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Power electronic conversion systems introduce different types of voltage stresses on high-voltage epoxy cast insulation in medium-frequency transformers (MFTs), which challenges the reliability of MFTs. The endurance of epoxy insulation at different voltages (AC, DC and pulse) and environmental (thermal and humidity) stresses was studied using encapsulated electrodes in the absence of partial discharge. To assess aging processes and select aging state indicators, various tests including AC breakdown strength (BDE), broadband dielectric spectroscopy, small-angle x-ray scattering (SAXS), Fourier-transform infrared spectroscopy and differential scanning calorimetry (DSC) were first conducted on aged flat samples. The increase of mesoscopic free volume from the SAXS result and local densification (physical aging) of epoxy network from the DSC result were both found. BDE is proved to be sensitive to various aging conditions and thus determined as a test method for encapsulated samples. It is found that the physical aging effect under thermal stress at early aging stages can cause a reversible increase in BDE compared to non-aged samples. This effect can be erased by coupled medium-low electrical stress during aging. In contrast, a sufficiently high electric field will deepen the physical aging extent. Occasional sample failures were observed simultaneously within this process. According to the SAXS and DSC results on flat samples, the failure of encapsulated samples is possibly attributed to the chain fracture around increased mesoscopic free volume during electron bombardment and microcracks generated by interfacial stress release during physical aging. At longer aging periods, the volumetric absorption and diffusion of chemical reactants (oxygen and water) in epoxy networks at high temperatures determines the eventual decrease in BDE, which can be accelerated by the electric field. Ages with different voltage types were gauged by the reduction of BDE compared to pure environmental stress. Bipolar pulses bring heavier aging effects than ACs at the same RMS value. However, the DC component has opposite effects on the BDE with and without thermal stress. [ABSTRACT FROM AUTHOR]

The current research mainly focuses on the influence of different voltage forms on partial discharge for the interturn insulation of a transformer, and the discharge characteristics and its mechanism of interturn insulation under the action of preload are unclear. Therefore, a partial discharge test platform under the synergistic action of preloading force and electrical stress is constructed based on the actual operation conditions of the interturn insulation of a 750 kV transformer. Then, the partial discharge characteristics and its mechanism is explored by using (OM, SEM, FTIR, XRD, EDS, FEA). It is found that the statistical parameters and damage degree of interturn insulation decrease first and then increase with the increase in preload. Moreover, there is an inflection point at 1000 N. The reason is that the preload causes the deformation of the holes and air gaps between the layers of insulating paper and in the insulating paper. As a result, the contact area and volume of partial discharge are changed, which further changes the characteristics of partial discharge for interturn insulation. This study can provide a reference for the maintenance and structural optimization of 750 kV transformers. [ABSTRACT FROM AUTHOR]

AlGaN-based deep-ultraviolet (DUV) LEDs could realize higher optical power output when adopting a p-AlGaN contact layer instead of a p-GaN contact layer. However, this new type DUV LEDs exhibit poor reliability. Thus, this study thoroughly investigates the degradation behaviors of AlGaN-based DUV LEDs with a p-AlGaN contact layer through different aging tests, including single thermal stress, single electrical stress with air-cooling, single electrical stress, and thermoelectric complex stress. It can be found that both high temperature and large working current play crucial roles in accelerating the degradation of optoelectronic properties of the DUV LEDs, and the single high thermal stress without electrical stress can also bring obvious performance degradation to the DUV LEDs, which is a significantly different finding from previous studies. This is because thermal stress on DUV LED could bring some metal electrode elements entering the p-AlGaN layer. Thus, the degradation of optical and electrical properties under the thermal and electrical stress could be not only attributed to the degradation of the device's ohmic contacts, but also due to the metal electrode elements entering the p-AlGaN layer through thermal diffusion, leading to the generation of tunneling current and the generation of defects within or around the active region. Despite that the peak wavelengths of the DUV LEDs remained stable, the turn-on voltage and series resistance increased. Particularly worth mentioning is that the value of the optical power degradation under thermoelectric conditions is larger than the sum of the single thermal and single electrical optical power degradation, which is a result of the mutual reinforcement of thermal and electrical stresses to exacerbate the defect generation and ohmic contact degradation. Based on the study above, preparing p-AlGaN layers with hyperfine gradient aluminum fractions and reducing the junction temperature may help to improve the reliability of AlGaN-based DUV LEDs with the p-AlGaN contact layer. [ABSTRACT FROM AUTHOR]

Energy recovery from low-strength wastewater through anaerobic methanogenesis is constrained by limited substrate availability. The development of efficient methanogenic communities is critical but challenging. Here we develop a strategy to acclimate methanogenic communities using conductive carrier (CC), electrical stress (ES), and Acid Orange 7 (AO7) in a modified biofilter. The synergistic integration of CC, ES, and AO7 precipitated a remarkable 72-fold surge in methane production rate compared to the baseline. This increase was attributed to an altered methanogenic community function, independent of the continuous presence of AO7 and ES. AO7 acted as an external electron acceptor, accelerating acetogenesis from fermentation intermediates, restructuring the bacterial community, and enriching electroactive bacteria (EAB). Meanwhile, CC and ES orchestrated the assembly of the archaeal community and promoted electrotrophic methanogens, enhancing acetotrophic methanogenesis electron flow via a mechanism distinct from direct electrochemical interactions. The collective application of CC, ES, and AO7 effectively mitigated electron flow impediments in low-strength wastewater methanogenesis, achieving an additional 34% electron recovery from the substrate. This study proposes a new method of amending anaerobic digestion systems with conductive materials to advance wastewater treatment, sustainability, and energy self-sufficiency.

