最新刊期
卷 60 ， 期 5 ， 2024
- 摘要：DC GIS is the key equipment to realize the lightweight and compact offshore converter platform and the development of offshore converter platform to the deep sea in the future. The long term live test of DC GIS simulating the actual working conditions before its operation can fully predict the relevant performance of DC GIS in the long term operation under all working conditions and improve safety and reliability of DC power grid after operation of the DC GIS. In this paper, ±550 kV DC GIS is taken as the research object, and its relevant introduction is carried out. The long term live test scheme of ±550 kV DC GIS is proposed. The long term live test circuit is designed and the selection method of equipment in the circuit is analyzed. Finally, the actual test of ±550 kV DC GIS is carried out to verify the feasibility of the proposed long term live test circuit of ±550 kV DC GIS, which lays a solid foundation for further research on DC GIS long time performance under all working conditions.关键词：±550 kV;DC GIS;long term live test;test scheme;test circuit20|97|1更新时间：2025-04-26
- 摘要：The mechanical defect of gas insulated switchgear (GIS) is an important cause of equipment failure. In case of mechanical defects in GIS, abnormal vibration signals will be generated under the action of AC electrodynamic force. The detection and diagnosis on the mechanical defects of equipment can be achieved by measuring the mechanical vibration signals on the GIS enclosure. Either internal or external fastening looseness of GIS equipment is a common mechanical defect on site. However, at present, the vibration signal characteristics of internal and external fastening looseness defects are unclear, which restricts the detection and diagnosis of this type of defects on site. In view of this, such two kinds of defects as internal shield looseness and external anchor bolt looseness on real 550 kV GIS test platform are constructed, and the relevant relations among frequency domain characteristics, signal characteristic and load in case of vibration signals at different defects are compared. The result shows that neither internal nor external defects will cause the variation of 100 Hz fundamental frequency vibration signal, but only cause the slight increase of signal of other frequency points. Therefore, both internal and external looseness defects will not cause obvious increase of vibration signal amplitude of equipment; Comparatively speaking, the internal looseness defects mainly cause the increase of low-frequency signal components such as 200 Hz and 300 Hz, while external looseness defects mainly cause the increase of amplitude of high-frequency signal components above 1 500 Hz; The increase amplitude of low-frequency signal component due to internal looseness defect increases significantly with the increase of load current, while the increase amplitude of high-frequency component due to external looseness defect has little correlation with load current. The research result in this paper has provided theoretical support for the detection and analysis of internal and external looseness defects in field GIS.关键词：gas insulated switchgear (GIS);mechanical defect;vibration;fundamental frequency;frequency spectrum17|83|0更新时间：2025-04-26
- 摘要：For meeting the requirements of frequent switching of load current of flexible DC power distribution system to the operation life of switchgear and solving the difficulty of high cost and large volume due to the direct use of DC circuit breaker, a kind of DC load switch scheme based on couple negative voltage principle is studied in this paper. Firstly, its topology and working principle are introduced. Then, the fast mechanical switch in the main branch based on double-acting structure and electromagnetic repulsion mechanism, the converter unit based on the coupled negative voltage device and the power electronic valve unit using the anti-series topology, are designed respectively. Finally, according to the engineering requirements of a converter station in Suzhou, a 10 kV coupled negative voltage DC load switch prototype is developed and verified by tests. The result shows that the developed 10 kV DC load switch can frequently interrupt the rated current and the maximum breaking current within 3 ms, the volume at present is the smallest with the same parameters in China, and it has the advantages of low loss, high mechanical life and reliability. It fully satisfies the engineering requirements and, at the same time, provides a reference for the development of subsequent DC load switch products.关键词：DC power distribution;frequent switching;coupled negative voltage;DC load switch;double-acting structure;anti-series topology10|37|0更新时间：2025-04-26
