Fault Detection Based on Hierarchical Cluster Analysis in Wide Area Backup Protection System

In wide area backup protection of electric power systems, the prerequisite of protection device's accurate, fast and reliable performance is its corresponding fault type and fault location can be discriminated quickly and defined exactly. In our study, global information will be introduced into the backup protection system. By analyzing and computing real-time PMU measurements, basing on cluster analysis theory, we are using mainly hierarchical cluster analysis to search after the statistical laws of electrical quantities' marked changes. Then we carry out fast and exact detection of fault components and fault sections, and finally accomplish fault isolation. The facts show that the fault detection of fault component (fault section) can be performed successfully by hierarchical cluster analysis and calculation. The results of hierarchical cluster analysis are accurate and reliable, and the dendrograms of hierarchical cluster analysis are in intuition.

Inverse-time Backup Protection Based on Unified Characteristic Equation for Distribution Networks with High Proportion of Distributed Generations

The setting work of backup protection using steady-state current is tedious,and mismatches occasionally occur due to the increased proportion of distributed generations(DGs)connected to the power grid.Thus,there is a practical need to study a backup protection technology that does not require step-by-step setting and can be adaptively coordinated.This paper proposes an action sequence adaptive to fault positions that uses only positive sequence fault component(PSFC)voltage.Considering the influence of DGs,the unified time dial setting can be obtained by selecting specific points.The protection performance is improved by using the adjacent upstream and downstream protections to meet the coordination time interval in the case of metallic faults at the near-and far-ends of the line.Finally,the expression and implementation scheme for inverse-time backup protection(ITBP)based on the unified characteristic equation is given.Simulation results show that this scheme can adapt to DG penetration scenarios and can realize the adaptive coordination of multi-level relays.

Reliability of Substation Protection System Based on IEC61850

Although the new technology of protection and automation system of substation based on IEC61850 standard has developed rapidly in China,reliability measures depending on this technology need to be further researched.By taking advantage of convenient information sharing,two kinds of new schemes,shared backup protection unit(SBPU)and signal backup(SB),have been proposed to solve the failure problem of protective devices and current/voltage transducers respectively,and the working principle of these two schemes are also described.Furthermore,the key technologies of on-line diagnosis of protective devices'failure and on-line status diagnosis of optical or electronic current/voltage transducers to realize the two schemes are proposed.

Integrated dynamic shared protection algorithm for GMPLS networks

The path protection approach is widely investigated as a survivability solution for GMPLS networks, which has the advantage of efficient capacity utilization. However, there is a problem of the path protection approach that searching a disjoint backup path for a primary path is often unsuccessful. In order to resolve this problem, an integrated dynamic shared protection （IDSP） algorithm is proposed. The main idea of the proposed algorithm is that the path protection approach is first used to establish a backup path for the primary path; if the establishment is unsuccessful, then the primary path is dynamically divided into segments whose hop count are not fixed but not more than the limitation calculated by the equations introduced. In this proposal, backup bandwidth sharing is allowed to improve the capacity utilization ratio, which makes the link cost function quite different from previous ones. Simulation experiments are presented to demonstrate the efficiency of the proposed method compared with previous methods. Numerical results show that IDSP can not only achieve low protection failure probability but can also gain a better tradeoff between the protection overbuild and the average recovery time.

Efficient Routing Protection Algorithm Based on Optimized Network Topology

Network failures are unavoidable and occur frequently.When the network fails,intra-domain routing protocols deploying on the Internet need to undergo a long convergence process.During this period,a large number of messages are discarded,which results in a decline in the user experience and severely affects the quality of service of Internet Service Providers(ISP).Therefore,improving the availability of intra-domain routing is a trending research question to be solved.Industry usually employs routing protection algorithms to improve intra-domain routing availability.However,existing routing protection schemes compute as many backup paths as possible to reduce message loss due to network failures,which increases the cost of the network and impedes the methods deployed in practice.To address the issues,this study proposes an efficient routing protection algorithm based on optimized network topology(ERPBONT).ERPBONT adopts the optimized network topology to calculate a backup path with the minimum path coincidence degree with the shortest path for all source purposes.Firstly,the backup path with the minimum path coincidence with the shortest path is described as an integer programming problem.Then the simulated annealing algorithm ERPBONT is used to find the optimal solution.Finally,the algorithm is tested on the simulated topology and the real topology.The experimental results show that ERPBONT effectively reduces the path coincidence between the shortest path and the backup path,and significantly improves the routing availability.

