最新刊期
卷 60 ， 期 8 ， 2024
- 摘要：The ablation resistance and the anti-melt welding performance of CuCr contact material is an important factor affecting the life of vacuum interrupter. In this paper, the ablation of CuCr contact material under vacuum arc is the foothold, the ablation process and mechanism are described, and the microstructure of CuCr contact and the magnetic field type of vacuum interrupter discusses the relevant mechanisms affecting the ablation of CuCr contact. It is pointed out that the anti-melt welding performance is related to the tensile and thermal conductivity of the contact material. finally, the research progress of improving the contact’s resistance to ablation from the perspectives of surface modification and alloying is summed up, and the research direction of improving the resistance to ablation of contact is summarized.关键词：CuCr contact material;vacuum interrupter;ablation resistance;anti-melt welding;magnetic field type;surface modification;alloying33|23|0更新时间：2025-04-26
- 摘要：Fast clearance of short-circuit fault is vital to increase the transmission capacity of transmission lines of power grid and improve the transient stability of power system. The fast vacuum circuit breaker (FVCB) is a good candidate to achieve quick clearance of short-circuit fault. The objective of this paper is to design a new type of 72.5 kV single-break FVCB and verify its short-circuit breaking performance. A specially designed 72.5 kV vacuum interrupter with floating shields and reduced mass of moving components technology is used as an arc extinguishing device, an electromagnetic repulsion mechanism is used as an operating mechanism and a specially designed oil damper is used as speed adjuster. For meeting the short-circuit current breaking requirements, the opening speed characteristics based on the anode discharge mode are quantified as the average opening speed v1 is 5 m/s in the stroke of the first 15 mm, and the average opening speed v2 is 1.59 m/s in the full clearance of 30 mm. The opening and closing time of the developed 72.5 kV fast vacuum circuit breaker is (1.2±0.04) ms and (18±0.20) ms respectively through the test; The short circuit breaking performance verification at 40 kA (rms) and 80 kA (rms) of test duty of T100s (b) is performed. The breaking result shows that the developed single-break 72.5 kV fast vacuum circuit breaker has met the breaking requirement of full arcing time interval defined in GB 1984—2014.关键词：electromagnetic repulsion mechanism;fast vacuum circuit breaker;oil damper;opening speed characteristics;short-circuit current interruption39|27|0更新时间：2025-04-26
- 摘要：Large capacity generator protection circuit breaker is an important protection device for large generator sets, a motion device with different velocities of main and arc contact is adopted in its interrupter. The arc contact system adopts a new five-link mechanism and the stress characteristics of arc contact system of the motion device are analyzed in this paper. In view of such characteristics of the arc contact system for large capacity generator circuit breaker as high-speed motion, large power transmission and different velocities achieved by segmented continuous track, the inertial force is calculated firstly by means of dynamic force analysis combined with vector and matrix. Then, the common relation of the forces of each curve track on the roller is studied, thus a universal matrix model including inertial force is derived. Finally, the friction force is calculated by numerical iteration method, thereby the dynamical characteristics of the arc contact system with different-velocity are obtained. The dynamical research model and analysis method introduced in this paper can provide a theoretical basis for the force characteristics of the arc contact system for large capacity generator circuit breaker series products, and are suitable for the design and optimization of arc contact system for large capacity generator circuit breakers.关键词：generator circuit breaker;arc contact system;analytical method;numerical analysis;inertia force;friction force;dynamics19|15|0更新时间：2025-04-26
- 摘要：High-voltage circuit breaker is the key equipment in the power grid, mechanical defect is its main type of fault and it is important to diagnose the mechanical defect and perform maintenance in time. In this paper, a mechanical defect detection method based on computer vision, applying corner tracking method to extract motion trajectory and support vector machine to classify the defects, is proposed. Firstly, the high-speed camera is used to obtain the operation video of the operating mechanism of circuit breaker, and the angular displacement curve of the lever is obtained by corner tracking algorithm. Then, the high-dimensional feature vector is reduced to the low-dimensional feature vector by principal component analysis (PCA). Finally, the defect classification for reduced-dimensional feature vector is implemented by the support vector machine (SVM). The experimental test results show that the accuracy rate of 28 training sets and 8 test sets are 92.86%, 87.5% respectively, and good detection results are achieved. The proposed method, as a kind of non-contact measurement method without installation of sensor, is fast in measurement speed and high in accuracy, and has important significance for the maintenance at site.关键词：high voltage circuit breaker;mechanical defect;corner tracking method;principal component analysis;support vector machine20|10|0更新时间：2025-04-26
