High Voltage Environment Research Articles

Composite Micro-Nanoarchitectonics of MMT-SiO2: Space Charge Characteristics under Tensile State.

Low density polyethylene (LDPE) is a good insulating material which is widely used in cable materials due to its excellent insulation and processability. However, in the DC high voltage environment, pure polyethylene materials still face many problems, the most serious of which is space charge accumulation. The cable will inevitably be subjected to tensile stress during production, installation and operation. Therefore, it is of great significance to study the effect of stretching on the microstructure and space charge characteristics for polymers and their composites. In this paper, MMT/LDPE micro-composites, SiO2/LDPE nano-composites and MMT-SiO2/LDPE micro-nano-composites were prepared by melt blending. Mechanical stretching was carried out on pure LDPE materials and the above three kinds of composite materials. Each material was stretched according to four stretching ratios, which are 0%, 5%, 10% and 20%. The crystal morphology was observed by polarizing microscope (PLM), the crystallization perfection was tested by differential scanning calorimetry (DSC), and the space charge distribution inside each sample was measured by pulsed electro-acoustic (PEA) method. At the same time, the average charge density and apparent charge mobility for samples during depolarization were calculated and analyzed. The experimental results show that when the pure low density polyethylene sample is not stretched, its crystal structure is loose. Tensile stress can make the loose molecular chains align in LDPE and improve its crystalline structure, which is helpful to restrain the accumulation of space charge inside the sample. For MMT/LDPE, SiO2/LDPE and MMT-SiO2/LDPE composites, their internal crystal structure is compact. Stretching will destroy their original crystal structure at first, and then disorder molecular chains inside the three composite materials. With the increase of stretching ratio, the molecular chains begin to orient along the direction of force, the crystallization tends to be perfect gradually, and the space charge accumulation in samples also decreases. From the calculation results of apparent charge mobility for each sample, with the increase of stretching ratio, the trap depth and trap density inside samples firstly increased and then decreased.

Photoelectrocatalytic carbon dioxide reduction: Fundamental, advances and challenges

With the rising global population, increasing energy demand and rapid climate change, great concerns have been raised for environment and energy security in future. Solar-driven CO 2 reduction provides a promising way to deal with energy crisis and global warming, which has been widely concerned. Photoelectrocatalysis technology can effectively utilize solar energy and avoid to use high-temperature and high-voltage reduction environment by integrating the vantages of both photocatalysis and electrocatalysis, which exhibits a broad application prospect of CO 2 reduction with a high efficiency and excellent selectivity. In this review, basic principles of CO 2 reduction by photocatalysis, electrocatalysis and photoeletrocatalysis are briefly reviewed, also comparing the technical characteristics of the above technologies. Different photoelectrocatalytic systems for CO 2 reduction are described and compared. The several key influencing factors of photoelectrocatalytic performance of CO 2 reduction are discussed, including interaction between reaction molecules and catalysts, reaction conditions and influence of photoelectrode. Then, the advances on reaction mechanisms and strategies of performance enhancement by optimizing photoexcitation, charge separation efficiency and surface reaction were reviewed. Besides, the challenges and prospects of photoelectrocatalytic CO 2 reduction will be also discussed.

Analysis of the Influence of the Breaking Radiation Magnetic Field of a 10 kV Intelligent Circuit Breaker on an Electronic Transformer.

The development of the smart grid requires the distribution switch to not be limited to the original breaking function. More functional requirements lead to more complex switch structures, especially the intelligent processing unit on the secondary side. A technology called primary and secondary integration optimizes the structure of the switch, which greatly increases the intelligence level of the switch, but also has disadvantages. The secondary intelligent unit is arranged close to the primary high-voltage electromagnetic environment, and the distribution switch is prone to failure due to electromagnetic interference. In order to explore the influence of electromagnetic interference on it, a transient electromagnetic interference simulation test platform was built for a 10 kV intelligent distribution switch based on the principle of spherical gap arc discharge, and the interference signal of the intelligent distribution switch was measured; the law of the spatial magnetic field near the electronic transformer is mainly studied in this paper. The shielding effectiveness of the distribution terminal of the switch was analyzed, and the interference of the power line of the sensor merging unit circuit board was calculated. The results show that the electronic transformer may have serious faults under continuous strong transient electromagnetic interference. The electromagnetic transient simulation test system studied in this paper can evaluate the anti strong electromagnetic interference ability of the electronic transformer.