Research and Practice on Security Protection and Disaster Recovery Strategy of Oracle Database in Colleges and Universities

Database security protection, database backup and disaster recovery are important tasks for all colleges and universities to ensure the safe and stable operation of information systems. Based on the operating environment of the Oracle production database in China University of Geosciences (Beijing), combined with the practical operation and maintenance experience, this paper provides a design and implementation case of Oracle database security protection system and disaster recovery architecture. The network security protection architecture of the three-layer firewall and fortress machine, the detection and repair of security vulnerabilities, the management of system accounts and permissions, data encryption and database audit constitute the security protection system of the database. Oracle RAC (Real Application Clusters), Oracle DataGuard, redundant backup management and backup recovery constitute the disaster recovery architecture of the database. The case has practical significance for database operation and maintenance management in other colleges and universities.

应对变电站二次直流失电的超高压输电线路相间保护方案

变电站二次直流失电会导致本站继电保护装置等设备失去供电电源而无法动作,本站出线发生故障时需要依靠上级变电站的远后备保护进行切除。针对变电站二次直流失电情况下超高压输电线路发生相间短路故障时保护远后备灵敏度不足的问题,提出了一种应对变电站二次直流失电的超高压输电线路相间保护方案。首先,根据超高压电网相间故障时负序电流的自然分布特性,探讨了反时限负序过流保护的远后备应用可行性和相间距离保护的补充特性,确定了相间故障远后备保护的构成思路。接着,研究了助增系数和负序电流对反时限负序过流保护整定时间定值的影响,讨论了临界助增系数的确定方法和反时限负序过流保护的时间定值整定方法。然后,提出了反时限负序过流保护为主、相间距离保护为辅的应对变电站二次直流失电的超高压输电线路相间保护方案。最后,以IEEE 39节点系统和某实际500 kV电网作为仿真算例,对所提方案的有效性进行验证。

基于区间证据理论的多源融合广域后备保护

针对传统保护方案在光伏接入系统时存在的可靠性不足问题,该文提出了一种基于区间证据理论的多源融合广域后备保护方案。首先,将光伏输出电流对保护的影响解耦分析,提出了保护方案的基本概率分配函数,将传统保护结果的0,1值转化为描述故障概率的区间值,定量考虑了光伏接入对配网保护的影响。其次,利用改进的区间证据理论对多种保护的判别结果进行融合,得到每条线路的综合故障概率区间,进而识别故障线路。该方法将光伏接入对保护判别的影响定量化,利用了多个保护综合判断,提高了广域后备保护的可靠性。同时,改进的区间证据理论消除了冲突证据的影响,在保护存在数据缺失及错误时仍能可靠识别故障线路。最后仿真验证了该文方法的可靠性。

主变低压侧区内单相接地保护分析及引起负荷损失的思考

110 kV主变10 kV低压侧母线桥发生一起区内单相接地,仅有接地变保护动作跳闸变低开关且闭锁备自投,造成负荷损失。母线桥接地故障一直持续至运行人员手动切除主变高压侧断路器,故障存在扩大的隐患。文章对故障期间主变差动、主变高低后备保护、接地变和备自投动作行为进行分析,确认相关保护动作行为的正确性。为避免主变区内故障引起负荷损失,提出备自投采用变低自产零序电流反闭锁的判据优化方案。为及时切除故障避免故障扩大,提出备自投跳闸变低联跳变高的动作优化,对提高电源可靠性和设备安全性具有积极参考意义。

