Ultra-high Voltage Research Articles

Carbonated Beverage Chemistry for High-Voltage Battery Cathodes.

Advanced lithium-ion batteries utilize high upper cut-off voltages up to 4.8V versus lithium metal to reach extraordinary energy densities. Such a harsh environment challenges the cathode stability and requires the construction of robust cathode electrolyte interphases at their electrochemical interface. Inspired by carbonated beverages with supersaturated CO2, here, a surface modification strategy that produces effective passivation layer of low modulus from the weakest link, is proposed CO2 bubbles preferentially nucleate and grow at rough surfaces, which in oxide cathodes, are also the local regions offering fast degradation pathway. Metal ion exchange on carbonated layer assists the construction of highly elastic interface under the guidance of packing factor. This method enables surface reconstruction at both primary and secondary particle levels for various cathodes exemplified by high-voltage LiNi0.8Co0.1Mn0.1O2 (NCM811) and LiCoO2 (LCO). Remarkably, with ultra-high upper cut-off voltage of 4.8V versus Li+/Li, over 235 mAh g-1 discharge capacity, and over 900W h kg-1 discharge energy at cathode level, ≈90% capacity retention can be obtained for LiNi0.8Co0.1Mn0.1O2 over 100 cycles at 0.5 C with commercial carbonate electrolytes. This carbonated beverage chemistry is promising for constructing high-quality surface passivation in many extreme-condition applications beyond battery cathodes.

Analysis of heating defects in extension rods of extra-high voltage direct current overhead transmission lines

This paper studies the overheating defect of an extension rod in a ± 800 kV extra-high voltage direct current overhead transmission line, and proposes various factors that affect the overheating of the extension rod. Establish an equivalent model of an extra high voltage DC transmission line based on equipotential point and line parameter analysis, and calculate the model parameters. The proposed model can also be applied to ultra-high voltage DC overhead transmission lines such as ± 500 kV, and has strong universality. Simulation experiments show that if the equivalent resistance value of the split wire side is reduced by 0.01Ω, the power loss on the extension tie rod can be increased to 380.951 W; if the equivalent resistance value of the jumper side is increased by 0.01Ω, the power loss on the extension tie rod can be increased to 273.41 W. Combined with theoretical analysis and simulation verification, it is concluded that the main factor affecting the overheating of the extension rod is the change in the resistance value on the jumper side caused by the increase in contact resistance. A systematic troubleshooting plan for related defect problems is proposed, which has important reference and guidance significance for such line fault problems.

Experimental simulation of the generation of microwave radiation during the interaction of a lightning discharge with an aircraft

On a specialized testing installation — a high-voltage Marx generator, which allows the formation of a spark discharge up to 20 meters long, the process of the impact of lightning radio emission in the microwave range on an aircraft (AC) is simulated. A metal AC model made on a scale of 1:50 was placed in a 9 m long rod-plane spark gap. A positive voltage pulse was applied to the high-voltage electrode from the generator (front 100 μsec, duration 7500 μsec). The generated spark discharge passed through the AC model. It was found that when the spark channel passes through the body of the model, electromagnetic pulses of the microwave range with a duration of less than 500 psec and a rise time of less than 100 psec arise. The measurement of the resulting microwave pulses was carried out using special radio equipment in the subnanosecond range. High-speed photography of the discharge development, carried out synchronously with electromagnetic measurements, showed that microwave pulses (up to 10 GHz) arise at the stage of development of the spark discharge leader in the part of the “high-voltage electrode – insulated model” gap. Such pulses can be considered as a factor dangerous for various AC microwave radio systems, when the AC is struck by lightning, as well as for other objects, including power facilities, which contain equipment with microelectronics. Such microwave pulses can also occur during nearby lightning discharges (for example, in a lightning rod of a power substation), when a powerful streamer corona occurs on devices and wires of ultra-high voltage lines), and when a high-voltage spark discharge occurs when switching equipment (disconnectors, arresters) is triggered. In this case, disruptions are possible in the operation of control equipment (for example, relay protection devices) that contains microelectronics, as well as various communication means available at electric power facilities operating in the microwave range (above 1 GHz).