- 摘要：High-voltage circuit breaker is an important protection and control equipment in power system. The high-voltage circuit breaker can use spring operating mechanism to perform the opening operation. The opening time of circuit breaker refers to the time interval from the energized moment of the opening release of the spring operating mechanism to the time when the arc contacts of all poles are separated when the circuit breaker is at the closed position. The operation time of the opening release of the spring operating mechanism accounts for about 50% of the opening time of circuit breaker. Changing the operation time of the opening lock release of the spring operating mechanism is a key factor in adjusting the opening time of the circuit breaker. In order to effectively adjust the opening time of the circuit breaker, the opening lock system of the spring operating mechanism of high-voltage circuit breaker is taken as the research object based on the principle of the opening operation of circuit breaker, the mechanical dynamics simulation calculation and analysis methods are used to analyze the impact of the opening lock system on the opening time of the circuit breaker. The KOCOS mechanical characteristic tester and Phantom high-speed camera are used for experimental verification and, on this basis, optimization analysis is performed accordingly. The results show that changing the first level latch structure of the opening latch system of the opening lock system has a significant effect on changing the opening time of the high-voltage circuit breaker, and the method has a certain reference for the mechanical characteristics optimization of other circuit breakers or electrical equipment.关键词：high-voltage circuit breaker;spring operating mechanism;opening time;simulation calculation27|19|0更新时间：2025-04-26
- 摘要：In order to improve the fault isolation, current limiting and re-closing operation recovery ability of high voltage DC (HVDC) circuit breaker after the short circuit fault in flexible HVDC transmission system, a kind of HVDC circuit breaker with re-closing function (RCL-HDCB) is proposed based on the structural base of existing DC circuit breaker. The current limiting branch of circuit breaker is improved by the RCL-HDCB proposal, which can make it quickly for re-closing operation. The parameters are designed by the operation process and principle and, based on PSCAD/EMTDC simulation software, the dual-terminal DC transmission system by modular Multilevel Converter (MMC) is set up to simulate and verify the operating state of RCL-HDCB. The results show that the device can quickly and effectively break after short circuit fault, the fault current is suppressed better and, at the same time, the re-closing operation is stable. Therefore, the RCL-HDCB proposal has certain guiding significance for the flexible HVDC transmission system.关键词：flexible DC transmission system fault;current limiting DC CB;fault isolation;re-closing17|12|0更新时间：2025-04-26
- 摘要：In view of such issues as complicated mechanical fault and difficult fault extraction of high voltage circuit breaker, a kind of joint acoustic and vibration fault diagnosis method for circuit breaker based on the combination of VMD and KFCM-SVM is proposed. Firstly, VMD is used to decompose the denoised vibration and acoustical signals, and a series of intrinsic mode functions (IMF) reflecting the mechanical state information during operation of the circuit breaker are obtained. Then, Hilbert transform is performed on each IMF component to construct corresponding Hilbert marginal spectrum, and the energy entropy is obtained as the feature vector. Finally, kernel fuzzy C means (KFCM) is used to presort the features, and then the support vector machine (SVM) is used to set up a training model to achieve mechanical state identification. The experimental results show that the energy entropy of the Hilbert marginal spectrum of the acoustic vibration signal is sensitive to the mechanical state variation of high-voltage circuit breaker, and KFCM-SVM can accurately identify mechanical faults during the opening operation of high-voltage circuit breaker.关键词：high-voltage circuit breaker;VMD;Hilbert marginal spectrum;energy entropy;KFCM-SVM16|8|0更新时间：2025-04-26
- 摘要：CuW alloys have been widely used as contact materials in high-voltage SF6 circuit breaker and gas-insulated switchgear, and their erosion resistance performance determines the service life of the switchgear. The main preparation process of CuW contact materials include infiltration and powder sintering methods. It is found by the latest research progress that the key point of infiltration CuW alloys lies in the connection strength of the W skeleton, while the key of liquid-phase sintered CuW alloys lies in the wettability between the molten Cu and the W particles, which clarifies the research direction of the two processes. The research on the preparation of CuW alloy based on aluminothermic reduction process is described, and the proposed idea is to perform the sintering of precursor to reduce the activation energy of the reactants so as to promote the self-propagating reaction. At the same time, it is summarized that the current research on the modification of CuW alloy lies in the addition of reinforcing phases and deformation processing with the aim of providing guidance to the improvement of the technology on the industrial level, however, it still takes a certain amount of time on how to apply it in the industrial level. Finally, with focus on the whole research of the arc contact, it is clarified that the bonding strength between CuW and CrCu is a key factor for the whole of the arc contact material. Furthermore, a new direction for the improvement and development of the subsequent whole materials is provided.关键词：CuW contact materials;infiltration method;sintering method;aluminothermic reduction;CuW/CrCu integrated material36|20|0更新时间：2025-04-26