In this paper, the reliability of InP/InGaAs DHBTs under high reverse base–collector bias stress is analyzed by experiments and simulation. The DC characteristics and S parameters of the devices under different stress times were measured, and the key parameters with high field stress were also extracted to fully understand and analyze the high-field degradation mechanism of devices. The measurements indicate that the high-field stress leads to an increase in base current, an increase in base–collector (B–C) and base–emitter (B–E) junction leakage current, and a decrease in current gain, and different degrees of degradation of key parameters over stress time. The analysis reveals that the degradation caused by reverse high-field stress mainly occurs in the B–C junction, access resistance degradation, and passivation layer. The physical origins of these failure mechanisms have been studied based on TCAD simulation, and a physical model is proposed to explain the experimental results. [ABSTRACT FROM AUTHOR]

Cobalt (Co) is proposed to replace copper (Cu) as a conductor in the back-end-of-line (BEOL) interconnects of integrated circuits. In this study, the electric characteristics and reliability of the integration of Co with various dielectric films (SiO2, dense, and porous low-k SiOCH films) under thermal and electrical stress were compared. Thermal annealing repaired sputtering-Co-deposition-induced damage to the dielectric film but reduced the breakdown field and time-dependence-dielectric-breakdown (TDDB) times due to the diffusion of Co atoms. After annealing, the SiO2 film had the largest reductions in the breakdown field, TDDB failure time, and electric field acceleration factor, indicating that the diffusion of Co atoms dominates in the oxygen-rich surface. Under electrical stress, the drift of Co atoms favors the porous low-k film with the assistance of porosity. As a result, a barrier is required for Co metallization. To achieve barrier-free or barrier-less processing in Co metallization, the dense low-k film is the best option to integrate with Co. [ABSTRACT FROM AUTHOR]

This article performs a thorough evaluation of different environmental and electrical waveform characteristics affecting PDIV on electric motor winding insulation. Temperature received special attention, as it clearly affects PDIV. Additionally, the PDIV models found in the literature were reviewed. Considering that the winding of the electric motor can reach 180 ° C during operation, the experiments were performed at high temperatures in order to evaluate the performance of PDIV models. Several models were studied regarding their accuracy at high temperatures and the advantages and disadvantages of each one were identified. Based on the analysis, a simple analytical model to estimate the PDIV of twisted pairs depending on the temperature was proposed. All in all, the proposed model was the best compromise between computational requirements and PDIV estimation accuracy at high temperatures. Finally, future lines were identified. Further studies are necessary that consider the humidity, rise time, and pulse width effect on PDIV. Moreover, new models regarding both, environmental and waveform characteristics are necessary to accurately estimate PDIV. Extended volume–time theory seems to be a good basis for that. [ABSTRACT FROM AUTHOR]

This paper reports the critical reviews on the gassing tendency of different insulating fluids along with the precautionary measures to be considered during their fault diagnosis in transformer insulation. The experimental techniques and procedures for identifying the gassing due to electrical and thermal stress along with the stray gassing phenomenon has been elucidated. The different interpretation schemes used for determining the faults in transformers results in unexpected errors when the historical data relating to mineral oil is used for the other alternative fluids. Mineral oil and natural ester show a positive gassing tendency compared to synthetic ester which exhibit a negative gassing tendency. The stray gases are mostly due to breakage of C-C bonds under normal operating temperature of transformer. Among the different hydrocarbons, hydrogen and ethylene are more predominantly formed under lower temperatures. The silicone oil and ester fluids are more stable even under localised hot spots simulated observing a lesser gassing compared to the mineral oil. The impact of additives along with the oxygen and water content in the insulating fluids can lead to the stray gas's causing confusion towards the identification of actual faults occurring in transformers. Furthermore, the regeneration of insulating fluids using different adsorbents reduces the gassing tendency depending on the number of cycles used for its reclamation. [ABSTRACT FROM AUTHOR]

In this paper, the reliability of InP/InGaAs DHBTs under high reverse base–collector bias stress is analyzed by experiments and simulation. The DC characteristics and S parameters of the devices under different stress times were measured, and the key parameters with high field stress were also extracted to fully understand and analyze the high-field degradation mechanism of devices. The measurements indicate that the high-field stress leads to an increase in base current, an increase in base–collector (B–C) and base–emitter (B–E) junction leakage current, and a decrease in current gain, and different degrees of degradation of key parameters over stress time. The analysis reveals that the degradation caused by reverse high-field stress mainly occurs in the B–C junction, access resistance degradation, and passivation layer. The physical origins of these failure mechanisms have been studied based on TCAD simulation, and a physical model is proposed to explain the experimental results.

Two-dimensional materials have modernized a broad interest in electronic devices. Along with many advantages, their atomic-level thickness makes them sensitive under high electrical stress. This work proposes a protection design using a Graphene/Silicon (Gr/Si) Schottky diode as the protective device, which helps to improve the endurance for unwanted fluctuations in operating voltage of 2D heterostructure-based devices. In this scheme, the 2D heterostructure was configured parallel with the protective device (Gr/Si diode) for electrical measurements. It was found that Gr/Si diode handles a large portion of initial surge current peaks, which significantly increases the durability and lifetime of 2D material-based heterostructure devices. This scheme potentially bridges mature CMOS technology and novel 2D-based heterostructure applications for robust futuristic devices.

