Research on the longitudinal protection of a through-type cophase traction direct power supply system based on the empirical wavelet transform

This paper proposes a longitudinal protection scheme utilizing empirical wavelet transform(EWT)for a through-type cophase traction direct power supply system,where both sides of a traction network line exhibit a distinctive boundary structure.This approach capitalizes on the boundary’s capacity to attenuate the high-frequency component of fault signals,resulting in a variation in the high-frequency transient energy ratio when faults occur inside or outside the line.During internal line faults,the high-frequency transient energy at the checkpoints located at both ends surpasses that of its neighboring lines.Conversely,for faults external to the line,the energy is lower compared to adjacent lines.EWT is employed to decompose the collected fault current signals,allowing access to the high-frequency transient energy.The longitudinal protection for the traction network line is established based on disparities between both ends of the traction network line and the high-frequency transient energy on either side of the boundary.Moreover,simulation verification through experimental results demonstrates the effectiveness of the proposed protection scheme across various initial fault angles,distances to faults,and fault transition resistances.

Study on Lightning Protection Design of DCS in a Nuclear Power Plant

DCS （distributed control system） plays a decisive role in the overall operation of a nuclear power plant. If DCS fails, it will seriously affect the normal production of nuclear power plant, causing great losses. So it is very important to take perfect lightning protection measures on DCS of the nuclear power plant. In this paper, according to the actual situation of DCS in a nuclear power plant, by controlling lightning point, securely booting lightning into the ground network, improving low-resistance ground network, eliminating ground loops, determining the safety space, surge protection of power and signal, a set of complete lightning protection design scheme was systematically put forward. Some specific lightning protection measures were highlighted, such as the DCS grounding, equipotential bonds and shields, and some specific considerations were put forward. All of these could offer reference in the practical application.

Development and Application of Lightning Protection Technologies in Power Grids of China

In recent years,along with the rapid expansion of power grids,the increasing complication of grid structures,and the development of smart grids and energy technologies,the lightning protection of power grids becomes increasingly prominent.Power grids of China have acquired significant achievements on lightning protection technologies,which are reviewed in this paper.A technical route of lightning protection is introduced in detail; it allows us to find problems through detection and measurement of lightning,to analyze problems through evaluation and simulation of lightning,to solve problems through lightning protection measures,and to prevent problems through hazard risk warning of lightning.Following the route,the technical breakthroughs of these four aspects in China are presented,including the chinese lightning detection network(CLDN),natural lightning observations,lightning faults detection at transmission lines,lightning current measurements,progresses in lightning distribution maps,lightning fault replays,lightning hazard risk evaluations,and lightning simulated experiments,as well as novel lightning protection measures.The practical devices and systems corresponding to the technologies mentioned above are also introduced and discussed.Due to the progress of lightning protection technologies in recent years,despite the rapidly growing length of transmission lines in China,the lightning accident rate is controlled at a certain level.

Operation Control Method of Relay Protection in Flexible DC Distribution Network Compatible with Distributed Power Supply

A novel operation control method for relay protection in flexible DC distribution networks with distributed power supply is proposed to address the issue of inaccurate fault location during relay protection,leading to poor performance.The method combines a fault-tolerant fault location method based on long-term and short-term memory networks to accurately locate the fault section.Then,an operation control method for relay protection based on adaptive weight and whale optimization algorithm(WOA)is used to construct an objective function considering the shortest relay protection action time and the smallest impulse current.The adaptive weight and WOA are employed to obtain the optimal strategy for relay protection operation control,reducing the action time and impulse current.Experimental results demonstrate the effectiveness of the proposed method in accurately locating faults and improving relay protection performance.The longest operation time is reduced by 4.7023 s,and the maximum impulse current is limited to 0.3 A,effectively controlling the impact of large impulse currents and enhancing control efficiency.

