Table of Content

30 March 2020, Volume 0 Issue 3

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Overview

Summary of Intelligent Patrol Inspection Technology for Transmission Lines Based on Ubiquitous IoT

WU Kaidong, MIAO Xiren, LIU Zhiying, ZHUANG Shengbin, JIANG Hao, CHEN Jing

2020, 0(3):  1-7.  doi:10.16628/j.cnki.2095-8188.2020.03.001

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China's transmission lines cover a wide range,and the line distance is long.However,the information of on-line monitoring and inspection of transmission lines is not comprehensive and reliable.There is a problem of asymmetric information with substation,resulting in the unbalanced operation of safe and reliable operation of smart grids.The current development of ubiquitous power Internet of things (IoT) provides a new research and application direction for transmission line inspection technology.This paper proposed the basic framework of intelligent inspection system for transmission lines based on ubiquitous IoT.Based on its system composition and functional requirements,it focuses on the analysis of key technologies,including transmission line energy extraction technology and full autonomous navigation unmanned aerial vehicle (UAV) inspection technology.The inspection data is widely used in the IOT communication technology,inspection image target detection and intelligent fault identification technology.Effectively integrating intelligent transmission inspection systems for transmission lines in multiple technical fields can create higher economic and social benefits and have important engineering application value.

Research & Analysis

Research on Fatigue Life Simulation of Operation Mechanism of Molded Case Circuit Breaker

MA Longtao, DAI Minglei

2020, 0(3):  8-13.  doi:10.16628/j.cnki.2095-8188.2020.03.002

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In order to accurately evaluate the fatigue life of the operating mechanism of molded case circuit breaker (MCCB),a fatigue life simulation model for the operation mechanism of MCCB was established with software Solidworks,finite element analysis software,rigid body dynamics software ADAMS and fatigue analysis software nCode,based on rigid-flexible coupled theory,fatigue resistance theory and cumulative fatigue damage theory.With the simulation model,the fatigue life and weaknesses of the three main components of MCCB were obtained,the material selection of the main components was completed,and the feasibility of the proposed fatigue life simulation method was verified.

Study on Arc Transferring Characteristics of Pantograph Passing Different Arc Horn Segmented Insulator

CHEN Shaokun, JING Suoli, LIN Guanghua, LI Chengkun, DUAN Xuwei

2020, 0(3):  14-22.  doi:10.16628/j.cnki.2095-8188.2020.03.003

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When the pantograph passing through the segmented insulator,arc often generates,because of the thousands voltage at both ends of the segmented insulator,the arc will difficult to be extinguished,and the stagnation time is too long that will cause ablation damage to the insulator and affect the safe operation of the railway system.The transferring of arc in the segmented insulator and the evolution of the arc root have an important influence on the arc burning and extinguishing performance.Based on the magneto hydro dynamics (MHD) theory,a mathematical model of the arc of the pantograph passing the different arc horn segmented insulator was established.Through the analysis of the airflow field,electromagnetic force,temperature field and arc voltage,the main reason of the arc transferring is got.The study shows that with the arc horn increases,the arc transfer velocity first increases and then decreases.Besides the increasing of the angle makes the electrode gap smaller,which reduces the arc lengthen ability.Finally,the optimal solution of 60° arc horn is obtained.

Research on Simulation of Time-Varying Temperature Field of Multi-Core Arrester

HAO Shuang, CAO Yundong, GENG Lina, CUI Juyong, LI Jing

2020, 0(3):  23-27.  doi:10.16628/j.cnki.2095-8188.2020.03.004

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The arrester leakage current leads to a certain temperature rise of the core body,which in turn causes the aging of the zinc oxide resistance valve.The degree of aging depends on the temperature rise in addition to the temperature distribution.Therefore,it is of great significance to study the time-varying temperature field distribution of DC arresters.In this paper,a YH20WDB1-188 multi-column parallel DC zinc oxide arrester is taken as an example.Based on the heat transfer differential equation and supplementary equation,a time-varying temperature field simulation calculation is performed.The calculated results of the different positions of the arrester are consistent with the experimental data.It also compares and analyzes the overall temperature distribution and heating speed of the single-core core and the arrester.The simulation analysis results are helpful for the optimization of the structure of the multi-pillar parallel arrester and the analysis of the aging characteristics of the resistor chip.