The use of wide bandgap (WBG) semiconductor devices, which enable higher switching slew rates, and the increase in DC link voltage, which provides system-wide advantages, exposes the winding system of traction machines to enhanced electrical stress. The resulting nonlinear voltage distribution along the motor winding favors partial discharges (PD), which in low voltage (LV) machines causes excessive damage to the insulation system, and premature failure can occur. A simple solution by increasing the enamel thickness of the wires leads on the one hand to a lower copper fill factor. On the other hand, this measure is not necessarily accompanied by an increase in electrical resilience in the case of pulsed voltage. It is therefore essential to understand the phenomenon of partial discharges, which is composed of a large number of processes and mechanisms, to be able to make an estimation of aging. The ultimate goal is to derive a lifetime model that links the dynamic load collectives – ideally in conjunction with the environmental stress influences – of a traction application to a usage-dependent and realistic prediction of the residual lifetime. To this end, this paper provides an overview of the current state of science and technology in this interdisciplinary topic by describing, with reference to high voltage (HV) technology/engineering, the design of the insulation system, the discharge physics, the degradation mechanisms, the statistical effects to be considered, and the partial discharge measurement methods.

Liquid dielectrics are different from each other, but are used to perform the same tasks in high-voltage electrical equipment, especially transformers. In similar conditions, the insulation performance of transformer oils under different types of voltage will provide dielectric resistance. In this study, three different dielectric liquids applied in transformers, namely mineral oil, natural ester and synthetic ester, were tested. Tests under AC and negative DC voltage were performed at electrode gaps of 2.5 mm, 2 mm and 1 mm using disk and VDE type electrodes as per ASTM D1816-84A and ASTM D877-87 standards, respectively. In turn, the impulse voltage tests were performed under an electrode configuration suggested by the IEC 60897 standard. The current data of 500 ms prior to breakdown under AC electrical field stress was decomposed using the empirical mode decomposition (EMD) and variational mode decomposition (VMD) methods. These analyses were conducted before the full electrical breakdown. Although synthetic ester has the highest dielectric strength under AC and negative DC electrical field stress, mineral oil has been assessed to be the most resistant liquid dielectric at lightning impulse voltages. In addition, stabilization of mineral oil under AC and negative DC voltage was also seen to be good with the help of calculated standard deviation values. However, synthetic ester has a significant advantage, especially in terms of dielectric performance, over mineral oil in spite of the stability of mineral oil. This indicates that liquid dielectric selection for transformers must be carried out as a combined evaluation of multiple parameters. [ABSTRACT FROM AUTHOR]

The combined effect of total ionizing dose (TID) and electrical stress is investigated on NMOSFETs. For devices bearing both radiation and electrical stress, the threshold voltage shift is smaller than those only bearing electrical stress, indicating that the combined effect alleviates the degradation of the devices. The H bond is broken during the radiation process, which reduces the participation of H atoms in the later stage of electrical stress, thereby reducing the degradation caused by electrical stress. The positive charges of the oxide layer generated by radiation neutralize part of the tunneling electrons caused by electrical stress, and consume some of the electrons that react with the H bond, resulting in weaker degradation. In addition, the positive charges in shallow trench isolation (STI) generated by radiation create parasitic leakage paths at the interfaces of STI/Si, which increase the leakage current and reduce the positive shift of the threshold voltage. The parasitic effect generated by the positive charges of STI makes the threshold voltage of the narrow-channel device degrade more, and due to the gate edge effect, the threshold voltage of short-channel devices degrades more. [ABSTRACT FROM AUTHOR]

The degradation mechanism of GaN-based near-ultraviolet (NUV, 320â€"400 nm) light emitting diodes (LEDs) with low-indium content under electrical stress is studied from the aspect of defects. A decrease in the optical power and an increase in the leakage current are observed after electrical stress. The defect behaviors are characterized using deep level transient spectroscopy (DLTS) measurement under different filling pulse widths. After stress, the concentration of defects with the energy level of 0.47â€"0.56 eV increases, accompanied by decrease in the concentration of 0.72â€"0.84 eV defects. Combing the defect energy level with the increased yellow luminescence in photoluminescence spectra, the device degradation can be attributed to the activation of the gallium vacancy and oxygen related complex defect along dislocation, which was previously passivated with hydrogen. This study reveals the evolution process of defects under electrical stress and their spatial location, laying a foundation for manufacture of GaN-based NUV LEDs with high reliability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Dihydroethidium (DHE)-derived fluorescence is used to measure intracellular ROS. • Electrical stress is compared to t- BHP-induced oxidative stress with DHE. • DHE-derived fluorescence change after electrical stress is heterogenous and distinct. • DHE and Eth+ fluorescence patterns are identical after electrical stress. • DHE fluorescence changes after electrical stress are not primarily due to ROS. Intracellular reactive oxygen species (ROS) generation is widely suggested as a trigger for biological consequences of electric field exposures, such as those in electroporation applications. ROS are linked with membrane barrier function degradation, genetic damage, and complex events like immunological cell death. Dihydroethidium (DHE) is commonly used to monitor ROS in cells. DHE is linked to intracellular ROS by a primary oxidation product, Ethidium (Eth+), that shows increased fluorescence upon binding to polynucleotides. We observed changes in DHE-derived fluorescence in Chinese hamster ovary (CHO) cells post 300-ns electric pulse exposures, comparing them to tert -butyl-hydroperoxide (t- BHP) induced oxidative stress. Immediate intracellular fluorescence changes were noted in both cases, but with distinct localization patterns. After electrical stress, cytosolic DHE-derived fluorescence intensity decreases , and nucleolar intensity increases. Conversely, t- BHP exposure increases DHE-derived fluorescence uniformly across the cell. Surprisingly, fluorescence patterns after electrical stress in Eth+-loaded cells is identical to those in DHE-loaded cells, in kinetics and localization patterns. These findings indicate that DHE-derived fluorescence changes after pulsed electric field stress are not due to intracellular ROS generation leading to DHE oxidation, but rather indicate stress-induced intracellular microenvironment alterations affecting Eth+ fluorescence. [ABSTRACT FROM AUTHOR]