Research on Visual Detection Algorithm of 500kV High Voltage Live Operating Robot

The 500kV transmission line is exposed to the outdoor for a long time. It is affected by complex climate charge change and other factors which leads to line connection parts bolt loosening, wire breaking and fixture damage and other line failures. In order to ensure the stable transmission of electric energy, power operators need to wear shielding suits and work in the high-risk and high-voltage environment. Use of electric power operation robot instead of manual operation is an effective way to liberate maintenance staff labor. But robots still have some problems such as low degree of automation and low efficiency of power operation. Machine vision detection technology in recent years has been widely used in major areas including deep learning as emerging visual detection technology shows excellent performance. In this paper, the vision detection algorithm is studied respectively for the bolt fastening end working device and wire repairing end working device of the live transmission line robot to improve the operating efficiency of the robot.

Electric Field Mitigation in High-Voltage High-Power IGBT Modules Using Nonlinear Conductivity Composites

Wide bandgap (WBG) semiconductor devices are developing rapidly due to their superior performance compared to traditional silicon-based devices. However, the packaging technology of traditional devices has limited the application of WBG semiconductor devices because of the challenges in electrical insulation. The complex environment of high blocking voltage, high frequency, and high temperature is the major reason for insulation failure of encapsulation structure. Therefore, in this article, an epoxy resin composite with nonlinear conductivity is proposed to be used as a coating to improve the electric field distribution of high-voltage high-power IGBT modules. First, an electrical field simulation model was built considering the thermal stress. It was found that the electric field in high temperature was improved compared with that in room temperature due to the temperature-dependent conductivity of silicone gel. Nevertheless, the risk of insulation failure still exists. After the application of nonlinear conductivity materials (NCMs) coating, the maximum electric field at the triple junctions and the ratio of electric field distortion in high field areas were significantly decreased. Further analysis showed that the optimization ratio of electric field increased with the increase of the blocking voltages or power losses in the IGBT chip. The results have demonstrated that the NCMs can reduce the maximum electric field in the IGBT encapsulation structure by 73% under the operating conditions of 120 W 10 kV. Partial discharge (PD) tests show that the partial discharge initial voltage (PDIV) of the substrates with NCM coating is increased by 33% compared with the normal encapsulation structure and the coating significantly inhibits the growth of electric trees. The presented results indicate that the NCMs have the potential to improve the insulation performance of high-voltage high-power IGBT modules.

MoO42−-mediated engineering of Na3V2(PO4)3 as advanced cathode materials for sodium-ion batteries

Sodium vanadium phosphate [Na3V2(PO4)3] with high voltage platform, low cost and environment friendliness has been considered as one of the most promising candidates as cathodes for high-performance sodium-ion batteries. However, the sodium storage property of Na3V2(PO4)3 is limited because of its low electronic conductivity and poor kinetic performance. Herein, MoO42−-doped Na(3+2x)V2(PO4)(3-x)MoO4(x) [NVP-MoO4 (x), x = 0, 0.05, 0.10, 0.15] have been developed and prepared by a feasible solid-state reaction. The optimal NVP-MoO4 (0.10) delivers a high initial capacity of 108.9 mA h g−1 and presents an excellent capacity retention of 91.5% at 1 C after 150 cycles. In addition, the NVP-MoO4 (0.10) shows a good rate capability, delivering a relatively high capacity of 84.2 mA h g−1 at 50 C. The results of sodium storage measurement and density of states calculation indicate that MoO42− doping can significantly enhance the structural stability, promote the kinetics behavior and boost the electronic conductivity of the materials. In-situ XRD test reveals that the electrochemical reaction of the NVP-MoO4 (0.10) exhibits a highly reversible phase transition process. This work provides a new insight for the design of advanced cathodes for high-performance sodium-ion batteries by the strategy of unique anion doping.