- 摘要：For achieving the wireless sensing of contact temperature in GIS at 72.5 kV and above, the design idea of a set of wireless sensing system for contact temperature in GIS is described and developed in this paper. The effectiveness and feasibility of the system are verified through functional test. Finally, a working condition model of 252 kV GIS angle disconnector with good and weak contact is set up, and a series of local overheating wireless sensing tests are performed. The reliability of the system is verified by comparing the test data with the thermocouple test data. The test result shows that the system can achieve the wireless sensing of GIS internal contact temperature; When the contact resistance Rj>250 μΩ, the temperature of moving contact and fixed contact base rises rapidly; When Rj reaches 620 μΩ and the load current is 600 A, the temperature of the fixed contact base is close to 50 ℃, which can be barely detected by infrared imaging; When Rj reaches 1.8 mΩ and the load current is higher than 400 A, the contact temperature is growing all the time, which can be clearly detected by infrared imaging.关键词：contacts in GIS;wireless sensing;local overheating;infrared imaging;contact resistance14|67|0更新时间：2025-04-26
- 摘要：For achieving the fault diagnosis of high voltage circuit breaker and load switch as well as improve their safety and reliability, it is necessary to deeply study the relationship between motor current characteristics and the state of spring operating mechanism for high voltage circuit breaker and load switch. Since the traditional BP neural network has such defects as easily falling into local minimum points and slow network convergence speed, the use of genetic algorithm to optimize BP neural network can improve the judgment accuracy and diagnosis efficiency. The diagnosis results show that GA-BP algorithm can quickly and accurately judge the operating state of the equipment in accordance with the current data of of motor for the circuit breaker and load, has high accuracy and wide application prospect for engineering practice.关键词：load switch;high voltage circuit breaker;motor current;genetic algorithm;BP neural network;fault diagnosis11|368|0更新时间：2025-04-26
- 摘要：In the electric power industry, various mechanical faults of disconnector for in gas insulated switchgear (GIS) are often due to the stress variation of the driving mechanisms and conductive parts. The early manifestation of this kind of stress variation is mainly clogging defect. The identification and quantification of these clogging in GIS disconnector is of significant importance in preventing severe equipment failures. However, GIS disconnector faces challenges in identifying and quantifying the clogging defects due to the discrete nature of mechanical states resulting from industrial operational conditions. This limitation hampers the ability of maintenance personnel to effectively perceive the mechanical condition of GIS disconnector and predict potential failures. In this paper, the power curve of the driving motor under normal mechanical conditions of GIS disconnector is used as the refere; nce curve. The multi-window slope-based feature point identification method is adopted, the analysis of the switch’s operational physical processes is combined to segment the power curve of the motor. Within each segment of the switch’s operation, the Fréchet distance analysis is adopted to identify clogging defects of GIS disconnector. Furthermore, these defects are quantified by using the Fréchet distance between the standard curve and the operational curve. Finally, the effectiveness of the proposed technological approach is validated through experiments on a ZF12B-126 model GIS disconnector. The experiments demonstrate that the method adopted in this paper is sensitive to the identification of clogging defects during the early stages of its development.关键词：GIS disconnector;similarity analysis;mechanical failure;intelligent diagnosis10|40|0更新时间：2025-04-26
- 摘要：The fast vacuum switch with electromagnetic repulsion actuator as the operating mechanism has such advantages as high opening speed, short opening and closing time and low dispersion of opening and closing time, and at present has been widely used in a variety of power equipment. At present, there are many studies on the opening process of fast vacuum switch, but the problems associated with the closing process are less. In this paper, the contact bounce of the fast vacuum switch in the closing process is studied. A multi-physical coupling simulation model is set up to describe the closing process of the fast vacuum switch completely. The relationship between v1 and Dmax of the fast vacuum switch is obtained, where v1 is the instantaneous velocity of the first contact between the moving and fixed contacts in the closing process, and Dmax is the maximum bouncing distance of the moving contacts. According to this relationship, the critical instantaneous closing velocity vcri in the case of no closing bounce is determined. According to the limitation of vcri, a kind of new oil buffer is designed to adjust the closing travel curve of the fast vacuum switch and achieve the non- bouncing closing. A fast vacuum switch equipped with the new oil buffer is developed, and a special measured platform is constructed to test its closing characteristics. The measured result shows that the error between the measured results and the simulation results is no more than 10% and the non contact bounce closing operation is achieved.关键词：fast vacuum switch;electromagnetic repulsion actuator;multi-physical field coupling simulation;contact bounce11|42|0更新时间：2025-04-26
