Single-phase-to-ground fault protection based on zero-sequence current ratio coefficient for low-resistance grounding distribution network

Definite-time zero-sequence over-current protection is presently used in systems whose neutral point is grounded by a low resistance(low-resistance grounding systems).These systems frequently malfunction owing to their high settings of the action value when a high-impedance grounding fault occurs.In this study,the relationship between the zero-sequence currents of each feeder and the neutral branch was analyzed.Then,a grounding protection method was proposed on the basis of the zero-sequence current ratio coefficient.It is defined as the ratio of the zero-sequence current of the feeder to that of the neutral branch.Nonetheless,both zero-sequence voltage and zero-sequence current are affected by the transition resistance,The influence of transition resistance can be eliminated by calculating this coefficient.Therefore,a method based on the zero-sequence current ratio coefficient was proposed considering the significant difference between the faulty feeder and healthy feeder.Furthermore,unbalanced current can be prevented by setting the starting current.PSCAD simulation results reveal that the proposed method shows high reliability and sensitivity when a high-resistance grounding fault occurs.

Construction Technology of Lightning Protection Devices in Building Electrical Installation Engineering

To better improve the electrical safety of buildings and fulfill the role of lightning protection and grounding,this article combines cases and discusses seven aspects of lightning protection devices’construction technology.These aspects include the lightning protection classification of buildings,air terminals,down conductors,grounding devices,division of lightning protection zones,and lightning electromagnetic pulse shielding.Through the introduction of this article,readers can gain a comprehensive understanding of the application and value of lightning protection grounding construction technology in building electrical installation projects.

The Research on Grounding Protection for 110kV Resistance Grounding Distribution System

Using the neutral grounding method by the resistance in 110?kV system, it can limit the voltage sag and short circuit current when one-phase grounding fault occurred, but it will change the sequence of the network structure and parameters. This paper analyzes the size and distribution of zero sequence voltage and current when one-phase grounding fault occurred in the 110 kV resistance grounding system, and puts forward the grounding protection configuration setting principle of this system combining the power supplying characteristics of 110?kV distribution network. In a reforming substation as an example, the grounding protection of 110 kV lines and transformer have been set and calculated.

Protection of Zero-Sequence Power Variation in Mountain Wind Farm Collector Lines Based on Multi-Mode Grounding

The arc-suppression coil(ASC)in parallel low resistance(LR)multi-mode grounding is adopted in the mountain wind farm to cope with the phenomenon that is misoperation or refusal of zero-sequence protection in LR grounding wind farm.If the fault disappears before LR is put into the system,it is judged as an instantaneous fault;while the fault does not disappear after LR is put into the system,it is judged as a permanent fault;the single-phase grounding fault(SLG)protection criterion based on zerosequence power variation is proposed to identify the instantaneous-permanent fault.Firstly,the distribution characteristic of zero-sequence voltage(ZSV)and zero-sequence current(ZSC)are analyzed after SLGfault occurs in multi-mode grounding.Then,according to the characteristics that zero-sequence power variation of non-fault collector line is small,while the zero-sequence power variation of fault collector line can reflect the active power component of fault resistance,the protection criterion based on zero-sequence power variation is constructed.The theoretical analysis and simulation results show that the protection criterion can distinguish the property of fault only by using the single terminal information,which has high reliability.

Protection Measures for Buildings Based on Coordinating Action Theory of Ground, Foundation and Structure

Based on the theory of coordinating action of building ground, foundation and structure, this paper presents a modified method for calculating additional stresses on buildings in mining areas by considering the joint effect of cur- vature deformation and horizontal deformation on buildings. It points out that for buildings over the coal pillar, it is ad- visable to soften the intermediate ground of buildings when they are affected by mining. For buildings over the goaf, it is preferable to soften the ground at both ends of buildings. In order to enhance the ability of a building to resist tensile deformation, the key measure is to reinforce the bottom foundation of the building. In addition, the concept of “angle of break of building” is proposed. It is because of this angle that the protecting coal pillar is left, which is a better solution than prevailing solutions The findings provide a more scientific basis for mining under buildings.