- 摘要：Very fast transient overvoltage (VFTO) will be generated during the operation of the disconnector in GIS due to the repeated breakdown across open contacts. The high amplitude and steep wave front of VFTO seriously threaten the electrical primary insulation and cause electromagnetic interference problems. At present, in addition to using the disconnector with switching resistor to suppress VFTO in practical projects, the magnetic ring damping bus can also be used to suppress the VFTO. For assuring reliability of GIS, the suppression performance of the magnetic ring damping bus is very important. Therefore, it is urgent to research and propose a method for evaluating the magnetic ring suppression effect in the laboratory. In this paper, a special suppression performance test circuit is designed for the suppression performance of the magnetic ring damping bus, which mainly includes bushing, damping resistor, discharge gap, magnetic ring damping bus, GIS short busbar, VFTO sensor and VFTO measurement system. The rated voltage of the test circuit is 1 100 kV, the rated power frequency voltage that the bushing and busbar in the circuit can withstand is 1 100 kV, the resistance value of the damping resistor is 560 Ω or 1 500 Ω, and the discharge gap can be adjusted by the electrode spacing to generate different levels of discharge voltage and discharge steep wave, and the steep wave rise time can reach 30 ns. The test circuit is used to test the suppression effect of the magnetic ring damping busbar in the laboratory. The test results show that the test circuit can complete the test of the suppression effect of the magnetic ring damping busbar, and can quantitatively give the effect of the suppression effect. The method can be promoted to GIS products of other voltage levels, and can help to promote the realization of industrialized design, manufacture and inspection of magnetic ring damping busbar.关键词：UHV;GIS;magnetic ring damping bus;very fast transient over voltage (VFTO);suppression performance;simulation test18|11|0更新时间：2025-04-26
- 摘要：The insulating spacer is the core component in gas insulated metal enclosed switchgear (GIS). For reducing the size of the equipment and the usage of SF6 gas in the context of guaranteeing good dielectric strength, the insulating spacer for GIS in real project is taken as the research object, the design of the compact insulating spacer is developed based on the surface electric filed optimization and the influence of the tilt angle at the central conductor of the spacer, the distance from the root of the high voltage shield electrode to the central conductor of the spacer and the angle of the side wall of the spacer on the tangential field strength is mainly studied. The simulation results show that the tangential electric field strength of concave and convex sides of the compact insulating spacer presents a single and double peak structure variation, and the maximum tangential electric field strength of convex side increases significantly, and the overall maximum tangential electric field strength decreases by 5.5%. When the tilt angle of the central conductor is 6°-8°, the maximum tangential field strength on the concave side reaches a minimum. It is found through the negative lightning impulse assessment and margin test on the compact insulating spacer designed in this paper that the insulation margin increases instead of decrease and is up to 1.35 times, which provides a reference for the engineering promotion of compact insulating spacer.关键词：gas insulated switchgear;insulating spacer;surface discharge;tangential electric field strength;lightning impulse voltage27|16|0更新时间：2025-04-26
- 摘要：In view of such shortcomings as large error of traditional amplitude method and high hardware cost of TDOA method in UHF location of GIS partial discharge, an equivalent distance method is proposed to derive the location of partial discharge source by using the amplitude attenuation generated by the signal passing through the GIS component structure. Considering the influence of different measuring point layout and noise interference on location, the signal amplitude and waveform characteristics of 3-5 adjacent measuring points are compared firstly to determine the discharge interval, thus calculating the assembly of partial discharge source in accordance with the attenuation characteristic value. The corresponding software function modules are designed and integrated. The data acquisition and location verification experiments are carried out by using 252 kV GIS circuit breaker bay and GIL at the factory. The result shows that the equivalent distance method achieves 75% of the component level location accuracy and 95% of the sub-gas-compartment level location accuracy and takes into account the accuracy, economic performance and practicality, which is helpful to detect defects in time and reduce the scope of disassembly at the project site.关键词：UHF;partial discharge;location;equivalent distance;signal attenuation16|15|0更新时间：2025-04-26
- 摘要：The optical fiber interferometric GIS partial discharge ultrasonic sensing system is susceptible to environmental disturbances, which can lead to a decrease in ultrasonic detection sensitivity. The sensing system based on single-loop feedback can suppress the vibration interference, but the working point drift still occurs in long-time operation. In this paper, the reasons for the working point drift of the single-loop feedback sensing system is analyzed firstly and the influence of the hysteresis effect of piezoelectric ceramics is pointed out. Then, a fiber-optic interferometric ultrasonic sensing system based on dual-loop feedback for GIS partial discharge is constructed, and a secondary feedback loop is introduced to compensate for the low-frequency phase modulation error accumulated in the primary feedback loop. After that, through ultrasonic detection tests and GIS partial discharge detection tests under vibration interference, the sensitivity of ultrasonic detection under the dual-loop feedback system is proved. Finally, the real 126 kV GIS partial discharge detection test platform is set up, the partial discharge triggered by metal particles and beating acoustic signals are successfully detected by using the dual-loop feedback sensing system, and the minimum apparent discharge detected is 5.2 pC.关键词：GIS;partial discharge;fiber optic ultrasonic sensing;feedback control;hysteresis effect14|7|0更新时间：2025-04-26
