最新刊期
卷 60 ， 期 3 ， 2024
- 摘要：The voltage equalization problem of multi break vacuum switch can be solved by internal control measures and one of which is breaking speed. However, the research on speed regulation has not been studied deeply. In order to study the influence of the breaking speed of the operating mechanism on the dynamic voltage distribution of the double break vacuum switch, the two-stage speed control method is proposed on the basis of analyzing the influence of breaking speed on the voltage distribution. The two-break vacuum switch model is set up to simulate and analyze the voltage distribution in the case of synchronous, asynchronous and variable speed breaking. The speed regulation and control device of the vacuum switch is designed and the breaking speed test platform of the vacuum switch is set up. The test shows that, in case of synchronous breaking, the influence of the switching speed variation at high and low voltage side on the voltage distribution of the break is less. Both asynchronous breaking and variable speed breaking can regulate and control the dynamic voltage distribution by way of changing the breaking speed and dynamic voltage uneven factor can be reduced by up to 15%. The result in this paper can provide data reference for the study of voltage distribution of vacuum switch with multiple break through speed regulation and control.关键词：vacuum switch;IGBT breaking;two-stage speed control;dynamic voltage distribution15|38|2更新时间：2025-04-26
- 摘要：The primary and secondary fusion technology makes the arrangement of secondary intelligent sensor unit in the distribution switch close to the primary high-voltage electromagnetic environment, and the distribution switch has a large number of faults due to electromagnetic interference. In this paper, based on the principle of controlled arc discharge, a transient electromagnetic interference simulation test platform for a 10 kV primary and secondary fusion distribution switch is set up, and the interference signal of the outdoor primary and secondary fusion distribution switch is obtained, in which the law of spatial magnetic field near the intelligent sensor is mainly studied. The shielding effectiveness of the distribution terminals (FTU) is analyzed, and the interference of power line of the sensor merging unit is calculated. The results show that the intelligent sensor in the primary and secondary fusion distribution switch may have serious fault under the continuous strong transient electromagnetic disturbance. The electromagnetic transient simulation test system studied in this paper can check the anti-strong electromagnetic interference ability of intelligent sensor, and the existing standards cannot meet the detection requirements of anti-strong electromagnetic interference ability of intelligent sensor equipment under the primary and secondary fusion structure.关键词：primary and secondary fusion;electromagnetic interference;sphere gap breakdown;intelligent sensor11|29|0更新时间：2025-04-26
- 摘要：In view of such issues as high movement speed, multiple dynamic parameters and difficulty in accurate monitoring of the permanent magnet repulsion mechanism for short stroke DC vacuum circuit breaker, a kind of multiple parameter dynamic characteristic monitoring system is designed. The permanent magnet repulsion mechanism for 400 V/400 A/25 kA DC vacuum circuit breaker is taken as the research object, the optocoupler isolation technology is used to collect the voltage simulation signal of the opening and closing coil and, at the same time, the sensing technology and second-order filtering mode are used for noise reduction collection of the current and displacement signal. The upper computer display interface is developed independently based on the C# to achieve the real-time synchronous display of multiple parameters of the short stroke and fast operating mechanism. It is known through comparison and analysis of monitoring parameters of current sensor and mechanical characteristic tester that the collection error of the system can be controlled within 3.5%.关键词：DC vacuum circuit breaker;permanent magnet repulsion mechanism;mechanical characteristics;dynamic characteristics;opto-coupler isolation;error analysis10|47|0更新时间：2025-04-26
- 摘要：The increase of spring pressure of contact of vacuum circuit breaker will cause the circuit breaker not to close reliably. The four-bar structure will, to a certain extent, affect the output characteristics and mechanical benefits of the mechanism, and thus affect both reliability and stability of circuit breaker in closing operation. In this paper, the operation principle of vacuum circuit breaker is analyzed and the mathematical model of the spring operation mechanism is set up. The cam profile, angle and size of transmission lever, dimension parameters of connecting plate and closing roller in the mechanism are optimized, and the simulation model of spring operating mechanism is set up. The dynamic simulation shows that the pressure of the spring of the contact after optimization is increased by 58% (increase from 1 700 N to 2 686 N), which can still assure the reliable closing of the operating mechanism of the circuit breaker. The test results show that when the contact spring pressure is 2 500 N, the contact of the circuit breaker can engage reliably, the average closing speed is reduced to 0.68 m/s, and the bouncing time is shortened by 18.4%. The overall scheme after optimization meets the design requirements and has good reliability and stability.关键词：vacuum circuit breaker;spring operating mechanism;optimization design;Adams simulation;travel curve in closing operation26|69|1更新时间：2025-04-26