- 摘要：In view of frequent failure of closing operation of outdoor HV disconnector due to the action of such external forces as external environment, a kind of new type of anti-interference high voltage disconnector is designed. Firstly, through the analysis of the structure and working principle of the traditional three column horizontal rotating high voltage disconnector, the reason for the early rolling over of the conductive rod during the closing operation of the high-voltage disconnector is obtained. Then, the design scheme of the anti-interference disconnector and the set up of the three-dimensional geometric model are given in combination with the motion characteristics of the sheave clearance mechanism and the four linkage damping mechanism. Finally, the installation position of the spring in the four linkage damping mechanism is determined by numerical simulation, and the design target requirements are verified. The results show that the structure can effectively solve the interference of external force on the conductive rod of traditional high voltage disconnector, and can provide a reference evidence for the optimal design of structure of disconnector.关键词：high voltage disconnector;closing;anti-interference;rolling over15|52|0更新时间：2025-04-26
- 摘要：GIS disconnector plays a vital role in power system, but the problem of not opening and closing to the end will threaten safety of the system. The information inside the compartment which is reflected by the traditional status detection method is limited. In this paper, a new method based on electromagnetic transient processes is proposed. By utilizing the electromagnetic transient information generated during the opening and closing process of GIS disconenctor at live condition and through analyzing the relationship between the start and stop time of the electromagnetic transient signal and the position of the stationary and moving contacts of the disconnector, the status of the moving and the stationary contacts within the GIS disconnector compartment is inverted. At the same time, a method for extracting high-frequency electromagnetic transient signal features at a low sampling frequency is proposed, and corresponding acquisition device is developed. This method not only significantly reduces data collection requirements, but also successfully verifies the opening and closing positions of GIS disconnector. Finally, the effectiveness of the method proposed in this paper is verified by experiment.关键词：GIS disconnector;engineering application;electromagnetic information;fault diagnosis;non - intrusive detection12|45|0更新时间：2025-04-26
- 摘要：DC circuit breaker needs to be tested during the research process so to provide reference for the design and type test shall be performed for reliability verification after its manufacture. In this paper, the negative voltage coupling type hybrid DC circuit breaker at 15 kV is taken as an example to simulate its short circuit current interruption process and extract the key electrical stress. The two-level voltage source synthetic test method is described, the two-level voltage source synthetic test circuit which is suitable for the negative-voltage coupling hybrid DC circuit breaker is designed and the parameter selection is optimized. The simulation results of test circuit with the electrical stress required in the interruption process are compared. It is proved that the two-level voltage source synthetic test method can provide the voltage and current stress required for the interruption process. Both equivalence and feasibility of the two-level synthetic test method are verified. The results in this paper can provide reference for the research, design and experiment of HVDC circuit breaker.关键词：hybrid DC circuit breaker;equivalence;two-level voltage source synthetic test method10|78|0更新时间：2025-04-26
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Electric Field Analysis and Design of Secondary Insulation Structure of High Power Tesla Transformer
摘要：High power Tesla transformer is widely used in the area of pulsed power technology, but its secondary coils is in a non-uniform electric field, and the uneven distribution of inter-turn voltage of the coils is likely to lead to inter-turn insulation breakdown. In this paper, a set of dual magnetic core Tesla transformer is designed, an electric field simulation model of the secondary coil is set up by finite element method and the inter-turn electric field distribution is analyzed. Aiming at the problem of uneven distribution of inter-turn voltage, the two ends of the secondary coil are double-wired and a shielding ring is added to improve the electric field distribution so to keep the maximum field strength be less than the breakdown field strength of the tiny oil gap and assure insulation safety of the secondary coil of the transformer. It is found through simulation analysis that the double-wired winding of head and tail terminals can improve electric field distribution, but the number of double-wired turns shall not be too much. After addition of the shielding ring to the high-voltage terminal, the field strength distribution is more uniform, the maximum field strength is reduced by 62.9%, the maximum field strength is much lower than the breakdown field strength of the oil gap under the pulse condition, which can meet the insulation design requirements.