Search Results (60)

Grounding systems are critical for ensuring electrical safety, fault current dissipation, and electromagnetic compatibility in power installations across different voltage levels. This research presents a comparative study on the optimization of grounding configurations for 400 V, 10 kV, and 35 kV electrical installations, focusing on key performance parameters such as grounding resistance, step and touch voltages, and fault current dissipation efficiency. The study employs computational simulations using the finite element method (FEM) alongside empirical field measurements to evaluate the influence of soil resistivity, electrode materials, and grounding configurations, including rod electrodes, grids, deep-driven rods, and hybrid grounding systems. Results indicate that soil resistivity significantly affects grounding efficiency, with deep-driven rods providing superior performance in high-resistivity conditions, while grounding grids demonstrate enhanced fault current dissipation in substations. The integration of conductive backfill materials, such as bentonite and conductive concrete, further reduces grounding resistance and enhances system reliability. This study provides engineering insights into optimizing grounding systems based on installation voltage levels, cost considerations, and compliance with IEEE Std 80-2013 and IEC 60364-5-54. The findings contribute to the development of more resilient and cost-effective grounding strategies for electrical installations. Full article

Vibration sensors are important in many engineering fields, including industry, surgery, space, and mechanics, such as for remote and autonomous driving. We propose a novel, cutting-edge vibratory sensor that mimics human tactile receptors, with a configuration different from current sensors such as strain gauges and piezo materials. The basic principle involves the perception of vibration via touch, with a cutaneous mechanoreceptor that is sensitive to vibration. We investigated the characteristics of the proposed vibratory sensor, in which the mechanoreceptor was covered either in hard rubber (such as silicon oil) or soft rubber (such as urethane), for both low- and high-frequency ranges. The fabricated sensor is based on piezoelectricity with a built-in voltage. It senses applied vibration by means of hairs in the sensor and the hardness of the outer cover. We also investigated two proposed parameters: the sensor response time to stimuli to the vibration aiding the equivalent firing rate (e.f.r.) and the gauge factor (GF_,pe) proposed as treated in piezo-resistivity. The evaluation with the parameters was effective in designing a sensor based on piezoelectricity. These parameters were enhanced by the hairs in the sensor and the hardness of the outer cover. Our results were helpful for designing the present novel vibratory sensor. Full article

When a fault occurs in a power transmission system, voltages that are dangerous to people may occur. The aim of this work is to present the following method of protection: the use of protective foil installed at the appropriate depth around the transmission pole. Moreover, a procedure is presented for determining the optimal size of the protective film using a minimum number of finite element method calculations. In addition to the finite element method, evolutionary methods are used to determine the appropriate coefficients. Real earthing system data, earth data, and the fault current are obtained from the Slovenian system operator (ELES, d.o.o.) and used exclusively in the presented analyses. The results of determining the appropriate size of the protective foil for two transmission poles are presented, and the determination of the required breakthrough strength of the materials used is shown. The suitability of the proposed method is confirmed. This method is practical and useful when protection with protective foil is required, ensuring only as much as necessary is applied. Full article

In heavily loaded regional power grids, some AC transmission lines are confronting escalating pressures due to excessive short-circuit currents. To optimize AC channels, most research advocates for retrofitting existing AC lines into multi-line-commutated converter-based high-voltage direct current (LCC-HVDC) lines. However, there is a contradiction between limited land area for AC stations and the relatively large footprint of passive filters in LCC-HVDC; this paper introduces self-adapted LCC (SLCC) by replacing passive filter groups with a static var generator (SVG). Secondly, the reactive power compensation, harmonic filtering control methods of SVGs, and operation characteristics of the SLCC system are explored, and the harmonics of the grid-side current are reduced by nearly 14.6%. Then, to fill the gap of previous studies on solely AC or AC-DC line touching, inspired by emerging DC line-touching risks in double-circuit (LCC and SLCC) lines on the same tower, the equivalent models are formulated to elucidate the evolution mechanisms of voltage/current and extract fault features in various line-touching faults; it finds that the longitudinal differential current during line-touching faults can be capitalized. Based on the current feature, an effective protection algorithm tailored for the identification of DC line-touching faults is proposed. Finally, simulations are conducted to validate the efficacy of proposed control and protect methods, demonstrating the potential to enhance the reliability of AC to DC conversion projects. Full article