- 摘要：The long-term use of EPDM rubber sealing material for GIS equipment will occur aging phenomenon and will, in case of serious condition, lead to the sealing out of function as well as cause serious accident. Therefore, the thermal oxygen aging method is used in this paper to study the mechanical property variation of such two forms of EPDM rubber samples as sealing ring and sealing strip before and after aging, so to provide guidance for the long-term application of EPDM in GIS equipment. The results show that the Shore hardness will gradually increase with the increase of aging time, the tensile strength will increase firstly and then decrease, but the breakage elongation will always decrease. It is found by comparing the performance of the sealing ring and the sealing strip that the performance variation of the sealing ring and the sealing strip has the same trend, but in the process of the variation, the Shore hardness, tensile strength and breakage elongation of the sealing strip are greater than those of the sealing ring.关键词：EPDM;aging;Shore hardness;tensile strength;breakage elongation25|15|0更新时间：2025-04-26
- 摘要：Disconnector is an important component of GIS and, in case of foreign matter such as metal particles, insulation performance of the disconnector will be affected. Therefore, it is very important to calculate the electric field distribution of metal particles in disconnector of GIS. In this paper, the electric field intensity calculation of the disconnector without metal particles and with particles at different positions is performed by using the three-dimensional finite element analysis method. It is known by comparing the calculation result that the electric field distortion due to the metal particles attached to the surface of shield is the most serious. The metal particles on the surface of insulating rod and in SF6 will also increase the electric field intensity, likely causing discharge of disconnector. Based on the calculation results of electric field analysis, practical advice for the production and installation of disconnector is proposed.关键词：disconnector;metal particles;finite element method;electric field intensity25|17|0更新时间：2025-04-26
- 摘要：The study on temperature field of dry-type air-core reactors is very important for the design and manufacture of reactor. In view of large-capacity dry-type air core shunt reactor, a three dimensional reactor finite element simulation model, including the star-shaped support, sustaining bar and encapsulation insulation, is set up by using the electromagnetic-fluid-thermal multi-physical fields coupling method and considering the influence of temperature on the conductivity of aluminum conductor. The simulation analysis of BKGKL-40000/110 reactor in 110 kV transmission system is performed. The analysis results show that the temperature distribution of the reactor generally shows the trend of high at the upper part and low at the lower part, the air flowing velocity in the upper center of the reactor is the highest. The comparison between the experimental temperature measurement results and the simulation results is made, which is very close and shows the accuracy of the simulation method. In addition, the simulation results of the reactor with the rain cover are analyzed and compared. By analyzing the temperature distribution characteristics of the reactor, it provides reference for the design and manufacture of dry-type air-core shunt reactors.关键词：dry-type air-core shunt reactor;temperature field;finite element simulation;multi-physical field coupling15|12|0更新时间：2025-04-26
- 摘要：For solving the problem of partial discharge online location of cable of distribution network, a kind of two-terminal online location method of partial discharge of distribution cable based on pulse synchronization is proposed in this paper, and an online monitoring system of distribution cable for ubiquitous power internet of things is developed. First, the clock synchronization of the two-terminal system is achieved by injecting pulse signals into the cable, and the propagation speed of the high-frequency signal in the cable is obtained. The problem that the arrival time analysis method is difficult to synchronize in the application of the distribution cable is solved, the estimation of the partial discharge pulse arrival time based on the energy method is proposed to improve the robustness of the partial discharge location results. Then, the requirements and architecture of partial discharge (PD) online monitoring of cable of distribution network for the ubiquitous internet of things are described. Then, the realization method of key hardware, including high frequency current transformer with adjustable gain and inductive pulse injection device, is discussed in detail. Finally, partial discharge simulation tests are performed on 10 kV cable in the laboratory in order to verify the effectiveness of the proposed method and system. The experimental results show that, compared with the traditional location method based on GPS synchronization, the location accuracy of the proposed location method is significantly improved. In addition, the developed test system is used to test the real 35 kV cable in the wind farm at site, and the feasibility of the proposed method is verified.关键词：cable;partial discharge;location;synchronization;ubiquitous electric internet of things16|12|0更新时间：2025-04-26