Dynamic Characteristics Analysis and Simulation of Outland Harbour Power Station Network

CHAI Bing, ZHOU Junming, LI Weiwei, ZHAN Shanshan, ZHAO Xue

2020, 0(3):  28-37.  doi:10.16628/j.cnki.2095-8188.2020.03.005

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This paper studies the dynamic characteristics of the production operations in the outland harbour under the network structure of the independent power station network.Since the multi-way switchable mode is usually adopted,the dynamic range of the load working conditions is large,and different networking modes make the state analysis difficult to be solved by a single model,the design of the stable control system faces a great challenge.By structure analysis under different networking mode of the new ladder network,a dynamic characteristic model was built according to the new ladder structure,and the control system was designed to maintain the stability of the electromagnetic power and the output voltage.The analysis of the dynamic response was done according to the change of the topology.And the simulation of the fault status proves that the variability of the new structure can ensure electricity supply for the load.

Surface Discharge Audio Signal Recognition of 10 kV Solid Insulation Cabinet Based on Band Energy Feature Extraction

HOU Chunguang, SUN Xiaohan, ZHAO Changquan, CAO Yundong

2020, 0(3):  38-42.  doi:10.16628/j.cnki.2095-8188.2020.03.006

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In order to accurately monitor the insulation condition of 10 kV solid cabinets,a method based on wavelet packet frequency band energy identification for insulation state identification was proposed.An audio capture device is used to obtain audio signals from the surface discharge of the solid cabinet and the working environment.A wavelet packet base is established,and high frequency information and low frequency information are obtained by orthogonal decomposition.The energy of each frequency segment is calculated by analyzing the spectral characteristics of the audio signal for proper segmentation.Finally,the energy of each frequency segment is normalized to establish a feature vector as the basis for state recognition.The feature vectors of surface discharge sound and ambient noise are input into a support vector machine to classify and identify the insulation state.Through the analysis of experimental data,it is verified that the combination of wavelet packet analysis and support vector machine can accurately determine the surface discharge of solid insulated switchgear.

Electrical Design & Discussion

Design of Signal Detection Circuit of Dual Power Switch

HUANG Yulong, LI Jing, TIAN Xinjiang

2020, 0(3):  43-49.  doi:10.16628/j.cnki.2095-8188.2020.03.007

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The operation characteristics and power quality of the grid are affected by the properties of wind power generation such as fluctuation,intermittence,randomicity,and so on.As a guarantee of continuous power supply in power grid,dual power switch is widely used in various important load occasions.It is one of the primary tasks to complete the field parameters of power network signal and its detection.In view of the problem of power quality in the grid during the grid-connected operation of wind turbines,this paper designed the hardware and software respectively for the signal detection circuit of the double-power switch grid.The hardware design takes TMS320F28335 DSP as the core control module,and uses its internal analog/digital converter (ADC) and capture module (eCAP) to detect the voltage and frequency in the power grid.The network signal detection circuit has the advantages of high sampling accuracy,low hardware cost,simple detection algorithm and so on.

Study on Short Circuit Breaking Capacity of Small Size Two-Breakers Moulded Case Circuit Breaker

JIANG Guping, DING Fei, CAO Jian

2020, 0(3):  50-54.  doi:10.16628/j.cnki.2095-8188.2020.03.008

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In order to achieve overload and instantaneous characteristics,the small size two-breakers moulded case circuit breaker (MCCB) uses the direct heating bimetal sheet and solenoid electromagnet release device,but the structure of the release device can withstand less energy.By increasing the internal resistance,the current and energy of short circuit breaking can be reduced,and the high short circuit breaking capacity can be realized in the small size section.

