Characteristic Analysis of UHVAC/DC Hybrid Power Grids and Construction of Power System Protection

Strong DC coupling with weak AC and large-scale renewable energy integration are the two significant characteristics of ultra-high-voltage AC/DC(UHVAC/DC)hybrid power grids in China.Strong coupling between AC and DC grids and the different integration performance of renewable energy sources have profoundly changed the stability characteristics of the power system.The traditional stability control system is inadequate for the stability control of UHVAC/DC power grids.This paper analyzes the requirements for constructing an integrated defense system in a UHVAC/DC hybrid power grid(i.e.power system protection).The definition,connotation,and designing principles of power system protection are put forward.The relationship between the power system protection and the traditional three-defense lines is investigated.The design principles,general hardware structure and main functions of a power system protection are presented.Key problems and technologies are specified in the construction of the power system protection.

Improving the performance of power system protection using wide area monitoring systems

Wide area monitoring(WAM) offers many opportunities to improve the performance of power system protection. This paper presents some of these opportunities and the motivation for their development. This methods include monitoring the suitability of relay characteristics,supervisory control of backup protection, more adaptive and intelligent system protection and the creation of novel system integrity protection scheme. The speed of response required for primary protection means that the role WAM in enhancing protection is limited to backup and system protection. The opportunities offered by WAM for enhancing protection are attractive because of the emerging challenges faced by the modern power system protection. The increasingly variable operating conditions of power systems are making it ever more difficult to select relay characteristics that will be a suitable compromise for all loading conditions and contingencies. The maloperation of relays has contributed to the inception and evolution of 70 % of blackouts,thus the supervision of the backup protection may prove a valuable tool for preventing or limiting the scale of blackouts. The increasing interconnection and complexity of modern power systems has made them more vulnerable to wide area disturbances and this has contributed to several recent blackouts. The proper management of these wide area disturbances is beyond the scope of most of the existing protection and new, adaptive system integrity protection schemes are needed to protect power system security.

Developments of power system protection and control

Synchronized wide area communication has become a mature technology,which makes the real-time interaction between the substations and the wide area protection and control system possible.However,the present protection and control system to handle this real-time data has been recognized to be deficient.This paper begins by reviewing the development history of power system protection,with special attention paid to the recent development in the field of wide-area and integrated protections,in order to look into the future development of protection and control systems.Then the concept of integrated wide area protection and control is introduced,where it can be shown that a hierarchical protection and control system provides the protection and control for wide area or regional power substations/plants and their associated power networks.The system is mainly divided into three levels:the local,the substation/plant,and the wide area/regional.The integrated functions at each level are described in details with an aim to develop an optimal coordination mechanism between each level.The key element in the proposed system is the wide area real-time protection and control information platform,which not only enables the merger of three lines of defence for power system protection and control,but also provides a perfect tool for the application of cloud computing in substations and power networks.

Human reliability analysis in maintenance team of power transmission system protection

The requirement for reliable electrical energy supply increases continuously because of its vital role in our lives.However,events due to various factors in the power grid can cause energy supply to be interrupted.One of these factors is human error and thus human reliability analysis is a serious element in the industry.The first step is to identify the roots of human error,on which there has been limited research in this area.In this paper,the potential and actual causes of human error in maintenance teams of power transmission system protection are identified and predicted within a framework of human factors analysis and classification system method.Then,human error factors are ranked to help improve human reliability.The proposed method is implemented in the Fars Electricity Maintenance Company.

Serial Failure Diagnosis of a Transmission Line Protection Relaying System by Petri Nets

With the development of large-scale complicated modern power systems, the requirement for the associated protection scheme tends to be more stringent and its combination more complex. However, it is very difficult to figure out the factors of failure of such systems. This paper proposes a Petri net model of a transmission line protection relaying system, including three types of relays as well as an automatic reclosing device, and shows how to diagnose serial failure of the system by analyzing invariant sets of the model. Furthermore, it gives four basic types of failure sequences and its execution is much more intuitive and effective than the traditional method.

An Intelligent Approach for Intrusion Detection in Industrial Control System

Supervisory control and data acquisition(SCADA)systems are computer systems that gather and analyze real-time data,distributed control systems are specially designed automated control system that consists of geographically distributed control elements,and other smaller control systems such as programmable logic controllers are industrial solid-state computers that monitor inputs and outputs and make logic-based decisions.In recent years,there has been a lot of focus on the security of industrial control systems.Due to the advancement in information technologies,the risk of cyberattacks on industrial control system has been drastically increased.Because they are so inextricably tied to human life,any damage to them might have devastating consequences.To provide an efficient solution to such problems,this paper proposes a new approach to intrusion detection.First,the important features in the dataset are determined by the difference between the distribution of unlabeled and positive data which is deployed for the learning process.Then,a prior estimation of the class is proposed based on a support vector machine.Simulation results show that the proposed approach has better anomaly detection performance than existing algorithms.

