最新刊期
卷 60 ， 期 4 ， 2024
- 摘要：Copper-chromium alloy materials, as one of the most important contact materials in the field of electrical contacts, have been widely used in vacuum interrupter. CuCr55 contact materials are prepared by arc melting method and the micro-structures of fusion casting CuCr25, fusion infiltration CuCr50 and arc melting CuCr55 materials are compared and the vacuum arc ignition and ablation characteristics of arc melting CuCr55 contacts are particularly analyzed. A high-speed camera is used to photograph the arcing characteristic of short circuit current and the critical current for generating anode spots is obtained. The electron microscope is used to observe the micro-morphology of the contact surface after ablation, the material fracture, fine cracks or significant bulging are not happened on the contact surface. The research results show that the arc melting CuCr55 contacts have a micro structure with fine and uniform chromium particles, diffuse distribution of micro structure spheroidization, and good uniform ablation characteristics.关键词：vacuum interrupter;contact material;vacuum arc;material ablation19|293|0更新时间：2025-04-26
- 摘要：The critical breakdown electric field strength of hot gas is the basic data to assess the post-arc electrical breakdown characteristics of high-voltage circuit breakers. In this paper, the critical electric field strength of C5F10O/CO2 gas mixture in the range of C5F10O mixing ratio k=0-10% and intensity of pressure at 0.1-2.0 MPa and at 300-4 000 K is studied. Based on the mathematical model of the law of mass action, the equilibrium components of the gas mixture at different temperatures are obtained. The Boltzmann equation is solved by two-term approximation method. The electron energy distribution function, equivalent ionization and adsorption coefficient of the gas mixture are analyzed so to obtain the critical reduced electric field strength and critical electric field strength of the gas mixture. The results show that at 0.6 MPa, when the temperature is lower than 3 000 K, the critical electric field strength of the gas mixture with k=0-10% is gradually lower than that of SF6 with the decrease of temperature. However, in case of the temperature above 3 000 K, the critical electric field strength of the gas mixture is more than 1.2 times that of SF6, which has strong insulation ability. The research results can provide a reference for the study of post-arc dielectric breakdown properties of high voltage circuit breakers filled with C5F10O/CO2 gas mixture.关键词：C5F10O/CO2 gas mixture;SF6 alternative gas;electrical breakdown characteristics;critical electric field strength;particle component;Boltzmann equation13|156|1更新时间：2025-04-26
- 摘要：For studying the compatibility of vegetable insulating oil with insulating paper materials of transformer, 9 different types of insulating paper materials commonly used in transformers are combined with vegetable insulating oil to study the performance variation of vegetable insulating oil and insulating paper after 164 h of aging. The performance difference of the insulation paper and insulating oil before and after the thermal aging experiment is observed, and the movement viscosity, moisture content, acidity value, dielectric loss factor, breakdown voltage of the oil paper combination as well as gas chromatographic analysis of the oil are tested. The results show that the movement viscosity of the vegetable insulating oil has changed to some extent after aging, but the the structural integrity and functional stability remain good. Moreover, the vegetable-based insulating oil is highly compatible with 22HCC Dennison insulation paper. Compared to other test group, the compatibility of the electrical insulating paper and vegetable insulating oil is weak. After the thermal aging, the breakdown voltage of the metallized crepe paper, laminated paper board and the vegetable insulating oil is lower and the their compatibility is weak. These findings provide a basis for selecting insulation materials with good compatibility and optimizing insulation structures to ensure the safe and stable operation of vegetable-based insulating oil transformers. Furthermore, the study results help promote and apply vegetable insulating oil and promote the development of sustainable energy.关键词：vegetable insulating oil;paper-oil insulation;compatibility;thermal aging;dissolved gases11|165|0更新时间：2025-04-26
- 摘要：Epoxy resin is widely used as such insulation parts of electrical equipment as support insulators and insulating rods due to its excellent electrical insulation, heat resistance, mechanical properties and good plasticity. With the increase of voltage level of electrical equipment, the operation is becoming more and more critical and the insulation failure caused by mechanical stress is becoming more prominent. Based on the reference both at home and abroad, the research progress on insulation breakdown due to electrical tree deterioration of epoxy resin under mechanical stress is reviewed in this paper. The morphological characteristics of electrical tree growth under tensile and compressive stresses are introduced on the bases of different bearing stresses of epoxy resins, and the influence of mechanical stress on electrical tree growth under temperature conditions is summarized. The mechanism of electrical tree deterioration of insulation materials under mechanical stress is explored based on the physical micro-structure and charge transport characteristics of epoxy resin molecular chains and also from an energy perspective. The key issues and solutions for the study of electrical tree branches in epoxy insulation components of electrical equipment is described, which provides a reference for the development of epoxy resin insulation materials with high insulation performance.关键词：epoxy resin;tensile stress;compressive stress;temperature gradient;electrical tree;insulation breakdown15|297|1更新时间：2025-04-26