The promotion of sulfuric vacancy in two-dimensional molybdenum disulfide on the sensing performance of SF6 decomposition components

A long-running SF6 insulating gas decomposes without being detected in time would cause incalculable consequences, therefore, real-time monitoring towards SF6 status is of practical significance. Currently, the gas-sensitive properties of two-dimensional materials are the focus and hotspot of gas sensor research, however, in practical situations, material preparation and device fabrication will inevitably bring about defects. Therefore, the effects of sulfuric vacancy (SV) in molybdenum disulphide are proposed and explored, and a comparative study of gas-sensitive properties (pristine MoS2 vs SV- MoS2) is carried out using density functional theory based on the first principles. Constructing typical adsorption models for SF6 decomposition components on monolayer, together with analyzing the optimum adsorption structures, adsorption energy, density of states, molecular orbitals, electrical conductivity and co-adsorption behaviors. The results show that the SV brings a defective state to MoS2 monolayer, which contributes to an overall increase in the adsorption energy for the decomposition components (the increase > 0.15 eV), making the undifferentiated adsorption effect selective for SO2F2. The physical interaction between the decomposition products and SV-MoS2 monolayer is more favorable for desorption. These results indicate it is appropriate for detecting SF6 status in high-voltage insulation environments, with pointers to practical applications for two-dimensional materials.

Test Analysis of Insulation and Moisture Resistance of Insulation Support Plate of Electrical Penetration in Containment of Nuclear Power Plant

The variation trend with temperature and relative humidity of water absorption, dielectric loss, relative permittivity, insulation resistance, volume resistivity, surface resistivity, and dielectric strength of polysulfone are measured. Polysulfone used as the insulating support plate on the medium voltage electrical penetration is designed and produced by Nuclear Power Institute of China (NPIC). The result shows that the relative humidity of environment has a significant effect on the water absorption of polysulfone. When the ambient temperature is 23℃ and the relative humidity increases from 30% to 98%, the corresponding water absorption increases from 0.012% to 0.106%, with a growth rate of 783.3%. The insulation resistance decreases gradually with the increasing of ambient temperature and relative humidity, with a maximum decreasing of 99.82%. However, the interphase insulation resistance of the insulation support plate of the electrical penetration is always greater than 200 TΩ. At the same time, the insulation resistance is greatly affected by its surface resistivity. The variation trend of insulation resistance and surface resistivity with ambient temperature and relative humidity is very close. The relative permittivity and dielectric strength are little affected by the ambient temperature and humidity. The insulation support plate of the medium voltage electrical penetration designed and produced by NPIC is with excellent moisture resistance and electrical insulation performance, and can work stably and reliably in high voltage, high temperature and high humidity environment.

Spark Safe

Test engineers are adapting to the high-voltage environments of the next generation of aircraft with vital safety measures

A High Failure-Current Gate-Controlled Dual-Direction SCR for High-Voltage ESD Protection in 0.18-μm BCD Technology

To make a dual-direction silicon-controlled rectifier (SCR) that is highly robust in a high-voltage environment, a gate-controlled dual-direction SCR (GC-DDSCR) device is proposed. After analyzing the working principle of the device through the equivalent circuit and 2-D device simulation, the electro-static discharge (ESD) characteristics of the device are verified through the transmission line pulse (TLP) test. The failure current of the GC-DDSCR structure is greatly improved to 14.19 A compared with only 3.53 A of the same size traditional dual-direction SCR (TDDSCR) structure. The trigger voltage and the holding voltage of the GC-DDSCR are 24.23 and 20.15 V, respectively. In addition, this article explains the principle of GC-DDSCR devices with high protection capability. That is, because the device has a polysilicon gate electrode shorted to the anode (cathode), the electric field effect generated by the gate promotes carrier movement in the SCR path. Thus, the electric field force promotes the opening of the SCR path of the device and the direction of the electric field force is always consistent with the current direction. The overall failure capability of the device is effectively improved.

