Electrical Joints Research Articles

Effect of the contact load and rotation speed on the formation of rolling current-carrying arc and the corresponding material damage

The current-carrying arc is a critical factor that affects the electrical contact performance and material damage of contact pairs. In this study, a copper disk–copper disk pair was used to simulate the rolling electrical joint in a conductive rotating joint. Under operating conditions with a current of 2 A, rotation speeds from 4 to 600 r/min, and loads from 40 to 180 N, the dynamic behavior of the current-carrying arc and the surface damage mechanism were investigated. The movement characteristics of the arc at the friction interface were observed, and the arc generation difficulty and intensity were statistically analyzed based on the arc burning rate and arc energy. With increasing load and rotation speed, the generation of current-carrying tribological arcs became easier, and both the arc burning rate and arc energy increased. After the arc was generated, the arc root position was randomly distributed at the contact interface, exhibiting dynamic phenomena such as splitting and merging. Following the generation of the arc, the dominant damage mechanism at the current-carrying friction interface transitioned from mechanical damage to electrical damage. The manifestations of electrical damage included burning, oxidation, and roughening, with the degree of electrical damage positively correlated with the arc burning rate and arc energy. Surface oxidation could reduce the adhesion between metal contact pairs, contributing to a decrease in the current-carrying friction coefficient. Simultaneously, the film resistance caused by oxidation and the contraction resistance caused by roughening could lead to an increase in the average contact resistance.

Biomimetic Peripheral Nerve Stimulation Promotes the Rat Hindlimb Motion Modulation in Stepping: An Experimental Analysis.

Peripheral nerve stimulation is an effective neuromodulation method in patients with lower extremity movement disorders caused by stroke, spinal cord injury, or other diseases. However, most current studies on rehabilitation using sciatic nerve stimulation focus solely on ankle motor regulation through stimulation of common peroneal and tibial nerves. Using the electrical nerve stimulation method, we here achieved muscle control via different sciatic nerve branches to facilitate the regulation of lower limb movements during stepping and standing. A map of relationships between muscles and nerve segments was established to artificially activate specific nerve fibers with the biomimetic stimulation waveform. Then, characteristic curves depicting the relationship between neural electrical stimulation intensity and joint control were established. Finally, by testing the selected stimulation parameters in anesthetized rats, we confirmed that single-cathode extraneural electrical stimulation could activate combined movements to promote lower limb movements. Thus, this method is effective and reliable for use in treatment for improving and rehabilitating lower limb motor dysfunction.

Enabling magnetic pulse welding for dissimilar tubular arrester cable joints

Climate change exacerbates the need for resource-efficient and cost-effective production processes across manifold industries, including the field of electrical connections. This specific field is characterized by a conflict of objectives, i.e., weight reductions while maintaining joint strength and electrical conductivity. From a material point of view, the use of aluminum as a conductor material is suitable for this application, as it is lighter than copper, a classical conductor material. Electrical conductors are often used in the form of flexible cables, so-called stranded wires. This type of conductor as well as the fact that the sole use of aluminum in electrical systems is not feasible, e.g., because the predetermined connection terminals of power electronic components are made of copper, creates a substantial demand for dissimilar aluminum-copper cable arrester joints. However, traditional fusion-based welding processes have proved incapable of reliably producing these dissimilar aluminum-copper joints because of thermophysical effects and chemical incompatibilities, the latter eventually leading to the formation of intermetallic phases. These phases adversely affect the quality of the joint in terms of both mechanical and electrical performance. Yet, magnetic pulse welding, a pressure welding process, is ideally suited for producing dissimilar metal joints on the basis of a low energy input during the welding process. Consequently, the formation of intermetallic phases is restrained. However, magnetic pulse welding has not been sufficiently investigated for the reliable contacting of stranded cables to tubular arresters. As a result, this paper focuses on the fabrication of tubular stranded cable arrester joints using magnetic pulse welding. To shed light on possible material combinations, aluminum-to-aluminum and copper-to-copper joints as well as their dissimilar counterparts are welded. Subsequently, the joints are characterized with regard to their microstructure and quasi-static material strength. Electrical characterization comprises the four-wire Kelvin measurement method to evaluate the resistance of the electrical joints. The results demonstrate that magnetic pulse welding is ideally suited to join the aforementioned material combination and joint configuration due to its process characteristics eventually leading to material continuity. As a result, the stranded wires are welded to the tubular arresters rather than crimped. Consequently, a comparative analysis of the joint properties with those of the joining partners shows that the measured electrical resistances and mechanical tensile forces may be considered very good.