- 摘要：The charging coil spring is the core element of operating mechanism for high voltage circuit breaker and is prone to fatigue cracks or damage in its operation. Therefore, the ultrasonic guided wave detection on it is an important measures to ensure safe and stable operation of the power grid. In this paper, the influence factor analysis of the ultrasonic guided detection of the charging coil spring of the circuit breaker is developed by way of studying wave propagation mechanism of the charging coil spring of the circuit breaker. At the same time, a set of ultrasonic guided wave detection instruments for the non-destructive detection of the charging coil spring of circuit breaker is designed and developed, the detection difficulty of the charging coil spring of the circuit breaker in case of no disassembly has been solved through actual detection verification at site, which provides a new technical means for the charging coil spring network detection in the future.关键词：charging coil spring;ultrasonic guided wave;dispersion curve7|34|0更新时间：2025-04-26
- 摘要：For a long time, the researchers are lack of understanding the spatiotemporal evolution of the fire development in switchgear cabinet due to the enclosed characteristic of the switchgear cabinet. There is a dispute about weather the cable discharge can ignite and how to combust and targeted prevention measures are lack of basis. It is difficult to carry out full-scale test due to large difficulty in the combustion test. In this paper, the fire process caused by short-circuit of single-phase grounding cable of HV switchgear cabinet is studied. A full-scale test platform is set up to study and master the temperature distribution inside and outside the switchgear cabinet as well as the cable sheath in the short circuit fire process. The research of multi-physics field simulation is performed, the ignition model of the switchgear cabinet is constructed and the fire spreading is mastered. Based on the simulation and test results, the cable material decomposition process and the influence of material decomposition on the combustion are analyzed. Through the research mentioned above, the combustion mechanism of insulation fault of cable for HV switchgear cabinet is mastered. The cable sheath temperature can well reflect the internal fault temperature of the switchgear cabinet, which lays a foundation for the fire prevention of the switchgear cabinet.关键词：combustion simulation;fault of cable;numerical simulation;ignition mechanism;material pyrolysis10|43|0更新时间：2025-04-26
- 摘要：In view of the problems of large error, low efficiency, and difficulty in locating to the specific switchgear cabinet faced by current partial discharge locating method of high voltage switchgear cabinet, the locating technology based on the TEV signal of switchgear cabinet is studied in this paper and a TEV- cascade locating method is proposed. Through the wired cascade of distribution sensors, the time-sharing comparison method of double bus and the switching strategy of TEV sensor state, the single dual-channel acquisition card could collect and compare the TEV sensor signal pulse on multiple switchgear cabinets so as to quickly, efficiently and accurately locate the specific switchgear cabinet in the row of switchgear cabinets where the discharge source is located. Based on this method, a cascaded locating system of high voltage switchgear cabinet is designed. By using the bus cascade-modular design, the requirement of arbitrarily expanding the number of TEV detection node can be met without adding the number of high-speed acquisition channels, which make the reduction of the system costs maximum. The locating effect of this method is verified by setting up verification platform, the working efficiency of the cascade system is proved and the purpose of locating the defects to specific switchgear cabinet is achieved.关键词：high voltage switchgear;transient earth voltage (TEV);PD locating;pattern recognition;cascade system10|46|1更新时间：2025-04-26
- 摘要：The outdoor high voltage disconnector, as the core equipment of the power transmission system, is often affected by the failure of closing operation due to interference of external wind force. Therefore, a kind of new type of anti-interference high voltage disconnector is designed. For studying the mechanical characteristics of the new disconnector under wind load further, firstly, the calculation model of wind field resistance torque of high voltage disconnector is constructed in Fluent software, and the resistance torque generated by the direction of wind field flow on the conducting rod is calculated. Then, the finite element model of the new disconnector is set up in the finite element software Ansys. Finally, the mechanical characteristics of the new disconnector are analyzed by applying the resistance torque generated by wind load to the simulation model. The results show that the deformation and stress concentration position of the disconnector are located in the pin hole of the support, which is judged to be the weak link of the disconnector, and on which the reinforcement treatment should be particularly considered. The simulation analysis mentioned above provides the basis for the wind resistance optimization design of the disconnector.关键词：disconnector;closing;wind load;mechanics characteristic;stress analysis14|26|0更新时间：2025-04-26