Power supply for on-line monitoring device of power lines based on double-half ring core

In order to solve the problem of insufficient energy supply of the on-line monitoring device of the transmission line, a sensor energy acquisition scheme directly installed on the transmission line is proposed. In the current power supply, induction power supply is a kind of energy extraction method with better practical applicability. Since the monitoring devices and electronic equipment on the transmission line are often in a strong magnetic field and high voltage environment, designing a stable and reliable power supply is the guarantee for the stable operation of the monitoring devices and electronic equipment. This paper presents a structure of energy-absorbing iron core with two semi-circular magnetic cores, and studies the magnetic saturation problem in the inductive power supply and the design of the DC output circuit.

Internal Microscopic Diagnosis of Accelerated Aging of Proton Exchange Membrane Water Electrolysis Cell Stack.

The hydrogen production reaction of the proton exchange membrane (PEM) water electrolysis cell stack is the reverse reaction of the fuel cell, but the water electrolysis operation requires high pressure, and the high pressure decomposes hydrogen molecules, thus aging or causing failure in the water electrolysis cell stack. In addition, there are five important physical parameters (current, voltage, flow, pressure and temperature) inside the water electrolysis cell stack, which can change the performance and shorten the life of the cell stack. However, the present techniques obtain data only by external simulation or single measurement; they cannot collect the internal real data in operation instantly and accurately. This study discusses the causes for aging or failure, and develops an internal real-time microscopic diagnosis tool for accelerated aging of the PEM water electrolysis cell stack. A flexible integrated (current, voltage, flow, pressure and temperature) microsensor applicable to the inside (high voltage and electrochemical environment) of the PEM water electrolysis cell stack is developed by using micro-electro-mechanical systems (MEMS) technology; it is embedded in the PEM water electrolysis cell stack for microscopic diagnosis of accelerated aging, and 100-h durability and reliability tests are performed. The distribution of important physical parameters inside the PEM water electrolysis cell stack can be measured instantly and accurately, so as to adjust it to the optimal operating conditions, and the local aging and failure problems are discussed.

A Novel Dual-Directional SCR Structure With High Holding Voltage for 12-V Applications in 0.13-μm BCD Process

This article proposes a dual-directional silicon-controlled rectifier (SCR) with a novel structure and high holding voltage to improve the electrostatic discharge (ESD) design area efficiency in high-voltage environments. In terms of structure, by decreasing the emitter injection efficiency of the p-n-p parasitic bipolar transistor formed at the bottom of the gate region, the SCR positive feedback gain is reduced, which endows the proposed device with improved snapback characteristics compared with the conventional low-voltage triggering SCR (LVTSCR) and low-trigger dual directional SCR (LTDDSCR). This article conducted 2-D and mixed-mode simulations to compare and analyze the operating principles of the proposed and traditional devices. Additionally, experimental devices were fabricated under the same conditions using the 0.13- $\mu \text{m}$ process to verify their electrical properties and latch-up immunity by measuring the transmission line pulse (TLP) and transient latch-up (TLU). This article also conducted a detailed analysis on the optimization of electrical properties for the ESD design window of the proposed device according to the design variables and application of segment topology, and also analyzed the temperature reliability using a hot chuck control system. The measurement results reveal that the proposed device is highly suitable for the 12-V-class ESD design window, has improved reliability, and can provide excellent area efficiency in related applications.

Reliability limitations from crystal defects in thick GaN epitaxial layers

The vertical power switching devices made from GaN and related nitride semiconductors contain a high density of crystal defects, especially in the thick epitaxial drift layers. Most of these defects are present initially in starting wafers and some are generated during device processing. There is little conclusive evidence so far on the exact role that the crystal defects play on device performance, manufacturing yield, and more importantly, long-term field-reliability especially when devices are operating under extreme stressful high voltage environments. This paper provides the progress of characterization of thick GaN power semiconductor material epitaxial layers and the potential impact crystal defects may have on high-density power switching electronics. The investigation also presents simulated results of the electric field distribution through thick epitaxial (greater than 10 mm) region.

