Electrical Break Research Articles

Enhancing the reliability of power grids: A YOLO based approach for insulator defect detection

Insulators are crucial components of power grid systems, safeguarding against electrical conductor breaks. However, their prolonged exposure to complex outdoor environments renders them susceptible to defects. In this study, we address the importance of accurate insulator defect detection and propose an approach using the You Only Look Once (YOLO) object detection framework. In particular, we compare the performance of YOLO v8 against YOLO v7 in detecting two specific types of insulator defects—broken insulators and flashover damaged insulators. Leveraging the Insulator Defect Image Dataset, our results demonstrate that YOLO v8 achieves superior accuracy with a rate of 98.99 percent along with a mean average precision (mAP) of 99.10 percent. The findings underscore the efficacy of YOLO v8 in improving the reliability and resilience of power grid systems by allowing timely and accurate detection of insulator defects in complex outdoor environments. This research contributes to advancing the field of power grid infrastructure monitoring and maintenance, ultimately facilitating more effective strategies for mitigating the consequence of insulator defects on power grid system performance and reliability.

The effect of electrical current on lubricant film thickness in boundary and mixed lubrication contacts measured with ultrasound

This work explores experimentally the effects of DC electrical currents on lubricant film thickness alteration in lubricated sliding steel contacts in the boundary and mixed regime as measured by ultrasound. The experiments were performed in a two-electrode cell-based pin-on-disk tester instrumented with ultrasonic transducers. Unelectrified and electrified tribological tests were conducted on steel flat-on-flat contacts under various speeds and loads using both a mineral base oil and a gear oil. Film thickness, coefficient of friction (CoF), and electrical contact resistance (ECR) were measured during short experiments (30 s) in unelectrified and electrified (1.5 and 3 A) conditions. The results suggest that film thickness, CoF, and all ECR are altered by passing DC currents through the contact. In particular, film thickness increased and decreased, respectively, by applying electricity at the different speeds and loads tested. These alterations were majorly ascribed to oil viscosity decrease by local heat and surface oxidation caused by electrical discharge and break down at the interface.

Effect of thermal poling in sodium tantalum phosphate glass-ceramics

Eu3+-doped sodium tantalum phosphate glass-ceramics containing bronze -like perovskite crystalline phase Na2Ta8O21 were obtained with different crystalline states (degree of crystallinity and average crystallite size) by a suitable control of the heat-treatment time and temperature of the precursor glass. Luminescence properties of Eu3+ in these materials are in agreement with a progressive insertion of the rare earth ions in the sodium tantalate Na2Ta8O21 phase, as probed by a clear decrease of the intensity ratio between transitions [5D0 →] 7F2/7F1 and narrowing of characteristic emission bands. Thermal poling insights were performed on these glassy and glass-ceramic materials and the experimental conditions had to be carefully optimized in the glass-ceramics to avoid electrical sparks and sample break associated with dielectric breakdown of the samples. Suitable and stable thermal poling treatments could be performed at 250 °C and 900 V under N2 atmosphere on both glass and glass-ceramics. These first insights pointed out a lower migration kinetic of sodium ions when compared to the precursor glass as well as a lower content of depleted ions, since part of sodium is supposed to be “frozen” inside the crystalline phase in glass-ceramics. Despite these lower kinetic poling conditions, a poled sodium depleted layer whose thickness depends on the poling time was successfully formed at the anode side. Reflectance infrared spectroscopy was also used to investigate the structural changes in the poled layer. These IR data pointed out that structural changes induced by thermal poling are mainly promoted in the phosphate network rather than tantalate units in both glass and glass-ceramics in agreement with a selective sodium migration from the remaining glassy phase. Macroscopic induced SHG measured by the Maker fringes technique is also consistent with the EFISH model and quantitative simulations of these data allowed to estimate second order nonlinear optical susceptibilities χ(2) ten to twenty times lower in the glass-ceramics than in the precursor glass. Such electric behavior is discussed in terms of dielectric properties of heterogeneous materials and interfacial polarization mechanisms between crystallites and glassy phase.