Investigating the impact of X-ray irradiation on the SF6 gas discharge in GIS equipment

ABSTRACT Gas Insulated Switchgear (GIS) is extensively utilized in power grid systems. However, the existence of numerous photoelectrons in the SF6 gas during X-ray non-destructive testing in ultra-high-voltage (UHV) GIS equipment may induce gas streamer discharge in a strong electric field. To address this issue, in this work, the impact of X-ray irradiation on the SF6 gas discharge in GIS equipment was systematically analyzed. Firstly, one GIS engineering mode with a three-dimensional electric field was established, and a physical GIS model was established by the Geant4 and Garfield++ codes. Secondly, the electrons’ ionization, and multiplication processes in SF6 gas during the X-ray irradiation were studied. Finally, a test platform with an equivalent electric field tube, which had the same intensity as in the GIS equipment, was established to verify the physical GIS model. X-ray beams with 0.1 MeV, 0.16 MeV, 0.3 MeV, and 1.25 MeV energy were used during the test process. From our analysis, it was concluded that X-ray irradiation can cause an electron avalanche in SF6 gas and the intensity of the avalanche is low, which is far away from the appearance of the streamer discharge.

UHVDC transmission line diagnosis method for integrated community energy system based on wavelet analysis

With the large-scale development of renewable energy power, China has faced with the challenges of the reverse regional distribution of wind and solar resources and power load, as well as the intermittency and randomness of renewable energy power. Therefore, China is vigorously developing ultra-high voltage direct current (UHVDC) transmission technology to solve the problem of insufficient flexibility caused by the uncertainty of renewable energy and the fluctuation of multi-energy loads in integrated community energy systems. UHVDC plays an increasingly pivotal role in the west-east transmission system in China’s power system due to its high transmission capacity and long transmission distance. Once the fault occurs in the ultra-high voltage direct (UHVD) transmission line, quick and accurate fault location identification is of great significance. Hence, this paper proposes a UHVDC transmission line diagnosis method based on wavelet analysis for integrated community energy systems. Wavelet transform (WT) is used to decompose the transient signal on a multi-scale, and then power systems computer-aided design (PSCAD) software is utilized for simulation calculation to obtain the singular spectrum entropy of each layer and facilitate wavelet transformations for signal denoising with advanced tools such as MATLAB. The prediction results can distinguish outside the rectification side fault, within the rectification side fault, and outside the inverter fault with an accuracy of 100%. A large number of simulations demonstrate that combining singular spectrum entropy with support vector machines (SVM) has emerged as a robust technique for integrated community energy systems, suggesting its potential as a standard method in UHVDC transmission line diagnosis. This study is of significant reference for realizing the complementarity of multiple types of power supply and ensuring a reliable power supply.

Coordination structure regulation in non-flammable electrolyte enabling high voltage lithium electrochemistry

High-voltage battery systems bring significant increases in energy density but are also accompanied by fast degradation of electrochemical performance and serious safety issues. Herein, Li+ coordination structure regulation was conducted to formulate a non-flammable electrolyte, which consists of 1.5 M lithium bis (fluor sulfonyl) imide (LiFSI) in triethyl phosphate and methyl 2,2,2-trifluoromethyl carbonate (FEMC). The renamed TEP-FEMC-FEC (TFF) electrolyte exhibits an FSI−-dominated solvation structure contributed by the weakly-solvating ability of FEMC. The generated inorganic-rich interfacial layers are conducive to stabilizing the phase transition of high-voltage cathodes while suppressing the dendritic growth on lithium metal or co-intercalation behavior in graphite anode. This TFF electrolyte enables LiCoO2 || Li batteries to achieve capacity maintenance over 79% after 400 cycles with high-rate of 5 C at an ultra-high voltage of 4.6 V, and an outstanding capacity exceeding 100 mA h g−1 even at a super-high current density of 20 C. Additionally, the Ah-level LiCoO2 || graphite pouch cells also exhibit high capacity retention and satisfactory safety performance even under fast charging. This work provides a novel research direction for the pursuit of high energy density non-flammable electrolytes.

In Situ Construction of a Multifunctional Interphase Enabling Continuous Capture of Unstable Lattice Oxygen Under Ultrahigh Voltages.