- 摘要：Simply, feasibly, quickly and accurately assessing the real time temperature rise of cable is the base to release potential transmission capacity and improve operation efficiency. At present, the methods for assessing the temperature rise of cable core mainly includes measurement and calculation methods. The thermal circuit model of transient temperature rise of cable group introducing balance thermal resistance and thermal sensitivity is proposed with reference to the thermoelectric analogy method. However, in practical operation, the operating environment of the cable is much more complex. Such factors as the number of cable loop number and magnitude of load fluctuation may likely affect the accuracy of the mode. For fully validating the adaptability of the thermal circuit model, a finite element calculation example of the transient temperature rise of cable group is constructed at a complex environment and condition in this paper and compared with the thermal circuit model result. The verification result shows that, for different impact factors, the original thermal circuit model can be adjusted and extended flexibly without change of the parameter solving method and both convenience and accuracy of the model are free from influence. The loop number of cable, medium uniformity, load fluctuation magnitude, sunshine and environmental temperature variation do not remarkably reduce the accuracy of the model. The research results not only verify the model, but also provide an important reference for the test method of similar models.关键词：cable group;transient temperature rise;thermal circuit model12|7|0更新时间：2025-04-26
- 摘要：The typical three winding 240 MVA/220 kV power transformer, which is used widely in power system, is taken as an example, the working principle and four typical structural characteristics of high impedance transformer are described, the short-circuit resistance under different short-circuit conditions is analyzed, the short-circuit resistance performance of three high impedance transformers with typical structures is compared and analyzed and the pros and cons of the short circuit performance of the high impedance transformer is assessed. The results show that the high impedance transformer with high-voltage built-in and series reactance structure has good short-circuit resistance performance, and the series reactance structure has more advantages in the axial force and the compressive stress of high, medium and low winding, the circumferential stress of regulating winding, the end axial force of transformers and the overall short-circuit resistance is the best.关键词：transformer;high impedance;short circuit;stress;axial force17|10|0更新时间：2025-04-26
- 摘要：Dissolved gas analysis in oil can reflect the operation status of transformer. The accurate prediction of volume fraction of the dissolved gas can provide theoretical support for discrimination and warning of early fault of the transformer. Therefore, a prediction method of dissolved gas volume fraction in transformer oil based on time varying filter empirical mode decomposition and multi-model fusion is proposed. Firstly, the gas volume traction sequence is decomposed into multiple sub-sequences by time varying filter empirical mode decomposition to reduce its non-stationarity. Then, the multi-model fusion strategy is used to fuse and reconstruct the prediction results of four different single models. Since the weight coefficient of single model has a significant impact on the prediction results, the improved slime mold algorithm is used to optimize the weight coefficient to improve the prediction accuracy. Finally, it is shown through calculation variation that the proposed method, compared to traditional prediction model, has higher prediction accuracy, and can better predict the variation trend of gas volume fraction in the oil.关键词：prediction of dissolved gas in oil;time varying filter empirical mode decomposition;improved slime mould algorithm;multi-model fusion14|7|0更新时间：2025-04-26
- 摘要：Surge protection device (SPD) is an important electrical device for limiting over-voltage and releasing surge current in low-voltage power lines. With the development of the internet of things, the traditional SPD has gradually developed into an intelligent SPD with the functions of online monitoring, fault diagnosis and life prediction. Since the life of SPD is closely related to the life of its core component, namely metal oxide varistor (MOV). In this paper, the characteristics equations of MOV under different impulse current are obtained through test on the basis of the Weibull distribution and the impulse current life characteristics of MOV. A kind of residual life assessment method is proposed in accordance with the established impulse current life characteristics equations and the impulse current monitoring data of SPD in operation, which provides the theoretical support for the development of smart SPD.关键词：smart SPD;MOV;Weibull distribution;impulse current life;remaining life16|8|0更新时间：2025-04-26
- 摘要：For clarifying the pros and cons of the presently various measurement principles of the leakage current of the arrester, selecting the measurement principle with higher accuracy and better applicability, and solving the problem that the traditional online monitoring device is not sensitive to the early performance deterioration of the arrester and can not avoid the interference of the polluted current of the outer coat, such four current analysis methods as the full current method, the resistive current fundamental wave method, the capacitive current compensation method and the harmonic analysis method and their interference factors are analyzed in this paper. It is considered that for the AC power system at 110 kV and above, due to the small harmonic interference of the power grid, the use of the harmonic analysis method as the leakage current analysis method of the online monitoring device of the arrester is more accurate and reliable. A kind of built-in online monitoring device of the arrester based on the harmonic analysis method is proposed in this paper. The temperature and humidity as well as current sensors are built into the cavity of the arrester element, the monitoring data of the temperature and humidity of the arrester core and the leakage current are collected, and the operation state of the arrester is assessed in a multidimensional real-time manner. Compared with the traditional monitoring device of the arrester, the built-in monitoring device improves the accuracy of the measurement in terms of the design principle, has passed the operation reliability verification, and is a more effective state monitoring method.关键词：monitoring device;MOA;resistive current measurement;built-in monitoring device28|14|0更新时间：2025-04-26
