Table of Content

30 April 2023, Volume 0 Issue 4

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Arc Research & Analysis

Arc Fault Identification Method Based on Principal Component Analysis and Decision Tree

LIN Jingyi, WU Jianwen, LI Kui, SHAO Yang, WANG Yao, MA Mingshun, XIA Shangwen, TONG Ziang

2023, 0(4):  1-7.  doi:10.16628/j.cnki.2095-8188.2023.04.001

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The fault current of the fault arc is affected by the load and is not easy to be identified.To solve this problem,the arc fault identification method based on principal component analysis and decision tree was proposed.The principal component analysis method was used to reduce the dimension ality of eight temporal characteristic parameters of current generated by the fault arc.After removing the redundant information,the three kinds of principal components were input into the decision tree as characteristic values to establish a classification model.The proposed method can effectively simplify the decision tree classification model,reduce the time of fault arc identification,and reach the accuracy of fault arc identification of 95%.

Study on Post Arc Breakdown Characteristics of SF₆/N₂ Mixed Gas Circuit Breaker

LI Jinru, LI Jing, LIU Shuxin, LI Xue

2023, 0(4):  8-14.  doi:10.16628/j.cnki.2095-8188.2023.04.002

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Taking SF₆ and SF₆/N₂ gas mixture as the research object,the arc model under the condition of AC power supply,single nozzle and fixed electrode is established.The post arc thermal breakdown characteristics of substitute gas circuit breakers are studied by combining Mayr arc model.The Boltzmann equation is solved by using the two-term approximation method,and the critical breakdown field strength of mixed gas is calculated and compared with the actual field strength of the substitute gas circuit breaker model.The results show that when the SF₆ content in the SF₆/N₂ mixed gas is high,the performance of the post arc breakdown characteristics is close to that of the pure SF₆ gas circuit breaker.It basically has the post arc breakdown characteristics of SF₆ gas and can realize the replacement of SF₆ gas,which provides the theoretical basis for the research and development of SF₆ substitute gas circuit breaker,and has reference value for the research on the re-breakdown problem of the substitute gas circuit breaker.

Experimental Study on DC Arcing Characteristics Under Different Arc Extinguishing Medium

GUO Hongbin, ZHANG Tao, TANG Jianfang, MA Chi, LI Zhongxiang

2023, 0(4):  15-20.  doi:10.16628/j.cnki.2095-8188.2023.04.003

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In order to explore the arcing characteristics of H₂,N₂ and H₂-N₂ mixed media with different mixing ratios,a visual arc experiment platform was built.The "round-tablet-flat" carbon contact structure was designed to stabilize the arc.A high-speed camera was used to capture the arc shape.The voltage and current probe was used to collect the arc electricity volume and test the arc characteristics of different media.The arc voltage composition of the gas arc and the extraction of the near extreme voltage drop were analyzed.The electric field strength under multiple mixed gases was compared.It indicates that the arc voltage increases with the ratio of H₂ in the H₂-N₂ mixed medium,which can provide a reference for the selection of the gas medium of the DC contactor.

Research on Presure and Temperature Characteristics of Fault Arcing in GIS

WANG Zhining, PENG Haibo, ZOU Shun

2023, 0(4):  21-27.  doi:10.16628/j.cnki.2095-8188.2023.04.004

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In order to reduce the frequency of arcing fault in gas insulated switchgear (GIS) and reduce the harm caused by arcing fault,according to the parameters of ZF32-126 GIS,the influence of internal fault arcing on gas itself is considered on the basis of standard pressure and temperature calculation model,and an improved calculation model is adopted.The thermodynamic parameters of SF₆ under the fault arcing are calculated.On this basis,the thermodynamic parameters of SF₆ are applied to the calculation model of pressure and temperature.When the internal fault current is 40 kA,the pressure and temperature rise characteristics of each gas chamber in ZF32-126 GIS,the maximum ablation degree and average ablation rate of the shell under different protection time are obtained,which verifies that the improved standard algorithm has higher accuracy.

Simulation Analysis on Dynamic Characteristics of AC Relay Arc

XIE Yashuang, BAO Guanghai

2023, 0(4):  28-33.  doi:10.16628/j.cnki.2095-8188.2023.04.005

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The arc generated during the breaking process of relay contacts is one of the main reasons for electrical erosion of the contacts,which leads to relay failure.In order to facilitate the analysis of AC arc physical characteristics,through the secondary development of Fluent,the magneto-hydrodynamic (MHD) model of 3D AC arc is established based on the fluid dynamics equation and the electromagnetic field equation.Combined with the actual movement process of the contact,the dynamic process of the AC relay breaking arc is calculated and analyzed.By comparing with the measured data,the accuracy of the arc simulation is verified,which has certain guiding significance for the further understanding of AC arc characteristics and the optimizing product design.

Research on Partial Discharge of Switchgear Based on UHF and Acoustic Imaging Joint Detection

XU Xiaogang, HOU Chunguang, CHEN Zhengqing

2023, 0(4):  34-39.  doi:10.16628/j.cnki.2095-8188.2023.04.006

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Partial discharge is a manifestation of insulation degradation of electrical equipment during long-term operation,which eventually leads to insulation breakdown of equipment.It is extremely important that the partial discharge is detected promptly.Based on the accompanying physical phenomena in the partial discharge process,the joint detection method based on ultra-high frequency and acoustic imaging is proposed.The four types of defect discharge signals are collected by ultra-high frequency sensors,and the distribution characteristics and characteristics of the four types of graphs are analyzed.Statistical features to realize the identification and classification of 4 types of defect discharge faults.The acoustic signal emitted during the partial discharge process is collected through the spiral microphone array,and the acoustic signal of the discharge is processed by the beamforming algorithm.The discharge sound is displayed in the form of an image.The location of the source can realize the location of the partial discharge sound source of the switchgear and the identification of the discharge fault defect.

