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.

Protection Strategies against Cascading Failure for Power Systems of Ring Network

Power grid vulnerability is a key issue with large blackouts, causing power disruption for millions of people. The complexity of power grid, together with excessive number of components, makes it difficult to be modeled. Currently, researchers use complex networks to model and study the performance of power grids. In fact, power grids can be modeled into a complex network by making use of ring network topology, with substations and transmission lines denoted as nodes and edges, respectively. In this paper, three protection schemes are proposed and their effectiveness in protecting the power network under high and low-load attacks is studied. The proposed schemes, namely, Cascaded Load Cut-off (CLC), Cascaded Load Overflow (CLO) and Adaptive-Cascaded Load Overflow (A-CLO), improve the robustness of the power grids, i.e., decrease the value of critical tolerance. Simulation results show that CLC and CLO protection schemes are more effective in improving the robustness of networks than the A-CLO protection scheme. However, the CLC protection scheme is effective only at the expense that certain percentage of the network will have no power supply. Thus, results show that the CLO protection scheme dominates the other protection schemes, CLC and A-CLO, in terms of the robustness of the network, improved with the precise amount of load cut-off determined.

Distributed Adaptive Learning Framework for Wide Area Monitoring of Power Systems Integrated with Distributed Generations

This paper presents a preliminary study of developing a novel distributed adaptive real-time learning framework for wide area monitoring of power systems integrated with distributed generations using synchrophasor technology. The framework comprises distributed agents (synchrophasors) for autonomous local condition monitoring and fault detection, and a central unit for generating global view for situation awareness and decision making. Key technologies that can be integrated into this hierarchical distributed learning scheme are discussed to enable real-time information extraction and knowledge discovery for decision making, without explicitly accumulating and storing all raw data by the central unit. Based on this, the configuration of a wide area monitoring system of power systems using synchrophasor technology, and the functionalities for locally installed open-phasor-measurement-units (OpenPMUs) and a central unit are presented. Initial results on anti-islanding protection using the proposed approach are given to illustrate the effectiveness.

Technology and engineering application of cross area HVDC interconnection system high-precision simulation modeling based on ADPSS

In recent years, a large number of high voltage direct current(HVDC) transmission projects have been connected to AC systems. This has started to have an impact on AC/DC hybrid power grids, particularly receiving terminal power grids. An HVDC system is a large-scale power electronic integrated nonlinear system, and it includes a primary system and a control and protection system. Hence, the precision and degree of detail of HVDC systems directly affect the actual effect of simulation. In recent years, in the case of the normal operation and failure of AC power grids, the abnormal fluctuation and even locking of HVDC systems caused by the inappropriate strategies of the control and protection system component have strongly affected power grids. This has significantly affected the safety and stability of receiving power grids and normal operation. In this study, the actual engineering HVDC control logic provided by a manufacturer is analyzed and simulated based on the user defined component library of the ADPSS electromagnetic transient calculation program, and an HVDC control model based on an actual system is established. The accuracy of the DC control custom model based on ADPSS is verified through the simulation of an actual power grid.

Using Grey Target Theory for Power Quality Evaluation Based on Power Quality Monitoring Data

Smart grid puts forward higher requirements for power quality.Power quality evaluation can provide a decision-making basis for quality improvement.Based on power quality monitoring data,a grey target method is proposed for power quality evaluation.The grey target is composed of power quality evaluation standard and power quality monitoring data to be evaluated.Combining with the characteristics of each power quality evaluation index,the target center of the whole grey target system is found.Then,the power quality monitoring data to be evaluated and the power quality standard mode are compared and analyzed to construct the power quality grey correlation difference information space.Finally,the target center coefficient and target degree of power quality are calculated to realize the comprehensive evaluation of power quality,and the evaluation grade of power quality monitoring data to be evaluated is obtained.Compared with the evaluation results of the existing literature,the effectiveness of the proposed method is verified,which shows that grey target theory is reasonable in the comprehensive evaluation of power quality.

Reliable Remote Relay Protection in Smart Grid

As the false trips of remote protection relays are among the main reasons behind cascading blackouts, it is critical to design reliable relay protection. Even though common protection schemes on traditional power systems have been investigated for a few decades, cascading failures in recent years indicate more research needed in this area. Consequently, researchers have proposed agent-based methods on the Smart Grid （SG） to address this issue. However, these existing agent-based methods simply use TCP protocol without considering real-time communication requirements （such as bandwidth and delay）. To deal with this issue, several methods for efficient network resource management are proposed. Furthermore, these existing methods do not consider the potential issues in practical communication networks, which may result in delay violation and trigger relay false trips. We have discussed simple backup solutions in the previous work. In this paper, in addition to network efficiency, we focus on improving the system reliability by exploring known power system information and minimizing the chances of false trips of important remote relays, e.g., defining power line priorities based on their importance. Moreover, to further improve the. system reliability, we also in- vestigate the peer-to-peer protection approaches to address the single point of failure of centralized control center.