Adaptability of the Recloser-Fuse Protection Scheme in the Presence of Distributed Generation

This paper addresses the behaviour of an IEEE(Institute of Electrical and Electronics Engineers)test network when distributed injections are added to the distribution network.The penetration of different dispersed generation technologies,modifies the distribution system characteristics,with impact on a number of parameters,depending on their size and location on the network.For this purpose,this paper comprises three case studies:in the first case an exhaustive analysis is carried out of the occurrence of faults throughout the network,along with the introduction of distributed generators;in the second case the network behavior is assessed against the use of three of the most commonly used types of generators based on rotating machines;in the third case study an evaluation is made of the network performance when the three types of DG(distributed generation)units are distributed in multiple buses.In all cases the protection system is analyzed with the aim of ensuring coordination among the protection devices.All simulations are performed using the Power Factory software package from DigSILENT.From the simulation results,conclusions are drawn that provide insights into the behaviour of protection systems,highlighting the limitations of the original protections and coordination with different distributed generators technologies.

家户制、村落保护主义与农业现代化发展

家户制因素和村落保护主义因素在一定程度上都会影响农业现代化的发展。研究表明:村庄内部亲缘关系越紧密、村组间保护主义现象越弱、外地户口农户租入农地越难以及上一年非农户口比例越高,越有利于农地流转率的提高;村组内集体互助合作越差和上一年村组农业生产总值越高,越有利于机械化普及率的提高;其他村庄人员落户本村越困难、本村农户对外地机械进入本村组耕种越抵制、上一年村组农业生产总值越高以及上一年非农户口比例越高,越有利于农用机械总动力的提升;村庄内部亲缘关系越紧密和上一年非农户口比例越高,越有利于合作化率的提高。此外,家户制变量、村落保护主义变量以及社会经济变量对农业信息化率的提高没有显著性影响。

Micro-synchrophasor based special protection scheme for distribution system automation in a smart city

Introduction:Aspects of power system protection which contributes to mal-operations and blackouts can be improved by supervision of system behavior and response based analysis rather than condition-based or event-based analysis using wide area measurements based on synchrophasor technology.The paper explores the application of micro-Phasor Measurement Unit for time synchronized real-time distribution network monitoring and agile decision support schemes for system prognosis and control.Case description:The scheme is proposed as part of a project on“Power System Voltage Stability Analysis using synchrophasors in Distribution System of Kerala Grid”at Kerala State Electricity Board Ltd.An actual grid occurrence during the severe tropical cyclone Ockhi,is considered as the base case which motivated the work.Discussion and evaluation:A voltage stability index(VSI)based special protection scheme(SPS)for radial distribution network at a proposed smart city is presented in the present study.The proposed special protection scheme on actual implementation can use data from proposed local micro-Phasor Measurement Unit.The PMU is proposed to be placed at one of the key nodes of the distribution system network in the city.Conclusion:The VSI is derived using local phasor values and is used to initiate a Special Protection Scheme for N-1 contingency at the key node,so as to ensure availability of the most essential feeder which provides supply to a hospital campus housing several health institutes of prime importance.The voltage stability index derived is tested and SPS is validated using real-time grid data.

加快建设全国统一大市场的基本思路与重点举措

全国统一大市场是市场发展到一定程度后出现的一种高级形态,涉及时间、空间等不同维度,关系到制度规则、市场监管、商贸流通、城乡区域、基础设施等不同领域。当前,我国统一市场建设在基础制度、经济政策、要素市场、流通体系、市场监管等方面仍存在一定障碍。相关问题产生有央地财政关系未理顺、政绩考核制度不合理、法律法规体系不健全、重点领域改革进程慢等原因。加快推进全国统一大市场建设,要做好统一和统筹、协同和共享、培育和畅通、清理和破除、规范和整顿五方面的重点工作,确立公平竞争审查、现代市场监管体系建设、要素市场化改革、区域协同发展、市场交易平台和现代流通体系建设五大政策支柱,落实好建章立制和破除壁垒两方面政策,不断提高政策的统一性、规则的一致性、执行的协同性。

WTO反倾销制度与竞争政策的关联与冲突

贸易自由化与竞争政策目标在本质上具有一致性,决定了WTO的政策目标和法律体系中必须包括竞争政策,否则就是不完整的。但WTO反倾销制度与竞争政策之间存在相当程度的差异与冲突,在实践中反倾销制度正日益取代保障措施成为"保护工具的上策",必须对其进行改革。