Electrodynamic Analysis and Calculation of Contact Structure of a Large Capacity Earthing Switch

WANG Jiaxing

2020, 0(3):  55-58.  doi:10.16628/j.cnki.2095-8188.2020.03.009

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As the number of contact fingers of a high-capacity grounding switch is large,and the structure of static contact is complex,the conventional analytical method can not carry out accurate calculation in the case of the peak current.In this paper,the finite element method is used to establish the model for the complex case.The simulation method is used to analyze the current distribution on each finger.Combined with the formula,the electrodynamic force acting on the connection between the contact finger and the fixed contact is calculated,which is used as the design basis of the contact pressure of the touch finger spring,and verified by the test.

Test Analysis of Single Break Moulded Case Circuit Breaker in UL 489 High Fault Current Test

HU Gang

2020, 0(3):  59-62.  doi:10.16628/j.cnki.2095-8188.2020.03.010

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This paper introduced some problems of single-breakpoint moulded case circuit breaker in UL 489 high fault current test,and compared the judgment and external conditions of UL 489 and GB 14048.2 disconnection and its post-test,and analyzed single breakpoint for double breakpoint in the difference between the outgassing and the arc extinguishing.The conclusions obtained can provide a basis for the single-breakpoint moulded case circuit breaker to be used in UL 489.

Distributed Generation and Grid-Connection Technology

T-type Three-Level Fault Tolerant Control Based on Discontinuous Pulse Width Modulation

HOU Ruixin, ZHU Xuezhou, HU Daojiu

2020, 0(3):  63-69.  doi:10.16628/j.cnki.2095-8188.2020.03.011

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Aiming at the internal tube fault of T-type three-level inverters,this paper presented a fault-tolerant control strategy based on discontinuous pulse width modulation (DPWM).This strategy can not only operate safely and reliably after single-phase,two-phase and three-phase internal tube faults,but also minimize the fluctuation of neutral point voltage.Firstly,the control method of neutral point voltage is analyzed,and two modulation methods are put forward according to the influence of fault on current direction.Secondly,the necessary condition of system balance in fundamental wave period is explored,and the optimal clamping method in non-fault state is found.Thirdly,according to fault type and modulation method,the selection of clamping methods under various fault states is detailed analyzed,and the DPWM fault-tolerant control with minimum neutral point voltage fluctuation is realized.Finally,the feasibility and superiority of DPWM fault-tolerant control are verified by experiments.

Research on Flexible and Driving Control for Wind Power Pitch Control System

FAN Bishuang, LI Zeyang, WEI Guoqiang, YAO Ganzhou

2020, 0(3):  70-76.  doi:10.16628/j.cnki.2095-8188.2020.03.012

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In recent years,with the extensive use of variable pitch systems,quality problems of key load-bearing components of draught fan have frequently arisen.Due to the large output torque of the AC pitch drive motor,that the blades,gears and bearings frequently withstand excessive instantaneous torque,which is prone to structural damage such as cracking,and eventually leads to the damage of draught fan.The traditional control strategy only simply satisfies the principle of power optimization without considering the influence of its control on the fatigue life of the fan bearing components under different working conditions and wind speed.In addition,it cannot reduce the fatigue stress and impulse of key components of the unit when pitching.In view of the above problems,this paper starts with exploring the general law of the torque variation of the fan servo pitch drive with the fluctuation of wind speed.The torque smoothing increase coefficient and the torque smoothing decrease coefficient are designed to control the output torque recovery of the pitch drive.On the basis,it is ensured that the impacts of blades,gears and bearings can be well mitigated when the wind with different strength is changed,and the proposed method is verified and modified by simulation experiments.

Research on Three-Port Converter for Off-Grid Photovoltaic System

ZHOU Zhou, LI Huanhuan, MAO Xingkui

2020, 0(3):  77-82.  doi:10.16628/j.cnki.2095-8188.2020.03.013

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Because the output power of off-grid photovoltaic power generation system is intermittent and unstable due to natural factors,it is necessary to introduce energy storage system and its associated multi-input converter to cut the peak and fill the valley of photovoltaic output.Considering that the Buck/Boost circuit as a traditional energy flow bridge,uses more switching devices,a three-port converter with Boost circuit as the main circuit was proposed.It has the advantages of fewer devices,low cost and simple control on the basis of realizing the bidirectional energy conversion function at the energy storage terminal.Starting from the principle of system topology,this paper elaborated the energy flow mode under the dual-input and dual-output operation mode of the system,then discussed the specific control mode,and finally verified the correctness and feasibility of the system through simulation and experiment.

