Search Results (28)

The surge in electric vehicles (EVs) in Denmark challenges the country’s residential low-voltage (LV) distribution system. In particular, it increases the demand for home EV charging significantly and possibly overloads the LV grid. This study analyzes the impact of EV charging integration on Denmark’s residential distribution networks. A residential grid comprising 67 households powered by a 630 kVA transformer is studied using DiGSILENT PowerFactory. With the assumption of simultaneous charging of all EVs, the transformer can be heavily loaded up to 147.2%. Thus, a voltage-droop based autonomous control approach is adopted, where the EV charging power is dynamically adjusted based on the point-of-connection voltage of each charger instead of the fixed rated power. This strategy eliminates overloading of the transformers and cables, ensuring they operate within a pre-set limit of 80%. Voltage drops are mitigated within the acceptable safety range of ±10% from normal voltage. These results highlight the effectiveness of the droop control strategy in managing EV charging power. Finally, it exemplifies the benefits of intelligent EV charging systems in Horizon 2020 EU Projects like SERENE and SUSTENANCE. The findings underscore the necessity to integrate smart control mechanisms, consider reinforcing grids, and promote active consumer participation to meet the rising demand for a low-carbon future. Full article

With the development of society and the advancement of technology, the application of electricity in modern life has become increasingly widespread. However, the risk of electrical fires has also significantly increased. This paper thoroughly investigates the causes, classifications, and challenges of electrical fires in special environments, and summarizes advanced detection and extinguishing technologies. The study reveals that the causes of electrical fires are complex and diverse, including equipment aging, improper installation, short circuits, and overloading. In special environments such as submarines, surface vessels, and aircraft, the risk of electrical fires is higher due to limited space, dense equipment, and difficult rescue operations. This paper also provides a detailed analysis of various types of electrical fires, including cable fires, electrical cabinet fires, transformer fires, battery fires, data center fires, and residential fires, and discusses their characteristics and prevention and control technologies. In terms of detection technology, this paper summarizes the progress of technologies such as arc detection, video detection, and infrared thermography, and emphasizes the importance of selecting appropriate technologies based on specific environments. Regarding extinguishing technologies, this paper discusses various means of extinguishing, such as foam extinguishing agents, dry powder extinguishing agents, and fine water mist technology, and highlights their advantages, disadvantages, and applicable scenarios. Finally, this paper identifies the limitations in the current field of electrical fire prevention and control, emphasizes the importance of interdisciplinary research and the development of advanced risk assessment models, and outlines future research directions. Full article

Vehicular bridges accumulate damage over time due to overloads and material degradation. Non-visible structural damage in such large structures poses a serious risk, as small defects in critical elements can rapidly grow, potentially leading to catastrophic failure. Therefore, implementing simple yet effective methods for damage identification within a structural health monitoring (SHM) system is crucial for ensuring bridge reliability. This study presents a systematic comparative analysis of multiple damage detection algorithms, including six different fractal dimensions (FDs), the homogeneity index (HI), and the Shannon entropy index (SEI). These methods are applied to a high-fidelity finite element method (FEM) model of the Rio Papaloapan Bridge (RPB), a cable-stayed structure, to detect and localize two different types of damage (deck and cable failures) with varying severities and positions. To enhance practical applicability, realistic conditions are simulated by introducing noise to the vibration signals collected from both the undamaged and damaged bridge scenarios while a moving load, simulating a vehicle, is crossing. The results indicate that the HI and SEI not only detected and localized all damage scenarios but also effectively distinguished between different levels of severity, making them highly promising for SHM applications. Additionally, two of the six FD algorithms successfully identified all damage cases with minimal variation from the healthy condition, demonstrating their potential utility. The findings presented in this study are consistent with previous experimental and real-world bridge assessments, reinforcing their validity for real-life applications. Full article

In light of the issues associated with the laying process of transmission line cables, including concealed security risks and contact collisions between pulleys and cables, which primarily stem from reliance on drawings, this paper introduces a simulation methodology for the cable laying construction process utilizing Building Information Modeling (BIM) technology. Initially, two-dimensional DWG graphic data are employed to develop a model of the target equipment and construction environment using BIM software (Solid works 2020). Subsequently, the cable is accurately modeled by applying ADAMS virtual prototype technology, the bushing force connection method, and the macro command language. This allows for the construction of a three-dimensional real cable laying system for transmission lines, enabling the simulation of the dynamic cable laying process in the field. Subsequently, an error analysis is conducted to compare the axial tension and laying speed of the cable with theoretical calculation values. The study then proceeds to analyze tension fluctuations during the cable laying process and assess the load-bearing capacity of the pulleys, thus facilitating effective control of the construction process and enhancing safety measures. The findings indicate that the proposed method can accurately and efficiently simulate the on-site cable laying construction process, with numerical errors maintained below 5%, thereby validating the integrity of the model. Furthermore, the traction overload safety protection amplification coefficient is determined to be α = 1.5. It is highlighted that the bearing capacity of the block must exceed 60% of the load carried by the conductor at constant speed. This research provides a theoretical foundation for addressing safety hazards in cable laying engineering and holds certain engineering value. Full article