This article covers the analysis of voltages induced on the conductors of a de-energized circuit of a multi-circuit, multi-voltage HVAC transmission line. As a result of the multiplied interactions between the circuits in such lines, the expected electrical shock currents (touch currents) to which a lineman performing live work on such a line may be exposed are determined. A number of supporting structures of three- and four-circuit lines with various degrees of geometric asymmetry are analyzed. Analyses have shown that in multi-circuit lines in which circuits of different voltages are carried on a common structure, despite the outage of one of the circuits, touch voltages and electrical shock currents (touch currents) exceeding the permissible values can be expected on its conductors, endangering the safety of the lineman. The arrangements of s in such lines that provide the smallest values of touch currents are indicated. Full article

Plasma electrolytic polishing (PeP) is mainly used to improve the surface quality and thus the performance of electrically conductive parts. It is usually used as an anodic process, i.e., the workpiece is positively charged. However, the process is susceptible to high current peaks during the formation of the vapour–gaseous envelope, especially when polishing workpieces with a large surface area. In this study, the influence of the anode immersion speed on the current peaks and the average power during the initialisation of the PeP process is investigated for an anode the size of a microreactor mould insert. Through systematic experimentation and analysis, this work provides insights into the control of the initialisation process by modulating the anode immersion speed. The results clarify the relationship between immersion speed, peak current, and average power and provide a novel approach to improve process efficiency in PeP. The highest peak current and average power occur when the electrolyte splashes over the top of the anode and not, as expected, when the anode touches the electrolyte. By immersion of the anode while the voltage is applied to the anode and counterelectrode, the reduction of both parameters is over 80%. Full article

There is growing concern regarding air pollutants (NOx, SOx, and PM) and carbon emissions from ocean-going vessels in harbor areas and the role of high-voltage shore connection (HVSC) systems in mitigating these emissions during vessel berthing. The HVSC operates as a TN grounding system in humid environments, and it needs a proper grounding design to ensure safety when faults occur. This article intends to examine the overvoltage resulting from fault currents and its implications for the safety of operators when a single line-to-ground fault takes place within the design of HVSC grounding systems. The assessment is carried out by employing actual scenarios and parameters from a container berth at Kaohsiung Harbor in Taiwan. Considering site conditions, such as the wet ground surface, human body resistance, and electric shock duration, the tolerable safe voltage level is derived using IEEE Std. 80 and IEC 60479-1. Based on the shore power system grounding architecture specified in IEEE/IEC 80005-1, an equivalent circuit model is constructed to calculate the fault currents using symmetrical component analysis. The actual touch voltages generated in various locations are analyzed under scenarios of connecting or disconnecting the equipotential bonding between the ship and the shore using neutral grounding resistor (NGR) designs. This article delves into the scenarios of electric shock that may occur during the operation of an actual container ship’s shore power system. It evaluates whether various contact voltage values exceed current international standards and verifies the grounding design and safety voltage specifications of IEEE/IEC 80005-1. According to the results of this study, the use of NGR and protective earthed neutral (PEN) conductors in HVSC is crucial. This can limit fault currents, reduce touch voltage, and ensure the safety of personnel and equipment. Therefore, ensuring and monitoring equipment conductors and adopting NGRs of appropriate sizes are crucial elements in maintaining electrical safety in HVSC systems. Full article

Recently, natural material-based triboelectric nanogenerators (TENGs) have increasingly attracted attention in academic circles. In this work, we have developed an innovative triboelectric nanogenerator (BL-TENG) utilizing bamboo leaves to capture biomechanical energy. Bamboo leaf, as a natural plant material, possesses a diverse array of applications due to its remarkable durability, which surpasses that of many other types of trees. Furthermore, bamboo leaf has the advantages of low cost, widely distributed, non-toxic and environmentally protected. The output power of the BL-TENG (size: 5 cm × 5 cm) is able to generate approximately 409.6 µW and the internal resistance of the BL-TENG is 40 MΩ. Furthermore, the BL-TENG can realize an open-circuit voltage (Voc) of 191 V and a short-circuit current (Isc) of 5 µA, respectively. The biomechanical energy harvesting effect of the BL-TENG device means that it can drive 18 commercial light-emitting diodes (LEDs) through the full-wave bridge rectifier. Furthermore, the BL-TENG can also serve as a self-powered touch sensor to reflect hand touch states. This study proposed a novel plant-based TENG device that can enhance the development of green TENG devices and self-powered sensing systems. Full article