高海拔宇宙线观测站(LHAASO)电涌保护器选型简析

结合国家重大科技基础设施高海拔宇宙线观测站(LHAASO)项目工艺配电系统设计中的电涌保护器(SPD)选型设计实例,详细介绍在高原环境中低压配电系统SPD产品选型、主要参数校验的具体方法。

断路器后备保护和大短路电流下的上下级选择性研究

引入电流三区段概念,主要分析在选择性极限电流I_(s)超过上级断路器短路保护阈值时的上下级选择性问题,并就实际工程应用给出相关建议。

等容量替代发电厂发变组及启备变保护设计特点分析

随着时间的推移,国内越来越多的火力发电厂将进行延寿或等容量替代改造。对已执行的火力发电厂等容量替代改造工程中的保护设计特点进行分析总结,以期为今后同类工程设计提供指导和借鉴。

浅谈220 kV枢纽站变压器接地中性点选择

中性点直接接地系统有降低过电压、提升保护灵敏性的优点,但是由于故障电流限制、保护整定等原因,变压器中性点接地的方式须调度统一管理。介绍了中性点直接接地的管理制度,分析了典型220 kV枢纽站,即双母线3台变压器并列运行的变电站,不同中性点接地方式下,电网发生故障时保护的动作情况,解释了接地中性点的优先选项。

区域备自投在电网中的应用研究

结合区域备自投在电网中的实际应用,提出了区域备自投的动作逻辑及动作方案,针对接带有电源和备自投动作后造成设备过载情况制定了联切方案,同时对备自投动作后对零序保护整定计算的影响进行了分析,总结了实际联调试验,提高了电网运行的可靠性。

计及换流站控制响应的多端混合直流线路后备保护设计

多端混合直流系统故障暂态过程受直流控制响应的影响较大,针对其线路故障特征的分析和保护原理的研究,应当充分计及直流控制特性的影响。为此,根据多端混合直流系统的特点,计及故障后不同换流站的控制响应过程,对其直流线路故障暂态电流的变化趋势关系进行研究分析。并基于此提出了基于滑窗均值电流的多端混合直流线路区内、区外故障识别判据,给出了具体的保护方案。通过PSCAD/EMTDC对所提保护方案的可行性进行了仿真验证。仿真结果表明,所提方案能够可靠识别包含T接汇流母线在内的各种直流线路故障,天然具有故障选极能力,耐受故障过渡电阻能力和抗噪声干扰能力强,且无需数据同步,可作为多端混合直流线路的快速后备保护。

适用于半桥型MMC附加限流控制的直流线路纵联保护方案

半桥型模块化多电平换流器的附加限流控制能有效降低对线路保护速动性的要求、增强实体限流装置的限流效果,降低了故障暂态电流的上升梯度及其幅值,因此,基于故障暂态电流信息的直流线路保护会受到限流控制器影响。提出了计及附加限流控制器影响的直流线路自适应纵联保护方案:利用极线电压及其零模电压变化率构成或逻辑来启动限流控制器;推导了限流控制器作用下的直流侧故障电流解析关系,并根据限流控制器对故障电流抑制程度和换流阀两侧的故障电流信息,建立了一种基于换流阀两侧差流的纵联保护方案。该方案仅用到各站端的本地量,通过与其对端换流站交换判别结果,其不受线路分布电容影响、无需多端数据同步,具有自适应性。大量仿真实验验证了利用限流控策略的有效性和保护方案的可靠性。

祝融号火星车重要数据保护设计与实现

由于火星表面测控支持受限,祝融号火星车需要自主实现可靠生存、高效探测,而重要数据保护是这种自主能力的必要条件。由于能源约束,火星车内仅有少量设备处于长期工作状态,无法沿用基于器内信息网络的分布式重要数据保护方案。为解决这一问题,设计了一种分布式与集中式相结合的重要数据保护架构。由系统管理单元(system management unit,SMU)集中保存重要数据,并在其他设备加电时为其提供分布式重要数据服务。针对SMU复位、切机后的时间恢复需要,提出了一种基于多重备份的器上时间保护方法,低消耗、高可靠地实现了器上时间保护。为了在有限空间内保护更多延时指令,提出了一种专用存储区与公用存储区相结合的重要数据保护方法,有效提升了存储空间利用率。上述重要数据保护方案在火面测控、能源双重约束下为祝融号火星车提供了可靠的业务连续性保障,可为后续深空探测器的设计提供参考。