- 摘要：This paper aims to study the over-voltage in case of switching the parallel reactive power compensation capacitor banks in the power system. The switching capacitor bank model is set up through ATP-EMTP software and the over-voltage level of both general switch and series resistor switch is simulated under various conditions. For solving the problem of the ineffectiveness of series resistor switch in limiting two-phase reignition at two times, a solution using a series non-linear resistor combination switch is proposed, and the effects of the three schemes in limiting the over-voltage are compared. The simulation results show that the series nonlinear resistor combination switch shows excellent limiting effect under two-phase reignition conditions at two times, can effectively suppress the over-voltage and protect insulation of the capacitor bank. The combination switch can be used as a reference for the design of reactive power compensation system for shunt capacitor bank in power system.关键词：shunt capacitor bank;ATP-EMTP;reignition over-voltage;series resistance switch15|9|0更新时间：2025-04-26
- 摘要：For further understanding the superconducting characteristics of the superconducting tape and the rule of the establishment of quench resistance in the DC superconducting current limiter under the DC short circuit current, the direct current impulse experiment is performed on the superconducting tape, and the quench resistance characteristic of the tape under the action of the impulse current is measured. It is obtained that the quench resistance per unit length of the superconducting tape has a fixed functional relationship with its heat generation. Based on this, a simulation model of the resistance and temperature rise of the superconducting tape with variable length is set up, the reason for the irreversible damage of the superconducting tape is analyzed, and the reliability of the model is verified by experiments. Based on this model, the superconducting assembly in the 5 kV hybrid superconducting current limiter is designed. This method also has strong guiding significance for the design of other superconducting current limiters.关键词：hybrid superconducting current limiter;superconducting tape;DC impulse;quench characteristics;tape damage12|6|1更新时间：2025-04-26
- 摘要：The flexible low-frequency transmission system based on the modular multilevel matrix converter (M3C) has great application potential in the fields of long distance and large capacity transmission, urban power grid and offshore wind power transmission, and has received extensive attention in recent years. At present, the research on the startup control strategy of the flexible low-frequency transmission system based on M3C is less and, on this purpose, the relevant research in this field is performed in this paper. First, the structure of the flexible low-frequency transmission system and the basic principle of M3C are studied, and the problems to be faced in the startup process are analyzed. Then, a reasonable charging strategy is designed for M3C based on the characteristics of full bridge sub-module. And a reasonable startup logic is designed for the dual terminals M3C flexible low-frequency transmission system to ensure that the low-frequency circuit breaker can be closed without impact and the M3C stations can be connected without disturbance during the startup process. At the same time, the current impact can be reduced in the process of M3C deblocking and low-frequency voltage establishment. Finally, the correctness and feasibility of the proposed startup control strategy are verified by setting up a simulation model under the PSCAD/EMTDC simulation software. The startup control strategy proposed in this paper is safe, reliable and easy to implement and has high engineering application.关键词：flexible low - frequency transmission system;modular multilevel matrix converter (M3C);startup control strategy;closed without impact;connected without disturbance14|7|0更新时间：2025-04-26
- 摘要：The reliable operation of Modular Multilevel Converter (MMC), as the commonly used grid connection scheme of large scale PV collection system, is the key prerequisite for achieving the applications of large-scale PV collection dc systems. In recently years, many researches have been performed to enhance reliability of MMCs by optimizing the thermal distribution. However, such related researches as taking the MMC as the research object, summary and analysis of its electrothermal characteristic and corresponding optimization method are still lacked. Therefore, the thermal distribution characteristics of MMCs and their influencing factors are analyzed in this paper, and the latest progress of the electrothermal optimization, adjustment and control methods is summarized. Firstly, the thermal distribution characteristics between the inside of the MMC sub-model and sub-model inside the same arm and the reasons for the difference are analyzed. Then, the basic principles and control objectives of different MMC electrothermal regulation methods are introduced and their pros and cons are also discussed. Finally, the main challenges of different improvement methods and research directions in the future are analyzed so as to provide a reference for the research of thermal distribution improvement and reliability enhancement of MMC.关键词：thermal distribution improvement;modular multilevel converter;sub-module design;active thermal control14|8|0更新时间：2025-04-26