- 摘要：Non-cross linked insulating materials have become a research hot spot of cable insulating materials due to their such advantages as low energy consumption, recyclability and excellent electrical and mechanical properties. However, little research has been reported on the matching non-cross linked semi-conductive shielding materials. The dispersion of conductive carbon black has a significant impact on the performance of shielding materials. In this paper, non-cross linked cable shields are prepared by melt blending method using linear low density polyethylene (LLDPE) as the base resin and white oil as the dispersant. The effects of white oil content on the dispersion of carbon black, crystallization properties, volume resistivity and mechanical properties of shielding material are studied. The results show that the addition of white oil will promote the dispersion of carbon black, but the excessive content of white oil will reduce the crystallinity of the shielding material, increase its volume resistivity and reduce the tensile strength and breakage elongation. When the white oil content is 2 wt%, the shielding material has the lowest volume resistivity and the best mechanical properties. This study provides a reference for the application research of non-cross linked semi-conductive shielding material in vinyl non-cross-linked cables.关键词：semi - conductive shielding material;white oil;conductive carbon black;non - cross linked polyethylene;dispersant;linear low density polyethylene (LLDPE)9|102|0更新时间：2025-04-26
- 摘要：Under the background of ‘Dual Carbon’, carbon emission is one of the important evaluation criteria for the material selection of cable bracket. However, there is currently a lack of relevant models for calculating carbon emission of cable bracket. In this paper, a carbon emission calculation model for the whole life cycle of cable bracket based on the carbon emission factor method is constructed, in which the impact of brackets’ material consumption and eddy current losses on carbon emission activities is considered. The total consumable material of cable bracket in the whole life cycle is calculated considering the load-bearing performance and corrosion rate of different material, and the eddy current loss is calculated considering the induced current capability of different material and the corresponding carbon emission is calculated in combination with carbon emission factor. Finally, the Xiongdong-Zanxi 220 kV cable project in China is taken as an example, the whole life cycle carbon emission of the line using two different material brackets is calculated. The results show that the carbon emission of 304L stainless steel bracket is much lower than that of Q235 carbon steel bracket. While, 304L stainless steel as a new material for cable bracket has good energy-saving and emission reduction effects.关键词：carbon emission;life cycle;cable bracket;carbon steel;stainless steel12|269|2更新时间：2025-04-26
- 摘要：HTV silicone rubber composite insulator is an important part of the overhead transmission line, its abnormal febrile state will aggravate the aging of the shed in the long-term outdoor operation, which will, in case of serious condition, threaten the safe operation of the transmission line. Through 480 h artificially thermal aging test on the shed samples of the HTV silicone rubber composite insulator and measurement of such multiple performance parameters as Shore hardness, WCA, FTIR, micro topography and surface flashover voltage, the thermal aging characteristics of the sample are analyzed. The study results show that the hardening of the shed can be intensified and the hydrophobicity of the material is reduced after long-term thermal aging. With the increase of thermal aging time, the aging degree of the shed sample increases, and the surface flashover voltage increases first and then decreases.关键词：silicone rubber;composite insulator;thermal aging;hydrophobicity;surface flashover11|279|0更新时间：2025-04-26
- 摘要：With the gradual implementation of the ‘dual Carbon’ strategy, the cross arm with new composite material is gradually replacing the iron cross arm and its application in power lines is becoming more and more extensive. In this paper, a 66 kV lightweight and high-insulating composite insulation cross arm with a density of 1.1 g/cm3 is prepared and subjected to such test as water absorption, dye penetration, water diffusion leakage current, breakdown strength, thermal induction, mechanical and electrical performance. The test results show that the mass water absorption rate of the sample filled with core material is 0.141%, the water diffusion leakage current is less than 103.3 μA and the AC breakdown strength is higher than 71 kV/cm. All the performance indexes can reach the requirements of DL/T 1580—2016 technical specification for core bars for bar composite insulators in terms of physical and chemical properties, electrical properties and mechanical properties. Both the sample and the cross arm as a whole have no obvious defects and the cross arm has good aging resistance. At the same time, the lightweight and high-insulation composite insulation cross arm has good microscopic interface bonding performance, and the insulation performance is superior to that of the traditional solid cross arm, which meets the application needs of the new power system for clean, low-Carbon, safe and reliable applications.关键词：light-weight and high insulating material;composite insulated cross-arm;insulated core;electrical performance9|76|0更新时间：2025-04-26
