LOW VOLTAGE APPARATUS

Transformation and Upgrading of Low Voltage Electrical Appliance Industry Promotes “Double Carbon Target” and Circular Economy

MA Zhao

2021, 0(3): 1-5. doi:10.16628/j.cnki.2095-8188.2021.03.001

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Under the background of the revolution of energy digitalization and the “30/60” carbon emission target,the low voltage electrical industry is facing great challenges and unprecedented opportunities of product upgrading and enterprise transformation and upgrading. From the point of view of 30 / 60 carbon peaking,carbon neutralization and green consumption,circular economy (CE),this paper analyzes the technical characteristics of intelligent,electronic,digital and modular low voltage electrical appliances in the new era. The basic requirements of low voltage electrical appliances in the new era are put forward: functional safety,reliable performance,green technology,intelligent digital,economic,efficient and sustainable. Then,it puts forward how to seek the optimal solution in those five goals,and puts forward some suggestions for the low voltage electrical industry on how to comprehensively consider the circular economy,30/60 double carbon goal and green consumption.

Impedance Arc Model Considering High-Frequency Characteristics of Fault Arc Current

GAO Xiaoqing, CHEN Xiaojun, BAO Guanghai

2021, 0(3): 6-7. doi:10.16628/j.cnki.2095-8188.2021.03.002

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Aiming at the limitations of traditional arc models in the simulation of high-frequency characteristics of arc current,an impedance arc model considering the high-frequency characteristics of arc current was proposed.On the basis of arc resistance,arc column inductance,arc gap capacitance and line parameters on both sides of the arc gap are taken into account in the model.Moreover,the arc current is decomposed into low-frequency current and high-frequency current,which are generated by the low-frequency path and the high-frequency path respectively.Through the comparison of Simulink simulated waveforms and measured waveforms,the accuracy of the impedance arc model and its feasibility in series arc fault simulation are verified.

Modeling and Analysis of Contactor Contact Bounce Based on Impact Theory

TENG Menglan, ZHANG Haili, LIU Lanxiang, YANG Wenying

2021, 0(3): 13-17. doi:10.16628/j.cnki.2095-8188.2021.03.003

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In view of the background of a 35 kV power grid cabinet in a power station,the contact bounce in a power network is studied.Firstly,based on the collision contact impact theoretical model of multi-rigid system,the switch characteristics and bounce simulation of the universal contactor were studied.The purpose of this paper is to assist the power network in modeling and analyzing the contactor closing behavior from an algorithmic perspective.Besides,the model can simulate the dynamic characteristics of contacts under loads condition.After that,the motion orbits dynamic equations of the moving contact for contactor are given,and the physical mechanism of the bounce occurrence is studied through the model.The experimental results show that the developed bounce calculation program can effectively evaluate the dynamic characteristics of the contactor.Finally,combining the typical control circuits of power systems commonly used in power networks,the developed bounce calculation program is used to analyze the influence of contact gaps,load voltages,and contact resistances on their bounce characteristics under capacitive loads.It can provide a reference for bounce suppression study for similar switching appliances in subsequent power networks.

Risk Assessment of Minimum Design Environmental Temperature for GIS Equipment

FU Qing, CHEN Haiyan, WU Yaping, LU Wenjia, LI Yongming

2021, 0(3): 18-23. doi:10.16628/j.cnki.2095-8188.2021.03.004

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Sealing component of GIS equipment is selected according to the criterion of minimum temperature,and there is a risk that the equipment cannot operate normally due to the large area leakage accident caused by abnormal air tightness element under the condition of super design low temperature.Meteorological data from 1973 to 2016 in 9 sites in Shandong are investigated in this paper.The annual minimum temperatures are singled out to estimate the risk of extreme temperature lower than the design criterion with generalized extreme value (GEV) according to existing specification.Thereafter,the improved approach to decide design criterion is proposed and the associated risk is estimated.

Removing White Noise in Partial Discharge Signal of Cable Insulation Based on Improved Wavelet Transform Threshold Estimation Method

LU Xiaopeng, WU Juzhuo, NIU Haiqing, CHEN Shuyuan

2021, 0(3): 24-28. doi:10.16628/j.cnki.2095-8188.2021.03.005

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In order to suppress the white noise of partial discharge on-line detection,this paper proposed an Improved Threshold Algorithm of Lifting Wavelet Transform.The noisy signals are first processed by lifting wavelet decomposition to get the scale coefficients on the highest decomposition scale and wavelet coefficients on each decomposition scale.Then the scale coefficients are reserved and the wavelet coefficients are processed with an improved threshold selection method and a derivative threshold function.Finally,the de-noised signal can be obtained by reconstructing the scale coefficients and processed wavelet coefficients.The de-noising results of simulated partial discharge signals and measured partial discharge signals show that:compared with the traditional soft threshold function method,the proposed method has a better effect on removing the white noise.