Image stabilization technology based on inertial sensors and piezoelectric fast pendulum mirrors

Aiming at the interferences caused by vibrations on the target monitoring system of satellite platforms, an experimental system of optical–mechanical–electrical joint image stabilization based on inertial sensors and piezoelectric fast mirrors was studied. First of all, the data from the fiber optic gyroscope and the detector are combined and processed. After that, the predicted intentional velocity is subtracted from the real-time gyroscope data, and the vibration displacement is obtained using an integral. The feedback amount is calculated using the processor according to the vibration displacement, the piezoelectric fast mirror is controlled to compensate the vibration interferences, and the purpose of stabilizing the images is achieved. The experimental results show that under a vibration interference of 300μrad/s, the image stabilization control frequency of the system reaches 500 Hz, the relative error between image frames is better than 3μrad, and the intra-frame stabilization performance of the detector meets the requirements on stabilized image and target detection for space targets on the star-carrying platform.

Design and experimental verification of an electro-hydraulic dual system with reliable resistance to γ-irradiation

Remote handling constitutes a critical technological facet in the domain of fusion reactors. However, exposure to γ rays inflicts irreversible deleterious effects on both electronic assemblies and structural materials. In the present investigation, we meticulously engineered an electro-hydraulic dual system tailored for remote handling applications within fusion reactors. Subsequently, the system was subjected to γ irradiation employing 60Co as the radioactive source. After exposure to a dose of 4 MGy, the electro-hydraulic dual joint system demonstrates sustained functional integrity. In contrast, isolated electric and hydraulic joints manifests minor oil seepage after exposure to a radiation dose of 5 MGy. Additionally, the effectiveness of the selected O-ring sealing material, ethylene propylene diene monomer (EPDM), exhibits a significant decrement upon irradiation to a dose of 1–3 MGy. The observed γ-radiation resilience is attributed to strategic material selection, specifically in the choice of O-ring, as well as metal reinforcement. The findings furnish valuable insights for the development of remote handling systems capable of operating under γ irradiation and strenuous mechanical conditions.

Wire-type flexible micro-supercapacitor based on MOF-assisted sulfide nano-arrays on dendritic CuCoP and V2O5-polypyrrole/nanocellulose hydrogel

Wire/fiber-type micro-supercapacitors (micro-SCs) have great potentials in next-generation wearable and portable energy supply devices, due to their low weight, high flexibility, small size and excellent reliability. Herein, we designed 2D-3D S-doped CoZnNi-OH/CuCoP positive microelectrode with hierarchical structure on 1D metal fiber substrate for high-capacitance fibrous micro-SCs. Such unique architecture, which 2D S-doped CoZnNi-OH nanosheet arrays vertically aligned on 1D Cu wire garnished with 3D dendritic CuCoP through CoZn-MOF template, exposed ample electroactive sites, created robust electrical and mechanical joint between nanostructured material and metal fiber, and promote the transport/diffusion rate of ions. The achieved 2D-3D S-doped CoZnNi-OH/CuCoP/CW microelectrode exhibited the areal/volumetric/length capacitances of 2.9 F cm−2, 290.07 F cm−3, and 348 mF cm−1 at 4 mA cm−2, respectively, which is 18 times of the sulfide directly co-electrodeposited on 3D CuCoP foam without MOF template. Besides, negative microelectrode was prepared through electrochemical deposition of V2O5-PPy on 1D carbon fiber substrate decorated with rGO-nanocellulose (NC) hydrogel. The electrical double layer capacitance behavior combined with pseudocapacitive properties enhances charge storage performance of fibrous microelectrode in terms of specific capacitance, cycle stability and rate capability. The fabricated solid-state 2D-3D S-doped CoZnNi-OH/CuCoP/CW//V2O5-PPy/rGO-NC/CF micro-SC presents high areal energy density of 127.62 µWh cm−2 at a power density of 1.83 mW cm−2 and durability (93.7 % retention after 5000 cycles) with excellent mechanical flexibility. Giving the versatility of 1D carbon/metal fiber substrates, template-assisted 3D architecture, MOF-derived sulfide nanoarrays, and NC chemical reactivity, the proposed strategy can be used for construction of other next-generation miniaturized portable electronics.