中压配电网分布式智能后备保护方案

分布式保护是含高渗透率分布式电源接入的有源配电网保护发展的重要方向,因此提出了一种分布式智能后备保护方案。该方案采用动态阈值构成后备保护的启动判据,无需复杂的时延整定。各环网节点的后备保护利用与近邻之间的信息交互,可实现故障区段的定位和动作协同,在通信故障、智能单元故障、开关拒动等多种异常状况下实现有效的后备保护。通过有源配电网故障仿真算例验证了后备保护的有效性。

基于直流断路器动作响应的环状柔性直流配电网后备保护方案

直流配电网由于供电能力强、线路损耗小、电能质量高等优点,已经成为未来配电网的发展趋势。柔性直流换流器过载能力差,且直流线路故障时,换流器直流侧电容向故障点提供数值很大的放电电流,对环状直流配电网继电保护的快速性和选择性提出了极高的要求。此外,一方面直流故障电流分断困难,技术尚不成熟,直流断路器存在拒动风险;另一方面,即使换流器闭锁后,仍然需要继电保护识别故障位置并采取故障隔离措施,以保障重启动和恢复过程的顺利进行,因此环状直流配电网的后备保护也应得到足够的重视。提出一种基于直流断路器动作响应的环状柔性直流配电网后备保护方案,分析了直流故障线路一侧断路器拒动情况下,相邻非故障线路上限流电抗器的电压变化特性,提出基于直流电流二阶变化率的故障识别判据和故障隔离方案;其次,分别考虑了高阻故障和故障线路两端直流断路器非同期分断等问题,提出基于直流电流一阶变化率的辅助判据和基于电流二阶变化率数值和方向的闭锁判据,以提升后备保护方案的整体性能;最后,基于PSCAD/EMTDC平台搭建电磁暂态仿真模型,验证了所提方案的有效性,结果表明:该方案动作无需通信,耐过渡电阻能力强,不受交流侧故障影响,能够在直流断路器动作后快速启动并为柔性环状直流配电网提供有效的后备保护。

基于软件定义网络的高故障保护率的路由保护方案

软件定义网络(Software Defined Network,SDN)以其强大的可编程性和集中控制的优势得到了学术界的广泛关注。现有的SDN设备在执行报文转发时仍然使用最短路径协议,当最短路径中的结点发生故障时,网络仍然需要重新收敛,在此期间报文可能会被丢弃,进而无法传递至目的结点,给实时性应用的流畅性造成了冲击,影响用户体验。学术界普遍采用路由保护的方案来应对网络故障,现有的路由保护方案存在以下两个方面的问题:(1)故障保护率低;(2)当网络出现故障时,备份路径可能会出现路由环路。为了解决上述两个问题,首先提出了备份下一跳计算规则;然后基于此规则设计了一种软件定义网络下的高故障保护率的路由保护算法(Routing Protection Algorithm with High Failure Protection Ratio,RPAHFPR),该算法融合了路径生成算法(Path Generation Algorithm,PGA)、旁支优先算法(Side Branch First Algorithm,SBF)和环路规避算法(Loop Avoidance Algorithm,LAA),可以同时解决已有路由保护方法面临的故障保护率低和路由环路问题;最后在大量的真实网络拓扑和模拟网络拓扑中验证了RPAHFPR方案的性能。与经典的NPC和U-TURN相比,RPAHFPR的故障保护率分别提高了20.85%和11.88%,并且在86.3%的拓扑中可以达到100%的故障保护率,在所有拓扑中可以达到99%以上的故障保护率。RPAHFPR的路径拉伸度基本接近1,不会引入过多的时间延迟。