Data-Driven Method for Line Loss Assessment in Low Voltage Station Area

WU Kecheng, QU Yi, CHEN Quan, CHEN Yisen, OUYANG Sen

2021, 0(3): 29-35. doi:10.16628/j.cnki.2095-8188.2021.03.006

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In order to overcome the shortcomings that the traditional evaluation method can not tap the potential influencing factors of the line loss in low voltage station area,and the reliability of the line loss evaluation is not high,a line loss evaluation method based on data-driven is proposed.The 10 influencing factors of the line loss of low voltage station area are obtained,and divided into two categories of evaluation indicators of inherent attributes and operating attributes.The orthogonal signal correction method (OSC) is used to remove the orthogonal components of the influencing factors and the line loss of the low voltage station area,and the comparison sequence of gray relation analysis (GRA) is used to obtain the weight contribution of the evaluation index to the line loss of the low voltage station area.Taking 10 A-level power supply stations as an example,GRA,OSC-GRA,AHP-FA three algorithms are used to evaluate the line loss of the low voltage station area.The results show that OSC-GRA has the highest accuracy in digging the potential relationship between line loss influencing factors and performing ranking evaluation.

Analysis of Terminal Connector Construction Technology and Copper to Aluminum Adapter

YANG Ke, SU Shangliu, LIN Wengui

2021, 0(3): 36-40. doi:10.16628/j.cnki.2095-8188.2021.03.007

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In view of the heating problem of terminal connector,this paper analyzes the causes of the heating and its harm,summing up the measures for safety precaution and how to normalize the construction technology.From the comparison between different terminal connector,the paper proposes that the compacting terminal connector with copper to aluminum adapter should be used to remove the risk of heat in the budding stage to ensure the safety of the grid.

Test Method for Distribution Network Self-Healing System

YU Zhe, TANG Jun, LI Xingjian, LI Minghan, HUANG Hui

2021, 0(3): 41-46. doi:10.16628/j.cnki.2095-8188.2021.03.008

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The intelligent self-healing of distribution network can improve the reliability of power supply and reduce the interruption time of power supply caused by faults through the information interaction of distribution network terminals.There are many terminals in the self-healing system of distribution network,so it is very difficult to verify the nodes in different distribution network.In this paper,a test method and system were proposed,which uses multiple test equipment to interact with each circuit breaker state,topologize distribution network structure and judge the analog quantity status of different distribution network nodes to complete a simple simulation of distribution network.This method has low computational complexity and is suitable for the fast calculation of the embedded tester.It was verified that it meets the needs of the self-healing test of distribution network in terms of technical parameters such as synchronization.

Optimization Model of Distribution Network Reliability Investment Based on Index Decomposition

WANG Peng, LÜ Haixia, YANG Shuai, ZHU Yongmei, LIU Yong

2021, 0(3): 47-50. doi:10.16628/j.cnki.2095-8188.2021.03.009

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With the rapid development of power system and the promotion of power market-oriented reform,the main body of the market takes the maximization of the enterprise’s own benefits as the goal,thus reducing the investment,and the reliability problem is increasingly prominent.In this paper,based on the reliability index decomposition method of typical engineering scenarios,according to the cost-benefit ratio of investment,the investment priority planning is carried out,and under the objective of investment minimization,the optimal investment structure of reliability improvement is realized.

Research on Temperature Monitoring System of High Voltage Switchgear Based on Area Array Temperature Measurement

ZHANG Zhifeng, MIAO Xiren, JIANG Hao

2021, 0(3): 51-56. doi:10.16628/j.cnki.2095-8188.2021.03.010

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This paper proposed a non-contact area array temperature measurement method for monitoring the temperature of switchgear,and designed a set of temperature monitoring system for switchgear.The experiments show that the temperature sensitivity of the system reaches 0.01 ℃,which can effectively distinguish abnormal heating points in the measured area.In the field experiment of the switch cabinet,the effective identification of the abnormal operating state of the isolation switch is realized,which proves the feasibility and advanced nature of the surface array temperature measurement method of the switch cabinet.

Simulation and Calculation of Interruption Process of Generator Circuit breakers Synthetic Test

DU Zhaoxin, ZHOU Desheng, ZOU Xiaofeng, FENG Qian

2021, 0(3): 57-60. doi:10.16628/j.cnki.2095-8188.2021.03.011

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The Weil synthetic test circuit for generator circuit breaker breaking test is built in PSCAD/EMTDC,and the simulation calculation is carried out for the TRV conditions of the auxiliary circuit breaker and the tested circuit breaker during the breaking process.The calculation results show that the TRV parameters of the auxiliary circuit breaker are far lower than the TRV reference value specified in the standard,and the TRV parameters of the tested circuit breaker meet the TRV specified in the standard reference value.Furthermore,the simulation results show that the delay time decreases with the increase of inductance,but peak voltage and peak time are basically unchanged.