A method for the reproducible and accurate determination of electrical resistances based on multi-layer joints in lithium-ion batteries

The transition from fossil fuels to renewable energy sources is significantly influenced by the development of energy storage systems such as batteries. One of the crucial steps in the production of lithium-ion batteries is the electrical connection of the individual electrodes by weld seams. Various joining processes, such as laser beam welding or ultrasonic metal welding, are used for this purpose. An important quality feature of the connections is a low electrical joint resistance, which is essential for reducing cell-internal energy losses and avoiding thermal inhomogeneities in the cells.The aim of this work was to determine the electrical resistance of the joint between a stack of foils and an arrester tab. For this purpose, a measuring method was developed and applied to different sample configurations. The influence of different probe tips on the measurement results was compared using single current collector foils and arrester tabs. The measurement of the electrical resistance was possible in the considered range with a maximum relative uncertainty of 2.38%. Using the presented approach made it possible to evaluate the influence of the seam trajectory on the electrical resistance for cell-internal contacting. In addition, the measuring method is suitable for comparing different welding strategies and, thus, for designing the cell-internal joining processes regarding the resulting electrical joint resistances.

Applicability of the acoustic–electrical joint detection method to identify defects in gas insulated system

AbstractThere are many defects in gas‐insulated metal‐enclosed switchgear (GIS) and gas‐insulated transmission lines (GIL) that may cause accidents, such as floating potentials, metal particles, air gaps, and cracks in support insulators. Nevertheless, to‐this‐date, there is no effective method to recognize them to adjust their operation status. Accordingly, this study compared three typical defect models to explore the partial discharge process, and three typical experimental models were established to identify the characteristic parameters of acoustic and electrical information in the development of defects. The research study shows that that as the voltage increases, the partial discharge of free‐metal‐particle defects and air‐gap defects obtained by the pulse‐current method increase gradually. A sudden increase also occurred in the partial discharge of the floating potential defect. The discharge amount of free conductive particles obtained by an ultrahigh‐frequency detection method was distributed symmetrically on both sides of the applied voltage peak, and the other two defects were on one side of the peak and yielded an obvious phase difference. The particle collision signal obtained by the ultrasonic method was obvious, but had no obvious phase relationship with the applied voltage. However, the obtained floating potential defect information had obvious phase differences, and the ultrasonic method was not sensitive to air‐gap defects. The three typical defects can be identified by the combined method more accurately; this provides a theoretical basis and data support for GIS and GIS voltage tests, detection technologies, and online monitoring methods.