Electromigration at atomic-scale metal nanojunctions driven by “lucky electrons”

We have performed electrical break junction experiments on gold nanocontacts. When the nanocontacts are in the diffusive transport regime, we find that the number of atoms removed by Joule heating is rather small (less than 15%) and that the majority of atoms are removed at voltages determined by the surface self-diffusion potentials of gold. We propose a model in which a small fraction of electrons (“lucky electrons”) traverse the constricted region ballistically and transfer their kinetic energy to metal atoms and remove them. Electromigration experiments on other metal species of high melting temperatures (Ni, Pd) strongly support this interpretation.

The design and test of the electrical insulation break for the EAST Divertor primary heat transfer system

Experimental Advanced Superconducting Tokamak (EAST) is one of the important steady-state divertor Tokamak physical experiment platforms in the world. The main functions of the high-temperature and high-pressure Divertor Primary Heat Transfer System (DIV PHTS) are to provide high-pressure cooling water for the divertor to remove the heat load deposited on the divertor under the plasma operation mode and to provide high-temperature nitrogen gas for the divertor system to achieve vacuum condition during the baking mode. The stability and reliable operation of the DIV PHTS play an important role in the EAST tokamak plasma physics experiment. The high-temperature and high-voltage electrical insulation break are one of the important components of the system. The main function of the Electrical Insulation Break (EIB) is to break the closed circuit of the heat transfer system to avoid eddy current during plasma discharge affecting the magnetic field distribution characteristics of the tokamak. On the other way, it also needs to meet the requirement, there is no leak of the cooling water and nitrogen gas during cooling and baking operation mode. This paper proposes the design of an electrical insulating break (EIB) to meet the design requirements of EAST tokamak at first. Then the electric field analysis is carried out by using a finite element model to evaluate its electrical insulation characteristics. And the sealing structural characteristics are verified by applying the finite element method under two design modes. Finally, the sealing test result under the high-temperature baking and high-pressure cooling modes are presented to validate the design.

Improvement of current-carrying tribological behaviour via laser surface texture

ABSTRACT Three kinds of laser surface texture (LST), i.e. square pit-textured surface (SPTS), round pit-textured surface (RPTS) and groove-textured surface (GTS), are fabricated on the flat brass (H65) sample surfaces. The current-carrying tribological behaviour of these surfaces are investigated. It is noticed the COFs of smooth surface, SPTS and RPTS are all greater than 0.6 after the test, while the GTS has the lowest COF, which remains around 0.2 throughout the test. The vibration signals detected from all surfaces indicate the larger COF will not trigger the FIV generation in this state. All the texture surfaces will not cause electrical contact breaks. Worn surface analysis indicates the wear level of GTS is the weakest, with slight damage and debris accumulation occurs along the groove edges. Finite element analysis is performed to calculate the variation of contact force, contact temperature and voltage signal, and the test results can be well explained.

Design of warm dielectric terminations and electrical breaks for high-temperature superconducting power cables

Large electric transportation systems such as electric aircraft and electric ships have been designed with multiple high temperature superconducting (HTS) power cables as part of superconducting power distribution network, and a good electric insulation for the power cables is a critical design requirement needed to be considered. This is because terminations in HTS cable represent a location of significant electrical and thermal stresses and needs to be addressed to reduce the substantial heat load that might be introduced into the cryogenic system. The use of a warm dielectric termination is seen as a potential solution to reduce the electrical standoffs required as part of the design and allow for a high-power dense termination design. A warm dielectric termination design using commercially off-the-shelf ceramic breaks as electrical breaks is explored and withstand and partial discharge measurements are performed to determine the viability of the design concept.

Breakdown and Healing of Tungsten-Oxide Films on Microelectromechanical Relay Contacts