The increasing number of renewable energy sources in power systems contributes to overloads of power lines in emergency situations. Lines made with relatively small cross-section cables, which in the past were designed for an operating temperature of 40 °C, are particularly exposed to overloads. Currently, they constitute the so-called “bottlenecks” in network capacity. This is manifested in the fact that when carrying out expert opinions aimed at examining the impact of a source on the network, computational analyses show overloads of its elements. This article proposes a methodology for eliminating these overloads. It involves the use of two methods at the same time, namely optimal network reconfiguration combined with minimisation of the total power curtailment in RE sources. The search for the optimal network configuration will also allow for minimising power curtailment in renewable energy sources, and thus reduce the costs of this type of operation. With such a tool, network operators will be able to achieve the effect of relieving the line load with the lowest possible cost of redistribution. Based on the IEEE 118 bus test network, calculations were performed that confirmed the effectiveness of the proposed approach. The operation of the proposed methodology is presented with the example of two selected network failure states. The novelty of the proposed solution lies in the simultaneous use of two methods of eliminating line overloads. This streamlines the entire process and improves its effectiveness. Full article

The current trend in distributed electric aircraft propulsion systems is to utilize the DC bus system at higher voltage levels than conventional aircraft systems. With Boeing and Airbus utilizing the +/−270 V bipolar DC bus system, the research on high-voltage systems is increasing gradually, with voltage levels ranging from 1 to 10 kV systems or +/−0.5 to +/−5 kV DC bus systems. These voltage levels present considerable challenges to the distributed electric aircraft propulsion systems. In addition to partial discharge effects, there are other challenges, particularly the challenge associated with effectively limiting short-circuit fault currents due to the low cable impedance of the distribution system. The cable impedance is a significant factor that determines the fault current during fault conditions. Due to the low impedance, there is a sharp increase in fault current, necessitating an enhanced protection strategy, which ensures that the system is adequately protected. This paper introduces a coordinated protection strategy specifically designed for distributed electric aircraft propulsion systems to mitigate or prevent short-circuit faults. The proposed algorithm utilizes an I²t-based strategy and the current-limiting-based strategy to protect the system from short-circuit faults and overload conditions. Redundant backup protection is also included in the algorithm in case the circuit breaker fails to operate. Full article

The distribution grid comprises cables with diverse constructions. The insulating material used in low-voltage (LV) distribution cables is predominantly PVC. Furthermore, the presence of cables with different structures in the grid poses challenges in detecting the aging of the cable network. Finding a universal and dependable condition-monitoring technique that can be applied to various types of cables is indeed a challenge. The diverse construction and materials used in different cables make it difficult to identify a single monitoring approach that can effectively assess the condition of all cables. To address this issue, this study aims to compare the thermal aging behavior of different LV distribution cables with various structures, i.e., one cable contains a PVC belting layer, while the other contains filler material. The growing adoption of distributed generation sources, electric vehicles, and new consumer appliances in low-voltage distribution grids can lead to short, repetitive overloads on the low-voltage cable network. Hence, these cable samples were exposed to short-term cyclic accelerated aging in the climate chamber at 110 °C. The cable’s overall behavior under thermal stress was evaluated through frequency and time domain electrical measurements (including tan $\delta$ and extended voltage response) and a mechanical measurement (Shore D). The tan $\delta$ was measured in the frequency range of 20 Hz–500 kHz by using the Wayne-Kerr impedance analyzer. The extended voltage response measurement was conducted using a C# application developed in-house specifically for laboratory measurements in the .NET environment. The study observed a strong correlation between the different measurement methods used, indicating that electrical methods have the potential to be adopted as a non-destructive condition-monitoring technique. Full article