Single-phase earth fault current distribution between optical fiber composite overhead ground wire and ordinary ground wire in transmission system

It is important for the safety of transmission system to accurately calculate single-phase earth fault current distribution.Features of double sided elimination method were illustrated.Quantitative calculation of single-phase earth fault current distribution and case verification were accomplished by using the loop method.Influences of some factors,such as single-phase earth fault location and ground resistance of poles,on short-circuit current distribution were discussed.Results show that:1) results of the loop method conform to those of double sided elimination method;2) the fault location hardly influences macro-distribution of short-circuit current.However,current near fault location is evidently influenced;and 3) the short-circuit current distribution is not so sensitive to the ground resistance of poles.

Fault protection method of single-phase break for distribution network considering the influence of neutral grounding modes

With the rapid development of modern distribution network and the access of distributed generation,the network structure is becoming increasingly complex.Frequent single-phase break faults have seriously affected equipment and personal safety and stable operation of the power system.However,with the development and application of the composite neutral grounding modes,the protection of single-phase break fault is facing new challenges.This paper proposes a protection method of single-phase break fault for distribution network considering the influence of neutral grounding modes.The characteristics of neutral voltage and sequence current are analyzed under normal operation and single-phase break fault with different grounding modes.Following this,the protection criterion based on neutral voltage and sequence current variation is constructed.The protection method of singlephase break fault for distribution network is proposed,which is applicable for various neutral grounding modes.Theoretical analysis and simulation results show that the protection method is less affected by system asymmetry,fault location and load distribution.The method has higher sensitivity,reliability and adaptability.

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.

Fault Line Selection Method Considering Grounding Fault Angle for Distribution Network

In the distribution network system with its neutral point grounding via arc suppression coil, when single-phase grounding fault occurred near zero-crossing point of the phase voltage, the inaccuracy of the line selection always existed in existing methods. According to the characteristics that transient current was different between the fault feeder and other faultless feeders, wavelet transformation was performed on data of the transient current within a power frequency cycle after the fault occurred. Based on different fault angles, wavelet energy in corresponding frequency band was chosen to compare. The result was that wavelet energy in fault feeder was the largest of all, and it was larger than sum of those in other faultless feeders, when the bus broke down, the disparity between each wavelet energy was not significant. Fault line could be selected out by the criterion above. The results of MATLAB/simulink simulation experiment indicated that this method had anti-interference capacity and was feasible.

Research on Lightning Protection of Overhead Power Distribution Lines

There are two major protective methods against lightning outages on overhead distribution lines.One is a surge arrester,and the other is an overhead ground wire.The surge arresters have rather constant effect regardless of the cause of the lightning outage.On the other hand,the effect of an overhead ground wire is quite different in two major causes,the direct lightning hit and the induced overvoltage.It is sufficient to provide surge arresters with an interval of 300 m for protection against the induced overvoltage caused by the nearby lightning stroke.Use of an overhead ground wire together with surge arresters is effective for lightning protection against the direct lightning hit to a distribution line.Puncture of surge arresters is the popular outage when the outage caused by the insulation break decreases sufficiently.Also,the existence of nearby trees leads to the line break due to the side flash from a tree.Advanced lightning protection equipment with ZnO arrester components is popular in Japan.Modeling of a pole transformer and application of an electromagnetic analysis method,such as FDTD method,to surge phenomena is considerably advanced.

Lightning Protection for the Computer Room of Electronic Information Systems

An electronic information system is composed of multiple groups of components. With the improvement of technology, its accuracy is getting higher and higher. The voltage during normal operation is only a few volts, and the information current is only microamp, so the withstand voltage to lightning electromagnetic pulse is extremely low. In this paper, the negative impact of lightning and static electricity on the computer room of an electronic information system was analyzed firstly, and then the design for the lightning protection of the computer room was discussed.