- 摘要：The operational reliability of ultra-high voltage DC GIL depends on the reliability of the internal insulation design. In addition, such issues as selection of DC current density of conductive element, the positioning design of spring contacts, the treatment of wedge-shaped air gaps at the connection between insulation part and fitting in GIL components as well as the structural design details of support components in the busbar will have a significant influence on the operation reliability of product and cannot be ignored. For UHV DC GIL operating in a very harsh environment, a high airtightness structural design is proposed in this paper in order to assure the reliability of internal insulation work and reduce gas maintenance work. To meet the requirements of low temperature operation at -50 ℃, N2/SF6 gas mixture with very low liquefaction temperature is selected for the product. The ratio, pressure characteristics and insulation characteristics of the two gases are discussed and calculated. The reliability design of the monitoring system for partial discharge, gas density, and micro water content of the product will also affect directly the operational reliability of the product. The research results of the above issues are introduced in this paper, which can be used for the design of high-voltage DC products. A research plan is proposed for such unsolved new technologies as intelligent gas humidity and density monitoring devices based on the principle of cold mirror dew point testing and microelectromechanical technology as well as the initial field strength of partial discharge on the umbrella surface of high-voltage DC composite insulation sleeves. The multiple reliability design points for GIL operation proposed in this paper can be used as reference for other ultra-high voltage DC gas insulated apparatus.关键词：current density;spring contact positioning;wedge shaped air gap;high gas tightness design;new technology for monitoring and early warning of partial discharge and microwater16|63|1更新时间：2025-04-26
- 摘要：Compared to common high voltage circuit breaker, the increase of asymmetry degree of major loop current for T100a test of circuit-breaker intended for controlled switching leads to the parameters of current and transient recovery voltage (TRV) provided in IEC 62271-101:2021 appendix A and E not to be applicable any longer. In order to calculate these parameters quickly and accurately, it is proposed in this paper such method that takes the short circuit current symmetrical component as the foundation to calculate current parameters and obtain the TRV correction coefficient through the time-domain analysis, which is of simpleness, high efficiency, flexibility and wide application range. Its calculation result and the calcualtion value by the traditional formula are in agreement, and are also recognized by IEC WG67 as well as included in appendix N of IEC TS 62271-319 (DTS).关键词：asymmetric short-circuit;T100a;symmetrical component;transient recovery voltage (TRV);circuit-breakers intended for controlled switching10|32|0更新时间：2025-04-26
- 摘要：High-voltage AC current-limiting fuse has been used widely in distribution network, and is an important protective component to ensure safe operation of power system. Some high-voltage current-limiting fuses are installed with the strikers for indicating operation and driving other switching devices to open. The performance of the installed strikers is an important factor to ensure the correct coordination between fuses and switching devices in case of failure. It is therefore necessary to carry out research on the test technique of high-voltage AC current-limiting fuse strikers and analyze its feasible test verification method. In this paper, the research on operation test of the striker, including such contents as implementation of the operation test, measurement of released energy, measurement of the minimum withstanding force and measurement of duration of travel, is mainly performed through the research of performance verification and test method of high voltage AC limiting fuse and in combination with test requirement of the strikers in the standard, and both feasibility and rationality of the implementation of above research contents are proved by the test verification. The implementation method on performance test verification of high-voltage AC current-limiting fuse strikers proposed in this paper will be of great significance to the high-quality development of this kind of product and, at the same time, also provide help for reasonable selection of high-voltage current-limiting fuses for relevant switchgear.关键词：high - voltage AC current - limiting fuse;strikers;operation tests;measurement of the energy;withstanding force15|20|0更新时间：2025-04-26
