LOW VOLTAGE APPARATUS

Study on Arc Extinguishing Performance of DC C₄F₇N/CO₂ Mixed Gas

WANG Chengli, LI Jing, CAO Yundong, YU Longbin, CUI Juyong

2021, 0(6): 1-6. doi:10.16628/j.cnki.2095-8188.2021.06.001

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C₄F₇ N/CO₂ mixture gas is a new type of environmentally friendly gas,and the study of its arc characteristics is of great significance to the development of a new type of SF₆ to replace the gas circuit breaker.This paper takes SF₆,CO₂ and C₄F₇ N-90%CO₂ mixture as the research object,and establishes the arc model of CO₂,SF₆,C₄F₇ N/CO₂ mixture under the conditions of DC power supply,single nozzle and fixed electrode.The main difference of breaking performance between C₄F₇N/CO₂ mixture gas,pure CO₂ gas and SF₆ gas and the physical parameters closely related to breaking performance are found by analyzing the arc radial temperature distribution and arc energy diffusion velocity.The results show that under the same conditions,the radial temperature distribution of C₄F₇N/CO₂ mixture gas is closer to that of SF₆ gas,its radial heat transfer ability is stronger,and the arc heat dissipation rate is faster,which indicates that C₄F₇N/CO₂ mixture gas has better arc extinguishing characteristics,and can be used in the development of SF₆ gas circuit breaker.

Research on Identification Model of Low Voltage Arc Characteristics Based on Wavelet Analysis

SHAN Xiaojie, ZHENG Xin

2021, 0(6): 7-14. doi:10.16628/j.cnki.2095-8188.2021.06.002

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In order to solve the problems of accurate detection,quantitative characterization of arc state and the difficulty of recognizing arc voltage in a short time after zero,this paper proposed an AC arc recognition model based on different wavelet transform characteristics.Aiming at the time-frequency characteristics of series fault arc and switching arc,two identification models of orthogonal wavelet and dyadic wavelet were constructed and their effectiveness was verified.Introducing the concept of energy and combining dyadic wavelet to construct a wavelet energy spectrum model,the actual acquisition and analysis of the switching arc voltage waveform can realize the quantitative characterization of the switching arc state under different load conditions.The simulation and experimental results show that the AC arc recognition model based on wavelet analysis has a good effect in the recognition and extraction of arc feature,which provides a theoretical basis and new ideas for the diagnosis of arc fault and the on-line monitoring of switching arcs.

Variable Load Adaptive Constant Current/Constant Voltage Charging Complex Topology WPT System

XU Wenqiang, QIAN Xiangzhong, MEI Haojie

2021, 0(6): 15-22. doi:10.16628/j.cnki.2095-8188.2021.06.003

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Aiming at the output and switching problem of wireless power transmission system,the adaptive switching of battery constant current and constant voltage charging mode under fixed resonant frequency is realized by using compound LCC topology.Firstly,it is concluded that the composite LCC compensation topology has the ability of constant current and constant voltage output; furthermore,a constant current/constant voltage control strategy based on the basic theory of reflection impedance is proposed,which only needs to detect the voltage at both ends of the primary transmitting coil and the current flowing through the primary transmitting coil to control the switch to switch the constant current and constant voltage charging modes adaptively.This method does not need communication between primary side and secondary side and additional DC-DC converter,which reduces the design cost and control complexity of the whole system.Finally,a 6.6 kW system simulation platform and a 66 W experimental prototype are built to verify that the proposed method has the ability of adaptive switching constant current/constant voltage charging.

Evaluation Method for Composite Insulators Aging State Based on Fuzzy Synthetic Evaluation

CAO Bin, RAO Chengcheng, DAI Wenliang, LIU Kun

2021, 0(6): 23-29. doi:10.16628/j.cnki.2095-8188.2021.06.004

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The aging indexes of composite insulators are sorted out,and two layers of evaluation index system are constructed,with 14 evaluation indexes selected.Through the normalization of evaluation indexes and the selection of membership functions,on the basis of the constant weight determined by the improved analytic hierarchy process,the variable weight mode based on the equilibrium function is introduced,and the constant weight is modified to obtain the variable weight,so as to establish the fuzzy synthetic evaluation method for aging state of composite insulators.Finally,the aging model is verified by the experimental data of composite insulators.The results show that the fuzzy synthetic evaluation model based on the variable weight theory can reflect the aging state of insulators objectively.The method has a reference for the maintenance and replacement of composite insulators.