关键词：high power Tesla transformer;electric field distribution;double-wire parallel winding;shield ring;insulation design9|214|0更新时间：2025-04-26 - 摘要：The operation status of power transformers, the hub equipment in the operation of electrical power systems, is directly related to the safe operation of the entire system. For a long time, dissolved gas analysis (DGA) has served as an effective means for diagnosing transformer faults mainly due to its immunity to complex electromagnetic fields inside the transformers and external noise. For solving the limitations of existing DGA- based fault diagnosis method and improve accuracy of fault diagnosis further, a kind of fault diagnosis method for the oil immersed power transformer based on the capsule network (CapsNet) is proposed. The proposed method, by combining the unique capability of CapsNet to handle vectors and the characteristics of dissolved gases in transformer oil, can be able to accurately model the intricate nonlinear relationship between dissolved gases and types of faults, realizing the automatic extraction of key features of the realized training of the model through dynamic routing technique and back propagation algorithm. The test result based on real DGA data shows that the proposed method achieves 90.48%、82.46% and 87.93% on the fault diagnosis accuracy, macro average and recall geometric mean, and it outperforms both SVM and DBN, demonstrating its advantages in real-world transformer fault diagnosis applications.关键词：power transformer;DGA;fault diagnosis;capsule network;dynamic routing algorithm13|174|0更新时间：2025-04-26
- 摘要：In the fault diagnosis process of transformer, reasonable feature selection is contribute to improve the diagnostic accuracy of the diagnosis model. For that, a fault diagnosis model of transformer based on GJO feature optimization and AO-RF is proposed in this paper. Firstly, the golden Jackal optimization (GJO) algorithm is used to optimize the characteristic quantity of 21-d transformer dissolved gas-in-oil; Then, according to the feature optimization results obtained by GJO, the fault diagnosis model of transformer with random forest (RF) optimized by the aquila optimization (AO) algorithm is used to diagnose the fault of transformer. And it is compared with the diagnosis results that have different feature parameters and different fault diagnosis models. The experimental result shows that the fault diagnosis accuracy of the GJO optimized feature, compared with 21-d original feature, three-ratio method, non-coded ratio method and AO optimized feature, can be improved by 1.12%-25.78%, and the Kappa coefficient can be increased by 0.02-0.24; The fault diagnosis accuracy of AO-RF, compared with RF, SVM, ELM, SSA-RF, WOA-RF and GJO-RF models, can be increased by 1.84%-15.86%, and the Kappa coefficient can be increased by 0.02-0.16, which verify the effectiveness and accuracy of the proposed method.关键词：transformer;fault diagnosis;golden Jackal optimization (GJO);random forest (RF);aquila optimizer (AO)10|753|2更新时间：2025-04-26
- 摘要：UHVDC power transmission technology undertakes the important task of long-distance transmission of new energy, which can be a strong support to the ‘dual Carbon goal’. However, due to the fluctuation of new energy power, the converter transformer taps at the transmission end of the UHVDC transmission system operates frequently, which seriously affects the service life of the converter transformer. For reducing the number of operations of the tap, the mathematical relationship among such key influencing factors as DC transmission current, thyristor firing angle and tap gear are set up in this paper and, on the basis of the analysis of the insufficient existing tap control strategy, a new method of automatic resynchronization control strategy for the taps of pole converter transformers for UHVDC transmission system is proposed. Finally, the Yanhuai UHVDC transmission system is taken as an example, the traditional and improved strategy are compared by mathematical derivation and MATLAB/Simulink simulation. The results show that the proposed strategy can effectively reduce the number of tap operations and assure reliable operation of the UHVDC transmission system.关键词：UHVDC;new energy consumption;converter transformer tap;optimal control10|50|0更新时间：2025-04-26
