Search Results (72)

Distributed acoustic sensing sends laser pulses along a fiber optic cable and analyzes the backscattered light to identify acoustic signals along the entire fiber. Liquid slugs were produced in a 427 m vertical test well using surface-controlled gas lift valves. To enhance DAS monitoring, pressure pulses were induced by multiple acoustic shots from a fluid level gun. Visualization of the responses through frequency band energy plots and unfiltered phase shift measurements permitted tracking slug movement and estimating parameters such as velocity, location, and body length. The results demonstrate that DAS stimulated with acoustic pulses can effectively track liquid slugs in real-time. We observe that relying solely on flow-induced noise in multiphase flow environments may not provide sufficient signal strength for slug detection. Applications include real-time detection of liquid slugs for improved well monitoring and flow management. Full article

In this paper, the performance of a conventional distance protection relay employing a single ground compensation factor (k₀) per protection zone is investigated for non-uniform transmission lines consisting of mixed overhead line and underground cable sections. In such composite lines, the use of a single k₀ value may lead to inaccurate apparent impedance calculation during phase-to-ground faults due to significant differences in zero- and positive-sequence parameters among line sections. To address this limitation, a novel ground distance protection algorithm is proposed, which applies separate ground compensation factors corresponding to individual line sections within the same distance protection zone. The proposed algorithm dynamically identifies the faulted line section based on the measured reactance and selects the appropriate compensation factor accordingly. A three-section composite transmission line model is developed in the ATP–EMTP environment, including overhead and cable segments with different electrical characteristics. Phase-to-ground faults are simulated at various locations along each line section, and the apparent impedances calculated using the proposed algorithm are quantitatively compared with those obtained from the classical ground distance protection algorithm. Simulation results demonstrate that, under resistive fault conditions (Rarc = 1 Ω), the proposed method reduces impedance magnitude estimation errors from over 23% to below 7%, while maintaining comparable or improved angle estimation accuracy across the protected zone. Although the proposed algorithm introduces an additional computational step due to the selection of appropriate ground compensation factors for individual line sections, this aspect has not been evaluated under real-time conditions and is left for future implementation-oriented studies. Overall, the proposed approach offers a practical and effective solution for improving ground distance protection performance in non-uniform transmission lines. Full article

Grafted polypropylene (PPG) has demonstrated significant potential as a recyclable insulation material for high-voltage cables. While its fundamental electrical, mechanical and thermal properties have been widely studied, research on its long-term performance remains insufficient. This study comparatively investigates the thermo-oxidative ageing performance of PPG and traditional cross-linked polyethylene (XLPE) to evaluate the expected lifespan of cable insulation. The evolution of mechanical and electrical properties of PPG and XLPE was monitored during accelerated thermo-oxidative ageing experiments conducted at their respective maximum allowable operating temperatures, and the most sensitive ageing parameter was identified. Furthermore, the influence of thickness on the insulation ageing process was examined through experiments on samples of different thicknesses. Results indicate that the estimated thermo-oxidative ageing lifespan of XLPE at its maximum operating temperatures of 90 °C is 37.75 years, while that of PPG at 110 °C is 45.65 years. This work offers a practical methodology for polymer ageing lifespan analysis and provides valuable insights for assessing the long-term performance of PPG cables in high-voltage applications. Full article

The measured standard resistance at 20 °C ($R_{20}$) is a critical indicator for evaluating the quality of electric cables. Utilizing a thermal circuit model allows for the rapid determination of $R_{20}$. Focusing on civil electrical cables, this study constructs a thermal circuit model based on an equivalent circuit. Through mathematical derivation, model parameters are expressed as functions of the insulation cross-sectional area and conductor specification. Subsequently, the insulation area is fitted to the conductor specification, establishing a universal analytical thermal circuit model with the conductor specification as the sole variable. Ambient temperatures measured under specific operating conditions showed exponential variation. Using corresponding simulated conductor temperatures, the Differential Evolution algorithm was employed to train the model, achieving a training standard deviation of 0.0184 °C. Validation under different conditions demonstrated that for various cable specifications, the conductor temperature prediction deviation within 300 s remained within 0.368 °C, and the maximum estimation error for $R_{20}$ was less than 0.148%. These results indicate that the established model possesses high calculation accuracy and strong universality, offering a valuable tool for researchers and practitioners in fields relevant to civil electrical cables. Full article

