numerical simulation of wheeled armored vehicle with the enclosure and cables.

In order to further improve the all-weather combat capability of army armored equipment, the paper adopts the compact model of the CST MICROSTRIPES studio. The CST MICROSTRIPES studio is based on the numerical simulation technology of transmission line matrix algorithm and the paper has a study on the full-scale lightning strike numerical modeling and simulation. The induced electric field of the enclosures and the induced current of cables are analyzed. The simulation results showed that the method could effectively simulate the lightning response of armored vehicles, the electric field inside different enclosures and the lightning strike response of different cables are compared. It can provide reference for lightning protection design of armored vehicles and has a certain engineering application value.

Nonlinear dynamic analysis of long-span cable-stayed bridges with train\u2013bridge and cable coupling

Span lengths of newly constructed cable-stayed railway bridges continue to show increases relative to those of older bridges. Accompanying such increases is the importance of ensuring that vibrations of long-span cable-stayed bridges satisfy both safety and serviceability requirements, particularly for bridges that support train passages. In contrast to modern design of bridges that support roadway vehicles, current methods for analyzing cable-stayed railway bridges do not yet typically account for coupling effects that may occur between cables and the surrounding bridge structure during train passages. This paper presents a computational framework for the nonlinear dynamic analysis of railway bridges based on a coupled train–bridge analytical model and investigates the significance of accounting for cable-related coupling effects. A case study is then carried out, where coupled dynamic responses of cables, towers, and girders of an in-service railway bridge are computed and compared to those obtained using an uncoupled approach. These comparisons demonstrate the merits of accounting for coupling phenomena when computing dynamic characteristics of cable-stayed railway bridges and highlight benefits of the coupled analysis approach in bridge design applications.

Serviceability Assessment Method of Stay Cables with Vibration Control Using First-Passage Probability

As the construction of long-span bridges such as cable-stayed bridges increases worldwide, maintaining bridge serviceability and operability has become an important issue in civil engineering. The stay cable is a principal component of cable-stayed bridges and is generally lightly damped and intrinsically vulnerable to vibration. Excessive vibrations in stay cables can potentially cause long-term fatigue accumulation and serviceability issues. Previous studies have mainly focused on the mitigation of cable vibration within an acceptable operational level, while little attention has been paid to the quantitative assessment of serviceability enhancement provided by vibration control. This study accordingly proposed and evaluated a serviceability assessment method for stay cables equipped with vibration control. Cable serviceability failure was defined according to the range of acceptable cable responses provided in most bridge design codes. The cable serviceability failure probability was then determined by means of the first-passage problem using VanMarcke’s approximation. The proposed approach effectively allows the probability of serviceability failure to be calculated depending on the properties of any installed vibration control method. To demonstrate the proposed method, the stay cables of the Second Jindo Bridge in South Korea were evaluated and the analysis results accurately reflected cable behavior during a known wind event and show that the appropriate selection of vibration control method and properties can effectively reduce the probability of serviceability failure.

A 2D model for analysis of rain-wind induced vibration of stay cables

Rain-wind induced vibration of stay cables (RWIV) in cable-stayed bridges is a special aerodynamic phenomenon as it is easy to be influenced by many factors, especially velocity and impact angle of wind. This paper proposes a new assumption of the impact angle of wind on the cable in analyzing cable vibration response subjected to wind and rain. This angle is considered as a harmonic oscillation function around the equilibrium position that is the initial angle of impact, and its angular frequency equals of the rivulet and the cable. The amplitude of impact angle of wind depends on wind velocity, initial position and that of rivulet. The assumption is verified by comparison with experimental results. The effects of rivulet oscillation components and aerodynamic forces are also discussed in this paper.
 Keywords: cable; rain-wind induced vibration; rivulet; analytical model; vibration.

A methodology for cable damage identification based on wave decomposition

Vibration-based damage identification has been widely studied in the field of structural health monitoring (SHM) for several decades. It is well known, however, that low-order modal parameters, being among the most frequently used, are not sensitive to local damage. A suitable methodology is therefore needed to extract such damage features from the dynamic response of structures. In the present work, local bending behavior of cables is studied for damage identification. First, the dynamic response of a cable is decomposed into evanescent wave and propagating wave components. It is proven that the contribution of the evanescent wave is spatially concentrated, and is sensitive to local damage. A signal transform is proposed next, which allows the estimation of the wave components from the measured cable response. The reflection coefficient of the evanescent wave (REW), which can be calculated from the estimated wave coefficients, depends only on the characteristics of the local discontinuity, and proves to be a robust indicator for local damage. The feasibility of the proposed methodology is studied by means of a simulated experiment, considering a cable model with two locally damaged parts. The results show that the intensity of REW is significantly higher near the damage locations, allowing damage localization. From the estimated REW near the damage locations, the damage levels can be estimated, showing the potential of this methodology for damage assessment of cable structures.