- 摘要：Oil-immersed power transformer is one of the most important power equipments in power network system, and insulation oil is the main cooling medium of it. At present, mineral insulating oil is widely used, it is not easy to degrade and cause environmental damage after leakage. Natural ester as a new insulating oil for transformer can solve the above problems perfectly. It is a more ideal insulating cooling medium. However, the mechanical and electrical properties of natural ester insulating oil and mineral insulating oil are quite different, and its influence on transformer structure design and winding heat dissipation needs to be further studied. In this paper, a 110 kV natural ester insulated oil transformer is taken as the research object. Based on the finite element analysis, the temperature field distribution of its winding is calculated and the influence of natural ester and mineral oil on the heat dissipation of the winding are compared, which provides a feasible scheme for the design of large capacity natural ester insulated oil-immersed transformer.关键词：natural ester insulating oil;transformer;temperature field;finite element numerical calculation13|89|0更新时间：2025-04-26
- 摘要：In order to scientifically and reasonably assess the health level of power transformers in operation, a three-level assessment model, which is composed of ontology data, operating data and correction coefficient, is set up in accordance with the key characteristic information of transformer. The theory of health index is introduced to analyze the weight of different key characteristic information reflecting the insulation state of transformer, and the calculation method of health level of transformer three-level assessment model is proposed and, on this basis, the calculation formula of transformer residual life is obtained. Finally, it is proved in combination with an actual case that this method can scientifically and accurately assess the insulation state of power transformer in operation, and provide reference for engineers and technicians to assess the insulation state and residual life of transformer.关键词：power transformer;insulation condition assessment;health index;life prediction10|100|0更新时间：2025-04-26
- 摘要：The fault detection and prevention of dry-type reactor become the difficulty of operation and maintenance of substation equipment due to the lack of localization and technical judgment means for the early discharge fault of the dry-type reactor. In this paper, a kind of optical detection and localization method of reactor discharge based on the SiC solar-blind avalanche photodiode line array and photon irradiation image transformation is proposed. Firstly, the TracePro optical path simulation model of the reactor is set up and the optical propagation characteristics and irradiance distribution inside the equipment, in case of discharge at different positions between turns, is explored. Based on the above law, the optimal arrangement of the optical sensor line array is proposed, a linear ultraviolet (UV) solar-blind photoelectric push-sweep array for the reactor structure is designed and the response relationship of the discharge light source on each unit of the line array is obtained by simulation. On this basis, the characteristic of optical signal matrix is extracted. The KNN and CNN algorithms are used for data training and ultimately the three-dimensional localization of the inter-turn insulation discharge of the reactor is achieved. This research not only provides theoretical guidance but also serves as a practical basis for the development of push-sweep SiC solar-blind UV array of dry-type reactor.关键词：dry-type reactor;photon irradiation image;linear push-sweep array;feature extraction;discharge localization10|18|0更新时间：2025-04-26
- 摘要：The conventional DC fiber-optic current transformer (FOCT) cannot meet the high-speed response requirements of flexible DC transmission engineering, so the step response characteristics of DC FOCT and its dynamic performance improvement methods need to be studied. In this paper, a comprehensive simulation, calculation and experimental study of its dynamic characteristics are performed in combination with the discrete mathematical model of the DC FOCT. The results show that the key parameters affecting the step response characteristics of DC FOCT are transit time, forward channel gain, filter order and communication delay. A step response test platform for DC FOCT is set up, and the step response rise time of the DC FOCT is less than 50 μs after parameter optimization, which meets the relevant application requirements.关键词：DC fiber-optic current transformer;step response;transit time;forward channel gain;filter order;communication delay13|47|0更新时间：2025-04-26
- 摘要：For studying the influence of charged pollution particles on the surface pollution and electric field distribution of insulators as well as the corona discharge phenomenon in the air domain, the FXBW-35/70 insulator is taken as the study object, the coupling wind tunnel model of AC-DC, turbulence, charged particle interaction and particle motion is constructed by using the multi-physics coupling finite element software Comsol Multiphysics, and the distribution of corona discharge by charged particles on the surface of insulators, electric field and air domain is studied. The result shows that the higher the wind speed, the faster the pollution accumulation speed in the windward area compared to other areas, the larger the particle size, the more severe the pollution in the windward area, the less pollution in the leeward area, and the little change in the crosswind area. The surface potential and electric field distortion of the shed in the windward area are the most severe during pollution, followed by the leeward area. After pollution, the surface potential and electric field of the shed have eased, and the windward area is more severe than the leeward area. During the pollution, there is a risk of corona discharge in the air around a large and small shed near the high-voltage and low-voltage ends, and the first large shed near the high-voltage and low-voltage ends will experience corona discharge. After the pollution, there is a risk of corona discharge within 1mm at the root of large shed of low voltage side, and also round the whole large shed of the high voltage side as well as the root of the small shed.