- 摘要：Composite insulator is used widely in power grid due to its good performance. For improving both intelligent and automated level of live hydrophobicity detection of composite insulator, a kind of hydrophobicity diagnosis method of composite insulator based on lightweight convolution neural network is proposed in this paper. The EfficientNet algorithms is used in this paper to perform feature extraction and training on the water trace image data corresponding to the different hydrophobicity levels of the composite insulator. It is defined through comparison in such aspects as accuracy of model and the amount of parameters and also in combination with the model’s forward inference speed on the edge computing device that the EfficientNet-b3 model is the optimal model in this application scenario. The classification accuracy rate of this model is 96.43%, and the forward inference speed on Jetson Xavier NX is 57.16 FPS, which is superior to other classic convolution neural network comparison algorithms in terms of accuracy and speed. The classification effectiveness of the model in practical applications is verified by the the measurement results of the back contact angle. This model equipped with an unmanned aerial vehicle can measure the hydrophobicity of composite insulator in operation, and has certain innovative value and good application prospects.关键词：composite insulator;hydrophobicity;convolution neural network;EfficientNet;edge calculation10|64|1更新时间：2025-04-26
- 摘要：In case of applying DC voltage, a large amount of charge will accumulate on the insulating spacer of gas insulated switchgear (GIS), which will greatly reduce the flashover voltage along the surface, resulting in a series of faults of electrical equipment. Based on the above problems, the source and conduction path of the insulating spacer surface charge is analyzed in this paper, the two-dimensional axisymmetric simulation model is constructed and the relevant parameters are set by using finite element simulation calculation method, and the influence of voltage polarity, different voltage amplitudes and voltage polarity reversal on the distribution of insulating spacer surface charge is studied. The results show that under DC voltage, the charge which is oppotite to the applied DC voltage polarity is mainly accumulated in the concave side and the charge which is identical to the DC voltage polarity is mainly accumulated in the convex side and the charge density accumulated on the concave side is larger. In case of DC voltage at -100 kV after polarity reversal, the charge density originally accumulated on the surface of the insulating spacer shows a trend of increasing firstly and then decreasing gradually, and then the polarity is converted to reach saturation. The distortion degree of the electric field near the high voltage end and from 0-20 mm along the surface of the insualting spacer is obvious. The peak value of the electric field appears before variation of the surface charge polarity of the insualting spacer. Compared with the saturated state of the charge, the maximum field strength of the concave side of the insulating spacer is increased by 46%, and that of the convex side by 5.4%. This study can provide guidance for the distribution of the surface charge of the insulating spacer under DC voltage.关键词：surface charge distribution;insulating spacer;DC GIS;charge accumulation9|109|0更新时间：2025-04-26
- 摘要：The insulating spacer, an important part of GIS, is mainly fixed by flange bolts, but the looseness of bolts will cause such problems as uneven force and even gas leakage of the insulating spacer, which will seriously affect reliability and safety of GIS operation. In this paper, a kind of ultrasonic wave monitoring method for the looseness of flange bolts of GIS insulating spacer is proposed, the excitation and reception of ultrasonic signal is performed by using the piezoelectric sensor, and the piezoelectric sensor is installed on both sides of the flange connected by the bolt to be tested, and the degree of bolt looseness is judged in accordance with the energy attenuation rate of the ultrasonic response signal. The variation of ultrasonic response signal energy and its attenuation rate under different working conditions are studied through experiments. The results show that with increase of bolt looseness, the amplitude of the response signal decreases gradually and the signal energy attenuation rate gradually increases, the annentuation rate of the signal energy, in case of single bolt looseness and the looseness grade is 3, can be up to 40.8% and, at the same time, it is found that the annenuation rate of the receiving signal energy of the piezoelectric sensor which is closest to the bolt looseness is maximum. The method proposed in this paper can monitor the looseness of flange bolts of GIS insulating spacer, and has certain engineering application.关键词：ultrasonic wave;GIS;insulating spacer;piezoelectric sensor;bolt loosening monitoring8|49|1更新时间：2025-04-26