Research on Parameter Design of High Efficiency LLC Resonant Converter

REN Xingqiang, XIA Tian, JIANG Hongwei

2020, 0(3):  83-87.  doi:10.16628/j.cnki.2095-8188.2020.03.014

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The LLC resonant converter has the advantages of soft switch,low EMI,high power density,etc.It is widely used in communication power supply,LED,vehicle power supply and other fields.Under the condition of wide output range,for the calculation process of resonator,a waveform template calculation method is provided at the low resonant frequency,so as to obtain the accurate parameters of resonator.The parameters of LLC during resonance are simulated on the platform of Simplis.The simulation results verify the rationality of the parameter design.

Detection & Experiment

Analysis of Arcing Due to Internal Fault Test in Low Voltage Switchgear

ZHOU Dajun

2020, 0(3):  88-91.  doi:10.16628/j.cnki.2095-8188.2020.03.015

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This paper introduced the method and criterion of the arcing due to internal fault test in low voltage switchgear.The purpose and necessity of the test were described by the test analysis through the T waveform diagram.In addition,the switchgear arcing due to internal fault tests in different fields was compared.The reasons and key points of the differences among the arcing due to internal fault tests in industrial,nuclear and high pressure environments were analyzed.Moreover,the paper summarized the hazards and protective measures of the arcing due to internal fault.

Research on Qualification Test of Moulded Case Circuit Breaker in American Naval Ships

ZHANG Yingying, SHEN Haiying

2020, 0(3):  92-96.  doi:10.16628/j.cnki.2095-8188.2020.03.016

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Based on the study of the qualification test of American military specifications for moulded case circuit breakers(MCCB)in naval ships,and analyzing with its products,the characteristics of qualification test of American MCCB in naval ships are obtained.It has certain reference value for the development of the MCCB in China.

Energy Management

Systematic Classification of Energy Losses and New Energy Efficiency Evaluation Indices

ZHU Yongqiang, GAO Chenge

2020, 0(3):  97-103.  doi:10.16628/j.cnki.2095-8188.2020.03.017

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It is vital for energy utilization to reduce energy loss,to evaluate energy efficiency scientifically and to formulate effective energy saving measures.In this paper,energy losses were sorted systematically and some concepts were presented,such as direct energy loss,indirect energy loss,concomitant energy loss,independent energy loss,which is helpful to judge whether energy saving measures are effective and to determine the design direction of energy saving measures.Meanwhile,this paper illustrated energy consumption in production by proposing energy loss ratio.Moreover,indices of energy saving potential were defined and an application demonstration was given,which can help policymakers to develop energy saving measures and evaluate the effectiveness of different energy saving measures.

Power System Risk Avoidance Assessment Model Considering Wind and Solar Forecasting Error

LIU Junchao, FANG Shaofeng, ZHANG Qun, LIAO Shengtao, NIU Ben

2020, 0(3):  104-109.  doi:10.16628/j.cnki.2095-8188.2020.03.018

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In order to evaluate the wind and solar power accomodation in power system in a short time accurately,it is necessary to consider the prediction error of wind-solar joint power.Therefore,a probabilistic optimization model considering the wind-solar joint output was proposed,and CVaR was introduced to measure the risk loss of wind/solar curtailment and loss of load caused by uncertainty of wind and solar power.In the model,each wind-solar joint output value corresponds to a distribution probability,which is used to measure the operational risk in the power system.Aiming at maximizing the operational benefit and risk aversion of the system,this paper evaluated the impact of wind/solar forecast errors on the system operation from benefit side and risk side,to obtain the optimal dispatching scheme weighing risks and benefits.Compared with the traditional interval optimization model,the results of the example verify the rationality and effectiveness of the model.