关键词：insulator;charged particles;Comsol Multiphysics;electric field distribution;corona discharge9|54|0更新时间：2025-04-26
- 摘要：Cross linked polyethylene (XLPE) power cable is widely used in transmission and distribution network and, however, suffers from long-term aging degradation under continuous electrical stress, and cable aging can easily cause insulation breakdown. In order to improve the online assessment technology of cable insulation aging status, a three-core tube-type cable grounding current phase angle calculation model considering uneven aging of cable insulation is set up based on PSCAD. The phase angle characteristics of such three types of the grounding wire current as single-phase uneven aging, two-phase uneven aging and three-phase uniform aging are obtained through FFT variation. The result shows that compared to the current of steel armored grounding wires, the response of phase angle of shielding wire current to the aging characteristics is more sensitive. For the single-phase aging, the dielectric constant increases from 2 to 5, and the phase angle of the shielding wire current increases from -51.01° to -50.6°. For the two-phase aging, the amplitude of phase angle gradually increases with the increase of degree of aging; For the three-phase uniform aging, the phase angle increment of the shielding wire current is 0.24° compared to normal cables and, at the same time, the phase angle increment of the shielding wire current is maximum compared to single-phase aging and two-phase aging with the same dielectric constant of 2.8 (0.15° for single-phase aging and 0.17° for two-phase aging). The analysis of the phase amplitude of the shielded wire current can not only judge the aging status of the cable insulation, but also distinguish the aging phase and degree. The research results in this paper can provide important theoretical basis for assessing the insulation aging level of cables through the phase angle of grounding wire current.关键词：three core cable;insulation aging;dielectric constant;phase angle of grounding current9|38|0更新时间：2025-04-26
- 摘要：There are not only such solid medium as silicone rubber (SR), EPDM rubber (EP) and insulating self-adhesive tape, but also such liquid medium as dimethyl silicone oil or polyisobutene (PIB) in high voltage oil-filled cable terminals. The compatibility of liquid and solid mediums is directly related to the stability of insulation performance and reliability of high voltage oil-filled cable terminals. In this paper, the compatibility test among PIB, SR and EP at 120 ℃ is performed for 168 h firstly, then the physical and chemical properties and electrical properties of liquid solid medium index is measured. It is concluded that the compatibility of PIB and SR is superior to that of PIB and EP in accordance with the physical and chemical performance variation characteristics of the liquid and solid medium at different aging time and the that of different liquid and solid medium combination at the same aging time, as well as in combination with the physical meaning of the dielectric performance and comprehension comparison. For defining the compatibility mechanism among PIB, SR and EP, the Materials Studio software is used further in this paper to construct the molecular model and interface structure of liquid and solid medium. The enthalpy values of PIB -SR interface and PIB-EP interface at different temperatures are obtained by molecular dynamics technology. The calculation result shows that when the temperature is increased from 363 K to 393 K, the enthalpy variation of PIB-EP interface is less than 0 and tends to dissolve, while the enthalpy variation of PIB-SR interface is more than than 0. Therefore, the PIB-SR interface is more stable than the PIB-EP interface. The conclusion in this paper can provide a theoretical basis for the selection of liquid and solid medium in high voltage oil-filled cable.关键词：polyisobutylene;compatibility test;silicone rubber;ethylene propylene diene monomer;cable terminal8|50|0更新时间：2025-04-26