The synergistic effect significantly impact VCSEL's reliability for potential applications in spatial data communication. The synergistic effect of 3 MeV proton irradiation and electrical stress on 850 nm high-speed VCSELs is investigated. The degradation of VCSEL slow down under the influence of bias current. However, device degradation is more pronounced during irradiation under high bias current density. Low frequency noise (LFN) analysis results indicate that defects induced by proton irradiation are the primary cause of the optical-electrical parameter degradation in the device. The bias current density significantly influences the final defect yield, leading to variations in the degree of degradation after irradiation at different bias currents. At a bias current density of 6.03 × 105 A/m2, the degradation of the modulation bandwidth is reduced in comparison to the unbiased state. A mechanism investigation into the synergistic effect of proton irradiation and electrical stress on VCSELs lends support for accurately evaluating the radiation hardness of optical communication system composed of VCSELs in harsh radiation environments. • The key findings of the study on the synergistic effect of 3MeV proton irradiation and electrical stress on 850 nm high-speed GaAs-based VCSELs are highlighted, elucidating the intricate relationship between proton irradiation, electrical stress, and the resulting degradation in optical-electrical parameters of VCSELs. These results shed light on the impact of these factors on the reliability of VCSELs for potential applications in spatial data communication. • This research explores the interplay between bias current density and the final defect yield, resulting in variations in the degree of degradation after irradiation at different bias currents. The study's findings make a significant contribution to understanding the radiation hardness of optical communication systems comprising VCSELs in harsh radiation environments. • This research successfully demonstrates that bias current induces an annealing effect, explaining why VCSEL's sensitive parameters deteriorate more severely in a short-circuit state during irradiation compared to a biased state. The correlation between the bias current density and the total amount of injected charge adds depth to the understanding of the observed phenomena. [ABSTRACT FROM AUTHOR]

In realistic applications, silver nanowires (AgNWs) are encapsulated in optoelectrical devices to function as transparent conductors and electrodes. Environmental stressors along with the essential electrical stress are inevitably harmful to the AgNWs inside the devices. Herein, to investigate the degradation behavior discrepancy between materials-level and device-level tests, we adopted pseudo-module to mimic the encapsulation. The pseudo-module allows the application of electrical stress and facilitates the interim specimen access for materials characterization through assembly-disassembly. Indoor accelerated and outdoor weathering tests with applied electrical stress to the pseudo-module encapsulated AgNW networks were performed. The impaired optoelectrical properties and morphological changes of AgNWs due to multiple or individual stressor(s) are investigated. Results indicate UVA exposure at elevated temperature coupled with electrical stress is responsible for the electrical failure of AgNW networks. Sulfidation that depresses optical transparency of AgNW networks is prone to occur at lower temperature. This work provides unambiguous degradation behaviors of AgNWs inside encapsulants, helping to improve the design of AgNWs related optoelectrical devices in the applications of solar irradiation environments. [ABSTRACT FROM AUTHOR]

This article performs a thorough evaluation of different environmental and electrical waveform characteristics affecting PDIV on electric motor winding insulation. Temperature received special attention, as it clearly affects PDIV. Additionally, the PDIV models found in the literature were reviewed. Considering that the winding of the electric motor can reach 180 °C during operation, the experiments were performed at high temperatures in order to evaluate the performance of PDIV models. Several models were studied regarding their accuracy at high temperatures and the advantages and disadvantages of each one were identified. Based on the analysis, a simple analytical model to estimate the PDIV of twisted pairs depending on the temperature was proposed. All in all, the proposed model was the best compromise between computational requirements and PDIV estimation accuracy at high temperatures. Finally, future lines were identified. Further studies are necessary that consider the humidity, rise time, and pulse width effect on PDIV. Moreover, new models regarding both, environmental and waveform characteristics are necessary to accurately estimate PDIV. Extended volume–time theory seems to be a good basis for that.

Liquid dielectrics are different from each other, but are used to perform the same tasks in high-voltage electrical equipment, especially transformers. In similar conditions, the insulation performance of transformer oils under different types of voltage will provide dielectric resistance. In this study, three different dielectric liquids applied in transformers, namely mineral oil, natural ester and synthetic ester, were tested. Tests under AC and negative DC voltage were performed at electrode gaps of 2.5 mm, 2 mm and 1 mm using disk and VDE type electrodes as per ASTM D1816-84A and ASTM D877-87 standards, respectively. In turn, the impulse voltage tests were performed under an electrode configuration suggested by the IEC 60897 standard. The current data of 500 ms prior to breakdown under AC electrical field stress was decomposed using the empirical mode decomposition (EMD) and variational mode decomposition (VMD) methods. These analyses were conducted before the full electrical breakdown. Although synthetic ester has the highest dielectric strength under AC and negative DC electrical field stress, mineral oil has been assessed to be the most resistant liquid dielectric at lightning impulse voltages. In addition, stabilization of mineral oil under AC and negative DC voltage was also seen to be good with the help of calculated standard deviation values. However, synthetic ester has a significant advantage, especially in terms of dielectric performance, over mineral oil in spite of the stability of mineral oil. This indicates that liquid dielectric selection for transformers must be carried out as a combined evaluation of multiple parameters.