Vibration-based energy harvesting has garnered considerable attention from researchers over the past two decades, using different transduction mechanisms. In this context, the utilization of piezoelectric materials has proven to be highly successful, due to their power density, across a broad range of voltages. A primary challenge in environmental vibration harvesting lies in the frequency mismatch between the devices, which typically exhibit optimal performance at hundreds or thousands of hertz due to their small size (centimeter or millimeter) and the environmental vibration. The latter has considerable energy density around tens of hertz. For this reason, over the last 15 years, the scientific community has concentrated on exploring techniques for band broadening or frequency up-conversion by intentionally introduced (or designed) nonlinearities. This review, following an introduction to the topic of vibration energy harvesting, provides a description of the primarily developed mechanisms, presenting a chronological development for each, from the initial works to the most recent advancements. Additionally, the review touches upon implementation efforts at the micro-electromechanical systems (MEMS) scale for each described technique. Finally, the incorporation of nonlinearities through electronic circuits to enhance performance is briefly discussed. Full article

There is a growing demand for flexible pressure sensors in environmental monitoring and human–robot interaction robotics. A flexible and susceptible sensor can discriminate multidirectional pressure, thus effectively detecting signals of small environmental changes and providing solutions for personalized medicine. This paper proposes a multidimensional force detection sensor inspired by a wind chime structure with a three-dimensional force structure to detect and analyze normal and shear forces in real time. The force-sensing structure of the sensor consists of an upper and lower membrane on a polydimethylsiloxane substrate and four surrounding cylinders. A piezoelectric hemisphere is made of BTO/PVDF/PDMS composite material. The sensor columns in the wind chime structure surround the piezoelectric layer in the middle. When pressure is applied externally, the sensor columns are connected to the piezoelectric layer with a light touch. The piezoelectric hemisphere generates a voltage signal. Due to the particular structure of the sensor, it can accurately capture multidimensional forces and identify the direction of the external force by analyzing the position of the sensor and the output voltage amplitude. The development of such sensors shows excellent potential for self-powered wearable sensors, human–computer interaction, electronic skin, and soft robotics applications. Full article

Chemoresistive nanostructured gas sensors are employed in many diverse applications in the medical, industrial, environmental, etc. fields; therefore, it is crucial to have a device that is able to quickly calibrate and characterize them. To this aim, a portable, user-friendly device designed to easily calibrate a sensor in laboratory and/or on field is introduced here. The device comprises a small hermetically sealed chamber (containing the sensor socket and a temperature/humidity sensor), a pneumatic system, and a custom electronics controlled by a Raspberry Pi 4 developing board, running a custom software (Version 1.0) whose user interface is accessed via a multitouch-screen. This device automatically characterizes the sensor heater in order to precisely set the desired working temperature, it acquires and plots the sensor current-to-voltage and Arrhenius relationships on the touch screen, and it can record the sensor responses to different gases and environments. These tests were performed in dry air on two representative sensors based on widely used SnO₂ material. The device demonstrated the independence of the Arrhenius plot from the film applied voltage and the linearity of the I–Vs, which resulted from the voltage step length (1–30 min) and temperature (200–550 °C). Full article

Generating localized haptic feedback on touch displays has been a challenge in recent years. In this study, we introduce a haptic interface using transparent thin-film PVDF actuators to address this issue. The transparency feature can be used to mount the actuators at any location beneath the display, enabling localized haptic feedback as the generated vibration is primarily evident on the mounting area. Two different configurations are designed, simulated and prepared to explore the effectiveness of the proposed approach. The first configuration is used to characterize the haptic interface. Modal and forced-vibration analyses are performed to identify important design characteristics based on human factors. Subsequent 2AFC psychophysics experiments validate the characteristics. In the second configuration, eight actuators are attached to the touch surface in a 2 × 4 matrix formation and excited at different voltage amplitudes. Human experiments are conducted based on the results from corresponding forced-vibration analysis. The results show that subjects demonstrate an accuracy of 96% in identifying locations with haptic feedback when the actuators are excited with 232 V_pp. Overall, our study demonstrates the effectiveness of the proposed transparent haptic interface equipped with PVDF actuators in achieving localized haptic feedback on touch displays. Full article