The use of nickel-rich layered materials as cathodes can boost the energy density of lithium batteries. However, developing a safe and long-term stable nickel-rich layered cathode is challenging primarily due to the release of lattice oxygen from the cathode during cycling, especially at high voltages, which will cause a series of adverse effects, leading to battery failure and thermal runaway. Surface coating is often considered effective in capturing active oxygen species; however, its process is rather complicated, and it is difficult to maintain intact on the cathode with large volume changes during cycling. Here, we propose an in situ construction of a multifunctional cathode/electrolyte interphase (CEI), which is easy to prepare, repairable, and, most importantly, capable of continuously capturing active oxygen species during the entire life span. This unique protective mechanism notably improves the cycling stability of Li||LiNi0.8Co0.1Mn0.1O2 (NCM811) cells at rigorous working conditions, including ultrahigh voltage (4.8 V), high temperature (60 °C), and fast charging (10 C). An industrial 1 A h graphite||NCM811 pouch cell achieved stable operation of 600 cycles with a capacity retention of 79.6% at 4.4 V, exhibiting great potential for practical use. This work provides insightful guidance for constructing a multifunctional CEI to bypass limitations associated with high-voltage operations of nickel-rich layered cathodes.

A method for calculating space charge distribution in ultra-high voltage direct current transmission lines based on the transport of diluted species theory

The occurrence of corona discharge in ultra-high-voltage direct current transmission lines results in the generation of space charge, which significantly affects the nearby electromagnetic environment. To investigate the micro-physical mechanisms of discharge and provide better guidance for the calculation of the ground ion current density and total electric field, a method based on the theory of the transport of diluted species is proposed. This method enables the visualization and analysis of the movement process of space charge in air medium, as well as the calculation of the total electric field below the transmission lines. To validate the effectiveness of this algorithm, experimental tests of the total electric field are conducted on actual transmission lines. The experimental results demonstrate that the algorithm not only highlights the evident differences in the transient microscopic processes between positive and negative corona discharges but also accurately calculates the total electric field below the transmission lines. In addition, considering the weather conditions in the Chongqing region, relevant recommendations are provided under the influence of wind speed, aiming to offer protection guidelines for individuals engaged in activities near transmission lines.

Achieving Ultrahigh Voltage Over 100 V and Remarkable Freshwater Harvesting Based on Thermodiffusion Enhanced Hydrovoltaic Generator

AbstractEvaporative hydrovoltaic generators hold significant potential for alleviating water‐energy crisis, but low output voltage configurations due to the slow phase transition rate of water molecules and the intricate nature of integration limit their applications. Herein, a lotus‐inspired interfacial evaporation‐driven hydrovoltaic generators (IEHVG) is developed for efficient generation of water vapor and electricity from seawater instead of freshwater and achieves an ultrahigh voltage output higher than 100‐volt level through forested IEHVG integration. The biomimetic hydrogel is developed with specific liquid transport channels, graphene quantum dots/MXene nanocomposites, and gradient hydrophobic interface for highly enhanced photothermal evaporation and electricity generation by mimicking the transpiration process of a “stems‐leaves of lotus”. The synergistic thermodiffusion effect leads to the output power density of IEHVG reaches up to 45.6 µW cm−2 and can power electronic devices or charge commercial supercapacitors. The freshwater‐electricity cogeneration integrated system consisting of 192 IEHVG units can harvest a record‐breaking voltage reaching 105 V and a high freshwater harvesting rate up to 2.0 L m−2 h−1 from seawater in a well‐lit outdoor area. This work demonstrates that IEHVG offers a novel concept for modular freshwater and high‐voltage power sources access on offshore work platforms.

Experimental and theoretical study on the influence of bundle number on corona loss characteristics of ultra high voltage corona cage positive/negative DC conductors at high altitude

The corona loss generated by the conductor is one of the important factors in the design of ultra-high voltage (UHV) direct current transmission lines. This article is based on the high-altitude (2200 m) ultra-high voltage corona cage experimental platform built in Xining City, Qinghai Province. For the LGJ400-35 conductor used in the typical ± 800 kV DC transmission lines from Qinghai to Henan Province, positive and negative polarity corona experiments were conducted on LGJ400-35 conductors with 4, 6, 8, and 10 bundle under surface field strength conditions of 14–22 kV/cm. For the first time, corona loss data of bundle conductors in positive/negative polarity ultra-high voltage DC transmission lines were obtained, Fit the prediction formula for corona loss of transmission lines under different bundle numbers and surface electric field strengths of wires. And build a model in COMSOL Multiphysics software for simulation analysis, fitting the correction factor for the impact of wind speed on wire corona loss. The research results in the article can provide data reference and support for the construction of ultra-high voltage direct current transmission lines in high-altitude areas.