Manual handling tasks, both in daily activities and at work, require high dexterity and the ability to move objects of different shapes and sizes. However, musculoskeletal disorders that can arise due to aging, disabilities, overloading, or strenuous work can impact the natural capabilities of the hand with serious repercussions both in working and daily activities. To address this, researchers have been developing and proving the benefits of wrist exoskeletons. This paper, which is Part II of a study on wrist exoskeletons, presents and summarizes wearable wrist exoskeleton devices intended for use in rehabilitation, assistance, and occupational fields. Exoskeletons considered within the study are those available either in a prototyping phase or on the market. These devices can support the human wrist by relieving pain or mitigating fatigue while allowing for at least one movement. Most of them have been designed to be active (80%) for higher force/torque transmission, and soft for better kinematic compliance, ergonomics, and safety (13 devices out of 24, more than 50%). Electric motors and cable transmission (respectively 11 and 9 devices, out of 24, i.e., almost 50% and 40%) are the most common due to their simplicity, controllability, safety, power-to-weight ratio, and the possibility of remote actuation. As sensing technologies, position and force sensors are widely used in all devices (almost 90%). The control strategy depends mainly on the application domain: for rehabilitation, CPM (control passive motion) is preferred (35% of devices), while for assistance and occupational purposes, AAN (assistance-as-needed) is more suitable (38% of the devices). What emerges from this analysis is that, while rehabilitation and training are fields in which exoskeletons have grown more easily and gained some user acceptance (almost 18 devices, of which 4 are available on the market), relatively few devices have been designed for occupational purposes (5, with only 2 available on the market) due to difficulties in meeting the acceptance and needs of users. In this perspective, as a result of the state-of-the-art analysis, the authors propose a conceptual idea for a portable soft wrist exoskeleton for occupational assistance. Full article

Low-voltage (LV) network assets, although they do not play a significant role in reliability indices compared to medium-voltage (MV) assets like the transformer and switchgears, are required to be designed in a way that would mitigate the risk of sporadic failures, hence incurring an R&M cost. LV assets like LV cables, distribution panels, molded-case circuit breakers (MCCBs), and miniature circuit breakers (MCBs) generally do not have a planned maintenance (PM) schedule and are procured based on the run-to-failure concept in view of the huge volume. These assets are exposed to the harshest of environmental and operation conditions. Hence, it is imperative that we take the necessary measures during the design stage such that they are able to cater to their stringent duties, which include frequent short circuits, exposure to the environment, and thermal overloads. It is also important to periodically review the product design based on site feedback and product performance to re-calibrate the product and its associated processes. Through this technical paper, several case studies are presented wherein special terminal connectors with shear bolts were designed to mitigate the thermal hotspot issues causing frequent fire and failures—i.e., vertical fuse switch disconnectors (VFSDs) and miniature circuit breaker (MCBs). A case study on condition monitoring through a substation inspection schedule is also presented, through which potential failures were averted in time. The observations and measurements are mapped in an SAP system for trend analysis. With the adoption of effective product and process design, AEML has reduced asset failures. Full article

Due to the large scale of navigation ships, the fast speed of entering the lock, and the irregular mooring and the complicated flow conditions in the lock chamber, it is common for the floating bollards of the lock to suffer structural damage or even failure due to the overloaded mooring force. However, the traditional cable load measurement method cannot offer real-time feedback on force characteristics of floating bollards, making it difficult to accurately judge its service status. To this end, according to the floating bollard structure type and load condition of a representative ship lock project in China, this paper determines the theoretical model parameters of a floating bollard load response based on three-dimensional finite element numerical simulation test data and constructs a modified load response model of floating bollards. On this basis, an intelligent floating bollard monitoring system based on big data, internet, and cloud services is developed to intelligently perceive real-time floating bollard force characteristics and monitor the long-term service status. Relying on a representative ship lock in China, a field test of the floating bollard intelligent monitoring system is carried out. The relative error between the calculated values via the model (i.e., system exhibition results) based on the numerical results and the field-measured values is within 15%. This result verified the accuracy and effect of the monitoring system. This research supports the establishment of the digital perception monitoring platform for ship lock facilities and improves the automation level of ship lock operation and management as well as overall risk prevention and control capabilities. Full article

Distorted currents drawn by nonlinear loads used in power installations (including lighting) can cause many problems. With the constantly progressing increase in the number of these loads, these phenomena can accumulate, constituting significant causes of serious failures in both electrical and electronic devices, as well as installation components. The effects of disturbances introduced to the network by nonlinear loads may include, for example, line overloads, overheating of transformers and motors, capacitor failures, accelerated degradation of insulation, etc. The article presents examples of measurement results for luminaires with discharge and LED sources. Measurements of the electrical parameters of a three-phase outdoor lighting installation consisting of luminaires with low-power LED sources and luminaires with discharge sources are also discussed. Based on the recorded waveforms, the measurement results were determined. High harmonic values for the phase currents and the current in the neutral conductor were recorded. The results of measurements of the parameters of LED luminaires with control systems, the operation of which causes excessive heat generation, are presented. The methodology for cable selection in circuits with current harmonics is described. Full article