- 摘要：Pulse excitation can greatly improve the discharge efficiency of dielectric barrier discharge (DBD) load. Due to the limitation of experimental environment and materials, the traditional experimental research is unable to study the discharge characteristics of dielectric barrier discharge under pulse excitation in more detail. In this paper, the DBD load filled with argon (Ar) gas under voltage pulse excitation is taken as the research object. The discharge curve of the model and the discharge characteristics of DBD under different pulse parameters and dielectric layer parameters are studied by constructing an one-dimensional fluid model of DBD load. The results show that the DBD load produces two times of discharges with opposite polarity in one cycle, and the intensity of the first discharge is higher than that of the second one. In addition, it is concluded through the study of the temporal and spatial characteristics of the electrical quantity in the discharge process that the performance of the DBD load can be improved by increasing the amplitude of the pulse voltage, shortening the pulse rise and fall time, selecting materials with high relative dielectric constant and reducing the thickness of the dielectric layer.关键词：dielectric barrier discharge;pulse voltage;numerical simulation;characteristic analysis8|48|0更新时间：2025-04-26
- 摘要：The converter valve is one of the key equipment in high-voltage direct current converter station and its broadband characteristics are a matter of great concern. In this paper, the thyristor converter valve is taken as the object and a passive broadband equivalent circuit model for the converter valve is set up. The vector matching method is used to perform rational function approximation of the frequency impedance characteristics of thyristor, grading capacitors, and resistance capacitance circuits and a rational polynomial in pole residue form is obtained. The principle of network synthesis is used to decompose and synthesize rational polynomials and obtain a broadband active circuit network. Based on the condition of port passivity, sequential quadratic programming method is used for port passivity optimization, and global optimization algorithm is used for strict passive optimization to obtain the passive broadband equivalent circuit model of the converter valve.关键词：converter valve;broadband equivalent circuit model;vector matching method9|45|1更新时间：2025-04-26
- 摘要：Partial over-heating inside the SF6 equipment will generate the decomposition product with perfluorocarbon characteristic. For exploring the intrinsic relationship between the decomposition products of fluorocarbons and the thermal decomposition degradation process of PTFE, the synchronous differential scanning calorimetry (DSC)/thermogravimetry (TG)/gas chromatography (GC) joint technology is used to construct a thermal decomposition reaction model of sulfur hexafluoride (SF6) which can track the decomposition products of fluorocarbons. The pyrolysis heating rate/decomposition temperature/decomposition product content conditions are associated systematically with the characteristic decomposition products / insulating material erosion determined by experiments, and the chemical reaction history of the formed hexafluoroethane (HFE) and perfluoropropane due to thermal decomposition of SF6-PTFE in the temperature range of 500-600 ℃ is clarified. The results can be directly applied to the qualitative and quantitative detection of thermal erosion of PTFE nozzle of circuit breaker and can provide an experimental and theoretical basis for accurate analysis of failure of nozzle.关键词：PTFE;pyrolysis;SF6 decomposition product;nozzle erosion10|48|0更新时间：2025-04-26
- 摘要：In the patrol of transmission lines, key power components often have such defects as corrosion and shedding, resulting in false and missed detection as well as great increase of labor costs. In view of such problem, a kind of improved algorithm based on YOLOv6 is proposed in this paper. The RepFPN structure is mainly added in the neck part, and a bottom-up path aggregation network is added to enhance the expression ability of the output features and improve the performance of the model. However, it increases the computational cost. In order to reduce the amount of calculation, the RepVGG structure with a similar residual structure and rich gradient information is added. The experimental data show that when three RepVGG structures are used in replace of C3 layer, the accuracy of 1-2 points will be improved. At the same time, after the fusion of operator of ConvBNAct, only one Conv + inplace activation is needed to complete the original three times of Op calculations. In most cases, the identical numerical results can be obtained, which alleviates the problem of increasing the amount of calculation in the above improvements. The experiment shows that the improved model mAP_0.5: 0.95 is increased by 12%, the accuracy is increased by 3.9%, and each loss value is significantly reduced and, at the same time, various defects of power components and foreign objects on transmission lines are well detected.关键词：transmission line inspection;defect detection;YOLOv6;RepVGG;ConvBNAct14|195|0更新时间：2025-04-26
Research & Analysis