基于限流电抗器两侧特定频段暂态能量比的MTDC电网单端量保护方案

柔性直流输电技术有利于未来大量分布式能源接入电网,而配置快速、可靠的保护方案是柔性直流技术发展的关键。基于直流电网等效模型,提出一种基于限流电抗器两侧电压特定频段暂态能量比差异性的单端量故障区域识别方法。该方法依据贝瑞隆等效模型计算出限流电抗器两侧电压比,通过广义S变换提取限流电抗器两侧特定频段电压,根据故障时正负极限流电抗器的电压幅值差的差异性实现故障选极。最后在PSCAD/EMTDC平台搭建仿真模型,分析出发生区内外故障时差异性明显,具备较强的耐过渡电阻与抗噪声干扰能力。

构网逆变电源故障穿越控制策略及其对保护影响的研究综述

构网(grid-forming,GFM)逆变电源(inverter-based resources,IBRs)可模拟传统同步电机行为,自主提供电压以及惯量支撑,是实现高比例新能源接入电网的必然途径。继电保护是保障电力系统安全稳定运行的第一道防线,其动作性能取决于对系统故障特征的辨识能力,而构网逆变电源主导下电力系统的故障特征则与逆变电源的物理极限和控制策略高度相关。该文首先梳理了典型构网逆变电源在正常及故障穿越时的控制策略及特点;进而归纳了电源的简化等值模型及故障特性分析研究成果;最后,总结了构网型逆变电源并网系统相关的保护技术研究现状,初步评述了构网逆变电源对当前保护技术的影响以及该领域未来所面临的问题。

基于单端分支系数的四端柔直环网线路保护方案

为提升直流线路保护在柔性直流环网中的速动性与可靠性,提出一种基于单端分支系数的保护方案。分析了不同故障位置下各换流阀提供的故障电流分量,并根据单端换流阀极线电流突变量构造分支系数,结果表明线路保护区内故障下的单端分支系数小于区外故障,利用该特征构造区内、外故障识别元件。在线路高阻接地致使主保护失效时,根据桥臂最大允许电流决定线路纵联后备保护的开放时限,以优化现有主、后备保护方案之间的时序配合方案,保障各种直流线路故障工况下,换流阀不间断运行。保护方案不依赖线路边界元件,算法简单,大量仿真结果表明,该方案有良好的耐受过渡电阻能力,能在换流阀闭锁前实现故障区域可靠识别。

基于数字孪生模型的数字化电网能耗自动监测系统研究

当前使用的数字化电网中,存在感知终端种类较多,对于传统的能耗自动监测系统来说获取的数据传输实时性不足,导致监测结果出现偏差,为此设计一种基于数字孪生模型的数字化电网能耗自动监测系统。系统主要从硬件和软件两方面进行设计:在硬件设计中,根据不同的应用层次,设计系统的总体架构。主要对硬件中的无线通信网络进行搭建,选择基于LoRa无线通信技术的RTU设备作为通信主体。设计LoRa无线开关电路,实现ZigBee设备之间的无线数据传输和交换;软件设计中,设计能耗数据采集主线程,分析数字孪生模型映射交互关系,基于数字孪生模型与实际运行工况之间的映射关系实现能耗指标实时监测。实验结果表明,与传统系统相比,设计得到的检测结果与实际的能耗情况更加相符。

复杂大电网非预设性运行工况下的继电保护动作适应性仿真分析

非预设性运行工况下的突发事件多,导致继电保护逻辑的适应性较差,不合理区域较多,为此,进行复杂大电网非预设性运行工况下继电保护动作适应性仿真分析。分析历史常规故障,标记故障点最常发生位置,构建零序、负序方向元件模型、距离元件模型、纵联电流差动元件模型,观察复杂大电网非预设性运行工况下的电网参数变化情况,第一时间掌握电网的耦合性,不断选择电网所需的继电保护动作逻辑,确认继电保护动作适应性。仿真实验表明,将故障点设置在保护区域内和区域外,继电保护动作能够根据故障选择不同保护模型进行故障母线切除或者保护不动作,适应性好。

Developing a power monitoring and protection system for the junction boxes of an experimental seafloor observatory network

A power monitoring and protection system based on an embedded processor was designed for the junction boxes(JBs) of an experimental seafloor observatory network in China. The system exhibits high reliability, fast response, and high real-time performance. A two-step power management method which uses metal-oxide-semiconductor field-effect transistors(MOSFETs) and a mechanical contactor in series was adopted to generate a reliable power switch, to limit surge currents and to facilitate automatic protection. Grounding fault diagnosis and environmental monitoring were conducted by designing a grounding fault detection circuit and by using selected sensors, respectively. The data collected from the JBs must be time-stamped for analysis and for correlation with other events and data. A highly precise system time, which is necessary for synchronizing the times within and across nodes, was generated through the IEEE 1588(precision clock synchronization protocol for networked measurement and control systems) time synchronization method. In this method, time packets were exchanged between the grandmaster clock at the shore station and the slave clock module of the system. All the sections were verified individually in the laboratory prior to a sea trial. Finally, a subsystem for power monitoring and protection was integrated into the complete node system, installed in a frame, and deployed in the South China Sea. Results of the laboratory and sea trial experiments demonstrated that the developed system was effective, stable, reliable, and suitable for continuous deep-sea operation.