This work discusses the electrical break down of tungsten oxide films that form on contacting surfaces of tungsten electrodes in micro-electro-mechanical (MEM) relays. Electrical tests were applied to the contacts of 27 devices to measure the voltage, current and charge required to break down the oxide films, and also to measure the change in current through the contacts as the film healed. The oxide breaks down when an average of 58 <inline-formula> <tex-math notation="LaTeX">$\mu \text{C}$ </tex-math></inline-formula> of electronic charge passes through the oxide, which usually requires applying 1&#x2013;2 V to drive 100 nA-<inline-formula> <tex-math notation="LaTeX">$10~\mu \text{A}$ </tex-math></inline-formula> of current through the contact. The tungsten oxide heals quickly in laboratory ambient conditions: applying 0.5 V to a contact immediately after breaking down an oxide results in a contact current greater than <inline-formula> <tex-math notation="LaTeX">$5~\mu \text{A}$ </tex-math></inline-formula>, but the same test only induces 1 nA of current 1&#x2013;5 minutes later. The reduction in contact current with time follows a power law, which is characteristic of charge relaxation in oxides. Additionally, Holm&#x2019;s experiment shows that current conduction through the contacts is dominated by tunneling through an oxide. These facts together suggest that the break down and healing are electrical processes related to trap accumulation and relaxation in the tungsten oxide. [2021-0161]

Strong, high stretchable and ultrasensitive SEBS/CNTs hybrid fiber for high-performance strain sensor

Fiber-shaped strain sensors with flexibility and stretchability have attracted more and more attention due to their potential applications in health monitoring and wearable electronic devices. However, simultaneously achieving high sensitivity, wide response range, and high stretchability remains a major challenge. In this work, polystyrene-block-poly (ethylene butylene)-blockpolystyrene (SEBS)/CNT hybrid fibers with high electrical conductivity, high strength and break elongation were fabricated by a simple and scalable wet-spinning method. The hybrid fiber-based strain sensor possesses ultra-wide sensing range (471%), high sensitivity (Gage factor of 368), fast response time (270 ms), and excellent reliability and stability. Moreover, the SEBS/CNT hybrid fiber sensor can accurately monitor both large and subtle human motion in real time, demonstrating its potential application in health monitoring.

The mechanism of the electrochemical oxidation in the constant current mode of the porous silicon

In order to clarify the mechanism of the electrochemical oxidation (ECO) in the constant current mode of porous silicon (PS), the ECO process of PS in different concentration of electrolyte was studied in detail. According to the experiment facts, a hypothesis based on the mechanism of ‘electrical break’ was first proposed to explain the oxidation interruption that tends to occur in the lower concentration of the electrolyte. The experiment results show that the bottom of the porous layer is preferential oxidized in the ECO process since the oxidation process was governed by the holes injected from the substrate and supplied to the silicon-electrolyte interface. The appearance of the oxidation interruption during the ECO process is due to the electrical isolation between the Si substrate and electrolyte by the formation of a continuous oxide film at the bottom of the porous layer. The results obtained in this work indicated that it is easy to control the thickness of the oxide film by adjusting the concentration of electrolyte, which made the ECO method appears to be more attractive when incomplete oxidation is required. This present work is also contributes to the fundamental understanding of the ECO mechanism in the constant current mode of the PS material.

Woodpile EBG waveguide as a DC electrical break for microwave ion sources

AbstractThis article presents a dielectric waveguide, operating at 18 GHz that can sustain 40 kV DC voltages and can be used to feed microwave ion sources. The metallic‐to‐woodpile waveguide transition optimization gives a very low maximum insertion loss of 0.3 dB over a 3.75% bandwidth.

Modeling of eddy current distribution in the SST-1 tokamak

The time varying currents in the Ohmic transformer in the SST-1 tokamak induce voltages that drive large eddy currents in the passive structures like the vacuum vessel and cryostat. Since the vacuum vessel and the cryostat are toroidally continuous without electrical breaks in SST-1, this leads to a shielding effect on the flux penetrating the vacuum vessel. This reduces the magnitude of the loop voltage seen by the plasma as also delays its buildup. Also the induced currents alter the null location of magnetic field. This will have serious implications on the plasma breakdown and startup and corrective measures may be required in case of an insufficient loop voltage or an improper null. Further, the eddy currents distribution will be vital for the plasma equilibrium and need to be considered while reconstructing the equilibrium. Evolution of the toroidal eddy currents in SST-1 passive structures has been studied using a toroidal-filament model. The model calculations are compared with the measured signals in the magnetic diagnostics like the toroidal flux loops and magnetic pick-up coils installed on the SST-1.

The Effect of Ultraviolet Irradiation on the Electrical Breakdown and Hardness Properties of (Epoxy/Aluminum ,Nickel) Composites.