- 摘要：Under the background of ‘dual Carbon’, the digital transformation of the new power system places higher demands on power sensor technology. In view of weak temperature stability of optical electric field sensor, a chip type optical silicon based electric field sensor based on electro-optical polymer film is proposed in this paper. Firstly, the principle of electro-optical effect, the second-order nonlinear optical effect of electro-optical polymer and the electro-optical energy coupling method are introduced; Then, the processing flow of the sensor is designed and the preparation is finished and, at the same time, the electro-optical polymer is successfully coated on the sensitive chip; Finally, the linearity, AC response and temperature characteristic of the sensor are carried out by setting up the experimental test platform. The experimental results show that the prepared optical electric field sensor has good linearity and high sensitivity up to 0.945 mV·(kV·m-1)-1 under the power frequency electric field, and both output amplitude and phase of the sensor are stable in the temperature range of 0-75 ℃, with the maximum fluctuation of the amplitude ratio of 0.481 dB and the maximum phase difference of 3.82°. The structure of the sensor proposed in this paper practically and feasibly improves the temperature characteristics of the silicon-based integrated optical electric field sensor, and provides a reference for the use of silicon-based integrated optical electric field sensors in power systems.关键词：electro-optical polymers;optical chips;electric field sensors;temperature characteristics12|131|0更新时间：2025-04-26
Research and Application of Advanced Electrical Materials Under the Background of Dual Carbon Strategy
- 摘要：As for such demand as model construction, information interaction and dynamic simulation of digital twinning of high voltage equipment, the design and application technology of virtual sensor are analyzed. Virtual sensor is a computer simulation system with sensor behavior, which can decouple complex digital twin system based on function, structure and service requirements as well as reduce the complexity of engineering application. In this paper, the design requirements of the virtual sensor applied to the digital twin engineering of high voltage equipment are proposed, the design and application methods of the virtual sensor for observation, the virtual sensor for parameter calculation and the virtual sensor for prediction and alarm are given. The study results show that the virtual sensor has such advantages as componentization, service, easy reconfiguration and evolution, the function can be used as a digital twin cell level component design method so to solve the difficulties in data acquisition and fusion, the complicated coupling of simulation and prediction algorithms in current engineering applications, support the applications of comprehensive equipment state perception, accurate trend prediction, early risk warning and equipment life-cycle lean management.关键词：high voltage equipment;digital twinning;virtual sensor;joint observation;micro service;simulation and prediction10|261|1更新时间：2025-04-26
- 摘要：Broadband vibration signal includes both low frequency vibration signal within 1 Hz-20 kHz and high frequency ultrasonic signal within 20-500 kHz. In recent years, the method of using vibration signal to detect the state of such power equipment as transformer, capacitor and reactor is more and more mature. Using ultrasonic signal to detect and locate partial discharge of power equipment has also been an expertly application. In this paper, the condition monitoring method based on broadband vibration sensor is proposed. The vibration of the pulsed vibration source and the ultrasonic of partial discharge of the oil-paper insulated needle board electrode are measured simultaneously by the sensor. The ultrasonic time delay is corrected by simulation. The partial discharge is identified and compared with the results obtained by pulse current method. The results show that the proposed monitoring method can detect vibration and ultrasonic well and achieve the identification of partial discharge. The method proposed is feasible for the condition monitoring of power equipment.关键词：broadband vibration;condition monitoring;vibration signal;ultrasonic signal;composite sensor9|230|1更新时间：2025-04-26