To investigate the anti-slip characteristics of the main cables in a three-tower suspension bridge with spatial cable systems, this paper proposes an analytical calculation method for the anti-slip safety factor of the main cables and establishes an equivalent mechanical analysis model for multi-tower suspension bridges with spatial cable systems. Based on the deformation of the towers and cables under live load, as well as the equilibrium relationship of the main cable forces in loaded and unloaded spans, analytical formulas for the anti-slip safety factor of the main cables at the middle tower saddle are derived. A finite element model is developed to validate the formulas. The influence of parameters such as the spatial cable inclination angle, tower-to-cable stiffness ratio, dead-to-live load ratio, sag-to-span ratio, span length, and friction coefficient between the main cable and saddle on the anti-slip safety factor is analyzed. The results indicate that the formula proposed in this paper provides a highly accurate estimation of the slip resistance safety factor for main cables in spatial cable multi-tower suspension bridges. The adoption of spatial main cable configuration enhances the stability of the slip resistance safety factor at the intermediate tower saddle. The slip resistance safety factor of the main cable decreases with the increase in the tower-to-cable stiffness ratio, while it increases with the rise in the sag-to-span ratio. Moreover, the influence of the sag-to-span ratio on the slip resistance stability of the main cable becomes more pronounced with higher tower stiffness. The slip resistance safety factor of the main cable exhibits an approximately linear increase with the rise in the dead-to-live load ratio and the coefficient of friction. Furthermore, the slip resistance safety factor increases with the span length, and this rate of increase becomes more pronounced with smaller sag-to-span ratios. The research findings presented in this paper provide a theoretical basis for the design of spatial cable multi-tower suspension bridges. Full article

The article analyses the hosting capacity of low-voltage (LV) power grids for connecting distributed energy sources (DER), mainly photovoltaic installations (PV), considering technical limitations imposed by power system operating conditions. The main objective of the research was to develop a simple equation that enables the quick estimation of the maximum power of an energy source that can be safely connected at a given point in the network without causing excessive voltage rise or overloading the transformer and line cable. The analysis was performed on the basis of relevant calculation formulas and simulations carried out in DIgSILENT PowerFactory, where a representative low-voltage grid model was developed. The network model included four transformer power ratings (40, 63, 100, and 160 kVA) and four cable cross-sections (25, 35, 50, and 70 mm²), which made it possible to assess the impact of these parameters on grid hosting capacity as a function of the distance from the transformer station. Based on this, the P_HCI indicator was developed to determine the hosting capacity of a low-voltage network, using only the transformer rating and the length and cross-section of the line for the calculations. A comparison of the results obtained using the proposed equation with detailed calculations showed that the approximation error does not exceed 15%, which confirms the high accuracy and practical applicability of the proposed approach. Full article

This work proposes a method for fault location in onshore wind farms’ collector circuits based on metaheuristic optimization. The approach minimizes differences between voltage and current phasors measured and calculated at the Collector Bus (CB) using a Particle Swarm Optimization (PSO) algorithm. By optimizing this objective function, the method achieves accurate identification of fault locations. Additionally, to improve the method’s precision, the CB measurement data were employed to estimate the current injected by the wind generators during the fault. The proposed solution was evaluated through extensive simulations in PSCAD/EMTDC v5.0.2, covering short-circuit scenarios with variations in fault type, location, resistance, and affected segments, including both overhead and underground cables. The results demonstrated high fault location accuracy, even under diverse and challenging conditions. Additionally, the method successfully identified the fault resistance and the specific circuit segment where the fault occurred, thereby reducing the possibility of multiple fault locations. Sensitivity analysis further confirmed the robustness of the methodology, validating its applicability through errors in phasor measurements and line parameters. These findings highlight the proposed method’s potential as a practical and reliable tool for enhancing fault diagnosis and resilience in wind farm collector circuits. Full article

This review synthesises fault detection and diagnosis (FDD) methods for robotic actuation in healthcare, where precise, compliant, and safe physical human–robot interaction (pHRI) is essential. Actuator families—harmonic-drive electric transmissions, series-elastic designs, Cable/Bowden mechanisms, permanent-magnet synchronous motors (PMSM), and force–torque-sensed architectures—are mapped to characteristic fault classes and to sensing, residual-generation, and decision pipelines. Four methodological families are examined: model-based observers/parity relations, parameter-estimation strategies, signal-processing with change detection, and data-driven pipelines. Suitability for pHRI is assessed by attention to latency, robustness to movement artefacts, user comfort, and fail-safe behaviour. Aligned with ISO 14971 and the IEC 60601/80601 series, a validation framework is introduced, with reportable metrics—time-to-detect (TTD), minimal detectable fault amplitude (MDFA), and false-alarm rate (FAR)—at clinically relevant thresholds, accompanied by a concise reporting checklist. Across 127 studies (2016–2025), a pronounced technology-dependent structure emerges in the actuator-by-fault relationship; accuracy (ACC/F1) is commonly reported, whereas MDFA, TTD, and FAR are rarely documented. These findings support actuation-aware observers and decision rules and motivate standardised reporting beyond classifier accuracy to enable clinically meaningful, reproducible evaluation in contact-rich pHRI. Full article