Comparative assessment of fault detection methods in transmission line during power swing: analyzing single and hybrid networks for the southern Kerala grid

The blocking function of power oscillation is a highly effective feature found in distance relays. Its purpose is to prevent unintentional tripping of transmission lines. It is crucial to accurately differentiate between faults and power oscillations to minimise the occurrence of widespread power outages and monetary losses. Therefore, the detection and classification of faults arising from power swings are critical challenges in ensuring the smooth operation and overall health of transmission lines, particularly in extra-high-voltage (EHV) and ultra-high-voltage (UHV) power systems. Modern methods rely on machine learning methods which are in their infancy. The paper proposes to identify various fault conditions in transmission lines during power swing by using a hybrid Neural Network architecture. In this research, different designs such as 2-D convolution neural network (2D-CNN), 1-D convolution neural network (1D-CNN), long short-term memory (LSTM), and CNN-LSTM hybrid networks are investigated to understand the effect of various deep learning approaches. Along with the southern Kerala grid, the standard 9-bus system is selected as a test case to examine various fault circumstances of the system during power swing. Multiple tests were conducted to determine the optimal deep learning architecture, including model parameters and configurations, for accurate fault detection. For the 9 bus system, the 1D CNN network performs better with an accuracy of 98.70%, and for the Kerala grid, both networks are competitive, but the CNN-LSTM Hybrid method slightly outperforms the 1D CNN with an accuracy of 92.40%.

Dual modification engineering enabled efficient perovskite solar cells with high open-voltage of 1.233 V

Interface engineering take as a crucial role in enhancing the performance of perovskite solar cells (PSCs). Here, we propose a comprehensive strategy to improve the performance and stability of PSCs through dual-interface modification approach. This strategy involves simultaneously introducing lead-free Cs3MnBr5: Ce3+ nanocrystals (NCs) between SnO2 electron transport layer and the perovskite layer, as well as 1H,1H-Perfluorooctylamine iodide (PFOAI) at the interface between perovskite and Spiro-OMeTAD hole transport layer. Firstly, we successfully prepare Cs3MnBr5: Ce3+ NCs, which exhibits an extensive ultraviolet response and effective blue photoluminescence. The photoluminescence quantum yield of Cs3MnBr5: Ce3+ NCs can reach 90 %, demonstrating efficient photon down-conversion ability and efficient defect passivation. Simultaneously, the organic halide salt PFOAI with super-hydrophobic properties efficiently passivates defects on the surface of perovskite and improves moisture-resistance of perovskite films. Taking advantage of these synergistic effects, we achieve efficient PSCs based the Cs0.05(FA0.83MA0.17)0.95Pb(I0.83Br0.17)3 and Cs0.05(FA0.95MA0.05)0.95Pb(I0.95Br0.05)3 with power conversion efficiency (PCE) of 23.88 % and 24.24 %. We also achieved an ultrahigh open-circuit voltage (VOC) of 1.233 V, which represents one of the highest VOC values in a perovskite film with a bandgap of ∼1.60 eV. Additionally, the non-encapsulated double-interface modified PSCs exhibit long time, light and humidity stability. This study explores a novel and comprehensive strategy for manufacturing PSCs with high VOC, high PCE, and good stability.

Response and fragility of long-span truss structures in ultra-high voltage substation subjected to near-fault pulse-like and far-field ground motions

This study numerically investigates the seismic responses, bearing capacities, and fragilities of long-span truss structures (LSTSs) in ultra-high voltage substations subjected to near-fault pulse-like (NFP) and far-field (FF) earthquakes. The finite element model established in ABAQUS software considers the tower-line dynamic coupling effect, and it is excited by 20 NFP and 20 FF earthquakes. The seismic responses and bearing capacities are analyzed to generate the design recommendations for LSTS. According to five performance levels, the fragility curves are developed by performing a fragility method based on intensity measure. The peak displacement, acceleration amplification factor, bearing capacity, and fragility results significantly indicate that the seismic risk of LSTS under FF earthquakes is much higher than that under NFP earthquakes. Moreover, there are three typical failure modes (i.e., I – III) of LSTS under strong earthquakes. Mode I is a brittle failure while mode III is a ductile failure. Furthermore, the bearing capacity basically obeys a lognormal distribution, and the distributions subjected to NFP and FF ground motions are very close.