- 摘要：The online monitoring algorithm for leakage fire of new high voltage switchgear cabinet in substation has the phenomenon of incorrect collection of leakage data during the monitoring process. The completeness of fire information assessment is low, and the algorithm mechanism needs to be adjusted while monitoring, resulting in untimely warning and low monitoring accuracy. In response to this issue, online monitoring of leakage fires in the high voltage switchgear cabinet of the new substation is carried out. Firstly, leakage data is collected based on the leakage situation of the switchgear cabinet, the leakage information is judged based on the residual current, and accurate leakage area data is captured in a timely manner. The D-S evidence theory fusion algorithm is used to online monitor the fire situation of the obtained leakage data, construct an identification framework, extract similarity functions, judge the temperature threshold at which the fire occurs and complete the overall monitoring study. It is known according to the analysis results that the online monitoring method has strong monitoring and warning accuracy. Under the same conditions, the temperature difference of the fire signal collection is 1 ℃, the overall false alarm rate of the system is 0.001% and the residual current is 310 mA. The method can effectively monitor leakage information and fire occurrence and indicate its strong monitoring ability.关键词：high voltage switchgear cabinet for substation;leakage of switchgear cabinet;leakage fire;online fire monitoring;monitoring algorithm8|49|0更新时间：2025-04-26
- 摘要：The long-term operation of insulating part of switchgear cabinet in the humid and hot environment is prone to moisture and reduction of insulation performance, leading to partial discharge and flashover inside the switchgear cabinet and effecting seriously stable operation of the equipment. Aiming at a typical partial discharge fault of bus bushing of 40.5 kV switchgear cabinet after moisture, the insulation performance test of bus bushing with different damage degrees is performed, and the electrical and material properties of the insulating parts before and after baking test are compared. The test results show that the partial discharge, insulation resistance and glass transition temperature can reflect the moisture degree of the bushing. The insulation resistance of the bushing after drying increases from the order of MΩ to 100 GΩ, the partial discharge decreases significantly, the glass transition temperature of the material decreases and different samples increase with the increase of moisture degree. The insulation performance of the bushing burned by discharge is damaged, and the degree of moisture can not be reflected by the partial discharge but by the insulation resistance and glass transition temperature. The results can provide support for the moisture analysis and diagnosis of the insualtion parts of the switchgear cabinet, and further prove the importance of dehumidification and partial discharge detection of switchgear cabinet to improve the reliable operation of switchgear cabinet.关键词：switchgear cabinet;bus bushing;moisture;partial discharge;glass transition temperature18|38|0更新时间：2025-04-26
- 摘要：In view of the problem of destructive discharge of pole-mounted circuit breaker due to excessive potential of enclosure to ground during the power frequency voltage test of the load side or power side of the existing primary and secondary fusion pole-mounted circuit breaker with EVT (electronic voltage transformer), the insulation performance across-open contacts of the pole-mounted circuit breaker with EVT configuration is studied int his paper. Firstly, capacitance distribution theoretical analysis of the enclosure to ground discharge problem during the withstanding voltage test across open contacts of the pole-mounted circuit breaker is performed, and the voltage between the enclosure and ground during the withstanding voltage test across open contacts of pole-mounted circuit breaker made of EVT with different capacitance values is given. Secondly, the theoretical design basis for the existing China national grid standardization scheme on the primary and secondary fusion pole-mounted circuit breaker is given and the insulation design margin of the primary and secondary fusion pole-mounted circuit breaker equipped with EVT on the power side is pointed out. It is concluded that under the premise of meeting the requirements of switching performance and EVT accuracy, the capacitor with low capacitance value is used as much as possible for the HV arm of EVT so to reduce the the voltage of enclosure to the ground. Finally, a new structure of the primary and secondary fusion pole-mounted circuit breaker with EVT on both the load side and the power side is proposed under the existing test method, and the test results are given. The analysis and test results prove that in case of withstanding voltage test across the open contacts of the pole -mounted circuit breaker with the structure, the voltage of the enclosure to ground is less than 42 kV (phase to ground voltage) specified by GB/T 11022—2020, which avoids the phenomenon of the enclosure to ground breakdown during the withstanding voltage test across open contacts and the results have been widely used in engineering.关键词：capacitance distribution;pole-mounted circuit breaker;insulation across open contacts12|43|0更新时间：2025-04-26
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