- 摘要：The reaction mechanism function can effectively characterise the insulation ageing and deterioration process of GIS basin-insulators, which helps to reveal the failure mechanism of insulating materials and provides a new way to assess the insulation performance of basin-insulators. By resolving the differential equations of the reaction mechanism, an integral expression for the reaction mechanism function with four basic parameters is established, which can be modified for different reaction stages or paths and has a wider scope of application. On this basis, a structural form of this test function is derived based on the non-isothermal kinetic equations and the formulae for calculating the model are derived. Using this method it is also possible to calculate the finger front factor at the same time. The reaction mechanism functions for basin insulators and cross-linked polyethylene are further specified and the validity of the generic characterisation model and solution method for the reaction mechanism functions is verified based on the Coast-Redfern method and the modified Flynn-Wall-Ozawa method. The above work provides an effective method for analysing the reaction mechanism of the degradation process of insulator insulation materials.关键词：insulator;thermal dynamics;reaction mechanism function;activation energy8|20|0更新时间：2025-04-26
- 摘要：The insulating spacer, a key element of gas insulated metal closed switchgear (GIS), is prone to insulation defects and aging cracking due to long-term electrical thermal stress, which is one of the main reasons for the failure of GIS equipment. The characterization of activation energy can effectively describe the deterioration degree of the insulating spacer material, so it is important to study the effective calculation method of activation energy during the deterioration process of the insulating spacer. In this paper, the thermal analysis kinetics is studied based on the accelerated aging test samples. The pyrolysis process of the insulating spacer is analyzed by traditional thermal weightlessness test, and the activation energy of the insulating spacer is calculated by Flynn-Wall-Ozawa method. Furthermore, a method for calculating conductive activation energy based on leakage current is set up to perform conductive activation energy calculation of different aging experiment samples. Finally, it is found through comparison and analysis with the traditional Flynn-Wall-Ozawa method that the calculation results and the aging correlation of the two methods are basically identical. Furthermore, the characterization means and correlation of the aging degree of the two methods are analyzed in theory. The above research provides theoretical guidance and experimental analysis for calculating activation energy of insulating spacer without damage, and helps to reveal the pyrolysis aging mechanism of the insulating spacer.关键词：GIS insulating spacer;material aging;thermal weightlessness;leak current;activation energy12|25|0更新时间：2025-04-26
- 摘要：In view of excessive temperature rise of distribution transformer due to seasonal overload of power grid, it is proposed in this paper to install external cooling modules on the heat sink of oil-immersed distribution transformer to strengthen the heat dissipation ability of the transformer and reduce the hot spot temperature rise. For verifying the feasibility of this method, a set of type S13-M-200/10 distribution transformer is taken as the research object to set up a three-dimensional model. The external cooling module is set up on the heat sink of the transformer model. Four different calculation models are formed by changing the installation position and number of cooling modules. The finite volume method is used to calculate the hot spot temperature rise of each model under different load conditions. Some of the simulation results are verified by short circuit temperature rise test, and the error between simulation and calculation is less than 3 K. The test and simualtion results show that reasonable arrangement of external cooling modules can reduce the hot spot temperature rise of the oil immersed distribution transformer by approximately 10 K, which provides a new idea for reducing the temperature rise of the distribution transformer.关键词：distribution transformer;external cooling module;hot-spot temperature rise;finite volume method;temperature field12|45|0更新时间：2025-04-26
- 摘要：The air arc is a common plasma, and the study of its microscopic parameters in the steady state stage is of great significance for accurately grasping the reaction mechanism inside the plasma. Emission spectroscopy is a mature technique for diagnosing plasma electron density, which has such advantages as non-contact measurement, transient detection, high sensitivity, fast response, and simple instrumentation. In this paper, the Hα 656.28 nm spectral line is used as the characteristic spectral line, and graphite is used as the electrode material to measure the emission spectrum of the air arc under the conditions of 250 A and 200 V. Abelian inverse transformation and Viogt off-line fitting are performed on the emission spectrum obtained from the experiment, Stark broadening is obtained by deconvolution, and finally the radial distribution of the air arc electron number density is obtained. At the same time, the Thomson scattering method is used to measure the electron number density of the air arc under the same parameter conditions to verify the correctness of the emission spectrometry measurement results. It is verified that the measurement results of the two methods have good consistency. This experiment provides a reference idea and method for the measurement of air arc plasma electron number density.关键词：gas arc;emission spectroscopy;Thomson scattering;steady state;plasma9|46|0更新时间：2025-04-26