Protection Schemes for Uniline Zone in Bilateral AT Traction Power Supply System

With the rapid development of the construction of high-speed railway in china, higher levels of power quality and reliability of traction power supply systems are required.The combination of bilateral power supply technology with AT traction power supply technology can better meet the needs of development of high-speed railways, which will require new protection approaches to be proposed. Thus, corresponding protection schemes will be of great significance for the application and promotion of bilateral power supply technology.

Power supply arm protection scheme of high-speed railway based on wide-area current differential

When fault occurs on cross-coupling autotransformer(AT)power supply traction network,the up-line and down-line feeder circuit breakers in the traction substation trip at the same time without selectivity,which leads to an extended power failure.Based on equivalent circuit and Kirchhoff’s current law,the feeder current characteristic in the substation,AT station and sectioning post when T-R fault,F-R fault,and T-F fault occur are analyzed and their expressions are obtained.When the traction power supply system is equipped with wide-area protection measurement and control system,the feeder protection device in each station collects the feeder currents in other two stations through the wide-area protection channel and a wide-area current differential protection scheme based on the feeder current characteristic is proposed.When a short-circuit fault occurs in the power supply arm,all the feeder protection devices in each station receive the feeder currents with time stamp in other two stations.After data synchronous processing and logic judgment,the fault line of the power supply arm can be identified and isolated quickly.The simulation result based on MATLAB/Simulink shows that the power supply arm protection scheme based on wide-area current differential has good fault discrimination ability under different fault positions,transition resistances,and fault types.The verification of measured data shows that the novel protection scheme will not be affected by the special working conditions of the electrical multiple unit(EMU),and reliability,selectivity,and rapidity of relay protection are all improved.

Study of Lightning Damage Risk Assessment Method for Power Grid

Based on the idea of risk evaluation, the existing lightning damage risk assessment methods are reviewed and summarized in this paper. And the power grid lightning damage risk assessment system is established on the basis of lightning flashover risk evaluation methodology for transmission lines, and adopts the improved Analytic Hierarchy Process as the core algorithm. It can comprehensively evaluate the risk for transmission lines of regional grid, various sections of a line and each tower of the section, considering much more impact factors, including the running time of line, importance of grades, equipment damage, and the success rate of lightning stroke reclosing and so on. According to the calculation results of the risk assessment of the analytic hierarchy process and lightning flashover risk evaluation, the principles and methods of grade classification for power grid lightning damage risk map are studied, and give typical examples in the paper. It can describe the lightning withstanding ability much more scientifically and provide important references for the manage department of power system.

Research and Application of High-Voltage Power Supply and Distribution on Launch Vehicle

High-power electric actuators are generally used on solid propellant motors,which further enhances the requirement on onboard supply voltage and output power of a launch vehicle.In this paper,combined with the electrical demand of China’s new generation solid-liquid bundled launch vehicle(LM-6 A),high-voltage battery technology,high-power switch control technology,insulation protection technology under low pressure are studied,and the key technologies and schemes are presented.The flight test of LM-6 A shows that the high-voltage power supply and distribution technology adopted is reasonable and feasible,and can be used as a reference for the designs of other launch vehicles or spacecrafts.

Study on a Highly Stabilized Power Supply for Hybrid-Magnet Superconducting Outsert

The superconducting outsert of the 40 T hybrid-magnet in High Magnetic Field Laboratory （HMFL） of Chinese Academy of Sciences （CAS） requires a highly stabilized power supply. In this paper, two kinds of power supply design are briefly presented and both advantages and disadvantages are analyzed. In order to overcome the drawbacks of switching power supply, a series regulated active filter is adopted and a new design is proposed which ensures cooperative relationship between the feedback control loops of the switching converter and the series regulated active filter. Besides, unlike the traditional switching power supply, which can generate positive voltage only, this new design can also generate negative voltage which is needed in the quench protection for the superconducting magnet. In order to demonstrate the effectiveness of the methodology, a low-power prototype has been accomplished. The simulation and experiment results show that the power supply achieves high precision under the combined action of two feedback control loops. The peak-to-peak amplitude of the output ripple voltage of the prototype is 0.063%, while the peak-to-peak amplitude of the output ripple current is 120 ppm.