政府和农村集体土地收益分配关系实证研究——以我国土地征用—出让过程为例

由于集体土地入市存在“征地制度壁垒” ,导致政府征用集体土地过程中土地市场主体之间 ,尤其是政府和集体之间的经济利益冲突。本文通过分析全国 3 5个城市样点 ,对土地征用—出让过程中政府和农村集体土地收益分配关系进行实证研究 ,认为征地制度破坏了市场潜在的均衡 ,造成集体的经济福利损失。作者建议应该引入竞争因素 ,让竞争机制来决定政府和农村集体的土地收益分配比例。

基本药物招标采购中地方保护主义的经济学分析

目的:探讨基本药物集中采购中地方保护主义不应该存在的主要原因,并对如何减少地方保护主义提供相应的建议。方法:在原始产权模型的基础上建立新的市场产权模型,以此来分析目前基本药物集中采购中地方保护主义的现状,并对如何减少地方保护主义提供相应的建议。结果与结论:应建立并完善基本相应制度,消除基本药物集中采购中的地方保护主义。

论制度创新与遏制地方保护主义

我国体制转轨时期出现的地方保护主义具有特定的内涵、行为目标和实质。制度缺陷即制度安排缺陷、制度实施机制缺陷、制度变迁方式缺陷是地方保护主义产生的深层原因。以制度创新来遏制地方保护主义是治本之举。

美国量化宽松政策的原因及其影响

美国在财政政策和传统货币政策空间有限、国会的贸易保护主义环境和政党竞争激烈的情况下,为了刺激本国经济复苏,采取了量化宽松政策。短期来看对刺激美国经济有一定的作用,但是由于美元在国际货币体系中的中心地位,该政策会加大全球通货膨胀压力、助推大宗商品价格上涨、引起货币竞相贬值和更广泛的贸易保护主义。长期来看该政策增加的流动性大量外流,对美国经济刺激作用有限,并影响美元的地位。因此需要国际社会广泛合作审慎应对该政策的影响。

遏制全球贸易保护主义:基于WTO多边贸易体制的价值评价

目前,全球正陷入20世纪30年代大萧条以来首次最为严重的全球性经济衰退,而且这场危机尚未见底,仍在蔓延,对实体经济的影响不断加深。在金融危机的影响下,由于缺乏推动自由贸易的政治意愿和民意基础,加之迫于利益集团游说和选民压力,贸易保护主义已在全球范围内全面回潮。此次金融危机衍生成为全球性贸易保护主义浪潮,在使WTO多边贸易体制经历着严峻时代考验的同时,也迫使WTO扛起维护贸易自由化形象的旗帜,在对抗和遏制贸易保护主义过程中发挥更多的价值。世界经济何时止跌回升,在无法企及通过技术革命和制度创新来激发大规模投资的情况下,作为世界经济调整和复苏的重要牵引力,全球贸易则义不容辞地肩负着拯救世界经济的首要使命,而保障全球贸易率先复苏的全球多边贸易体制及尽早结束多哈回合谈判理应成为各国拯救世界经济的共同期待。

流通企业影响力的制度分析

与生产企业相比,流通企业的发展较少受技术水平的影响,而主要取决于资本和劳动力投入。而我国长期以来对中外资企业、公有制和私有制企业实行区别对待的政策,致使各种所有制企业处于不公平的竞争环境中,由此严重地影响了我国流通企业的竞争力和影响力。尽快建立公平的外部竞争环境,是提升我国流通企业影响力的必要条件,也是完善市场经济体制的必然要求。

试论WTO体制下的贸易保护主义及应对策略

贸易保护主义的愈演愈烈,已对WTO的自由贸易体制造成了冲击。对WTO体制下贸易保护主义的表现及特性进行分析,并提出应对策略,是学术界的重要任务。

WTO反倾销法律制度的演进思考

最早的倾销产生于重商时代的欧洲,20世纪随着倾销行为的加剧,西方各国相继开始用反倾销的国内立法来抵制外国的倾销,保护本国工业。为了规范各国的反倾销行为,国际社会于1947年达成GATT第6条,标志着国际反倾销法律制度的建立,其后为了发展与完善之,相继达成1967年《反倾销守则》、1979年《反倾销守则》和WTO《反倾销协定》。但在反倾销法律制度的建立与发展中,其核心内容却逐渐背离了公平竞争原则,与其理论上预期的目标渐行渐远。

金融危机正在改变世界

当前金融危机是经济周期的必然结果,其直接原因是以美元为核心的单体国际货币体系和保护主义日益严重导致的全球经济的长期失衡,要通过这场金融危机来平衡全球金融体系和经济的关系。因此,建立多元的国际货币体系,是这次金融危机之后最重大的金融制度的变革。目前金融还是现代经济的核心和心脏,不能因为金融危机而停止中国金融的市场化改革的步伐;同时,金融危机给中国带来了两个难得的机遇,即人民币的国际化和全球金融中心的构建。