- 摘要：Generator circuit breaker (GCB) is located between the generator set and booster transformer. For high capacity units with load current up to 50 kA and fault current up to 200 kA, the current conducted and interrupted by the GCB is far above that of line circuit breaker. During the interruption period, very serious transient recovery over voltage is generated on both sides of the GCB, threatening reliability of GCB. Based on the actual wiring of a large nuclear power station with capacity of sing unit at 1 722.2 MVA, the electromagnetic transient characteristics of TRV, in case of interruption of GCB at various faults, is calculated and studied by the use of EMPT-RV simulation and the influence effect of capacitor with different capacity configuration on amplitude and steepness of TRV is analyzed. The method of suppressing TRV by adding non-linear damping resistor of auxiliary open contacts is proposed, the principle of parameter selection of the non-linear damping resistor is given and its feasibility is verified by simulation. As for the out of step fault, the non-linear damping resistor can reduce the TRV amplitude by 29.2%, which has higher flexibility and economic performance.关键词：high capacity generator;generator circuit breaker;transient recovery over-voltage;out of step fault;three phase short circuit;nonlinear damping resistor9|65|1更新时间：2025-04-26
- 摘要：DC circuit breaker (DCCB) is an important means to solve the short-circuit fault of DC system. In view of such a series of defects as weak current limiting effect, short operation life of arrester and slow fault isolation speed of the existing DCCB, a kind of hybrid high-voltage DC circuit breaker topology solution with current limiting capability (CLC-HDCCB) is proposed in this paper. The CLC-HDCCB current-carrying branch and transfer branch adopt double-bridge structure and possesses bidirectional on-off capability. The current-limiting part adopts current-limiting resistor inductor in parallel to limit the current, which significantly reduces the peak value and rise rate of fault current. The designed bleeder resistor bypasses the current-limiting inductance during the circuit breaking process, which reduces the energy absorbed by the arrester in single breaking operation. In addition, various conditions occurred in such DC system as breaking fault current, normal closing operation and breaking small current of the CLCHDCCB scheme is analyzed in detail and also the parameter selection method is given. Finally, the simulation verification is carried out on the PSCAD/EMTDC platform, and the results show that the proposed CLC-HDCCB scheme has certain advantages compared with the existing DCCB scheme in terms of fault current limiting, arrester energy absorption and fault clearing time.关键词：DC circuit breaker;fault current limiting;re-closing;breaking at small current;energy absorption10|221|0更新时间：2025-04-26
- 摘要：The contact ablation and deterioration of circuit breaker after capacitor bank switching can change the pre-breakdown time of closing operation, which will not only affect the effect of phase selection closing, but also indicate that the duration of pre-breakdown arc can be used as one of the indicators to measure the ablation status of the contacts. An electric-fluid coupling simulation model is set up for the pre-breakdown process of interrupter of 126 kV SF6 circuit breaker, and the pre-breakdown characteristics of the contact in the process of contact deterioration are studied. Moreover, the live detection method of the pre-breakdown time is proposed. The results show that the maximum point of the electric field strength always appears on the surface of the stationary arc contact during the closing process. The density of SF6 gas in the interrupter remains almost unchanged. At 110 kV phase voltage, the test value of the pre-breakdown duration of the contact with the variation of ablation degree is in agreement with the simulation value. From the perspective of electric field distortion, the variation of the pre-breakdown duration corresponding to the increase of the surface ablation deterioration of the contacts is explained. The results can provide theoretical guidance for the phase selection and closing strategy of the circuit breaker as well as the state evaluation of the contacts.关键词：SF6 circuit breaker;pre-breakdown characteristic;multi-physical field coupling simulation;phase selection closing;contact status assessment9|180|0更新时间：2025-04-26
- 摘要：The insulation rod, as the key element for connecting the contact and operating mechansim of UHV GIS circuit breaker, needs withstanding external stress during the operation. For mastering the dynamic stress characteristics and the material’s mechanical charcateristic of the insulating rod, the force sensor is arranged in the UHV GIS circuit breaker to measure the dynamic stress of its main insulation rod during the operation period. According to the measurement results, the compression test of tubular sample of the insulation rod is carried out, and the compression buckling characteristics of samples with different length diameter ratio are simulated and analyzed. The test results show that the insulation rod is subjected to alternating impact loads during operation. The peak of the pressure applied by the operating mechanism to the insulation rod is close to that of the tensile force in the test, and both of them are above 110 kN. Therefore, the compression characteristics of the material of insulation rod should be paid attention to. The compression test results show that the length, inner and outer diameters will directly affect the compression performance of the tubular insulation rod, plastic deformation and buckling instability under compressive force are more likely to occur for the insulation rod with large aspect ratio, and the bore maximum compressive load is smaller. Based on the compression test of the material, the approximate relationship between the critical buckling load and length of the insulating rod is set up through simulation calculation, and a method to obtain the critical buckling load of the original-sized rod is proposed through the compression test of the tubular specimen. The research results of this paper can provide reference for the material testing, design and manufacture of insulation rod for UHV GIS.关键词：insulation rod;dynamic stress characteristics;compression characteristics;critical buckling load10|134|0更新时间：2025-04-26