The combined effect of total ionizing dose (TID) and electrical stress is investigated on NMOSFETs. For devices bearing both radiation and electrical stress, the threshold voltage shift is smaller than those only bearing electrical stress, indicating that the combined effect alleviates the degradation of the devices. The H bond is broken during the radiation process, which reduces the participation of H atoms in the later stage of electrical stress, thereby reducing the degradation caused by electrical stress. The positive charges of the oxide layer generated by radiation neutralize part of the tunneling electrons caused by electrical stress, and consume some of the electrons that react with the H bond, resulting in weaker degradation. In addition, the positive charges in shallow trench isolation (STI) generated by radiation create parasitic leakage paths at the interfaces of STI/Si, which increase the leakage current and reduce the positive shift of the threshold voltage. The parasitic effect generated by the positive charges of STI makes the threshold voltage of the narrow-channel device degrade more, and due to the gate edge effect, the threshold voltage of short-channel devices degrades more.

The effect of gamma (γ)-irradiation on AlGaN-based light-emitting diodes (LEDs) in the short-wavelength ultraviolet (UVC, 210–280 nm) spectral range under electrical stress is characterized by electroluminescence and current–voltage measurement. Different from previous reports that γ-irradiation can hardly damage nitride devices, we observe that the optical power decreases and leakage current increases obviously after electrical stress under γ-irradiation. To delve into the nature of degradation, variation of defects is studied using temperature-dependent low-frequency noise measurement. After stress, the ~0.78-eV defects attributed to N antisite are generated and lead to device degradation, which is accompanied by a reduction of the intrinsic Ga vacancy with an energy level of ~0.38 eV. The variation of defects after stress in γ-irradiated environment is more evident than that in nonirradiated environment, which is well corresponding to the performance degradation behavior. In conclusion, γ-irradiation is found to accelerate degradation induced by electrical stress, and the study can help improve irradiation resistance in AlGaN-based UVC LEDs. [ABSTRACT FROM AUTHOR]

The mapping of the current induced by a focused electron beam in a scanning electron microscope (SEM) has been used to localize electrically stressed regions in the AlGaN/GaN-on-Si Schottky barrier diode (SBD) structures cross-sectioned by the focused ion beam (FIB) technique. We have shown that homogeneously distributed electron beam induced current (EBIC) intensity detected below the Schottky contact at 0 V changes with increasing reverse voltage VR and peaks at the edges of a field-plate region. The build-up of local microavalanches at high electric voltages has been indicated by overexposed EBIC signal at areas following the edges of the field plate structure. Interpretation of EBIC measurements is supported by electro-physical modeling and simulations employing the 2-D finite element method in Synopsys TCAD Sentaurus. The simulations prove that the electric field intensity in the SBD locally reaches values sufficiently high to trigger multiplication of the excessive carriers generated by an electron beam, which helps one to visualize and localize critical regions in GaN-based power electronic devices by the EBIC method. [ABSTRACT FROM AUTHOR]

Energy recovery from low-strength wastewater through anaerobic methanogenesis is constrained by limited substrate availability. The development of efficient methanogenic communities is critical but challenging. Here we develop a strategy to acclimate methanogenic communities using conductive carrier (CC), electrical stress (ES), and Acid Orange 7 (AO7) in a modified biofilter. The synergistic integration of CC, ES, and AO7 precipitated a remarkable 72-fold surge in methane production rate compared to the baseline. This increase was attributed to an altered methanogenic community function, independent of the continuous presence of AO7 and ES. AO7 acted as an external electron acceptor, accelerating acetogenesis from fermentation intermediates, restructuring the bacterial community, and enriching electroactive bacteria (EAB). Meanwhile, CC and ES orchestrated the assembly of the archaeal community and promoted electrotrophic methanogens, enhancing acetotrophic methanogenesis electron flow via a mechanism distinct from direct electrochemical interactions. The collective application of CC, ES, and AO7 effectively mitigated electron flow impediments in low-strength wastewater methanogenesis, achieving an additional 34% electron recovery from the substrate. This study proposes a new method of amending anaerobic digestion systems with conductive materials to advance wastewater treatment, sustainability, and energy self-sufficiency., Competing Interests: The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (© 2024 The Authors.)

The first 500 kV AC cross‐linked polyethylene (XLPE) cable in the world has been installed in China in 2019. The insulation performance of insulation material under the electro‐thermal stress is the basis for its service life. At here, the AC breakdown voltage values and the breakdown time of the 500 kV AC XLPE submarine cable insulation material under the electro‐thermal step stress was analyzed. The lifetime prediction accuracy of a new proposed model was compared to the classic FALLOU, SIMONI/RAMU and CRINE lifetime model. Results show that the AC breakdown strength and lifetime of the XLPE samples increase slowly at low temperatures (40–65°C) and decrease rapidly at high temperatures (65–85°C). The lifetime prediction error of the classic FALLOU, SIMONI/RAMU and CRINE models present that their fit goodness cannot meet the accuracy requirement. The new lifetime model using stepwise regression method could optimize the combination of variables, which considers the coupling effect of electrical and thermal stress. The evaluation error of the new proposed model is better than the FALLOU, SIMONI/RAMU and CRINE model, which is suitable for analyzing the lifetime of the AC 500 kV XLPE submarine cable insulation material. [ABSTRACT FROM AUTHOR]

Surface tracking and erosion is an irreversible degradation occurring on the insulator surface, and this can ultimately lead to failure of the insulator. Polymeric materials such as silicone rubber have many advantages; including a superior hydrophobic surface. However, polymers are exposed to ageing and degradation resulting from electrical and environmental stresses. The rotating wheel dip test is adopted to conduct a comparative study of surface conduction on the two insulators. A conventional design has been selected and compared with insulators having textured surface. Monitoring of the shed surface and insulator trunk using an IR camera were carried out to assess the temperature distribution along insulator profiles. A spatial analysis was also performed to identify key features of the two designs. Localised surface conductance measurements are proposed in this study. This helps to understand and distinguish the trends of conductance and its distribution on each surface, helping to predict the future surface degradation associated to each design.