Local resolution of currents through electrical joints consisting of materials with different conductivity

Within this work the impact of contact materials with higher volume resistivity as leaded solder are investigated in terms of comparability of the current conduction through the joint. An approach was developed to experimentally determine the qualitative local current density by magnetic field imaging (MFI) at ribbon-to-ribbon contact samples. The result reveals that the MFI technique on a symmetric sample design allows the evaluation of the current paths in two-dimensional contact areas. Different resistivities of the contact material result in characteristic differences in current distribution through the joint. Low resistive Sn60Pb40-soldererd contacts exhibit localized current injection whereas the tested contact based on electrically conductive adhesives (ECAs) show an extended current flow through the ECA-based contact. A FEM-based simulation model to mimic the used setup was developed and confirmed the results by taking different contact material resistivities into account. For materials with resistivities larger than 1 · 10−3 Ω · cm current injection was found to spread-spatially within the tested contact geometry. Contact material development as well as contact design can benefit from that approach, allowing consumption and material composition optimization. A further advantage is the feasibility of the method to study production failures like inhomogeneous ECA distribution enabling a non-destructive monitoring of process stability and root cause analysis.

Long-Term Behavior of Clinched Electrical Contacts

Joining by forming operations presents powerful and complex joining techniques. Clinching is a well-known joining process for use in sheet metalworking. Currently, clinched joints are focusing on mechanically enhanced connections. Additionally, the demand for integrating electrical requirements to transmit electrical currents will be increased in the future. This integration is particularly important, for instance, in the e-mobility sector. It enables connecting battery cells with electrical joints of aluminum and copper. Systematic use of the process-specific advantages of this joining method opens up the possibility to find and create electrically optimized connections. The optimization for the transmission of electrical currents will be demonstrated for clinched joints by adapting the tool geometry and the clinched joint design. Based on a comparison of the electrical joint resistance, the limit use temperature is defined for the joining materials used based on the microstructural condition and the aging condition due to artificial aging. As a result of the investigations carried out, reliable current transmission at a constant conductor temperature of up to 120 °C can be achieved for clinched copper–copper joints. In the case of pure aluminum joints and mixed joints of aluminum and copper, long-term stable current transmission can be ensured up to a conductor temperature of 100 °C.

TiB2-modified PDC electrical solder joints for electrical interconnection in extreme environments

The use of electrical solder joints for die attachment and interconnection in harsh environments remains a significant challenge. The interconnections between traditional metal solder joints and ceramic/semiconductor devices often fail during thermal cycling owing to mismatched coefficients of thermal expansion. In this study, TiB 2 -modified polymer-derived ceramic (PDC) electrical solder joints were developed for electrical interconnections. Owing to the close contact between the PDC paste and the metal/ceramic/semiconductor, as well as the TiB 2 percolation path formed inside the solder joint, the solder joint exhibited extremely low resistance and reliable electrical connection. Thermal cycling tests showed that the PDC solder joints had negative resistance temperature coefficients, excellent repeatability, and oxidation resistance up to 800 °C. After being oxidized at 800 °C for 24 h, the resistance at the solder joint only changed by 1.4 Ω. This solder joint can not only be used for metal devices but also for ceramic/semiconductor device electrical interconnections in harsh environments. • A TiB 2 -modified PDC solder joint was developed for metal/ceramic/semiconductor device interconnections in harsh environments. • The solder joint exhibited excellent thermal stability and high-temperature oxidation resistance. • The feasibility of solder joints for thin-film sensor interconnections was verified.

Determining the management of pain in people with spinal cord injury by physiotherapists in South Africa

BackgroundPain after spinal cord injury (SCI) is common, and physiotherapy plays a pivotal role in alleviating pain for people with SCI.ObjectiveTo determine the modalities that physiotherapists in South Africa use to treat SCI-related pain and the factors that guide the selection of treatment modalities.MethodA quantitative, cross-sectional design using a self-developed online survey was distributed to physiotherapists belonging to the South African Society of Physiotherapy and the Physiotherapy Association of South Africa. Data were analysed using SPSS v26, where descriptive data were analysed using frequency, percentages, means and standard deviations, and Fisher’s exact tests for inferential analyses. Open-ended questions underwent thematic analysis.ResultsForty-six responses were received. The most-used modalities were transcutaneous electrical nerve stimulation (29.8%), exercises (27.7%) and joint mobilisations (29.8%). Most physiotherapists used standardised measurements to objectively assess pain characteristics, with the visual analog scale being the most used (70.2%). Except for the cost of treatment, the factors that guided the selection of the modalities included the pain type, onset, duration, location and intensity, pain interference, duration of treatment, patient’s preferences, other treatments that the patient was receiving for pain and psychosocial factors (87.2%).ConclusionsLocal physiotherapists use pain management modalities that are supported by the evidence to treat SCI-related pain.Clinical implicationsThis study highlights the common modalities used by physiotherapists to treat SCI-related pain, as well as the selection criteria for the modalities. Owing to the low response rate, we caution against generalising these findings across the SCI pain management field.