- 摘要：The anhydride curing agent is widely used in the epoxy resin composite casting system for power equipment due to its such advantages as good heat resistance, small curing shrinkage and good insulation performance. The power system is developing in the direction of high voltage and large capacity, which puts forward higher requirements on the performance of power equipment. For obtaining high-performance epoxy composite insulation materials, the influence of five common anhydride curing agents on the performance of epoxy resin composite material is studied, finding that the phthalic anhydride has excellent performance, but there are problems of weak curing process and large dispersion of cured properties. Furthermore, a phthalic anhydride/hexahydrophthalic anhydride compound curing agent is prepared. The influence of the compound curing agent on the mechanical and electrical properties of epoxy composites is also studied. The experimental results show that when the molar ratio of phthalic anhydride/hexahydrophthalic anhydride is 1∶3, the melting point of the compound curing agent has the lowest melting point and better curing process. The maximum tensile, flexural and breakdown strength of the cured product are slightly reduced, yet the average value has increased significantly, the dispersion is significantly reduce and the arc resistance performance has increased by 49%.关键词：anhydride curing agent;power equipment;compound curing agent;dispersion14|12|0更新时间：2025-04-26
- 摘要：In view of inconsistent response speed of distributed energy storage primary sag controller of the distributed energy storage of each power grid due to differences in impedance of different grids in smart grids, difficult coordination of multiple sag control methods (P-f/Q-U sag, improved P-f/Q-U sag and improved P-U/Q-f sag, etc.) as well complex design of the controller design, a kind of autonomous control method for distributed energy storage system in smart grid based on multi-agent consistency theory is proposed in this paper so to achieve high efficient coordination of different sag control modes, effectively improve the voltage frequency control effect at distributed energy storage PCC and the accurate power distribution of each energy storage system. First, the distributed energy storage control sag model under different impedance power grid conditions is studied deeply by the method, the distributed control theory is adopted to design a distributed energy storage unified secondary controller to control the frequency and voltage of the distributed energy storage PCC points, and proportionally distribute the active and reactive power output of the energy storage system. Then, due to the long distance between different power grids, the communication delay will affect the control effect and even destroy stability of the control system. The multi-agent correlation theory is adopted in this paper to design a directional communication method, and the delay upper bound condition to achieve the control goal without losing the stability of the control system is deduced. Finally, the effectiveness of the proposed method is verified by simulation analysis on the improved IEEE 118 node power system.关键词：cooperative secondary control;sag control;distributed energy storage;multi-agent system;smart grid13|7|1更新时间：2025-04-26
- 摘要：C4F7N gas mixture is an environmentally friendly insulating alternative gas to SF6 for new electrical equipment. C4F7N gas mixture, in case of being used as an insulating gas in high-voltage equipment, has similar problems with SF6 equipment, and the quality of the gas mixture affects normal operation of the equipment. The C4F7N gas mixture, in case of moisture exceeding the limit, is likely to occur such problem as reduction of insulation performance of equipment due to discharge. It is therefore particular important to develop the operation, maintenance and detection device for the use of C4F7N gas mixture. In this paper, the quantitative detection technology of micro moisture content in C4F7N by tunable laser infrared absorption spectroscopy is mainly studied. The spectroscopy theory of the tunable laser, the principle of harmonic detection and the infrared absorption characteristics of moisture are studied, and the influence of C4F7N as background gas on the accuracy of micro moisture detection is introduced. Then, the TDLAS structure design, hardware design and type selection are introduced. The DFB laser is used to design and manufacture the photoelectric conversion module, the light source driving module, the infrared multiple reflection pool, the circuit as well as software parts. The micro-moisture detection device for C4F7N gas mixture is developed based on the tunable laser, which removes the influence of interference components, improves the accuracy of micro moisture detection and can detect a low limit down to 1 μL/L. The performance results of the device show that it meets standard requirement, has high accuracy of quantitative detection of micro-moisture, and is beneficial to the correct judgment of the operating state of the equipment.关键词：C4F7N micro water detection;TDLAS;environmental gas11|7|0更新时间：2025-04-26
Research & Analysis
- 摘要：The DC voltage equalizing resistors in the TFM board for UHVDC converter valve has high operating temperature and obvious hidden danger in application. In this paper, an improved resistance cooling improvement scheme compatible with the original board design and interface is proposed on the basis of theoretical analysis as well as through simulation and test. The feasibility and reliability of the proposed scheme are further verified based on such tests as thermal stress, vibration, partial discharge and board function. The engineering application of the improved scheme and its temperature measurement results show that the proposed scheme is compatible with the original TFM board design and interface and, at the same time, reduces the operating temperature of resistor remarkably.关键词：converter valve;TFM board;DC grading resistance;drop the temperature18|8|0更新时间：2025-04-26