Control-oriented model for the dynamic response of a damped cable

Designing effective control schemes to mitigate the violent vibrations of a stay cable subjected to dynamic loads requires an efficient and accurate computational model for the cable response. In this study, a control-oriented numerical model for evaluating the dynamic response of a stay cable equipped with a damper/actuator is proposed based on the mode superposition method (MSM) with enhanced shape functions. This enhancement accounts for the effect of the truncated higher modes by introducing a static correction term, which is the static displacement of a cable subjected to a point load at the damper location. The exact form is derived analytically and included as a shape function term. Moreover, in the case of a fixed-fixed cable, the outer ends of the sinusoidal shape functions were replaced by polynomials to adapt to the boundary condition. The accuracy and computational efficiency of the proposed model is evaluated through numerical examples and compared to other existing approaches for both passive and semi-active/active control. Results show that the number of modes required to satisfy the convergence criterion would substantially decrease when the static correction term is included. Also, the convergence rate and the numerical accuracy of the proposed model are superior to other methods, which makes it an ideal tool for control design applications.

Probabilistic seismic performance evaluation of SMA-braced steel frames considering SMA brace failure

This study explores seismic performance of steel frame buildings with SMA-based self-centering bracing systems using a probabilistic approach. The self-centering bracing system described in this study relies on superelastic response of large-diameter cables. The bracing systems is designed such that the SMA cables are always stressed in tension. A four-story steel frame building characterized until collapse in previous research is selected as a case-study building. The selected steel frame building is designed with SMA bracing systems considering various design parameters for SMA braces. Numerical models of these buildings are developed by taking into account the ultimate state of structural components and SMA braces as well as the effect of gravity frames on lateral load resistance. Nonlinear static analyses are conducted to assess the seismic characteristics of each frame and to examine the effect of SMA brace failure on the seismic load carrying capacity of SMA-braced frames. Incremental dynamic analyses (IDA) are performed to compute seismic response of the designed frames at various seismic intensity levels. The results of IDA are used to develop probabilistic seismic demand models for peak inter-story and residual inter-story drifts. Seismic demand hazard curves of peak and residual inter-story drifts are generated by convolving the ground motion hazard with the probabilistic seismic demand models. Results show that steel frames designed with SMA bracing systems provide considerably lower probability of reaching at a damage state level associated with residual drifts compared to a similarly designed steel moment resisting frame, especially for seismic events with high return periods. This indicates reduced risks for the demolition and collapse due to excessive residual drifts for SMA braced steel frames.

Fatigue load estimation of a spar-type floating offshore wind turbine considering wave-current interactions

This paper considers the effects of current and wave-current interactions in fatigue analysis of floating offshore wind turbines (FOWTs). Surface water waves experience frequency shifts and wave shape modification when traveling on underlying currents. The wave-current interactions are known to be important for the responses of offshore structures, however, they have not been considered in FOWT fatigue analysis. To include such interactions, a nonlinear mooring hydrodynamics model is presented which is able to consider the cable geometric nonlinearity, seabed contact, and the current effect. The mooring model is then coupled with a spar-type FOWT model which simulates the structural dynamics of turbine blades and tower; aerodynamics of the wind-blade interaction and wave-current actions on the spar. Analytical wave-current interaction models based on Airy’s theory considering the current effect are applied for generating the flow field. Based on a spar-type FOWT and the wave-current interaction model, numerical simulations have been performed for three cases with only waves, wave and current without and with interactions. The comparison of the structural responses shows that the current and the wave-current interaction can have significant influences on FOWT tower and cable responses. Furthermore, cable fatigue life is estimated for two particular cases when the cable tension is decreased and increased respectively due to the presence of current. It is found that if the current tends to increase the cable tension, neglecting the current and wave-current interactions leads to overestimate of the cable fatigue life.

Finite element cable-model for Remotely Operated Vehicles (ROVs) by application of beam theory

Increasing autonomy, efficiency and safety for Remotely Operated Vehicles (ROVs) is crucial for future subsea operations and requires accurate models for optimal control, operations and design. This involves precise modeling of the cable in conjunction with the ROV response. This paper presents a novel three-dimensional cable model for Remotely Operated Vehicles using Euler-Bernoulli beam theory. The presented model is implemented in Matlab and takes into account the most important effects related to the response of underwater cables and ROVs. Following beam theory bending stiffness is also included, making the model applicable for low tension scenarios. The presented model is modified to allow for compression of the cable. The resulting non-linear equations are discretized spatially by the Galerkin finite element method and solved temporally by the Newmark-β time integration scheme.The model is verified experimentally in ocean tank experiments on a real ROV system. A numerical example is presented and the results are compared to previous published results. Lastly, a sensitivity analysis for the hydrodynamic parameters is presented.