- 摘要：LCC-FHMMC hybrid HVDC system can completely solve the problem of commutation failure at inverter side, and has broad application prospects in the field of power supply to passive network. The mathematical model of double ended hybrid DC transmission system is set up and, on the basis of the analysis of the fault mechanism at the sending end and the characteristics of the passive network, a kind of fault ride-through control strategy based on the bridge arm voltage control is proposed. By allowing the load to actively participate in regulating the unbalanced power of the converter station, the load switching can be avoided at the time of quickly restoring the DC power transmission. Meanwhile, the fault ride-through of the receiving converter station and the load can be achieved. The regulation range of DC voltage at the inverter side is expanded by way of relying on the characteristic that the full bridge sub-module topology can output negative level, the blocking of converter station caused by excessive discharge of sub-module capacitor is avoided, which effectively reduces the DC impulse current after fault clearance. The selection principle of relevant parameters under different severity of AC fault is designed, and then the simulation model of double ended hybrid DC transmission system is set up based on electromagnetic transient simulation software to verify the effectiveness of the proposed control strategy.关键词：hybrid HVDC transmission system;passive network;fault ride-through;induction motor12|34|0更新时间：2025-04-26
- 摘要：In recent years, HFO-1234ze(E) is considered to have great application potential in medium and low voltage equipment due to its good environmental protection characteristics and excellent insulation performance. At present, the test exploration on the gas is relatively less. Firstly, the liquefaction temperature of HFO-1234ze(E)/CO2 gas mixture under different pressures is calculated in this paper. Then, the influence of gas pressure and the mixign ratio on the insulating performance of HFO-1234ze(E)/CO2 gas mixture is studied respectively by using the gas insulation performance test platform and the optimal mxing ratio as well as gas pressure value in actual engineering application is discussed. After that, the gas chromatography-mass spectrometry (GC-MS) is used to perform qualitative analysis of the decomposed product and, at the same time, the decomposed product is simulated and calculated. The research results show that under different uniform field conditions, the insulation performance of HFO-1234ze(E)/CO2 gas mixture increases with the increase of the mixing ratio and the breakdown voltage shows approximately linear increase. In case of not changing the mixing ratio, increase of gas pressure can significantly improve the insulation performance of HFO-1234ze(E)/CO2 gas mixture and, at the same time, under the condition of 0.3 MPa, the gas mixture containing 20%-25% HFO-1234ze(E) not only has a good insulation level, but also the influence due to uneven electric field is less and is applicable for practical engineering applications. The HFO-1234ze(E)/CO2 gas mixture has a good self-recovery insulation performance. The decomposed products are mainly hydrofluorocarbons (HFC) and hydrocarbons (HC). The simulation results show that the decomposed products are relatively stable. The results of comprehensive experiments and simulation calculations show that HFO-1234ze(E)/CO2 gas mixture has the potential to replace SF6 gas and applicable for medium and low-voltage insulation equipment.关键词：environmental protection gas;HFO-1234ze(E) gas mixture;electric field unevenness;insulation characteristics11|29|0更新时间：2025-04-26
- 摘要：The pyrolysis mechanism of polyisobutylene (PIB) which is commonly used as a filler in high-voltage cable terminals remains unclear. In this paper, the pyrolysis products of PIB under 2 400 K and 3 000 K conditions, and their generation paths are obtained by using ReaxFF molecular dynamics software. The study results show that the content of pyrolysis products of PIB at 3 000 K is higher than at 2 400 K, indicating that the aging temperature increase can accelerate the pyrolysis of PIB and the generation of characteristic gases, and H2 and CH4 can be used as the main characteristic products of PIB pyrolysis. The thermal aging of PIB is performed at at 473 K to verify the effectiveness of the numerical simulation results. Meanwhile, for exploring the key factors affecting the gas production characteristics of PIB, the thermal-electric combined aging experiment of PIB and thermal-electric aging asw ell as thermal-electric aging experiment of PIB affected by moisture are performed further. Gas chromatographic analysis results show that, in case of spark discharge, the content of each gas component in PIB is the highest, followed by partial discharge, and the lowest in case of thermal aging. The change of C2H2 content can be used as the assessment basis of PIB discharge. In particular, the results of accelerated aging experiments of PIB with different degrees of moisture show that moisture would promote the pyrolysis of PIB and the formation of various characteristic products. This paper can provide theoretical guidance for further study of PIB fault criterion.关键词：polyisobutylene;molecular simulation;pyrolysis mechanism;cable terminal12|23|0更新时间：2025-04-26