Research on Common Grounding Electrode Technique in HVDC

This paper discusses the characteristics of DC transmission common system ground electrode type and shared ground electrode, established the mathematical model of two circuit DC systems share ground electrode, analyze effects of the shared loop ground DC transmission system electrode on the operation of HVDC system size under different operation modes, and compare with the independent ground electrode, ground electrode impact on environment under different operation mode, and the paper finally puts forward some solving measures for the influence of the shared ground electrode on the environment and public ground electrode effects on DC system operation problems.

Natural Ionizing System of Electrical Protection and Energies against Atmospheric Discharges （Lightning）

This is the new highest technology, 100% Venezuelan and unique in the world, technological innovation, world patent for maximum protection, security and zero risk （0） to all electrical and power generation systems： hydroelectric and thermoelectric power plants, wind, nuclear and solar power plants, etc.; it is the only technology around the world that has the potential to disperse and propagate to land mass the enormous energies associated to the atmospheric discharges （lightning）, which are in the order： 200,000 to 500,000 Amperes; 1,000 million kilowatts and high-level transient voltage of 100 million volts. This new high technology is the solution to the paradigm of Benjamin Franklin and it is the mechanism to end ＂blackouts＂ that produces so many damages and losses of billions of dollars to both generators and users of electrical service, throughout the world.

Accident of Large-scale Wind Turbines Disconnecting from Power Grid and Its Protection

There were many accidents of large-scale wind turbines disconnecting from power grid in 2011.As singlephase-to-ground fault cannot be correctly detected,single-phase-to-ground fault evolved to phase-to-phase fault.Phase-to-phase fault was isolated slowly,thus leading to low voltage.And wind turbines without enough low voltage ride-through capacity had to be disconnected from the grid.After some wind turbines being disconnected from the grid,overvoltage caused by reactive power surplus made more wind turbines disconnect from the grid.Based on the accident analysis,this paper presents solutions to above problems,including travelling waves based single-phase-to-ground protection,adaptive low voltage protection,integrated protection and control,and high impedance fault detection.The solutions lay foundations in theory and technology to prevent large-scale wind turbines disconnecting from the operating power grid.

Biological protection of plants in agricultular landscape—state of the art, problems and ways of their decision

Biological protection of plants: definition and objectives. Technologically, biological protection of plants (hereinafter bioprotection) is a high agricultural technology involving agricultural landscape approach and basee on an ecological imperative, namely “use living beings against living beings”. In a wide sense, present-day bioprotection is a fundamental and applied field of knowledge providing harmless suppression of harmful agents during cultivation and storage of agricultural crops by use natural and (or) artificially constructed organisms (including genetically modified ones having pesticidal properties) and products of their live cycle. The overall objective of bioprotection consists in producing harmless, profitable and high-quality vegetative raw material, food, fodder. At the same time, bioprotection agrotechnologies are important environment forming and environment maintaining factors, steady and positively influencing the health of both rural ethnos, and agrosphere as a whole. Realization of integrated bioprotection approaches should provide minimum destruction of beneficial and non-target organisms, excluding the succession of harmful species and appearance of species resistant to biocontrol agents. 2. Theoretical foundation of bioprotection. The following postulates and imperatives of biosphere science, agrarian and social ecology make the scientific basis of bioprotection: “The Nature knows the how and why of things better”; Steady, balanced development of agrosphere (proceeding from a presumption of life support) is based on biocentrism and biosystem relations, or consortism of its consorbents; Control of the agrosphere by human beings could be effective only in case of primary realization of biocenotic regulation; Biocenotic regulation, dynamics of the number and species diversity of agrosphere is realized through trophically similar cenoconsorcia and tritrophic systems, that provides maintenance and preservation of trophically proved critical level of harmful species; Biotic and man-caused effects on argosphere are regularly registered and the degree of these effects on non-target biota is comprehensively estimated, operative measures to prevent its elimination are taken, if necessary. Thus, artificial agrocenoses and agroecosystems are immanent components of the agrospehere. Functioning of their bioresources meets the same laws of the Nature, as the functioning of the biota of natural ground ecosystems. When agrocenoses and agroecosystems make a single whole with the elements of preserved natural ecosystems, reproduction of bioresources, their protection against expansion of competitive and cosmopolitan species are realized at a level of steadily functioning agrocenoconsorcia, where “living beings protect living beings”. 3. Bioprotection and agrosphere. Present-day bioprotection is based on agrolandscape approaches. The major global function of the agrolandscape involves utilization of maximum quantity of solar energy. Modern geosystemic definition of the agrolandscape emphasizes not only its production abilities, but also its social and design-aesthetic functions: “... is an existing geosystem anthropogenically modified for agricultural use and formed with the purpose of the most effective and ecologically safe use of natural and anthropogenic resources for manufacturing economically and socially reasonable quantity of agricultural production and creation of the welfare and spiritual environment for harmonious development of humans” (A.V. Zaharenko, 2004) . The paradox is, that current plant growing (initially based on the use of gratuitous, inexhaustible solar energy and renewed resources of agrosphere) has turned in the most resource uneconomic branch of economy by the beginning of XXI century. Therefore agricultural technologies, including protection of plants, should mostly use renewable, instead of exhaustible resources and not renewable sources of raw material and energy, materialized in agrochemicals, chemical pesticides, oil