In this paper, dielectric charging process in dielectrics under bias voltage is investigated. Dielectric materials, used in numerous devices in microelectronics, can be subjected to significant electrical stress. These high electric fields impact the device lifetime. Actuation voltage measurements of capacitive RF MEMS as a function of stress time have been performed. Results show that the actuation voltage varies because of charge storage in the dielectric thin film. In this work a simulation code has been developed to model charge transport phenomena in insulators. This model takes into account tunnel and thermal effects in the dielectric and at the dielectric-metal interfaces. Thanks to this model, charge carrier distribution in the dielectric layer can be calculated. The actuation bias shift versus time, which can be responsible for RF capacitive structure failure, can also be determined. Experimental results can be reproduced thanks to simulations. This simulation tool is then used to define the optimal operating voltage value for a given RF MEMS device. It may also be used to assist in device design in microelectronics. Indeed for a given material set, the optimal operating voltage value is calculated as a function of device properties. [ABSTRACT FROM AUTHOR]

This paper proposes an equivalent circuit model to obtain the transient electrical stress quantitatively in medium voltage medium frequency transformers in modern power electronics. To verify this model, transient simulation is performed on a 1.5 kV/1 kHz transformer, revealing voltage overshoot quantitatively between turns and layers of the transformer’s HV winding. Effects of rise time of the input pulse voltage, stray capacitance of the winding insulation, and their interactions on the voltage overshot magnitude are presented. With these results, we propose limiting the voltage overshoot and, thereafter, enhancing medium voltage medium frequency transformer’s insulation capability, which throws light on the transformer’s insulation design. Additionally, guidance on the future studies on aging and endurance lifetime of the medium voltage medium frequency transformer’s insulation could be given.

The non-inverting buck boost (NIBB) converter has attracted significant attention in recent years, as it shares ground between input and output, and the voltage stress of switches is lower. In order to investigate the differences between NIBB and conventional buck boost converters, a comprehensive comparison and analysis of these two converters were conducted in terms of their operation principles, which includes multi-mode control strategy and dual-edge modulation here, and also the characteristics of switches and passive components in the two converters were analysed. The results show that NIBB is better than conventional buck boost circuit in these aspects of electrical stress, power loss, cost, passive component volume, and so on. Two prototypes for the two converters with 10 kW/20 kHz were designed and simulated, respectively, for verifying the results. Analytical and simulated results confirmed the conclusions.

Modeling the lifespan of an organic light-emitting diode (OLED) is a complex task as it depends on different potentially interacting factors. As the literature on this subject is still scant, new parametric models for calculating the lifespan of the OLED are proposed in this article. The design of experiment (DoE) methodology is used for cost and accuracy reasons. Different lifespan models based on thermal and electrical experimental aging tests are proposed. As stress factors, current density, temperature, and their interactions, which are rarely taken into account in aging studies, are simultaneously involved. The analysis of the model parameters highlights the prevalence of temperature compared to current density on the luminance performance of OLEDs. Nonlinear models appear as the most accurate. [ABSTRACT FROM AUTHOR]

In any sustainable electrical systems, various high‐voltage (HV) power apparatuses such as electrical cable, transformer etc. play a pivotal role to transfer electrical energy from the generation end to the consumer end. The degradation due to electrical stress is very unlikely to avoid in operation. Prominently, the insulation system is mostly expected to be strong enough, and its degradation always provides a constant threat to the reliable operation. Moreover, the continual deterioration can gradually lead to the complete breakdown of HV equipment. To assess the overall dielectric properties, the regular monitoring/diagnosing of electrical insulation has a paramount importance in power systems. One of the potential tools for diagnostic assessment is the tan‐delta (tan δ) measurement. Considering different aspects at various frequencies, this study elucidates a comprehensive review of tan δ measurement. First, a detailed review and explanation of multiple challenges associated with dielectric loss measurement are presented. Various dielectric losses, their contribution to tan δ, measurement techniques and their comparisons are also discussed. This study further reviews the analogy of different physical dipolar theories, modelling and a brief analysis of commercially available measurement instruments. [ABSTRACT FROM AUTHOR]

Prior research has reported that the device characteristics of amorphous indium–gallium–zinc-oxide (a-IGZO) thin-film transistors (TFTs) have been changed by instabilities due to electrical stress. Because positive bias stress and high current stress produce a positive threshold voltage shift, if the digital logic circuit is designed using a-IGZO TFTs, there is a high possibility that the circuit suffers from malfunction. In this letter, the dynamic and the static logic circuits using n-type a-IGZO TFTs are compared in terms of stability for electrical stress. In order to compare the stability of the two circuits, DC and AC signals are applied. The measurement results suggest that the dynamic logic circuit is much more stable than the static logic circuit regarding electrical stress. [ABSTRACT FROM AUTHOR]

The electrical stress induced variation of forward conduction mechanism in ultraviolet light emitting diodes in UV-A spectral range is usually attributed to the increase of trap density. The influence from trap energy level, which plays an equally significant role in the trap-assisted tunneling (TAT) theory, is nevertheless neglected in previous studies. In this work, the effect of electrical stress on the forward conduction mechanism of UV-A light emitting diodes has been studied using temperature-dependent current-voltage measurement and the variation of trap physical parameters has been monitored using deep level transient spectroscopy (DLTS) measurement. For the first time, it is demonstrated that, the rate of TAT increases after electrical stress, and has a much stronger correlation with trap energy level as compared to the trap density. [ABSTRACT FROM AUTHOR]