The design of a compliant, safe, and reliable substation earth grid is not a straightforward process; in most cases, it requires some additional measures to be taken due to various constraints that differ from environment to environment, such as soil resistivity, a high fault level, a limited surface area, construction budget, etc. The IEEE Std 80-2013 proposes various refinement methods that can be applied to address different situations. For this study, the current limiting method, current diversion method, and touch and step voltage increment method were applied using the Electrical Transient Analysis Program (ETAP). A power system was designed, where a fault current generated by the supply transformers and back-fed by the power system’s motors was exported to the earth grid. Using this fault current, various simulations were conducted to assess the performance of the earth grid. The analysis results show that the application of the current limiting method using neutral earthing resistors has a great impact on the design of the earth grid as this method significantly reduces the fault current injected into the earth grid. Furthermore, by applying the current diversion method, the amount of fault current injected into the earth grid is reduced by a fair amount, which improves the performance of the earth grid. Lastly, increasing the tolerable limits of touch and step voltages by reducing the fault clearance times significantly improves the compliance of the earth grid as the clearance time is reduced. From this study, it is therefore concluded that, by implementing the refinement methods depending on the design requirements and feasibility of the application, one can improve the compliance state of an earth grid. Full article

This paper presents a numerical investigation regarding the possibility of using electrically conductive concrete (ECON) combined with concrete-encased electrode (CEE) technology to develop new substation grounding systems (SGSs) called ECON-EE as a replacement for conventional copper or galvanized steel grounding grids. In the first step, the validation of the commercial FEM software used to perform grounding system analysis was performed in terms of the grid resistance (R_G), ground potential rise (GPR), and step and touch voltages, using a symmetrical 70 m × 70 m conventional copper SGS. Next, several numerical simulations of an ECON-EE grounding system with the same dimensions as the conventional copper grid used for FEM software validation were performed. Thus, several parameters of the ECON-EE grounding system were studied, such as the geometry, dimensions, and resistivity of ECON and the diameter of the rebar. The numerical results obtained permit us to demonstrate that ECON-EE grounding systems can perform better than conventional SGSs equipped with vertical rods, particularly in the case of high ground resistivity. Moreover, it was demonstrated that the two main ECON-EE parameters affecting the grounding resistance and the touch and step voltages are the section area and the resistivity of the ECON. As discussed in detail in this paper, the proposed ECON-EE grounding system can offer several advantages compared to conventional SGSs in terms of efficiency and durability, as well as in terms of simplicity of conception and implementation. Full article

In this study, polyethylene oxide (PEO) and curdlan solutions were used to prepare PEO/curdlan nanofiber films by electrospinning using deionized water as the solvent. In the electrospinning process, PEO was used as the base material, and its concentration was fixed at 6.0 wt.%. Moreover, the concentration of curdlan gum varied from 1.0 to 5.0 wt.%. For the electrospinning conditions, various operating voltages (12–24 kV), working distances (12–20 cm) and feeding rates of polymer solution (5–50 μL/min) were also modified. Based on the experimental results, the optimum concentration for the curdlan gum was 2.0 wt.%. Additionally, the most suitable operating voltage, working distance and feeding rate for the electrospinning process were 19 kV, 20 cm and 9 μL/min, respectively, which can help to prepare relatively thinner PEO/curdlan nanofibers with higher mesh porosity and without the formation of beaded nanofibers. Finally, the PEO/curdlan nanofiber instant films containing 5.0 wt.% quercetin inclusion complex were used to perform wetting and disintegration processes. It was found that the instant film can be dissolved significantly on the low-moisture wet wipe. On the other hand, when the instant film touched water, it can be disintegrated very quickly within 5 s, and the quercetin inclusion complex was dissolved in water efficiently. Furthermore, when the instant film encountered the water vapor at 50 °C, it almost completely disintegrated after immersion for 30 min. The results indicate that the electrospun PEO/curdlan nanofiber film is highly feasible for biomedical applications consisting of instant masks and quick-release wound dressings, even in the water vapor environment. Full article