- 摘要：The back-to-back capacitor bank switching test is an important type test item for assessing the re-strike probability of circuit breaker in switching the capacitor banks. In view of the difficulty in accurately adjusting the making inrush current peak Ibi and the inrush current frequency fbi during the testing process, a three-phase switching test circuit using the impulse generator as power source is proposed on the basis of analysis of requirements of China National Standards. The general calculation formulas for inrush current peak Ibi and inrush current frequency fbi are derived by using equivalent circuits, and the quantitative relationship among the line length l, capacitance CS and inrush frequency fbi is obtained at the test voltage of 12 kV, the inrush current of 20 kA, and the breaking current of 400 A and 800 A, respectively. The results show that the line length l is positively correlated with with CS and negatively correlated with fbi. Finally, the back-to-back capacitor bank switching test of circuit breaker at rated voltage of 12 kV is performed by using a 3 200 MVA impulse generator test system, together with three-phase capacitor banks of power circuit and load circuit, both the making inrush current peak Ibi and inrush current frequency fbi meet the standard requirements, and the correctness and effectiveness of the calculation method as well as the test circuit in this paper are verified.关键词：circuit breakers;back-to-back capacitor bank;inrush making current;inrush current frequency;impulse generator17|10|0更新时间：2025-04-26
- 摘要：The key parts of the disconnector is taken as the research object, a high and low temperature test chamber is designed to study the influence degree of environmental temperature variation on the material properties of the key parts of disconnector. First, through the experimental research on such key performance index as tensile strength, end face shrinkage, 0.2% non-proportional elongation strength, elastic modulus and Poisson’s ratio of such four kinds of material as 6005-T5, T2Y, ZL101, Q235, the variation of the key performance index of the 4 kinds of materials with the ambient temperature is mastered. Then, the high and low temperature test platform is set up and a contact system which can rotate continuously is designed so to study the influence of ambient temperature on the contacting pressure of contact finger, spring force, and wear resistance of the silver plating layer. The variation rate of the contacting pressure of the contact finger at 5 temperature points is basically between ±6%, and the variation rate of contact finger spring force is less than 3%, the wear amount of the silver plating layer on the contact finger decreases first and then increases with the increase of temperature. At 0 ℃, the wear amount of the contact finger of the contact is the smallest. Based on the structural characteristics of the disconnector, measures have been proposed in terms of materials, structural design, and high and low temperature adaptability tests, which lay a theoretical foundation for further improving the stability of the disconnector in high and low temperature environments.关键词：disconnector;performance index;contact finger finger;silver plating;adaptability27|15|0更新时间：2025-04-26
- 摘要：In view of the driving failure due to the cutting of driving key of the bevel gear and bevel gear shaft of the driving mechanism for 252 kV GIS disconnector in a power grid substation project, the flat key used in this fault position is GB1096A type 4×4×10 key. In order to analyze the cause further, the faulty level gear, driving shaft and the broken flat key are returned to the factory from site and are subject to materials and hardness inspection. The cause of the failure is found from the aspects of design and assembly analysis, the corresponding solution measures are formulated, the safety risks of such problems are eliminated, which lay a foundation for the subsequent production of this product, improve reliable operation of the power grid and reduce the operation accident rate of power grid.关键词：driving failure of disconnector;cause analysis;optimization and improvement34|14|0更新时间：2025-04-26
- 摘要：The abnormal mechanical operation of the vacuum circuit breakers in C-GIS (cubicle type gas insulated switchgear) at 40.5 kV occurs occasionally under low temperature conditions. Thus, it is an urgent need to improve the mechanical operation reliability under low temperature. The influencing factors of the mechanical operating performance of the vacuum circuit breaker under low temperature environment are deeply analyzed, and the mechanical operating performance under low temperature is studied through experimental methods. The test results indicate that ①The viscosity resistance of the lubricating grease is the main factor affecting the abnormal operation of vacuum circuit breakers under low temperature. ②The special low temperature lubricating grease can assure the normal operation of transmission chain kinematic pair in vacuum circuit breakers for environment temperatures as low as -30 ℃. The optimization of the transmission chain kinematic pair in the vacuum circuit breaker and the low-temperature lubricating grease selection can improve stability and reliability of vacuum circuit breakers mechanical operation.关键词：vacuum circuit breaker;low temperature;mechanical operation;transmission chain;lubricating grease31|18|0更新时间：2025-04-26
- 摘要：In this paper, several resonance cases of power system resonance are analyzed in detail, the the condition to generate resonance in the system and the multiple abnormal characteristics reflected in GIS equipment during system resonance are summarized, and fast qualitative judgment by observing these abnormal phenomena is analyzed so as to take correct and effective measures to eliminate hidden dangers, avoid damage of equipment and ensure safe operation of the system. At the same time, the subsequent measures to suppress resonance are also discussed in detail in order to provide reference for improving the stable operation of power system and avoiding resonance failure.关键词：power system;resonance case;measures26|19|0更新时间：2025-04-26
Technical Discussion
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