100 kA/10kV thyristor stack design for the quench protection system in CRAFT

Thyristors have longer lifetimes,higher reliability,and very high voltage and current ratings and they require less maintenance than other high-power semiconductor devices.As a result,they are particularly suitable for quench protection systems(QPSs),which protect the superconducting magnets in large fusion devices from damage.In this paper,we propose a design for a 100 k A/10 k V thyristor stack supported by both theoretical and simulation-based analyses as well as experimental verification.Due to the ultrahigh electrical performance requirements imposed on the QPS by the Comprehensive Research Facility for Fusion Technology(CRAFT),three main issues must be considered:the voltage-balancing problem caused by multiple thyristors in a series structure,the increased junction temperature problem caused by extremely high currents,and the reverse recovery phenomenon that arises from the thyristor’s physical structure.Hence,a series of detailed theoretical analyses,simulations,and experiments,including a thyristor junction temperature prediction method and reverse recovery process modeling,were carried out to optimize the design.Finally,the reliability and stability of the thyristor stack were verified by a series of prototype experiments.The results confirmed the correctness and accuracy of the proposed thyristor stack design method and also indicated that the proposed thyristor stack can meet the application conditions of a 100 k A QPS in the CRAFT project.

Fusion power supply advances by the J-TEXT engineering team

To meet the stringent requirements of the fusion power supply for large-scale fusion devices,the J-TEXT engineering team has carried out key technology research and applications in several important directions of fusion power supply.This article presents the advances made by the J-TEXT engineering team in recent years in the following areas:(1) a high-voltage power supply for an auxiliary heating system;(2) a breakdown protection device for an auxiliary heating power supply;(3) magnetic field compatibility;(4) a high-voltage pulsed power supply for a fieldreversed configuration;(5) a large physics experimental facility control system.The research backgrounds,technical progress,test results,applications,summaries and prospects are described in detail in each part.These innovative research results and valuable engineering experience can promote the progress of fusion power supply technology,and also lay a foundation for the development of power supplies with higher parameters in the future.

基于PROFINET的井下保护与监控一体化系统设计

针对现有保护系统无法可靠实现煤矿井下高压供电线路短路保护的选择性,提出了一种基于实时以太网PROFINET的井下高压供电系统保护与监控一体化系统。系统主要由PROFINET网络、监视器、控制器及具有PROFINET IO接口的综保器构成,可实现保护与电力监控网络的融合,完成短路保护的选择性,同时具有电力监控功能,能够迅速确定故障点位置,缩短故障排查时间,提高供电网的安全性与可靠性。仿真结果表明,PROFINET实时性满足保护要求,系统能够可靠实现井下短路保护的选择性及电力监控功能。

Lightning Overvoltages on Rural Distribution Lines

This paper presents information concerning the characteristics of lightning overvoltages on overhead power distribution lines.Discussion on the protection measures against transients caused by both direct and indirect strokes is also presented.

Research on protection system of resonant network in CSNS magnet power supplies

Purpose Chinese Spallation Neutron Source(CSNS)is one of the key projects of China,in which the main magnet power supplies adopt the structures of resonant networks(Wang et al.in Sci China Phys Mech Astron 54(Suppl 2):239-244,2011).Since each network contains a lot of components,and the working state of all the components will affect the whole accelerator,it is necessary to monitor the operation of each part in the resonant network.Methods In this protections system,a supervision to 314 switch signals and 118 analog signals is realized using a chip of field programmable gate array(FPGA).The details about the hardware and software designs are introduced in this paper.Results This protection system has been used in CSNS project,and the result proves that the RCS has been well monitored by this system.Conclusions This system is a self-developed protection system according to the engineering needs of CSNS.It can realize the real-time monitoring and protection of the working state of resonance network by processing a large number of data using FPGA.