Research on Node Site Selection and Capacity Configuration Technology of Clustered Energy Storage Power Station

GU Suping, LU Mingyue, WU Haitao, LI Lin

2021, 0(6): 30-35. doi:10.16628/j.cnki.2095-8188.2021.06.005

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In order to solve the problem of capacity and location planning of cluster energy storage power stations in wind power grid connected power system,this paper proposes a method of node location and capacity allocation of cluster energy storage power stations.Firstly,according to the distribution coefficient of power transmission,the influence mechanism of zoning capacity distribution and active frequency regulation capacity of energy storage power station is analyzed and demonstrated,and the ideas of constant capacity and location of energy storage power station are proposed.Secondly,considering the similarity of system power sensitivity,active power frequency modulation and energy storage investment comprehensively,the system is divided by the sensitivity of system power disturbance,and the integrated planning model of constant capacity-site selection of cluster energy storage power stations is built with the objective of minimizing the active power proportion and the annual investment cost of power station and energy storage power station.Finally,a 30-node network in Matpower tool is taken as an example to verify the effectiveness and feasibility of the proposed method.

Study on Temperature Rise Characteristics of Outdoor 1 000 A Low Voltage Fuse

WANG Guoqing, XIONG Jun, JIAO Xianan, LIU Chun, ZHANG Yan, LIU Xun

2021, 0(6): 36-40. doi:10.16628/j.cnki.2095-8188.2021.06.006

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Taking a commonly used outdoor 1 000 A low voltage fuse as a study object,the variation law of temperature rise and pre-arc time with various factors,such as material parameters,ambient temperature and heat dissipation characteristics,is studied by using Ansys.It is shown that with the change of the parameters of the outdoor fuse,the variation law of the temperature rise characteristics,the pre-arc time and the maximum temperature rise is different.The change of the ambient temperature leads to the small change of pre-arc time;the increase of the resistivity of the fuse and the decrease of the air convection heat transfer coefficient has a great influence on pre-arc time.If the steady temperature rise near the rated current of outdoor low voltage fuse exceeds the melting point of the fuse,the fuse may be slightly molted and will lead to light fuse molten fault.

Thermal Overload Protection for Low Voltage Apparatus and Simulation of Thermal Bimetal

XU Wenliang, HE Weilong

2021, 0(6): 41-46. doi:10.16628/j.cnki.2095-8188.2021.06.007

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Thermal overload protection is an important function of low voltage apparatus.With the simple structure and reliable operation thermal bimetal is used for this function.The design of thermal bimetal is a multi-disciplinary problem involving electrical,thermal,mechanical and so on.This paper takes a certain type of miniature circuit breaker as an example to introduce the method for simulation and design of thermal bimetal.And experimental verification is carried out.

Modeling and Implementation of East China Power Grid Security and Stability Control System Based on Digital Twin

ZHOU Yi, ZHOU Liangcai, SHEN Yingping

2021, 0(6): 47-51. doi:10.16628/j.cnki.2095-8188.2021.06.008

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Based on the idea of digital twins,this paper constructs a virtual operation model of security control through comprehensive multi-scale power grid operation information and can check and do early warning of the collected device information.The actual operation of the power grid in East China shows the effectiveness of the method.

Dynamic Simulation of Air Circuit Breaker Based on NX Motion

XU Xiaodong, LIAN Yunfei, GAO Fei

2021, 0(6): 52-57. doi:10.16628/j.cnki.2095-8188.2021.06.009

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The dynamic model of air circuit breaker mechanism is established in the NX Motion software,and motion joins,contacts and springs are created according to physical truth.Many performance parameters are obtained by the dynamic simulation analysis of air circuit breaker,such as the principle axis rotation angle,closing and opening time,the angle between the upper and lower links,final pressure,opening range,overtravel,energy storage torque,tripping force and so on.The angle between the upper and lower links is go through the dead point angle,when closing the air circuit breaker.The correctness of the simulation model is verified by the comparison between dynamic simulation results and experimental results.The results of the dynamic simulation provide reference basis for the design and optimization of air circuit breaker.The dynamic simulation technique shortens the development cycle and reduces development costs compared with traditional method.