- 摘要：For predicting accurately the trip risk of overhead transmission lines under the condition of mountain fire and improve safe operation level of power grid, the breakdown voltage characteristics of conductor-plane gap under the condition of typical high-risk vegetation fire of Southern Power Grid are studied. The fire combustion characteristics simulation test platform and mountain fire gap breakdown simulation test platform are set up for the study of flame combustion characteristics and gap breakdown characteristic of such five vegetations as the pinus yunnanensis, metasequoia, eucalyptus, shrubs, and thatch, and the replationship between the flame temperature of different vegetation, flame height, ash content, and fuel heating value and breakdown characteristic of conductor-plane gap is studied. The study results show that the relationship between the above factors and the average gap breakdown voltage gradient is approximately linear and its multiple linear regression formula is obtained by curve fitting. It is found by using the entropy-weight method that flame temperature has the highest weight in vegetation combustion characteristics, and pinus yunnanensis has the highest risk of fire trip among the five vegetations. The study results can provide a reference for predicting risk assessment of mountain fire trips of overhead transmission lines.关键词：overhead lines;risk of tripping;mountain fire;vegetation type;gap breakdown characteristic8|249|0更新时间：2025-04-26
- 摘要：In the process of acquisition and transmission, the infrared image of power equipment is easily affected by Gaussian and impulse noise, thus destroying the real information of the image. In order to meet the requirements of image quality to the process of image processing, a kind of filtering method aiming at the mixed noise of the infrared image is proposed in this paper. Firstly, the Gaussian noise in the infrared image is filtered out effectively by using trilateral weighted sparse coding (TWSC) model, and then the separation and removal of residual impulse noise is achieved by the combination of image structure and texture decomposition and median filtering algorithm so that the edge structure information of the image can be well preserved while the mixed noise of the infrared image is filtered. It is shown with combination of example that the method in this paper can effectively filter out noise and obtain higher peak signal to noise ratio (PSNR) as well as structural similarity (SSIM).关键词：mixed noise;trilateral weighted sparse coding;image decomposition;median filtering10|40|0更新时间：2025-04-26
Research & Analysis
- 摘要：Vacuum arc current commutation is an important part in the interruption process in natural commutated hybrid DC circuit breaker (NHCB). In this paper, it is concluded through setting up the vacuum arc current commutation model of NHCB that the main factors influencing vacuum arc current commutation are vacuum arc voltage, internal stray resistance and inductance parameters and the series-parallel structure of power electronic devices. From the point of view of experiment, the influence of series-parallel structure of power electronic devices on the characteristics of arc current commutation is studied by changing the number of power electronic devices in series or parallel in the power electronic switch, and the influence influence of internal stray resistance and inductance parameters on the characteristics of arc current commutation is studied by changing the value and position of stray inductance or resistance in power electronic switches. Finally, the method to promote arc current commutation is explored. This research can provide theoretical foundation for the structure and parameter optimization of NHCB.关键词：hybrid DC circuit breaker;arc current commutation;vacuum arc voltage;stray parameters13|42|0更新时间：2025-04-26
- 摘要：The closing resistor of circuit breaker can effectively suppress the closing inrush current and switching over-voltage and play an important role in stable operation of power grid. The closing resistor will, once in case of fault and of correct operation and out of operation, causing huge equipment and safety accidents. Since the 1 100 kV GIS circuit breaker is of mostly multi-break structure, the coordination time sequence deviation across open contacts and the interference of contact bounce factor often lead to the characteristics of the closing resistor with no way to be measured, or the error of the test result is too large. As for such event that the pre-switching time and the resistance of the closing resistor of 1 100 kV GIS circuit breaker has no way to be detected, its structure and test principle are analyzed. It is concluded, through increasing the test frequency to obtain the complete test waveform, that one of the reasons that the pre-switching time and its resistance of the closing resistor have no way to be measured is the failure of across open contacts of closing resistor at one side. It is found through disassembly and inspection that the moving contact at one side of the closing resistor peels off due to breakage of the fixing bolt, and the conclusion that the operation characteristic has no way to be detected due to failure of open contacts of the resistor is verified. Finally, the corresponding suggestions and improvement measures are proposed from such aspects as manufacturing process, test items, test instruments and detection means, which can provide reference for process control and fault diagnosis of the same type of equipment.关键词：1 100 kV GIS;circuit breaker;closing resistor;fault detection10|43|0更新时间：2025-04-26