Aging performance investigation and improvement of modified polyurethane composites for composite overhead transmission line towers

Fiber reinforced plastic has the characteristics of light weight, high strength, good aging performance and strong insulation performance, so the composite overhead transmission line tower may become a substitute for the traditional iron tower in the future. At present, the researches on the composite transmission tower mainly focused on the electrical properties, few on the aging performance, which is an unknown influence on the transmission line with composite transmission towers. In this paper, a 5000 h multi-factor accelerated aging test was used to investigate the aging performance of modified polyurethane (PU) composites for composite transmission towers. The test periodically simulated the environment of high voltage, rainfall, humidity, alternating high and low temperatures, ultraviolet and salt fog. The results show that pultrusion process PU composites are more suitable to be used as the materials of composite towers because of its higher bending modulus. Then, a research on PU composites aging performance improvement scheme was carried out by another multi-factor accelerated aging test. The results show that the mixture of ultraviolet absorber and ultraviolet stabilizer is helpful to improve the aging performance of PU composites, and the addition of 0.275wt% of the total amount with a ratio of 1:1 is a viable scheme.

SmartConnector: A Self-Powered IoT Solution to Ease Predictive Maintenance in Substations

The increased dependency on electricity of modern society makes reliability of power transmission systems a key point. This goal can be achieved by continuously monitoring power grid parameters, so possible failure modes can be predicted beforehand. The deployment of Internet of Things (IoT) solutions and new low-cost sensors eases this task. This paper presents a self-powered IoT solution for real-time monitoring of different parameters of a high-voltage substation connector. This new family of power connectors is called SmartConnector, which incorporates a thermal energy harvesting system powering a microcontroller that controls a transmitter, and several electronic sensors to measure the temperature, current and voltage drop across the connector to estimate the electrical contact resistance (ECR) of the connector. These measurements are sent remotely via a Bluetooth 5 wireless communication module to a local gateway, which transfers the measured data to a database server for storage and further analysis and visualization. Different experiments are presented to validate the feasibility of the SmartConnector in terms of measurement accuracy in comparison with a wired system. The proposed thermal energy harvesting is tested to calculate the optimum data transfer rate needed for extending the lifetime of the SmartConnector . A shielding solution for the electronics operating under this high voltage environment is also proposed.

Sensor Comparison for Corona Discharge Detection Under Low Pressure Conditions

Low pressure environments, situate insulation systems in a challenging position since partial discharges (PDs), corona and arc tracking are more likely to develop. Therefore, specific solutions are required to detect such harmful phenomena before major failure occurrence. This paper deals with three low-cost and small-size sensing methods, i.e., a single loop antenna, a visible-UV imaging sensor and the measurement of the leakage current to detect corona in the early stage, thus anticipating the appearance of severer effects such as arc tracking or disruptive breakdown. The three studied methods can be applied for an on-line monitoring of corona activity under low pressure environments, thus being compatible with predictive maintenance approaches. This on-line monitoring can be used to develop improved electrical protection devices able to detect such effects in an initial stage, thus improving current solutions which are unable to do so. All three studied sensors give consistent linear responses within the studied pressure range, i.e., 10-100 kPa, with almost no drift. The sensitivity of the visible-UV imaging sensor is slightly lower than that of the others, but it has the advantage of directly locating the discharge points. Results presented in this paper can be very useful for the more electrical aircraft (MEA), which is forcing electrical distribution systems to operate at higher voltage levels. Due to the little experience and scarcity of published data, the experimental results presented in this paper can be valuable for a better understanding of the combined action of high voltage and low pressure environments.