This work includes preparation particles composite materials by adding Aluminum particles (Al) , Nickel particles (Ni) and mixture of (Al +Ni) particles with grain size (40 m) to Epoxy resin with weight fractions (2%, 4%, 6%, 8%). Experimental results showed that, the values of electrical break down decrease with increasing of the weight fraction of additive particles for all samples in normal condition, the same case for other samples which reinforced with (Ni) particles or (Al+Ni) particles after irradiation the samples by (UV) , as well as the hardness value increases with increasing of the weight fraction of additive particles before and after (UV) irradiation .

Electric-field control of conductance in metal quantum point contacts by electric-double-layer gating

An electric-field control of quantized conductance in metal (gold) quantum point contacts (QPCs) is demonstrated by adopting a liquid-gated electric-double-layer (EDL) transistor geometry. Atomic-scale gold QPCs were fabricated by applying the feedback-controlled electrical break junction method to the gold nanojunction. The electric conductance in gold QPCs shows quantized conductance plateaus and step-wise increase/decrease by the conductance quantum, G0 = 2e2/h, as EDL-gate voltage is swept, demonstrating a modulation of the conductance of gold QPCs by EDL gating. The electric-field control of conductance in metal QPCs may open a way for their application to local charge sensing at room temperature.

ROMP‐based boron nitride composites

ABSTRACTThe present work focuses on the investigation of the thermal and dielectric properties of composites obtained by surface‐modified hexagonal boron nitride (hBN) and ring‐opening metathesis polymerization (ROMP) based polymer. A new kind of high performance composites was developed based on using amino silane functionalized hBN (AS‐hBN) and bromine functional group possessing homo and copolymers synthesized via ROMP pathway. Aminosilane capped boron nitride (BN) and bromine bearing polymer backbone enhance the interaction between filler and the polymer chains. The effects of surface‐modified BN (AS‐hBN) and its content on the dielectric properties, and thermal resistance of composites, are systematically investigated and discussed. The resultant composites possess high electrical break over voltages. While all of the ROMP‐based films exhibit low ɛ′ value in a wide frequency range, in the case of the composite with 20% AS‐hBN and poly(bromooxanorbornene‐co‐cyclooctadiene) (ROMP‐BN‐6) displays very low dielectric constants in around 1.5 up to 1 MHz at 20 °C. This value is significantly lower than that of common polymer dielectrics, which is usually in the range of 3–6. Besides the lowest dielectric constant of ROMP‐BN‐6, it has also the smallest dielectric loss tangent even at high temperatures. Tan δ of ROMP‐BN‐6 is 0.003 and 0.0067 at 10 Hz–1 MHz at 20 °C, respectively. Thermal stability of polymers was also improved by introducing surface‐modified hBN. Polymers bearing 20% AS‐hBN are highly thermally stable up to ∼350 °C and gave 25% char yield at 800 °C. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45658.

Short-term wind power forecasting based on dynamic system of equations

The aim of this study is to identify a class of models that appropriately describe the wind power production in wind farms and to provide reliable forecasts in a 72-hour horizon. The activity of the turbines in a wind farm determines the total power produced at a point in time. Their functioning depends on climatic conditions and on electrical and/or mechanical breaks. The latter can be either controlled (in case of maintenance) or uncontrolled (in case of dysfunctions). Therefore, both the uncertainty related to the climate (wind speed, direction, air density etc.) and to the functioning of turbines affect the total power generation in the wind farm. We propose a new approach for modeling these sources of variability, focusing on the average power production rather than on the overall wind farm power production, like the previous literature. The advantage of this strategy is to reduce the high variability of the total power, separating the climatic component from the mechanical functioning of the turbine...