Underwater Wireless Sensor Networks with Energy Efficient Routing Protocol Using Load Balancing Technique

Underwater Wireless Sensor Networks is effective and intelligent utilization of energy for routing protocol in longer network lifetime. Energy Consumption and load balancing are the vital roles for a network lifetime. The use of load balancing in WSN is granted as the best resource of sink mobility which protects energy sources to organize. The aim of this paper is to evaluate various deployed strategies involving sink mobility. Multiple mobile sinks are capable of performing computational operations like collecting information from electric joints instantly, storage and also communication capability. It evaluates the results and the effect of sink mobility by comparing with another routing protocol GEDAR.

Acoustic-Electrical Joint Localization Method of Partial Discharge in Power Transformer Considering Multi-Path Propagation Impact

Efficient and accurate localization of partial discharge (PD) is of paramount importance to ensure the safe operation of power transformers. However, the multi-path propagation effect introduced by the reflection, refraction and diffraction of the ultrasonic signal may add significant computational complexity to the localization process and degrade the localization accuracy. This paper proposes an acoustic- electrical joint method for partial discharge location in the power transformer with the full consideration of the multi-path propagation impact. Unlike the conventional error analysis methods, a partial discharge localization model is proposed for characterizing the multipath propagation impact without the prior knowledge of the transcendental error probability. Based on the matrix inequality transformation and relaxation, the high-dimensional nonlinear localization equations are transformed into a set of second-order convex optimization equations that can be solved using the convex second-order cone program (SOCP). The proposed solution can significantly reduce the computational complexity and improve the localization accuracy as well as avoid the local optimum and slow convergence. The solution is assessed through extensive experiments based on simulations, testbed and trial deployment in comparison with the existing solutions with the localization error of about 0.1 m.

Effective Tuning of the Performance of Conductive Silicon Compound by Few-Layered Graphene Additives.

Electric conductive silicon compounds are widely used and essential in electric power, energy and information industries. However, there are still problems such as insufficient stability of physical and chemical properties and weak electrical conductivity. To address the problem of low contact reliability of electrical joints in high-power transmission and distribution equipment, we assessed the influence of mechanically exfoliated graphene (MEG) content on the physicochemical properties of electrical joint compound (EJC). Varying amounts of few-layer MEG prepared with the conventional mechanically exfoliated method was added to the conductive silicon compounds, of which various physicochemical properties, such as penetration, drip point, volume resistivity and frictional properties were systematically assessed and compared with those with copper additive. We found that the addition of MEG effectively enhanced the temperature and mechanical stability of EJC and significantly reduced the material volume resistivity. This work paves the way to improve the key performance of electric conductive silicon compounds with advanced nanomaterials.

Application of Copper Thermal Spraying for Electrical Joints between Superconducting Nb3Sn Cables.

This manuscript reports on the application of copper thermal spraying in the manufacturing process of an electrical connection between Nb3Sn cables for superconducting magnets of fusion reactors. The joint is realized through diffusion bonding of the sprayed coating of the two cables. The main requirement for such a connection is its electrical resistance, which must be below 1 nΩ at B = 8 T, I = 63.3 kA and T = 4.5 K. Micrographs of the joint prototype were taken to relate the joint resistance with its microstructure and to provide feedback on the manufacturing process. Optical microscopy (OM) was used to evaluate the grain size of the coating, presence of oxide phases and to analyze the jointed surfaces. Scanning electron microscopy (SEM) and, in particular, energy-dispersive X-ray spectroscopy (EDX) were used to confirm the elemental composition of specimens extracted from the prototype. It is shown that the copper coating has an oxide concentration of 40%. Despite this, the resistance of the prototype is 0.48 nΩ in operating conditions, as the oxides are in globular form. The contact ratio between the jointed surfaces is about 95%. In addition, residual resistivity ratio (RRR) measurements were carried out to quantify the electrical quality of the Cu coating.