Influence of Power Factor and Closing Angle on Short Circuit Test of Miniature Circuit Breaker

HUANG Bin, ZHANG Yuxing, LIU Cheng

2021, 0(6): 58-62. doi:10.16628/j.cnki.2095-8188.2021.06.010

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The short circuit test is a conventional type test for miniature circuit breakers.GB/T 10963.1—2005 specifies the relevant requirements of test parameters (test voltage,test current,power factor,closing phase angle,etc.) in detail.However,the influence of power factor and closing phase angle on short circuit test is not clear,which brings some troubles to testers.In this paper,the short circuit current mathematical expression is taken as a starting point,combined with the common short circuit test cases,from the theoretical analysis and test results analysis,the influence of power factor and closing phase angle on the miniature circuit breaker short-circuit test is analyzed,to deepen the understanding of circuit breaker short-circuit test.

SVG Model Parameter Test Method Based on Controller Hardware-in-Loop

CAO Bin, CONG Yu, YUAN Shuai, ZHANG Xiaolin, WANG Qi, WANG Liqiang, ZHAO Yongfei

2021, 0(6): 63-66. doi:10.16628/j.cnki.2095-8188.2021.06.011

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As the main reactive power source of new energy power station,static var generator(SVG) needs to provide its model parameters to the dispatching organization.However,due to the high voltage level and large capacity of SVG,the existing detection devices can not meet the requirements of model parameter test.To solve this problem,this paper proposes a hardware-in-the-loop(HIL) testing method for SVG model parameters.Firstly,based on the requirements of power system simulation analysis,the parameter requirements of SVG model are proposed and the test conditions are selected.Then,a model parameter test platform for controller hardware in the loop simulation is established to test the model parameters of the controller,which is the core component of SVG.Then,the hardware in the loop test data are used as the measured data to carry out the SVG model parameter identification.Finally,an SVG test case is used to verify the feasibility and correctness of the proposed method.

Comparison and Analysis of Power Frequency Detecting Methods Based on DSP

WU Weidong, HUANG Fang, WANG Guozhong, CAO Yefeng, PAN Lijie, ZHAO Fei

2021, 0(6): 67-72. doi:10.16628/j.cnki.2095-8188.2021.06.012

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The control system with high-speed data acquisition and analysis is designed in this paper.When the voltage of power changes to the specified angle,the circuit is turned on to realize precise phase selection control.Because frequency detection of voltage is an important step of precise control,this paper chooses three methods to carry out the experiment:software zero-crossing detection,hardware zero-crossing detection and FFT frequency detection.Compared with the experimental data,the software zero crossing detection method is selected as the voltage frequency acquisition method.

Comparative Study on AC and DC Breaking Characteristics of Moulded Case Circuit Breakers

PENG Chenyi, CHENG Shaoyong, FU Zhichao

2021, 0(6): 73-78. doi:10.16628/j.cnki.2095-8188.2021.06.013

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Based on the experimental studies for the designed moulded case circuit breakers(MCCBs),this paper analyzed the short circuit breaking characteristics and the key influencing factors of AC circuits and DC circuits.It is found that the arc voltage and the recovery voltage affect the DC breaking and AC breaking respectively.The prospective breaking current and the air-blast affect both the DC breaking and the AC breaking at different degrees,and should be seriously considered in the design of MCCBs.