- 摘要：The SF6, micro water, micro oxygen and solid insulating materials in the interrupter of SF6 circuit breaker will decompose and generate new component gas under the action of arc. For studying the variation of decomposition product content after the current interruption during the full electrical life cycle of SF6 circuit breaker, a whole life simulation ablation test platform of the circuit breaker is set up. 69 times of ablation tests are carried out on the circuit breaker, the voltage and current parameters as well as the decomposition contents of each gas during the ablation period are measured. The results show that SOF2, CF4 and SO2 are the main products, the contents of SO2F2 and SOF4 are low and the H2S can not be detected stably. The contents of SOF2, CF4, SO2 and SO2F2 increase with the increase of the number of ablations. Among the main decomposition products, the production of SOF2 and SO2 has a linear relationship with arc energy, while there is no obvious rule between the production of CF4 and arc energy, which may be due to the randomness of arc to the ablation of solid insulating materials. The adsorption of adsorbent to SOF2 and SOF4 is significant, but the adsorption of other products is not obvious. Finally, the method of assessing the residual electrical life of circuit breaker by way of SO2 volume fraction is proposed.关键词：SF6 circuit breaker;gas decomposition product;arc energy;electric life10|142|0更新时间：2025-04-26
- 摘要：Deeply mining the electrothermal corrosion information of the decomposition products of SF6 improves the accuracy of latent fault diagnosis of GIS equipment. Studying thermal decomposition reaction of the SF6-epoxy system and clarifying the corresponding relationship between carbon-based characteristic decomposition products and degradation of insulating materials can solve the contradiction between the singularity of the characteristic components and the diversity of their source. In this paper, the thermal decomposition process of SF6-epoxy is systematically measured by synchronous thermogravimetry (TG)/differential scanning calorimetry (DSC), which characterizes the temperature range and heat release of three distinct pyrolysis stages. Nine decomposition products of carbon, sulfur and oxygen are identified by the online gas chromatography. According to the panoramic pyrolysis reaction mechanism of the SF6 -epoxy system, CO2 is proposed as the characteristic decomposition component to judge the thermal corrosion deterioration of epoxy resin at high temperature (> 500 ℃). CH4 directly responds to the thermal degradation of epoxy insulating materials at 300-500 ℃. SOF2, H2S and H2 comprehensively determine the ultra-low water concentration of SF6-epoxy system.关键词：epoxy resin;thermal decomposition;SF6 decomposition product;thermal analysis10|203|1更新时间：2025-04-26
- 摘要：The study of charge motion characteristic of conductive particle is of great significance for the treatment of conductive particle defect in gas insulated switchgear. At present the method of studying charge motion of particle with numerical simulation is less and is only limited to Eulerian simulation. In view of the above problems, a kind of new strategy to calculate the motion of particles based on discrete element method is proposed. The correctness of the algorithm is verified by comparing the results of experiments and calculation data, the motions of multiple spherical particles/dust and linear particles have been successfully simulated as well. The application advantage of the algorithm and the further development value and potential are proved.关键词：conductive particles;motion;DEM;algorithm development8|48|0更新时间：2025-04-26
- 摘要：In the process of opening and closing of high voltage circuit breaker, the strength of transmission system directly affects the mechanical fatigue life of the product. For the 550 kV circuit breaker, the voltage level is improved compared with previous products, which means it is more difficult to meet the requirement of mechanical life. So it is necessary to predict and improve the structural strength of static side transmission system more accurately to meet the fatigue life target. In this paper, the flexible transient dynamic model for static side transmission system of double moving self-energized interrupter is established. The model is based on Hypermesh for pre-processing. The transient dynamics is solved by Ls-dyna. During the analysis process, the explicit algorithm is used, and the grid type, contact type, gap influence, collision impact are fully considered. The stress