A coupled finite difference mooring dynamics model for floating offshore wind turbine analysis

This study develops a coupled nonlinear hydrodynamic model of a mooring system consisting of multiple cables for analyses of floating offshore wind turbines (FOWTs). The model is based on a finite difference model of submerged cables which considers cable-seabed interaction, current effect, cable bending and torsional stiffness. The implementation of the model proposes a parallelization scheme for solving the cable responses to improve the computational efficiency. The developed program is then coupled with a spar type FOWT and verified using an experimentally validated open source mooring simulation program. Furthermore, the model is used to study the impact of nonlinear dynamics of the mooring system on FOWT responses in the presence of current. Both static responses of a spar FOWT under current load and dynamic responses of the spar FOWT under wind, wave and current loads are investigated. Responses are compared where varied mooring models are used including the linear model, quasi-static model and nonlinear mooring models without and with current effect on cables considered. The results show that the current effect on cables can have a considerable impact on the restoring effect of the mooring system and hence the spar and cable responses. The current effect on mooring cables needs to be properly considered in the FOWT analysis.

Wake-flow-induced vibrations of vertical hangers behind the tower of a long-span suspension bridge

Violent vibrations have been reported in the vertical hangers of long-span suspension bridges, especially for those located in the vicinity of the towers. In the present study, an experimental investigation is performed to characterize the wake-flow-induced vibrations of vertical hangers behind the tower of a suspension bridge. The tower column and vertical cable models are determined by using a long-span suspension bridge with a geometrical scale ratio of 1:10. Regular vortex shedding from the tower column model is detected in the near wake with a Strouhal number (St) of 0.20, and the turbulence intensity of the wake flow behind the tower column model is found to be quite high. Arranged at different stations behind the tower column model, the vertical cables experience violent vibrations. The vibration frequencies of the vertical cables are synchronized with the vortex shedding from the upstream tower model within a certain velocity range, during which severe cable vibrations take place. When the incoming wind speed becomes high, the cable vibrations exhibit multimode characteristics. It is also found that the vertical cables arranged at the rear are subject to the combined interferences of the tower column model and the front cables. As a result, the vibration responses of the rear cables are more violent than those of the front cables.

Frequency and Time Domain Responses of Cross-Bonded Cables

Cross-bonded cable models are compared against their versions with normal bonding (no bonding) for propagation characteristics, frequency, and time-domain responses. Contrary to no-bonding cables, coaxial modes cannot propagate in cross-bonded cables. Instead, intercore modes propagate, being always accompanied by intersheath modes. The latter property cannot be observed if a cross-bonded cable is modeled with its homogeneous equivalent. It is shown that sheath cross-bonding induces intersheath modes circulating between grounding points and impacts on the cable response at resonant frequencies. Alternate models for cross-bonded cables, including both homogeneous and nonhomogeneous equivalents, are compared based on frequency- and time-domain responses, including a field test on a 225 kV 64 km cable with 17 major sections.

Dielectric and rheological study of the molecular dynamics during the cure of an epoxy resin

ABSTRACTComposite manufacturing is currently one of the most challenging processes for industrial lightweight applications. To date, the process conditions for polymer‐based composite manufacturing are evaluated by laboratory measurements: usually, the flow behavior and the curing of the polymer matrix material are characterized by rheology and quality assurance is performed by thermo‐physical analysis in postprocess measurements. In contrast a dielectric in‐mold sensor offers the possibility to measure the real‐time behavior of the polymer during processing. This study focuses on the correlation of simultaneous rheological and dielectric measurements on Hexcel RTM6 using a coupled setup of both techniques. For dielectric measurements a reusable in‐mold sensor was used and a calibration, taking into account the cable response, was performed. The results show good agreement with respect to glass‐transition temperature and the gel‐point. This can be understood by the fluctuation–dissipation theorem that explicitly relates molecular dynamics to the macromolecular mechanical properties under dynamic time‐dependent load. Furthermore, it was found that the dynamic viscosity can directly be related to the electrical conductivity. This proves the high potential of dielectric analysis as online‐capable technique for material characterization during composite manufacturing. © 2018 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2018, 56, 907–913