Causes and Countermeasures of Heating of Electrical Joints in Substation Operation

Causes and Countermeasures of Heating of Electrical Joints in Substation Operation

Joint geophysical prospecting for groundwater exploration in weathered terrains of South Guangdong, China.

Groundwater occurrence in a hard rock terrain is strongly controlled by the weathered/fractured zones. However, delineation of such zones is a challenging task given their structural heterogeneity. Traditionally, large numbers of well tests are conducted to assess the subsurface formation. But, such tests suffer from efficiency in terms of cost, time, and data coverage. Non-invasive geophysical methods can be the best alternative of expensive drilling methods. However, a geophysical method alone is ambiguous to interpret the highly heterogeneous subsurface formation. In this study, joint application of electrical resistivity tomography (ERT), magnetic method, and joint profile method (JPM) was conducted for groundwater exploitation in a weathered terrain of South Guangdong, China. ERT, magnetic, and JPM data were acquired along different geophysical profiles via a variety of survey parameters. The interpreted 2D models of electrical resistivity and magnetic data coupled with the local accessible boreholes and hydrogeological information constrain the subsurface geologic formation into four discrete layers with specific electrical resistivity range, i.e., topsoil cover, highly weathered saturated layer, semi-weathered saturated layer, and un-weathered substratum. Incorporation of JPM (ER, SP, and IP methods) with ERT and magnetic models reveal three faults (F1, F2, and F3) and several saturated intense fractures/discontinuities. The groundwater reserves associated with the weathered/fractured rock were estimated via hydraulic parameters, namely hydraulic conductivity and transmissivity. The results suggest that high-yield groundwater resources are found within the weathered/fractured zones. Geophysical results of this joint application fit pretty well to the local hydrogeological data of the study area. Our novel approach reduces any ambiguity caused in the geophysical interpretation and provides clearer insight of the subsurface formation with more confident solutions to the most challenging problems of the hard rock sites. This hydrogeophysical study provides important contributions to groundwater exploration in areas where weathering has significant effects on the hard rock aquifer system. Compared with traditional methods, this approach is more advantageous for assessment of groundwater resources in hard rock terrains.

Research Progress of the Temperature Monitoring Technology of the Electric Joints in the Ring Main Unit

This article summarizes several existing temperature monitoring methods for cable joints inside the ring main unit, mainly introducing infrared temperature measurement, fluorescent optical fiber detection, passive wireless surface acoustic wave temperature measurement, and wireless temperature sensor measurement. Then, the above methods were compared, and the advantages and disadvantages of each method were clarified. Finally, the research on the temperature monitoring method of the cable joints in the ring main unit is summarized. And the follow-up development direction of the passive wireless surface acoustic wave temperature measurement method in the temperature measurement of the cable joints of the ring main unit is prospected. It provides some reference for the research on the temperature monitoring method of the cable joints inside the ring main unit in the future.

Routing Protocol Based On Energy Efficient For Under Water Wireless Network

Underwater Wireless Sensor Networks is effective and intelligent utilization of energy for routing protocol in longer network lifetime. Energy Consumption and load balancing are the vital roles for a network lifetime. The use of load balancing in WSN is granted as the best resource of sink mobility which protects energy sources to organize. The aim of this paper is to evaluate various deployed strategies involving sink mobility. Multiple mobile sinks are capable of performing computational operations like collecting information from electric joints instantly, storage, and also communication capability. It evaluates the results and the effect of sink mobility by comparing with another routing protocol GEDAR.