Three-Phase Power Quality Adjustment Device for Distribution Network Based on Phase Sequence Adaptive Technology

LI Xinyuan, MA Jun, GAO Peng, YU Haoran, LIN Yan, LÜ Haichao, SHEN Zhendong

2021, 0(3): 61-67. doi:10.16628/j.cnki.2095-8188.2021.03.012

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In order to solve the problem that the three-phase power quality adjustment device can not work normally due to the incorrect phase sequence of the grid voltage,a phase sequence adaptive method applied to the three-phase power quality adjustment device was proposed.This method starts with the control strategy of the three-phase power quality adjustment device,studies the influence of the different phase sequence on the control of the three-phase power quality adjustment device,and modifies the control strategy to successfully realize the phase sequence adaptive technology.The simulation and experiment verify the unbalance,reactive power,harmonic and inter-harmonic compensation functions of the device from the positive sequence and the negative sequence respectively,verifying the feasibility of the algorithm.

Harmonic Analysis of MMC-HVDC System in Asymmetric AC Power Grid

CHEN Heyang, GUO Feng, YE Rong

2021, 0(3): 68-75. doi:10.16628/j.cnki.2095-8188.2021.03.013

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When an asymmetrical fault occurs in the AC system connected to the MMC-HVDC,the AC bus voltage of the converter station is no longer balanced,and there are negative sequence components and zero sequence components,which makes the distribution of harmonic on the AC-DC side of MMC-HVDC more complicated.In order to study the transmission law of harmonic voltage and harmonic current on the AC-DC side of the system,as well as the instantaneous power fluctuations of the bridge arm in this case,this paper firstly derives theoretically based on the symmetrical component method and dynamic phasor,and then builds the simulation model in PSCAD/EMTDC.Finally,the voltage and current harmonic distribution in the steady state and the fault state are analyzed according to the simulation results,and it verifies the transmission of harmonics on the AC-DC side and the law of bridge arm power fluctuations in the asymmetric fault state which provides references for related suppression and control strategies.

DC Type Voltage Sag Protector (VSP) and Its Optimized Control Method

MA Zhiyuan, LUAN Le, MO Wenxiong, XU Zhong

2021, 0(3): 76-80. doi:10.16628/j.cnki.2095-8188.2021.03.014

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Aimed at the voltage sag compensation of sensitive loads,this paper proposed a DC type voltage sag protector (VSP) and its optimal control method.The super capacitor is used as the energy storage unit,and a bidirectional DC-DC is used to realize voltage sag compensation and super capacitor charging,which improves the efficiency and power density of the VSP.The optimized control method based on DC bus detection proposed in this paper does not need to detect the AC side,which greatly simplifies the control method and further improves the response speed and reliability.The method is applied on a 200 kW VSP prototype which is used on an adjustable speed drive (ASD) of a factory.The operation results show that the control method can response within 1ms,and the effect is obvious.

Voltage Sag Evaluation Considering Action Characteristics of Protection Based on Sequential Monte Carlo Simulation

XU Pengcheng, LIN Yan, LIN Di, GUAN Yu, CHEN Youjian

2021, 0(3): 81-87. doi:10.16628/j.cnki.2095-8188.2021.03.015

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Based on the characteristics of the line protection configuration scheme,the effects of different protection action characteristics on voltage sags were analyzed.The statistical model of fault information in uncertain conditions was established and a method of voltage sag evaluation based on sequential Monte Carlo simulation considering the action characteristics of line protection was proposed.The proposed method was applied to IEEE-30,and the simulation results show that the method can quantitatively calculate the voltage sag index in the time dimension.The characteristic of protection system has an obvious effect on voltage sags frequency assessment.The evaluation of voltage sag should consider the configuration of line protection,and the operating characteristics of different protections should be introduced into the evaluation model.

Analysis of Frequent Burnout of Resistance Capacitance Series Buck Rectifier Circuit

PAN Yingji

2021, 0(3): 88-91. doi:10.16628/j.cnki.2095-8188.2021.03.016

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Resistance capacitor series rectification is a common circuit used to provide DC power supply.When the circuit is used as the working power supply of single-phase electronic watt hour meter (WHM for short),the resistance is burned out frequently in operation.Through the analysis of theoretical and measured data,it is identified that the high-order harmonic current generated by nonlinear load flows through the working power supply of the electric energy meter,which causes the fundamental voltage distortion,and changes the operating parameters of the capacitor element,so as to increase the loop current,which is the main reason for the resistance burnout.In order to solve this problem,a high-order harmonic wave trap is connected in series in the power supply circuit of the WHM to ensure the safe and reliable operation of the WHM.

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