Electrical Design & Discussion

Autonomous Design of DC Relays for Rail Transit Vehicles

YIN Zhiyong, LI Yu, LI Liang

2023, 0(4):  40-46.  doi:10.16628/j.cnki.2095-8188.2023.04.007

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The key technologies of protection system,magnetic circuit system,contact system and arc extinction mode of the imported relay are studied in depth.The independent design is put forward according to its characteristics of large current breaking capacity,forced guiding structure,special environment resistance,long electrical life and high mechanical durability.By using the three-dimensional integrated design the electromagnetic simulation and the structural strength analysis technology,the key core technology of rail transit vehicle relay is autonomous and controllable,which improves the competitiveness of rail transit products.

Structural Design and Analysis of Smart Miniature Circuit Breaker’s Electric Operating Mechanism

WEI Bo, ZHAO Zhisheng, ZHAO Ming, SHENG Yongbing, REN Changbin

2023, 0(4):  47-55.  doi:10.16628/j.cnki.2095-8188.2023.04.008

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Smart miniature circuit breakers play an irreplaceable role in some power-consuming places and electrical equipment.Specifically,the structure of the electric operating mechanism for smart miniature circuit breakers is designed,including the layout of position switches,the analysis of operation logic,motor selection,the calculation of gear system transmission ratio and the gear design,etc.The theoretical calculation results are interspersed with the actual product data.References and comparisons are used to verify the feasibility of design methods and design ideas.It can provide reference for the design of similar products and effectively shorten the research and development cycle.

Research On Low Power Consumption Magnetic Latching Relay

ZHU Jinbao

2023, 0(4):  56-60.  doi:10.16628/j.cnki.2095-8188.2023.04.009

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Aiming at two technical requirements in JB/T 10923—2020:electrical clearances through air no less than 5.5 mm and short-circuit current carrying capacity,a kind of relay using bistable magnetic latching electromagnet as the driver is proposed.Firstly,the analog design of electrical gap and short-circuit current carrying is described.Secondly the design and simulation analysis reducing the power consumption of electromagnet are carried out.Finally,it is concluded that the electromagnet can provide the requirements of large electrical clearance through air and the travel and force required for the high short-circuit current carrying capacity.Simultaneously it provids a set of engineering design ideas and methods,providing a reference for the lowpower optimization design of the electromagnet.

Distributed Generation and Grid-Connection Technology

Design on Heat Dissipation Structure of High Power Electrical Control Box

GUO Qing

2023, 0(4):  61-66.  doi:10.16628/j.cnki.2095-8188.2023.04.010

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Based on the differential equation of heat conduction,fluid motion control equation,and radiation heat transfer equation,a mathematical model of coupled heat transfer in an electrical control box is established.The three-dimensional temperature field and airflow field are numerically calculated under steady-state conditions of the electrical control box.The relevant temperature rise tests are carried out.The calculated results are in good agreement with the test results.The error meets the actual engineering requirements.Finally,the highest temperature portion and heat dissipation law of the current carrying circuit are pointed out.The proportion of radiation heat exchange in the total heat dissipation of the current carrier circuit is calculated.The temperature rise of the current carrying circuit is simulated for different current carrying circuit emissivity and different heat dissipation box structures.The results show that improving the surface emissivity of the current carrying circuit and changing the top brim to open the shutter can effectively reduce the temperature rise of the electrical control box.

Development of Reactive Power Optimization and Safety Improvement Device for Distributed Photovoltaic Inverter

XUE Bing, YANG Huanhong, GE Yunfang, LIU Shupei, CHENG Fengping, CHAI Lei

2023, 0(4):  67-71.  doi:10.16628/j.cnki.2095-8188.2023.04.011

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In view of the adverse effects caused by the large-scale distributed photovoltaic access to distribution networks,such as unreliable island effect protection,overvoltage,reactive power disturbance,and reverse transmission of fault current in the distribution network,a distributed photovoltaic inverter reactive power optimization and safety improvement device is proposed.The adaptive performance of distributed photovoltaic access to the distribution network has been effectively improved through the design of fast overvoltage protection circuits,anti reverse fault current circuits,island auxiliary protection circuits,reactive power optimization circuits.The proposed device has good practical value.

MPPT Control and Performance Optimization of BOOST Solar Collector

ZHENG Zhao, ZHENG Jinbing, ZHENG Mingcai, ZHAO Xiaochao, ZHAO Jinqing

2023, 0(4):  72-78.  doi:10.16628/j.cnki.2095-8188.2023.04.012

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In order to maximize the efficiency of solar energy collection,the operation behavior of BOOST solar collector is studied.The characteristics of output current and output power of photovoltaic cells in BOOST solar collector under different working conditions are analyzed.Aiming at the problems of conventional BOOST solar collector under maximum power output tracking (MPPT) control,an improvement measure of series current limiting resistor is proposed to ensure the realization of MPPT control target.Theoretical analysis and simulation results show that controlling the operation behavior of BOOST solar collector can achieve the maximum power output of photovoltaic cells and optimize the performance of solar collector.