This paper analyses the neutron irradiation impact on the electrical performances of unstressed, ON-state, OFF-state, and negative gate bias (NGB) stressed AlInN/GaN HEMTs. These irradiations have resulted in the creation of electron traps that are causing a decrease in the drain current and an increase in the access resistance of the unstressed, ON-state, or OFF-state stressed AlInN/GaN devices. These degradations have been correlated with gamma spectrometry measurements and transmutation reactions occurred during the thermalized neutron irradiation have been highlighted. Despite these phenomena, a rise in drain current and a reduction in access resistance have been observed when NGB stressed AlInN/GaN HEMTs were irradiated with a fluence of $1.2\times 10^{\mathbf {12}}$ neutrons/cm2. The differences between the electrical behaviors of unstressed, ON-state, OFF-state, and NGB stressed devices observed after the neutron bombardment are related to the presence of electron traps in these device structures. [ABSTRACT FROM AUTHOR]

The non-inverting buck boost (NIBB) converter has attracted significant attention in recent years, as it shares ground between input and output, and the voltage stress of switches is lower. In order to investigate the differences between NIBB and conventional buck boost converters, a comprehensive comparison and analysis of these two converters were conducted in terms of their operation principles, which includes multi-mode control strategy and dual-edge modulation here, and also the characteristics of switches and passive components in the two converters were analysed. The results show that NIBB is better than conventional buck boost circuit in these aspects of electrical stress, power loss, cost, passive component volume, and so on. Two prototypes for the two converters with 10 kW/20 kHz were designed and simulated, respectively, for verifying the results. Analytical and simulated results confirmed the conclusions. [ABSTRACT FROM AUTHOR]

Abstract Partial shading and dirt areas are the main external reasons inducing via electrical and thermal stresses hot spots in photovoltaic (PV) modules or panels reducing their instantaneous performances and at best their lifetime, at worst a rapid total degradation of the functioning. Even if manufacturers add by-pass diode in the topology of the PV panel, performances of the panel under or after stresses are not taken into consideration in their datasheet which only gives the characteristics under Standard Test Conditions (STC). To test the role of electrical and thermal stresses on the performance of PV module, we performed several series of experimental measurements in the most used commercial modules, i.e. a series of monocrystalline silicon ones. Using a Deep Level Transient Spectroscopy (DLTS) spectrometer based on a double-boxcar system in the post-stress period, this work focusses on the analysis of defects present in stressed PV solar modules for measurements of electrical characteristics of the module. Various reverse currents and temperature levels were applied to induce the stress in dark condition into the solar module structure. The output voltage was measured before and after the applying stress in the same condition for several common periods of time. The changes in efficiency and parameters of PV cells and modules being exposed to shadow effects compared to that in normal working mode are discussed based on output voltage done in the present study. [ABSTRACT FROM AUTHOR]

The aim of this paper is to identify the electrical signatures of degradations of large-area organic light-emitting diodes (OLEDs) (41 cm² active area), subjected to various stress conditions. Three Philips GL55 OLEDs were stressed under three distinct temperature values: 23 °C, 40 °C, and 60 °C at a stress current density of J = 15 mA/cm² (rated current density: Jn = 9.49 mA/cm²). Under thermal and electrical stresses, an increase of the operating voltage was observed with stress time but thermal stress alone did neither affect the operating voltage nor the luminance values up to 60 °C. [ABSTRACT FROM AUTHOR]

Blue and white light emission is observed when high voltage stress is applied using micrometer-separated tungsten probes across a nanoforest formed of ZnO nanorods. The optical spectrum of the emitted light consistently shows three fine peaks with very high amplitude in the 465–485 nm (blue) range, corresponding to atomic transitions of zinc. Additional peaks with smaller amplitudes in the 330–650 nm range and broad spectrum white light is observed depending on the excitation conditions. The spatial and spectral distribution of the emitted light, with pink–orange regions identifying percolation paths in some cases and high intensity blue and white light with center to edge variations in others, indicate that multiple mechanisms lead to light emission. Under certain conditions, the tungsten probe tips used to make electrical contact with the ZnO structures melt during the excitation, indicating that the local temperature can exceed 3422 °C, which is the melting temperature of tungsten. The distinct and narrow peaks in the optical spectra and the abrupt increase in current at high electric fields suggest that a plasma is formed by application of the electrical bias, giving rise to light emission via atomic transitions in gaseous zinc and oxygen. The broad spectrum, white light emission is possibly due to the free electron transitions in the plasma and blackbody radiation from molten silicon. The white light may also arise from the recombination through multiple defect levels in ZnO or due to the optical excitation from solid ZnO. The electrical measurements performed at different ambient pressures result in light emission with distinguishable differences in the emission properties and I–V curves, which also indicate that the dielectric breakdown of ZnO, sublimation, and plasma formation processes are the underlying mechanisms.