This paper proposes a two-layer adaptive proportional–integral–derivative (PID) controller for precise pose control of a six-degree-of-freedom cable-driven parallel robot with eight cables, specifically designed to handle dynamic changes caused by the movement of attachment points. The positions of the attachment points on the base are adjusted to avoid collisions between humans and cables, where humans and robots are working in a shared workspace. The inherent nonlinearity of the robot system was addressed using model identification based on the recursive least squares (RLS) algorithm equipped with an adaptive forgetting factor. This method enables real-time updates to the dynamic model of the robot, thereby ensuring accurate parameter estimation as the attachment points move. The combination of the PID controller and RLS algorithm enhances the system’s ability to respond effectively to changing dynamics. Simulation results highlight the superior accuracy, robustness, and adaptability of the proposed approach, making it well suited for applications requiring a reliable performance in dynamic and unpredictable environments. The proposed method can guarantee human safety, while the end effector tracks the desired trajectory. Full article

This study aims to analyze the wind-induced effects and vibration control of a long-span cable-stayed bridge with a steel truss girder under strong marine wind conditions during its maximum single-cantilever state. During the cantilever construction stage of cable-stayed bridges, the reduction in structural stiffness and damping may lead to excessive wind-induced responses, affecting construction accuracy and safety. Focusing on a newly constructed sea-crossing railway cable-stayed bridge with a steel truss girder and a main span of 364 m, this research utilizes field-measured data and finite element simulations to analyze the buffeting responses of the bridge in the maximum single-cantilever state during construction. The vibration suppression effects of different wind-resistant measures are compared, and we propose an economical and efficient vibration mitigation solution. The results indicate that using the turbulent field parameters and unit aerodynamic admittance function recommended in JTG/T 3360-01—2018 Wind-resistant Design Specification for Highway Bridges leads to conservative in predictions regarding the buffeting responses, and this approach can be used in the preliminary design of large-span bridges. The measured turbulent field parameters can effectively estimate the bridge buffeting responses, especially in the transverse direction. Measuring wind speeds at the bridge site is crucial for the rational design and construction of cable-stayed bridges in strong marine wind environments. The effectiveness of vibration reduction decreases in the order of temporary piers, inclined struts, tuned mass dampers, and wind-resistant cables. The inclined strut scheme achieved vibration reductions of 84.45% in the transverse direction and 68.17% in the vertical direction, slightly lower than those of the auxiliary pier scheme (89.04% and 85.47%). However, the installation of temporary piers during the construction of a sea-crossing bridge would significantly increase construction costs, whereas the inclined strut scheme requires only temporary steel structures near the main tower and piers without substantially increasing the construction workload. Therefore, the inclined strut scheme is recommended as an effective and economical vibration control measure for large-span sea-crossing cable-stayed bridges. Full article

Due to the slender geometry and low-amplitude vibrations of stayed cables, existing vision-based methods often fail to accurately identify their full-field dynamic parameters, especially the higher-order modes. This paper proposes a novel holographic vision-based method to accurately identify the high-order full-field dynamic parameters and estimate the tension of the stayed cables. Particularly, a full-field optical flow tracking algorithm is proposed to obtain the full-field dynamic displacement information of the stayed cable by tracking the changes in the optical flow field of the continuous motion signal spectral components of holographic feature points. Frequency-domain analysis is applied to extract the natural frequencies and damping ratios, and the vibration frequency method is used to estimate the tension. Additionally, an Eulerian-based amplification algorithm—holographic feature point video magnification (HFPVM)—is proposed for enhancing weak visual motion signals of the stayed cables, so that the morphological motion information of the stayed cables can be visualized. The effectiveness of the proposed method has been validated through experiments on the stayed cable models. Compared with the results obtained using contact sensors, the proposed holographic vision-based method can accurately identify the first five natural frequencies with overall errors below 5% and a maximum deviation of 6.86% in cable tension estimation. The first three normalized holographic mode shapes and dynamic displacement vectors are successfully identified, with the MAC value reaching up to 99.51%. This entirely non-contact vision-based method offers a convenient and low-cost approach for cable tension estimation, and this is also the first study to propose a comprehensive, visual, and quantifiable strategy for periodic or long-term monitoring of cable-supported structures, highlighting its strong potential in practical applications. Full article