Evaluation of the Impact of Distributed Generation Access on Distribution Network Operation Index

LI Guodong, WANG Zheng, HAO Shuai, ZHAO Fengzhan, ZHANG Qicheng, LIU Chuanghua, MAN Yuyan

2021, 0(6): 79-85. doi:10.16628/j.cnki.2095-8188.2021.06.014

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The position and capacity of distributed generation(DG) access to distribution network will affect voltage deviation,static voltage stability and network loss.In order to achieve quantitative assessment of these effects,firstly,voltage deviation index,static voltage stability index and network loss index are defined.And then a comprehensive impact index of DG access distribution network is proposed,which is based on the voltage deviation reduction,system static voltage stability improvement value and system loss reduction,and the value and significance of this index is analyzed based on the IEEE 33 node system.

Reactive Power Optimization of Distribution Network Considering Doubly-Fed Fan Access

LI Zhuxing, LU Jialin, GAO Qi, YIN Jun, LU Guangcai

2021, 0(6): 86-91. doi:10.16628/j.cnki.2095-8188.2021.06.015

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Wind power is intermittent and random.Aiming at improving the power prediction accuracy of the power generation side and using the reactive power compensation capability of the doubly-fed wind turbine to improve the traditional reactive power optimization model,this paper first uses the particle swarm algorithm to optimize the initial weights and thresholds of the BP neural network based on the weather forecast and the historical output data of the wind farm,and uses the improved BP neural network algorithm to predict the output curve of the wind turbine.To minimize the active power loss and the voltage deviation of each branch as the objective function,considering the combination of the reactive power compensation capability of the doubly-fed wind turbine and the traditional reactive power optimization measures,the particle swarm algorithm is used to solve the reactive power optimization model.Finally,the improved IEEE 30 node system is used for simulation verification.The results show that the research has practical significance for improving the voltage safety level of the distribution network and reducing the power loss.

Power Quality Analysis Considering Edge Computing Task Allocation Optimization

LI Xuejun, GUO Jianhua, ZHAO Ermin, ZHANG Zhennan, WEI Kai, YUAN Tiejiang

2021, 0(6): 92-98. doi:10.16628/j.cnki.2095-8188.2021.06.016

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Systematic power quality analysis requires the deployment of a large number of monitoring stations on the low voltage side,and there are certain requirements for the data transmission and computing capabilities of communication channels and computing equipment.To this end,this paper proposed a power quality analysis method that takes into account the optimization of edge computing task allocation.First,it builds a power quality analysis system framework under the cloud-side collaboration mode,deploys the power quality analysis algorithm Hilbert-Huang Transform (HHT) at the edge layer,thereby building a power quality analysis model based on edge computing.Then the task allocation problem of power quality monitor is analyzed,the genetic algorithm is used to solve it,and to generate the optimal task allocation strategy.Taking the electric energy data under a certain area as an example,the reliability and accuracy of the analysis method in this paper are verified.At the same time,the results of task allocation optimization are compared with the existing methods.The optimization method in this paper has a lower energy efficiency cost and can be widely used in actual engineering.

Research on Power Supply Capability Margin of Distribution Network Considering DG and Diversified Loads

XU Haidong, HUANG Ming

2021, 0(6): 99-105. doi:10.16628/j.cnki.2095-8188.2021.06.017

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In order to solve the impact of distributed power sources such as photovoltaic power generation and hydroelectric power generation,as well as diversified loads such as electric vehicles and energy storage components on their power supply capacity and margin after they are connected to the distribution network,firstly,the maximum power supply capacity and margin model of the distribution network is established,and its objective function and constraint conditions are defined.Then,based on the influence of distributed power supply and diversified load on the power supply capacity of the distribution network,the maximum power supply capacity and margin model of the distribution network considering distributed power supply and diversified load is established.Finally,the simplified particle swarm optimization algorithm is used to carry out the calculation.Through a practical distribution network application,it is proved that the algorithm can provide a good reference for distributed power supply and diversified load access network,has the optimization and effectiveness,and lays a solid foundation for the promotion of low-carbon and green power grid work.

Research on Standard of Residual Current Operated Protective Device with Self-Test Function

LI Renjie, WANG Yuxuan

2021, 0(6): 106-109. doi:10.16628/j.cnki.2095-8188.2021.06.018

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This article introduced the general situation of the residual current operated protective device (RCD),and analyzed its failure of residual current protective function.The technical route of RCD with self-test function is proposed,and its standard home and abroad is mainly introduced.

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