The objective of this contribution was to study the behaviour of new and regenerated insulating oil used in power transformers under the influence of an electric stress. To estimate the degradation rate of the dielectric fluids, one thousand (1000) successive breakdowns were generated according to the IEC 60156 standard. The parameters such as dissipation factor (Tan δ), resistivity, total acid number (TAN) and oil water content were measured and examined following IEC/ISO standards. Good correlations have been obtained between TAN/resistivity and Tan δ which might provide a 'picture' of the fluid condition. The dissolved oxidation products for the two dielectric fluids (after the application of electric breakdowns) was evaluated by Fourier‐transform infrared spectroscopy. The results obtained indicate that the degradation of the parameters is significant and confirms the influence of an alternative electric field (AC) on the new and regenerated oils. It was also suspected that inhibitors and antioxidants were removed from the oil after regeneration. Their concentration should therefore be monitored and replenished when necessary. [ABSTRACT FROM AUTHOR]

Dynamic contact resistance measurement (DRM) is an effective technique to evaluate the contact conditions of high voltage SF 6 circuit breaker. However, the relations between DRM characteristics and contact performance remain ambiguous, the influence of the electrical stress on the DRM curves is equivocal as well, and there is no contact erosion evaluation method based on DRM. To investigate the relations between DRM characteristics and contact erosion, the DRM results of high voltage SF 6 circuit breaker at various degrees of erosion obtained from the designed experiments are presented. The experiments demonstrate that with the degradation of the contacts, the average arcing contact resistance ( R a ) increases, and the arcing contact wipe ( D a ) decreases. Then, the simulation of the erosion test is performed to analyse the relations between R a and D a and the contact performance. The results show that with the decrease of R a , the threshold of D a to ensure the success of the current commuting from the main contacts to the arcing contacts becomes shorter. Moreover, the influence of the electrical stress on R a and D a are investigated. Results demonstrate that R a reflects the influence of arc by-products and contact geometry caused by electrical stress, and that D a reflects the influence of the interrupted current, the arcing time, the contact geometry, and the contact material. Finally, an evaluation method of the contact erosion for SF 6 circuit breaker based on DRM is proposed. [ABSTRACT FROM AUTHOR]

This study aims to examine the electrical stress effects on the switching power dissipation in n-channel VDMOSFET. We set up a resistive load NMOS inverter as a test circuit. At first step of measurement, VDMOSFETs are subjected to the high constant voltage (55V DC ) up to 6 h and this degradation process is continued until just prior to the oxide breakdown. Stress induced changes in output voltage and current are extracted using the resistive load NMOS inverter. The static and dynamic power dissipations, and power-delay product are calculated accordingly. In addition, assuming that the inverter load is selected as n-channel VDMOSFET, the power dissipation is calculated. In resistive load NMOS inverter, it is observed that the static power dissipation is decreased by 5.3%, the dynamic power is increased by around 60% and the total power dissipation is decreased by 5% compared to before the stress. In enhancement load NMOS inverter, the total power dissipation has a decrease of around 92%. [ABSTRACT FROM AUTHOR]

AlGaN/GaN high-electron mobility transistors (HEMTs) and metal–oxide–semiconductor (MOS)-HEMTs using HfO2 as a gate dielectric have been analyzed at room temperature, after short thermal annealing (STA) and thermal cycle tests, during off-state electrical step stress, high-temperature reverse bias (HTRB), and positive bias temperature instability (PBTI) tests. The results showed that the leakage current in as-fabricated MOS-HEMTs decreased by 106 and the on/off ratio increased by over 104 than the HEMTs. Moreover, it was even higher after an STA test, up to 108, in the MOS-HEMTs, and the surface trapping effects were mitigated, especially if a KOH cleaning was used before HfO2 deposition. The MOS-HEMTs also showed higher electrical stability after off-state step electrical stress, HTRB, and PBTI tests. [ABSTRACT FROM AUTHOR]

The influence of constant current stress on the conduction mechanism of reverse leakage current in ultraviolet (UV) light emitting diodes (LEDs) in the UV-A spectral range has been investigated for the first time using temperature-dependent current-voltage measurement from 370 K to 55 K. Below 220 K, variable range hopping mechanism dominates in UV-A LEDs. While, above 220 K, the leakage current is attributed to Poole-Frenkel emission mechanism within the bias range of −3 ∼ −6 V. With the increasing of the reverse bias, the conduction mechanism transforms from Poole-Frenkel emission to space-charge-limited conduction mechanism. In particular, applying electrical stress yields an alteration of the transition voltage from −7.5 V to −6.5 V. We propose that stress could lead to a reduction of the thermal activation energy, and therefore alters the transition voltage. [ABSTRACT FROM AUTHOR]

• Impact of electrical stresses on PD activity in the insulation defects. • Evaluation of severity of insulation defects through PD characteristic features. • Trend analysis of PD features in insulation defects by increasing electrical stresses. • Development of Tobit regression to identify the trends and to predict the PD behavior. Assessments of aging and insulation degradation in power components are important to observe and track their condition during operation. Partial discharge (PD) diagnostics is an efficient method for health estimation of the components' insulation. PD is initiated when the dielectric strength of localized insulation part is decreased. The intensity of PD increases with time, which may lead to insulation failure. This paper investigates the influence of the electrical stresses on the behavior of PD activity in medium voltage (MV) cable containing insulation defects. For this purpose, insulation defects such as internal, surface, and corona are developed in the MV cable environment under laboratory conditions. PD behavior is studied in these defects at gradually increased voltage levels by observing different PD characteristic features including PD inception voltage (PDIV), pulse repetition rate, accumulated apparent charge, average discharge current, discharge power, and quadratic rate. The Tobit regression model is developed for these progressing defects to identify the trends and to predict the behavior based on PD characteristic features. The presented work proposes a framework for the evaluation of the progression of insulation degradation due to increased electrical stress. The study is carried out on XLPE cables, however, the developed approach can be equally implemented on other types of dielectrics and components. [ABSTRACT FROM AUTHOR]