The increasing penetration of distributed generation sources in low-voltage distribution grids, electric vehicles, and new appliances from the consumer side can generate short repetitive overloads on the low-voltage cable network. This work investigates the change in the dielectric properties of low-voltage cable insulation caused by short-term overloads, examining how the cable structure affects the dielectric characteristics of the cable specimens in the case of cyclic short-term thermal aging. PVC-insulated low-voltage cable samples were exposed to an accelerated aging test in a temperature-controlled oven after changing their structures by removing different layers. Three aging cycles, each of six hours, were applied to the samples. After each cycle, the tan $\delta$ and capacitance were measured by an Omicron DIRANA Dielectric Response Analyzer in the laboratory at room temperature 24 $\pm 0.5$ °C. Furthermore, the polarization and depolarization currents were also studied. The results show that changing the cable structure impacts the dielectric parameters; in particular, the effect of the belting layer is significant. From the point of view of aging, the PVC belting layer protects the diffusion of the plasticizers of the inner structure. The findings of the study show that an asymmetric aging phenomenon can be observed in different polymeric components of the cables, even though the cables were aged in an air-circulated oven ensuring a homogeneous temperature distribution in the samples. Full article

Rock bolts are one of the most effective and conventional support techniques widely used in underground mining and tunneling operations to stabilize excavations and jointed rock masses. External factors such as corrosion, overloading, and improper installation can weaken rock bolts, which could result in ground failure causing injury or loss of life and production. Monitoring the health condition of rock bolts will reduce the risk of accidents providing a safer environment for workers and equipment. This paper reviews monitoring methods currently used to assess the condition of installed rock bolts. Furthermore, we classify the surveyed techniques depending on the type of problems they attempt to solve. Presented are methods such as ultrasonics, fiber optics, piezoelectric, electromagnetics, impact echo, acoustic emission, and numerical algorithms. Each method is based on a unique physical principle that aids in evaluating corrosion and strain levels in the rock bolt. However, recent research to detect corrosion has primarily focused on rebar type of rock bolts used in concrete structures. Consequently, more research is needed to monitor the condition of the other types of rock bolts used in the industry such as cable bolts and split set bolts. In conclusion, the paper highlights various methods of studying rock bolt failure initiated by strain, corrosion, and improper installation of the grouts. It also explores the research advancement made for the study of rock bolt failure. This investigation is specifically beneficial to the mining and tunneling industry for better understanding and prediction of rock bolt failure. Full article

In this paper, a flexible numerical framework to provide thermal performance assessment for the underground buried cables, considering different geological and meteorological conditions, has been presented. Underground cables tend to retain the heat produced in the conductor, so complex coupled thermo-hydraulic response of the porous medium surrounding the cables needs to be assessed to prevent cable overheating and the associated reduction in cable capacity for carrying current. Applying a coupled thermo-hydraulic model within the developed numerical framework to conduct a health assessment on a subset of National Grid Electricity Transmission’s underground cables, this study provides novel insights into the thermal behaviour of buried circuits. The results indicate that backfill and surrounding native soil have the dominant effect on the thermal behaviour of cables, while the amount of precipitation and ambient temperature were found to have less impact on cable’s thermal behaviour. The findings strongly infer that the nature of the overloading which is undertaken in practice would have no ongoing negative impact, suggesting that more frequent or longer duration overloading regimes could be tolerated. Overall, this study demonstrates how the developed numerical framework could be harnessed to allow safe rating adjustments of buried transmission circuits. Full article

Injuries to the shoulder are very common in sports that involve overhead arm or throwing movements. Strength training of the chest muscles has the potential to protect the shoulder from injury. Kinematic and kinetic data were acquired in 20 healthy subjects (age: 24.9 ± 2.7 years) using motion capture, force plates for the bench press exercises and load cells in the cable for the cable pulley exercises with 15% and 30% of body weight (BW). Joint ranges of motion (RoM) and joint moments at the shoulder, elbow and wrist were derived using an inverse dynamics approach. The maximum absolute moments at the shoulder joint were significantly larger for the cable pulley exercises than for the bench press exercises. The cable cross-over exercise resulted in substantially different joint angles and loading patterns compared to most other exercises, with higher fluctuations during the exercise cycle. The present results indicate that a combination of bench press and cable pulley exercises are best to train the full RoM and, thus, intra-muscular coordination across the upper limbs. Care has to be taken when performing cable cross-over exercises to ensure proper stabilisation of the joints during exercise execution and avoid joint overloading. Full article