Wireless underwater acoustic beamforming using chip-scale atomic clock timers

Obtaining the directionality of the sound field is typically performed using a cabled array of hydrophones, connected to a central data collection device. The cable introduces vulnerability wherein an electrical break in the line or dragging by currents or anchors may render the array inoperable. An underwater wireless beamforming system, which transmits time and recorded low-frequency sounds using directional high-frequency acoustic communications between elements, is presented here. Each element is contained in a standalone housing that contains batteries, amplifiers, signal conditioning hardware and a field-programmable gate array (FPGA)-based signal processing computer. Low-frequency sounds are recorded at a sampling rate of 2 kHz, then transmitted using binary phase-shift-key (BPSK) encoding at a center frequency of 750 kHz. Inter-element spacing estimates are facilitated by the time-stamped high-frequency signals. System timing is controlled by a Symmetricom® SA.45s chip-scale atomic clock (CSAC) embedded in each unit, connected to the FPGA. In addition, a CSAC output waveform is divided and modified to form the high-frequency multiplier waveform for the BPSK signal. The elements were deployed in shallow water offshore of Panama City, FL, in August 2015. [This work was supported by the Office of Naval Research.]

Effects of donor W6+-ion doping on the microstructural and multiferroic properties of Aurivillius Bi7Fe3Ti3O21 thin film

Aurivillius phase Bi7Fe3(Ti3−xWx)O21+δ (x=0 and 0.06) thin films were deposited on Pt(111)/Ti/SiO2/Si(100) substrates by using a chemical solution deposition method. The W6+-ion doped Bi7Fe3Ti3O21 thin film exhibited tremendous improvements in the electrical and multiferroic properties, namely a low leakage current density, good stability against electrical breakdown, large ferroelectric polarization and large magnetization as compared to the un-doped thin film. The Bi7Fe3(Ti2.94W0.06)O21+δ thin film was stable against electrical break down at applied electric fields up to 1275kV/cm, at which the measured remnant polarization (2Pr) and the coercive field (2Ec) values were 33.5μC/cm2 and 825kV/cm, respectively whereas, the measured 2Pr value of the un-doped Bi7Fe3Ti3O21 thin film was 3.5μC/cm2 at an applied electric field of 318kV/cm. Furthermore, the Bi7Fe3(Ti2.94W0.06)O21+δ thin film showed a well-saturated ferromagnetic hysteresis loop with large magnetization at room temperature.

Simulation of Electromagnetic Transients in ITER Thermal Shield Manifolds

A study of eddy currents and forces associated with electromagnetic (EM) transients for the event of current quench in the ITER thermal shield manifolds is presented. EM response of the tokamak passive structures with respect to their inductive coupling has been estimated using the shell approximation. The external field obtained within the model, assuming their 40-degree symmetry, has been applied to the local model of the thermal shield (TS) manifolds covering the 360-degree domain. Fields sources are modeled accurately to the input data description. At this stage of the study related to first estimates of EM loads, acting on the TS manifolds, the electric contact between the cooling tubes and adjacent TS plates was neglected. The current flow is restricted between the neighboring panels. Such simplification uncouples galvanically the manifold tubes from other TS conducting shells, which makes possible a local simulation of eddy currents and EM loads on the manifolds. Two design options with/without electrical breaks in outlet manifolds have been considered. Detailed temporal and spatial distributions of eddy currents and EM forces were obtained. The simulated results were validated in a comparison with a lumped equivalent circuit. Maximal EM loads per unit length were evaluated and found to be low.

Mechanical performance degradation of glass fiber insulation material after neutron irradiation

Epoxy based glass fiber reinforced plastic composites G-10 CR grade are suitable material for electrical insulation breaks of the superconducting fusion device. At IPR, under the national fusion program, characterization of G-10 CR material with the neutron irradiation dose is studied. This study will help us towards the indigenous development project of electrical insulation breaks for future superconducting fusion magnets under the radiation environment. The insulation material has been irradiated by 14 MeV neutrons D-T generator in the Fusion Neutronics Laboratory, I.P.R. The mechanical and electrical performance was investigated after irradiation (with a fluence of 8.63×1014 n/m2) at room and cryogenic temperature condition. The results show that the mechanical degradations (by ∼ 9 to 30%) after neutron irradiation in tensile strength and impact strength at 300 K and 77 K. In this paper, we present the experimental details of the neutron irradiation and the data have been compared using MCNP code for flux calculation on glass fiber insulation composite along with Stycast 2850 GT epoxy. Investigation of mechanical, electrical, SEM analysis for internal surface morphology, glass transition temperature measurement of insulation material and its test results at 300 K and 77 K before and after neutron irradiation will be presented.