Doping with KBr to Achieve High-Performance CsPbBr3 Semitransparent Perovskite Solar Cells.

Wide-bandgap semitransparent perovskite photovoltaics are emerging as one of the ideal candidates for building-integrated photovoltaics (BIPV). However, surface defects in inorganic CsPbBr3 perovskite prepared by vapor deposition severely limit the optoelectronic performance of perovskite solar cells. To address this issue, a strategy of doping a trace amount of KBr into perovskite by vapor deposition is adopted, effectively improving the quality of the film, reducing surface defect concentration, and enhancing the transportation and extraction of charge carriers. Simultaneously, fully physical vapor deposition technology is employed to fabricate perovskite solar cells with an average visible light transmittance of 44%. These devices exhibited an ultrahigh open-circuit voltage of 1.55 V and a superior power conversion efficiency (PCE) of 7.28%, demonstrating excellent moisture and heat resistance. Moreover, the corresponding 5 cm × 5 cm modules achieve a PCE of 5.35% with great thermal insulation capability. This work provides an approach for fabricating highly efficient all-inorganic perovskite solar cells with high average visible light transmittance, demonstrating new insights into their application in building-integrated photovoltaics.

Failure analysis of strain clamps on a ± 800 kV transmission line

During X-ray testing of a ± 800 kV ultra-high voltage direct current transmission line tension clamp, it was found that the internal steel core had broken. To investigate the cause of the steel core fracture, the failed clamp was dissected and analyzed, including chemical material testing, mechanical performance testing, fracture morphology inspection, and analysis of the compression process of the tension clamp. A preliminary judgment was proposed on the cause of the internal steel core fracture of the tension clamp, And verification experiments and simulation analysis were conducted to preliminarily determine the cause of the steel core fracture, and it was ultimately concluded that the main reason for the steel core fracture was the incorrect compression sequence of the large cross-section wire tension clamp.

Characterization of electric field distribution in valve-side casing of 500 kV converter transformer considering AC and DC mixed voltage

The converter transformer, as one of the indispensable core devices in the ultra-high voltage direct current (UHVDC) transmission system, exhibits highly complex electric field distribution characteristics within the valve-side bushing. In-depth research into the electric field distribution characteristics and variation patterns of the valve-side bushing under both alternating current (AC) and direct current (DC) voltage conditions is crucial for ensuring the reliable operation of the transmission system. This study focuses on investigating the electric field distribution of the valve-side bushing under AC and DC voltage excitations. A full-scale finite element model of the valve-side bushing of the converter transformer is constructed using finite element simulation software for modeling and research purposes. The results indicate that the internal electric field distribution of the bushing is generally similar under both AC and DC voltage excitations. However, in the SF6-filled region, a steeper voltage drop is observed under DC excitation compared to AC. The space charges generated in the DC electric field due to field polarization have a significant impact on the distortion of the electric field on the inner and outermost layer electrode plates. These conclusions provide theoretical guidance for the insulation design of the valve-side bushing in converter transformers at the 500 kV voltage level and similar ratings.

Power frequency shunting property of whole group 500kV UHV Series compensated MOVs containing 10 Served and 1 New MOVs

Metal OxideVaristors(MOV) are widely used as protective devices of series compensation capacitor banks for Extra-High Voltage and UHV (Ultra High Voltage) large capacity long-distance transmission lines. As MOVs work in the strong nonlinear part of the V-I curve, the aging and deterioration degree of different MOVs in parallel connection are different, leading to one or two MOVs in the entire heavy-duty group being the first to be damaged. The uniformity of current is an important criterion for how to control the power frequency shunting of multiple parallel MOVs for series compensation capacitor banks. In order to investigate whether replacing damaged MOVs with newly manufactured MOVs of the same specifications can meet the uniformity requirements, the power frequency reclosure tests are carried out with an average voltage peak of 166.3 kV on MOV group with 10 served and 1 new MOV for the first time with actual 500 kV MOVs. Research finds that when the DC (Direct Current) U2mA mean absolute error of MOVs is 0.2%, the current mean absolute error is about 6%. After testing, the temperature rise of each MOV ranges from 22.9 to 36.3 °C. The test results in this paper provide a direct data basis for confirming the criterion of DC reference voltage and shunt uniformity at large power frequency current on actual 500 kV series compensation MOVs apparatus.