风电场集电线路单相接地故障柔性电压消弧与动态保护新原理

为解决风电场集电系统长期存在的线路单相接地故障处理难题,提出风电场中性点柔性接地方式,理论推导获得柔性接地风电场三序等效电路,与集电线路单相接地故障复合序网模型,建立风电场零序电压柔性调控理论,提出集电线路单相接地故障柔性电压消弧方法,可主动将故障点电压及故障残流迅速抑制到零,实现单相接地故障电弧的可靠消除。进一步提出基于零序电流动态增量的高阻故障辨识与保护方法,通过柔性调控零序补偿电流,逐渐放大故障残流,实现永久性单相接地故障的灵敏感知与保护。利用PSCAD/EMTDC搭建含双馈异步风电机(doubly-fedinduction generator,DFIG)的规模化风电场模型,模拟多种运行与故障条件对所提方法进行验证,仿真结果表明,该方法能够在考虑系统不平衡电压的情况下精准调控集电线路故障点电压,实现瞬时性单相接地故障快速可靠消弧,动态感知并持续抑制永久性单相接地故障残流,实现集电线路高阻接地故障的灵敏保护。该技术有望提升风电场运行灵活性与故障防御能力,有力保障新能源电能外送的持续性、可靠性。

“光储直柔”建筑配电系统应用研究

以某项目为例分析“光储直柔”在建筑物中的应用,并对“光储直柔”系统的应用场景、建筑直流配电系统的关注点及“光储直柔”系统关键设备进行阐述。

励磁系统交流侧接地对转子接地保护的影响

励磁系统交流侧接地将引起注入式转子接地保护、乒乓切换式转子接地保护误动作。本文介绍了一起相关案例,并对引起误动的基本原理进行了深入分析和定量计算,总结了励磁系统交流侧接地引起采样数据变化的典型特征,提出了关于缩小转子接地保护定位范围的思考。当转子一点接地保护动作后,应首先根据采样数据的变化,对故障点位于励磁系统交流侧还是直流侧做出初步判断,缩小故障定位范围,为快速查找故障提供决策依据。

空地协同场景下具有隐私保护的高效异构认证方案

在空地协同场景下车辆与无人机频繁通信存在异构认证效率低、隐私容易泄露、计算开销较大等问题,为此提出高效的异构认证方案.设计基于Schnorr签名和物理不可克隆函数的高效异构认证协议以抵抗克隆攻击、物理攻击和重放攻击等安全威胁;设计基于模糊提取器和身份令牌的车辆假名生成方法,在保护用户隐私的同时准确追溯恶意车辆的身份信息,实现有条件的隐私保护;设计基于密钥共享的切换认证协议,减少认证过程中的计算量,降低认证过程中无人机的能量消耗.实验结果表明,所提方案有效提高了车辆与无人机认证效率,与现有方案相比,平均降低了54.8%的计算开销.