The design of the superconducting wiggler power supply system for HEPS-TF

Purpose This paper describes the design of power supply system for superconducting wiggler in the project of high energy photon source-test facility.It includes three sets of high precision DC stabilized current power supplies for superconducting magnet excitation and three sets of quench protection assembly(QPA).A special magnetic load which has a very large time constant is studied in this paper.In this paper,a stable superconducting excitation power supply is developed,which can adjust the response quickly under the condition of very large load time constant.Meanwhile,the energy dissipation circuit of the QPA is integrated into the power supply in an active quenching protection mode to accelerate the energy release of the superconducting magnet and protect the superconducting magnet.Method The main circuit topology,control algorithm,quenching protection circuit and interlocking logic function are designed for the superconducting magnet with large inductance.The upper computer controls the switch of the three main power circuits through the serial port,sets the output current and adjusts the parameters according to the load.Conclusion Through a series of scientific and rigorous experiments,the rationality of superconducting wiggler magnet power supply scheme is demonstrated.The output current stability test and output voltage ripple test of the power supply meet or exceed the requirements of the magnet system.

“工业上楼”建筑电气设计要点浅析

随着经济的发展,城市产业发展往往面临产业转型升级加速和土地资源紧张的双重压力,“工业上楼”举措成为了当今城市产业发展的趋势和研究方向。“工业上楼”面向的产业类型较多,不同产业类型对电气设计的需求也不同,因此“工业上楼”建筑电气设计也相对复杂,对电气设计也带来一定挑战。本文将针对“工业上楼”建筑电气设计关键要点进行探索,以供参考。

基于Simulink/MATLAB的实际地铁线路供电系统短路试验仿真分析

直流牵引供电系统在城市轨道交通中扮演着关键角色,其安全可靠的运行对整个城市轨道交通系统的运行至关重要。该文首先介绍地铁牵引供电系统的结构和功能,并建立地铁外部交流电源、整流机组和牵引网络的仿真模型。该仿真模型根据实际地铁牵引供电系统的结构和参数进行构建,旨在研究不同短路情况下的短路特性,包括电源出口短路、近距离短路和远距离短路。通过评估供电系统在短路故障下的稳定性和可靠性,得出若干研究结果。这些结果为地铁供电系统选择合适的一次设备提供理论依据,有助于确保城市轨道交通供电系统的稳定性和可靠性。

隧道牵引分区所雷击暂态特性及其二次设备电磁兼容研究

牵引供电系统遭受雷击会在分区所内产生过电压与过电流,对分区所开关柜中二次设备产生瞬态电磁干扰,影响其正常运行。文中针对电气化铁路隧道分区所,建立雷击暂态仿真模型,计算了接触网不同位置遭受雷击时分区所的过电压与过电流,建立了27.5 kV开关柜的电磁场有限元仿真模型,分析开关柜中不同区域的瞬态电场、磁场分布。结果表明:雷击接触网会在分区所内产生幅值较大、频率较高的过电压与过电流,在其作用下开关柜低压室瞬态电场可达147.2 V/m、瞬态磁场可达1.3 kA/m,断路器室前壁处瞬态电场可达822.9 kV/m、瞬态磁场可达15.85 kA/m,超过标准规定的幅值,二次设备需要考虑相应的电磁屏蔽措施。论文结果对牵引供电系统雷击过电压/电流防护以及二次设备电磁兼容设计具有参考价值。

矿用隔爆高压配电装置保护及控制电源设计

针对目前井下矿用隔爆高压配电装置保护及控制电源与供电系统同源存在的问题进行分析,提出了矿用独立电源供电的方式。对矿用隔爆高压配电装置保护及控制供电方式进行了分析与设计;对矿用隔爆高压配电装置用独立电源进行了设计;对矿用隔爆高压配电装置保护控制供电方式进行了研究,进一步对其进行了保护控制供电设计和电源切换装置设计。实现了保护及控制供电一用一备独立供电,保障供电系统的安全运行。目前该供电方式已经在潞安化工集团、晋能控股集团的大型矿井实现了井下应用。