To address the limitations of low detection efficiency and poor spatial resolution of traditional cable insulation diagnosis methods, a novel cable insulation diagnosis method based on impedance spectroscopy has been proposed. An impedance spectroscopy analysis model of the frequency response of high-voltage single-core cables under different aging conditions has been established. The initial classification of insulation condition is achieved based on the impedance phase deviation between the test cable and the reference cable. Under localized aging conditions, the impedance phase spectroscopy is more than twice as sensitive to dielectric changes as the amplitude spectroscopy. Leveraging this advantage, a multi-parameter diagnostic framework is developed that integrates key spectral features such as the first phase angle zero-crossing frequency, initial phase, and resonance peak amplitude. The proposed method enables quantitative estimation of aging severity, spatial extent, and location. This technique offers a non-invasive, high-resolution solution for advanced cable health diagnostics and provides a foundation for practical deployment of power system asset management. Full article

Commonly, accelerometers are used to determine the tension force in cables through an indirect process; however, it is necessary to know the mechanical parameters of each element, such as mass and length. Typically, obtaining or measuring these parameters is not feasible. Therefore, this research proposed an alternative methodology to indirectly estimate them based on historical information about the so-called classic instruments (accelerometers and hydraulic jack). This case study focused on the Rio Papaloapan Bridge located in Veracruz, Mexico, a structure that has experienced material casting issues due to inadequate heat treatment in some cable top anchor over its lifespan. Thirteen cables from the structure were selected to evaluate the proposed methodology, yielding results within 3.8% of difference compared to direct tension estimation generated by a hydraulic jack. Furthermore, to enhance data collection, this process was complemented using a computer vision methodology. This involved remotely measuring the vibration frequency of cables from high-resolution videos recorded with a smartphone. The non-contact method was validated in a laboratory using a vibrating table, successfully estimating oscillation frequencies from video-recording with a fixed camera. A field test on eight cables of a bridge was also conducted to assess the performance and feasibility of the proposed method. The results demonstrated an RMS Error of approximately 2 mHz and a percentage difference in the tension force estimation below 3% compared to an accelerometer measurement approach. Finally, it was determined that this composed methodology for indirect tension force determination is a viable option when: (1) cables are challenging to access; (2) there is no line of sight between the camera and cables outside the bridge; (3) there is a lack of information about the mechanical parameters of the cables. Full article

AC power cables play an important role in power systems, in the transmission and distribution of electrical energy. For this reason, to ensure high operational reliability, voltage withstand tests and diagnostic tests are performed at every stage of their technical life to determine the condition of cable insulation. Due to the large electrical capacitances of cable systems, modern testing methods use very low frequency (VLF) and damped oscillating (DAC) voltages. The research presented in the article analyzed the effect of the test voltage waveform parameters on the partial discharge (PD) inception conditions in spherical gaseous voids present in the XLPE insulation of AC cable model. Using COMSOL 6.1 and MATLAB R2021b, a coupled electro-thermal model of a 110 kV AC cable was implemented, for which the critical gaseous void dimensions were estimated and phase-resolved PD patterns were generated for the rated voltage and the VLF and DAC test voltages specified in the relevant standards. In the analyses for the rated voltage, the influence of internal temperature distribution, which causes modification of XLPE permittivity, was taken into account in the numerical cable model. Full article

Reactive power sharing in distributed generators (DGs) is one of the key issues in the control technologies of greenship microgrids. Reactive power imbalance in ship microgrids can cause instability and potential equipment damage. In order to improve the poor performance of the traditional adaptive droop control methods used in microgrids under high-load conditions and influenced by virtual impedance parameters, this paper proposes a novel strategy based on the deep reinforcement learning DQN-VI, in which a deep Q network (DQN) is combined with the virtual impedance (VI) method. Unlike traditional methods which may use static or heuristically adjusted VI parameters, the DQN-VI strategy employs deep reinforcement learning to dynamically optimize these parameters, enhancing the microgrid’s performance under varying conditions. The proposed DQN-VI strategy considers the current situation in greenships, wherein microgrids are generally equipped with cables of different lengths and measuring the impedance of each cable is challenging due to the lack of space. By modeling the control process as a Markov decision process, the observation space, action space, and reward function are designed. In addition, a deep neural network is used to estimate the Q function that describes the relationship between the state and the action. During the training of the DQN agent, the process is optimized step-by-step by observing the state and rewards of the system, thereby effectively improving the performance of the microgrids. The comparative simulation experiments verify the effectiveness and superiority of the proposed strategy. Full article