simulation results show high stress risk in the key parts during opening and closing operation under different speed conditions. Taking the pull rod pin as an example, the high stress distribution map and stress time domain curve are listed. The peak stress reaches about 380 MPa, and there is room for optimization. At the same time, the results of contact force, velocity curve and system energy between components are also output. These simulation results show that the magnitude and direction of contact force and the change of speed are in line with the actual movement trend. The hourglass energy has never exceeded 5% of the peak internal energy, and there is no obvious slip and penetration in the contact. So these results ensure the rationality of the simulation analysis. Then the design concept is optimized for the high stress area and compared with the baseline concept by simulation. The comparison results show that the peak stress of each risk point is significantly reduced, and the stress reduction ratio of the risk point on the cross beam, guide rail and small gasket can reach up to 50%, which means the optimization effect is obvious. The fatigue life of the optimization scheme is analyzed, and results show that the stress risk point of the key parts can reach more than 10 000 times. Finally, the mechanical life experiment is carried out, and results show that the optimization scheme can meet the requirements of ten thousand mechanical life without excessive wear, which verifies the effectiveness of the simulation results and the optimization design.关键词：high voltage circuit breaker;transient dynamic;explicit algorithm;static side transmission system;optimization12|90|0更新时间：2025-04-26
- 摘要：Insulating spacer is the key insulation element of GIS. It is fastened and connected with the flanges of the gas compartment on both sides by bolts. The bolts, in case of loose, will lead to uneven stress distribution of insulating spacer, thus affecting both safety and stability of the insulating spacer. In this paper, a method for detecting the bolt looseness of insulating spacer flanges based on ultrasonic critically refracted longitudinal waves (LCR) is proposed. The looseness of bolts is reflected in accordance with the acoustic time difference of LCR wave propagation on the surface of the insulating spacer flanges. The results show that, in case of looseness of the adjacent bolts, the LCR wave has the largest change in the flange surface acoustic time difference between the loose bolts, and the magnitude of variation is greater than 24 ns; While, when the non-adjacent bolts are loose, the acoustic time difference on the surface of flange of LCR on the opposite side of the loose bolt is maximum and the acoustic time difference is greater than 10 ns, and the greater the bolt looseness, the greater the ultrasonic propagation acoustic time difference. The detection method can achieve the detection of the looseness of the flange bolts of the insulating spacer, judge the number and position of the loosening of the bolts and has certain engineering practical value.关键词：insulating spacer;critically refracted longitudinal wave;Snell’s law;flange bolt;looseness detection8|87|0更新时间：2025-04-26
- 摘要：Distribution cable is an important part of equipment of power grid. Partial discharge and overall insulation aging due to its insulation defects are main reasons leading the the cable failures. For preventing cable failures and ensuring safe and reliable operation of the distribution power grid, it is of great significance to study the test method of distribution cable. In this paper, the existing test standards both at home and abroad are summarized, the principles and test specification of various test methods for distribution cable, including power frequency voltage test, series resonance voltage test, oscillation wave voltage test, very low frequency sinusoidal wave voltage test, very low frequency cosine rectangular wave voltage test, are described. And the study status and the existed problem of the oscillation wave and very low frequency voltage test method is reviewed in detail and the partial discharge characteristic of cable is discussed. Finally, the prons and cons of the test method mentioned above is summarized and its main development trends of their application in the insulation condition diagnosis of distribution cable are discussed.关键词：distribution cable;withstand voltage test;partial discharge;dielectric loss;series resonance;oscillating wave;very low frequency10|219|0更新时间：2025-04-26
- 摘要：The skin effect of high-frequency current increases the heat loss caused by the current in the conductor, which provides a new technical method for deicing on transmission lines. In this paper, a kind of high frequency deicing method based on LC oscillating discharge is proposed. The high frequency current is obtained by controlling the voltage square wave by using the characteristics of current change caused by capacitor charge and discharge when the RLC series circuit is converted from one to another steady state. This method can effectively reduce switching frequency of IGBT and reduce switching loss. According to the characteristics of IGBT, a set of deicing power supply is designed. The simulation experiments show that an effective deicing current of 1 kHz can be obtained for LGJ-400/50、LGJ-240/40、LGJ-120/25 and LGJ-70/10 of wire with lengths of 40 km and 35 km.关键词：deicing;oscillatory discharge;skin effect;high frequency power supply;voltage control9|69|0更新时间：2025-04-26