- 摘要：In high voltage environment, the existence of micro-defect structure can lead to electric field distortion in insulating materials, and is one of the most important factors that influence the insulation strength of alumina ceramics. For studying the influence of typical defect structures of alumina ceramics on the electric field distribution, a mesoscopic model with defect structures of alumina ceramic is set up, and the influence of the existence of grain size, glass phase and porosity on electric field distribution is s analyzed by using the finite element software analysis. The results show that the influence of grain size on electric field distortion is less, while the existence of glass phase has a great influence on the electric field distortion. The influence of glass phase on electric field distortion is related to grain boundary direction. The bigger the included angle between grain boundary direction and electric field direction, the higher the electric field distortion at the glass phase. Compared with the influence of the grain size and glass phase, the influence of the existence of porosity defect on on the electric field distortion inside the alumina ceramics is highest. Specifically, the maximum electric field due to the porosity in the grain is increased by 46.8%, and that due to porosity at the grain is more than doubled. The influence range of porosity on electric field distortion is higher and on the maximum value of the field strength is lower.关键词：alumina ceramics;finite element method;electric field distortion;grain size;glass phase;pore10|60|0更新时间：2025-04-26
- 摘要：In order to avoid tripping of line due to ice coating and not affect operation of line in the ice melting, the live ice melting system for ultra-high voltage line ground wire and optical fiber composite overhead ground wire (OPGW), including ice melting power supply, ice melting device, over-voltage protection system, OPGW and ground wire circuit, is developed. The check of OPGW/ground wire melting parameter and melting device parameter, type selection of transformers, smoothing reactors, bridge arm over-voltage protectors and design of the insulation transformation and insulation coordination of melting ice lines are performed, and an OPGW live melting ice system for ultra-high voltage lines is developed. The actual measurement at site shows that, in case the both ends of the ice melting circuit are open, the induced voltage of OPGW/ground wire can reach 13.7 kV. When the single end of the ice melting circuit is grounded, the induced voltage decreases to 0.6 kV. The calculation shows that the selected rated parameters of 10 kV/10 MW for the live ice melting device can meet the ice melting requirements at site. The surface icing of OPGW/ground wire is irregular, and the growth of ice length, diameter, and thickness is a nonlinear process. The actual measurement at site shows that after the ice melting device outputs a 260 A DC current for 75 minutes, the maximum temperature of OPGW rises to 20.7 ℃, completing safely the live ice melting of ultra-high voltage lines. The live ice melting system for OPGW of ultra-high voltage transmission lines developed in the paper provides a guarantee for safe operation of ultra-high voltage DC lines in rainy, snowy, and freezing weather.关键词：ultra high voltage transmission line;optical fiber composite overhead ground wire;live ice-melting;induced voltage;insulation coordination;fiber optic temperature8|37|0更新时间：2025-04-26
- 摘要：As an important component of transmission line, the identification and location of insulator defects is of great significance in patrol inspection of power grid. For accurately locating and identifying the insulator state in foggy condition, the YOLOX target detection network is improved. Firstly, in order to speed up the network training, the activation function is improved; Secondly, for solving the problem that the small target samples are less than the whole samples and the samples are unbalanced, the image enhancement method and loss function are improved; Finally, the improved YOLOX network is compared with four target detection networks on the data set. The experimental results show that on the foggy data set, the accuracy, average precision and the number of frames per second of the improved YOLOX are improved to a certain extent, which meets the requirements of UAV patrol inspection.关键词：insulator defects;target detection;patrol inspection in foggy condition;improved YOLOX16|202|2更新时间：2025-04-26
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