All-Wood-Based Ionic Power Generator with Dual Functions for Alkaline Wastewater Reuse and Energy Harvesting.

Water-induced electricity harvesting has gained much significance for energy sustainability. Bio-based hydrovoltaic materials increase the attractiveness of this strategy. Although promising, it faces a challenge due to its reliance on fresh water and its inherently low power output. Herein, the energy from alkalinity-gradient power generation demonstrated the feasibility of reuse of alkaline wastewater to develop an all-wood-based water-induced electric generator (WEG) based on ion concentration gradients. The intermittent water droplets bring about uneven distribution of electrolyte and endow delignified wood with the difference of ion concentration along aligned cellulose nanochannels, thus supplying electrical power. The practice of using alkali reservoirs, including industrial wastewater, further contributes to electricity generation. The cubic WEG with a side length of 2 cm can produce an ultrahigh open-circuit voltage of about 1.1 V and a short-circuit current of up to 320 μA. A power output of 6.75 μW cm-2 is correspondingly realized. Series-connected WEGs can be used as an energy source for commercial electronics and self-powered systems. Our design provides a double value proposition, allowing for sustainable energy generation and wastewater reuse.

A fluorine-based strong and healable elastomer with unprecedented puncture resistance for high performance flexible electronics

There is usually a trade-off between high mechanical strength and dynamic self-healing because the mechanisms of these properties are mutually exclusive. Herein, we design and fabricate a fluorinated phenolic polyurethane (FPPU) elastomer based on octafluoro-4,4′-biphenol to overcome this challenge. This fluorine-based motif not only tunes interchain interactions through π−π stacking between aromatic rings and free-volume among polymer chains but also improves the reversibility of phenol-carbamate bonds via electron-withdrawing effect of fluorine atoms. The developed FPPU elastomer shows the highest recorded puncture energy (648.0 mJ), high tensile strength (27.0 MPa), as well as excellent self-healing efficiency (92.3%), along with low surface energy (50.9 MJ m−2), notch-insensitivity, and reprocessability compared with non-fluorinated counterpart biphenolic polyurethane (BPPU) elastomer. Taking advantage of the above-mentioned merits of FPPU elastomer, we prepare an anti-fouling triboelectric nanogenerator (TENG) with a self-healable, and reprocessable elastic substrate. Benefiting from stronger electron affinity of fluorine atoms than hydrogen atoms, this electronic device exhibits ultrahigh peak open-circuit voltage of 302.3 V compared to the TENG fabricated from BPPU elastomer. Furthermore, a healable and stretchable conductive composite is prepared. This research provides a distinct and general pathway toward constructing high-performance elastomers and will enable a series of new applications.

Meteorological Characteristics of a Continuous Ice-Covered Event on Ultra-High Voltage Transmission Lines in Yunnan Region in 2021

Yunnan plays a pivotal role in transmitting electricity from west to east within China’s Southern Power Grid. During 7–13 January 2021, a large-scale continuous ice-covering event of ultra-high voltage (UHV) transmission lines occurred in the Qujing area of eastern Yunnan Province. Based on ERA5 reanalysis data and meteorological observation data of UHV transmission line icing in China’s Southern Power Grid, the synoptic causes of the icing are comprehensively analyzed from various perspectives, including weather situations, vertical stratification of temperature and humidity, local meteorological elements, and atmospheric circulation indices. The results indicate a strong East Asian trough and a blocking high directing northern airflow southward ahead of the ridge. Cold air enters the Qujing area and combines with warm and moist air from the subtropical high pressure of 50–110° E. As warm and cold air masses form a quasi-stationary front over the northern mountainous area of Qujing due to topographic uplift, the mechanism of “supercooling and warm rain” caused by the “warm–cold” temperature profile structure leads to freezing rain events. Large-scale circulation indices in the Siberian High, East Asian Trough, and 50–110° E Subtropical High regions provided clear precursor signals within 0–2 days before the icing events.