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.

电网二三维融合画面的多终端展示研究

随着各种新型输变电设备特别是直流输电设备发展,设备种类越来越多,复杂度越来越高,传统二维画面难以满足电网设备监控的要求,二三维融合的监视方式在设备全面监视方面得到越来越多的应用。然而,限于二维和三维的技术差异以及传统开发技术路线转型难度大,此类融合监视画面存在Web发布难的问题,难以做到“一端维护、多端展示”的目标,给工程实施带来较大难度。针对这个难点,研究一套电网二三维融合画面的多终端展示框架,以HTML5页面为三维模型渲染载体,消除不同终端三维渲染方式的差异,实现二三维融合画面“一端维护、多端展示”的目标,保证了多终端画面内容的一致性,有利于融合画面的推广应用。

基于层次分析法的微电网并网运行电能质量安全监测模型

为了满足日益增长的电力能源需求,微电网并网运行是电力系统的主要发展趋势,其虽然能够提升电力能源的供应,但难以保证供电质量,不利于电力系统的后续发展。该现象的产生主要是由于分布式电源出力具有随机性与不稳定性,会对供电质量造成直接影响。对此,提出基于层次分析法的微电网并网运行电能质量安全监测模型构建研究。深入分析电能质量干扰源,以此为基础,选取适当的电能质量安全监测指标,应用层次分析法计算电能质量安全监测指标权重数值,确定电能质量安全监测模型,制定电能质量安全判定规则,从而实现电能质量安全的准确监测。实验数据显示:构建模型应用后,电能质量安全监测指标完整度最大值为96%,电能质量安全监测结果与实际结果一致,充分证实了构建模型具备更好的电能质量安全监测效果。

无功优先控制对风电场集电线保护影响分析及改进措施研究

电网电压跌落时能够向系统提供无功支撑是对并网风电机组的基本要求。风电机组无功支撑对故障电流有着直接影响,可能使集电线电流速断保护灵敏度下降,同时可能使保护失去选择性。文章首先根据双馈异步电机(double feed induction generator,DFIG)数学模型及无功电流支撑原理,分析了浅、深度故障运行下DFIG分别通过转子侧变流器(rotor-side converter,RSC)与网侧变流器(grid-side converter,GSC)调节输出无功对故障电流的影响。针对DFIG无功优先控制可能造成集电线电流速断保护灵敏度降低以及其与箱变熔断器失去配合的问题,提出了在DFIG无功优先控制计算整定初值基础上根据集电线电压跌落程度附加自适性补偿量的定值调整方法。通过仿真验证,表明整定值改进后能够在保证全线速动的前提下大幅提升保护的选择能力。

基于双频信号注入法的船舶交流电网绝缘监测装置应用探析

为了解决船舶交流电网绝缘故障实时在线监测定位问题,提出了一种基于双频信号注入法的船舶交流电网绝缘监测装置设计方案。对双频信号注入法的工作原理进行研究,系统以STM32F103ZE芯片为控制核心,运用基2时间抽取1024点FFT实现注入低频信号的提取。明确了注入信号的频率选取原则,试验分析确定注入信号频率为15 Hz和5 Hz。经过实际运行测试与结果分析,基于双频信号注入法的船舶交流电网绝缘监测装置最大误差率不超过2%,完全满足对地绝缘电阻测量精度±5%的设计要求。试验结果验证了船舶交流电网绝缘监测装置的可靠性和有效性,所提出设计方案大大降低船员工作强度,提高了舰船电力系统的供电连续性和安全性。

一种柔性接地线状态指示装置的设计与应用

提出了一种采用快速磁场检测方法的柔性接地线状态快速指示装置,并给出了其详细的设计和应用方法。在所设计的柔性接地线状态快速指示装置中,状态检测单元利用微型三维磁场实现实时高速磁场监测,状态报警单元通过3个阈值实现局部声光报警,而无线信号发送单元实现状态信息云显示。实验结果表明,所提出的柔性接地线状态快速指示装置可以有效地实现对接地线电流的智能监测,从而避免了接地装置误挂和接地不良造成的检修事故。

计及新型柔性限流器的直流系统故障暂态特性分析研究

为解决传统柔性限流装置在直流电网中存在经济性、实用性不足的问题,提出一种新型直流柔性限流装置,采用模块化限流电感结构,并提出模块化限流电感投入方案,基于该结构提出与其相适应的控制设计方案。该结构提升柔性限流装置的经济性,增强限流装置的容错率,并快速、有效抑制故障电流,实现直流线路永久性故障快速隔离,瞬时性故障无断路器动作行为的自行恢复。为进一步验证所提新型柔性限流装置的有效性,在软件平台搭建多端柔性直流仿真系统,并进行直流线路永久性与瞬时性故障仿真分析。

基于Android的分布式电源监控系统的研发

采用基于样本集约化的熵权法对分布式电源的电能质量进行综合评估,在此基础上建立相应的监控模型,形成目标函数。利用Java语言开发了基于Android的分布式电源监控系统,对分布式电源的有效运行具有重要的指导意义。