- 摘要：For solving the phenomenon of DC bias due to UHVDC transmission, a method for identifying key sites in the transmission-end power grid based on complex network theory under DC bias conditions is proposed. PSCAD is used to set up the autotransformer model and conduct the DC bias simulation study of transformer. In order to control the DC bias existing in the substations in Jiuquan area, the simulation model is set up based on the structure parameters of actual grid so to identify and control the critical site which is subjected to the large influence of the bias current. The concept of node entropy and line entropy is defined of which its size reflects whether the node current and line current distribution in the governed area is uniform, and the DC bias control standard is specified so to judge whether the control effect is qualified. The simulation results show that after identifying and managing the key sites, the node entropy and line entropy have decreased significantly and the total bias current in the area has been effectively suppressed.关键词：HVDC;autotransformer;complex network;DC bias;site identification12|142|0更新时间：2025-04-26
- 摘要：The insulation problem of Ultra High Voltage Direct Current (UHVDC) wall bushing is the research focus of UHVDC transmission technology. In actual working conditions, the wall bushing is often at ambient temperatures above room temperature due to the influence of internal and external environment, which causes the insulation performance to be affected to a certain extent. For studying the variation of flashover voltage of epoxy resin under AC and DC voltage and the mechanism of temperature influence, an epoxy resin flashover test platform is set up to measure flashover voltage of the epoxy resin under different temperature within the constant SF6 gas pressure, and the reason of flashover voltage variation is analyzed by simulation. The results show that the flashover voltage of epoxy resin first decreases slightly and then increases with the increase of temperature in the range of 25 ℃ to 70 ℃. It shows that there is a minimum flashover voltage in this temperature range. This phenomenon is caused by the joint action of the electric field distribution at the gas-solid interface, the critical electric field strength of SF6 gas and the energy level of surface-trap of epoxy resin. The study results can provide experimental basis for optimizing the insulation configuration of UHVDC wall bushing.关键词：wall bushing;epoxy resin;surface flashover;temperature10|248|1更新时间：2025-04-26
Research & Analysis
- 摘要：The insulating oil with low water content has high insulation level and is an important assurance of safe and stable operation of power grid. Thus, the water content of the insulating oil needs to be maintained in a low range and the problem about super hydrophobic filter membranes used for removing water from the insulating oil needs to be solved. In this paper, the super hydrophobic SiO2 nanoparticles are uniformly bonded to the surface of the PP filter element, filter cloth, and filter paper by adopting the spraying method so to obtain the hydrophobic filter membrane. On this basis, the hydrophobic PP filter element is suitable for the large-flux primary filtration of insulating oil due to its low precision. The hydrophobic filter cloth combined with tandem filter device is used for secondary stage filtration, which can withstand higher oil pressure while removing the water from the insulating oil further. The super-hydrophobic filter paper is suitable for the efficient tertiary filtration due to its outstanding ability of water removal. This multistage filtration can reduce the water content of the insulating oil below 10 mg·L-1. Multi-stage filtration not only has high water removal efficiency, but also meets the water removal requirements of different types of insulating oils.关键词：insulating oil;super-hydrophobic;water removal;multi-stage filtration9|123|0更新时间：2025-04-26
- 摘要：The analysis and treatment of abnormal ultrasonic wave in the disconnecting switch (DS) compartment of PT of 110 kV GIS is introduced. It is judged through amplitude location, time delay location and the change of equipment operation state that the defect is from the inside of the DS compartment. Multiple kinds of spectrum analysis on the partial discharge ultrasonic signal are performed, thinking that the free metal particle at the bottom the compartment is the main reason which causes abnormal ultra sonic wave signal. It is found by opening the enclosure that the grading cover of the stationary contact of the blade has obvious scratches and many black solid debris are at the bottom of the gas compartment. The weak installation process of the blade causes the metal debris to drop at the bottom of the gas compartment, generating partial discharge and causing the ultrasonic wave signal abnormal. The discharge of disconnecting switch of PT is a typical metal particle discharge case, which has provided experience and reference for the analysis of the similar abnormal situation in the future.关键词：GIS equipment;free metal particle discharge;abnormal ultrasonic wave;DS14|130|0更新时间：2025-04-26
Technical Discussion
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