The Synthesis of Soil Resistivity and EMF of underground Cable combined with 3-D Electromagnetic Field Study in Analyzing the Grounding Touch

The earthing analysis is proposed in this paper. The effects of 3-D electromagnetic field and the influences of stray currentare considered in the text simultaneously. The activity in the high-voltage environment is risky of being injured by electricshock. The safety of personnel in and around electric power the installations has been a prime concern. Specially, the safety isgenerally in terms of the allowable touch and step voltages. These voltages are related to the earthing resistance of human foot.I ofn order to increase the safety of personnel, a high resistivity surface layer of gravel is normally existed in the substationswitchyards or other high voltage areas. The thickness of this layer will affect the calculation of the earthing resistance ofhuman foot. Thus, the effect of soil resistivity will be considered in this paper. Among them, the electromagnetic field andhumidity factors are also considered in this paper. As a result, the surface layer of gravel can be used to reduce the earthingresistance of human foot. The equivalent model of human foot was modeled by the circular plate conductor in the past. Whichconsider the beauty of the environment, most of the transmission lines are in the surface, so the transmission line generated bythe discrete current will affect the earthing resistance estimation, thus the proposed paper will consider the composition of thespecial function which is the mathematical calculus popularized by the basic theorem of calculus. On the other hand, the dampingredients, temperatures, and soil resistivity on the surface will also be considered in this paper. This paper research into theproposed method for estimating the earthing resistance of human foot and proposes an equivalent model for calculating thegrounding resistance of human foot. The comparisons of the method are also shown in this paper.

A hybrid gel polymer electrolyte with imide groups modified by the coupling agent and its application in electrochromic devices

Herein, a new class of hybrid gel polyelectrolytes (GPEs) through sol–gel technology has been synthesized and characterized. The reaction mechanism of gel polymer electrolyte is based on the hydrosilylation and sol–gel reactions of poly(propylene glycol) bis(2-aminopropyl ether), pyromellitic dianhydride, glycidoxypropyltrimethoxysilane, and 3-isocyanatepropyltriethoxysilane. The gel polymer electrolyte exhibits excellent ion-conductive and thermostability performance. The maximum ionic conductivity value of 3.1 × 10−4 S cm−1 and Li-ion transference numbers (t+) reaching 0.49 at 25 °C are achieved for the gel polymer electrolyte. The thermogravimetric analysis results show that the electrolyte samples are nearly 1% weight loss when the temperature reaches up to 100 °C. The gel polymer electrolytes display a prominent electrochemical stability, which could bear potential up to 10 V. In addition, the prototype electrochromic device using electrolyte sample as the conductive layer presents excellent coloration efficiency of 198.9 cm2 C−1, stable cycle of 125 periods under 5-V high-voltage environment, and stable cycling performance (achieving 300 stable cycles from the voltage of −3.5 to 2.5 V). As a result, the GPEs exhibit an excellent electrochemical performance, which is suitable for electrochromic application and offers a remarkable prospective.

Electric field effects on oxidation coking deposition of n-pentane in needle-tube flow reactor

For the purpose of inhibiting carbon deposition in the low-temperature oxidation process of aviation fuel in the fuel injector, a new multi-field coupling method was proposed. 95% pure n-pentane was selected as the experimental fuel. A needle-tube flow reactor that could provide a high voltage environment was designed. Thermal oxidation deposits under the voltage from 0 V to 5000 V were compared at inlet fuel temperature of 600 K. The deposits on the wall and the electrode of the reactor under different voltages were measured by scanning electron microscope (SEM) and temperature programmed oxidation (TPO). The experimental results show that the discharge can reduce the diameter of the deposits and with the increase of the voltage, the maximum coke formation on the reactor wall was reduced by 19.01%. Through oxygen content analysis, the discharge consumed more dissolved oxygen. The flow field in the reactor was studied by numerical simulation. Maxwell and Navier-Stokes equations for a three-dimensional physical model were solved by the finite volume method. The secondary flow and the increased velocity caused by the discharge retarded the accumulation of deposits. This paper used the fuel stable discharge phenomenon to provide new means for suppressing the oxidation deposition.