换流变压器非电量保护误动原因分析及解决措施

超高压直流输电系统换流变压器非电量保护类型众多,运行中多次出现非电量保护误动的情况,引起多次超高压直流输电系统非计划停运。介绍了超高压直流输电系统在运换流变压器非电量保护配置情况,指出了非电量保护误动的原因,提出加强非电量保护继电器的维护、合理地设置非电量保护的动作后果和修改非电量保护的动作逻辑,避免非电量保护误动,提高超高压直流输电系统的运行可靠性。     

低频功率振荡中距离Ⅲ段动作特性

电网事故过程中的低频功率振荡可以引起输电线路距离保护的不合理动作,扩大停电事故范围.提出距离Ⅲ段保护动作的临界振荡角度和临界振荡频率的直接算法.根据线路两端等值电源电压,建立多项式形式的保护动作条件,直接求解临界振荡角度,在此基础上,分析继电器参数设置、等值电源阻抗和线路充电电容对保护动作条件的影响.假设振荡频率恒定,根据临界振荡角度计算振荡轨迹在保护范围内的停留时间,从而得到不同保护整定时间下引起距离Ⅲ段保护动作的临界振荡频率.仿真分析验证了所提出的算法的可行性和有效性.     

A Novel Multi-Objective Protection Coordination Scheme for a Microgrid with Optimal Deployment of Dual-Setting ROCOV Based Relays

Relay coordination is crucial in electrical power systems to protect against malfunctions and damage caused by unexpected events like short circuits. To address the challenge associated with the reverse direction of fault current, dual-setting (DS) directional over-current relays have evolved but failed to provide proper coordination during changes of load, generation, and network. In the meantime, with the increasing number of DS relays, the total relay operating time tends to saturate. Therefore, this paper proposes a protection scheme based on the optimal deployment of conventional and dual-setting rate of change of voltage (DS-ROCOV) relays in distribution systems. This holds true for varying network topologies and is unaffected by variations in load and generation. The objective of the proposed scheme is to ensure reliable and efficient protection against faults in distribution systems by minimizing the overall operating time with the optimal number of DS-ROCOV relays. The proposed protection scheme''s performance is evaluated for different coordination time interval values as well as in different microgrid scenarios. This paper outlines the design and implementation of the proposed protection scheme which is validated on the modified IEEE 14-bus system using simulations in Matlab/Simulink.     

线路和变压器零序反时限保护及其整定配合

从事故分析的角度出发,在全网需设置高阻接地故障保护前提下,提出线路保护、主变压器保护均需配置零序反时限过流保护,并且500kV和220kV电压等级都可采用此配置。同时探讨其整定配合问题,提出了零序反时限曲线中时间常数的选取方法。实时数字仿真器（RTDS）试验用电网实例验证了采用零序反时限过流保护的静态和动态特性。     

Effective Installation Strategies of Fault Current Interrupting Arcing Horns Considering Operational Coordination with Responses of Line Protection Relays

The Fault Current Interrupting Arcing Horns (FCIAH) is a new type of arcing horns, which operates to break fault current within one cycle of alternating current and contributes to reducing the instantaneous power interruption due to the opening of a circuit breaker. However, reportedly the transmission line is often tripped by the line protection relay in some power utilities, even though the FCIAH successfully could break fault current. In this paper, we have investigated primary factors in the unwanted operation of the line protection relays at the current interruption by the FCIAH, and have proposed effective installation strategies of the FCIAH considering the operational coordination with the responses of the line protection relays.     

距离保护在风电接入系统中的适应性分析

大规模风电接入交流输电网使得风电系统表现出越来越多异于常规电网的故障特征,传统继电保护应用于风电接入系统时存在适应性问题。距离保护广泛应用于电力系统输电线路保护,研究其对风电系统适应性意义重大。针对距离保护的适应性问题,首先通过各距离保护的基本原理得出其最佳应用条件,然后基于该条件结合风电系统的一般故障特征从理论上对其适应性进行分析,得到距离保护适应性的一般结论。研究结果表明,风电系统的弱馈性和系统阻抗不稳定性使得基于工频变化量的距离保护不适用于风电接入系统,风电系统的高谐波和频偏特性使得工频量距离保护存在相量提取问题,时域距离保护动作性能良好。仿真结果验证了理论分析的正确性。     

GPS(全球定位系统)同步电流差动保护的应用

介绍数字式电流差动保护在输配电网络中作为主保护的应用情况。讨论电力部门为降低成本而租用电信通道时遇到的问题，分析说明GPS同步数字式电流差动保护如何通过同步数字级（SDH或SONET环）曜网而实现保护的高可靠性。     

Implementation of Directional Over-current Relay Coordination Approaches in Electrical Networks

As the smart grid concept is employed in the electric power system, network load flow and topology changes intensively to meet the best generation-demand balancing point. These changes must account for protection devices to enhance their performance. The coordination of directional over-current relays is most commonly studied based on fixed network operation and topology within a mesh power system. But sub-transmission and distribution systems constantly operate differently to satisfy the variety of load demand levels throughout the day and year. Hence, if the setting of directional over-current relays changes according to the different operations of the system, then relay operation time and sensitivity can both be enhanced. This can potentially improve the protection performance in a smart grid system. Therefore, this study is carried out based on the comparison among three coordination approaches: conventional (fixed settings), discrete (groups of settings), and continuous or real time (dynamic settings).     

用线路保护接地距离Ⅲ段作变压器相间故障的远后备——LFP-941保护装置动模试验验证

按电力行业标准,１１０ｋＶ电网继电保护必须采用远后备原则。对两种接线方式的距离阻抗元件运行特性进行了详细分析,通过具体试验,验证了用１１０ｋＶ线路保护接地距离Ⅲ段适合作为本线路末端变压器相间故障的远后备。     

基于小波理论的全线相继速动保护方案

针对传统中低压系统三段式保护的保护范围小、动作时限长的缺点，提出了一种基于小波变换理论的全线相继速动保护新方案。该方案用此小波提取故障后线路对侧断路器跳闸时本侧零序电流与负序电流之和产生的突变；并判断对侧断路器跳闸稳态后本侧零序和负序电流幅值是否小于定值，以区分本线路末端与下条线路出口的故障，作为本侧保护加速动作的依据。大量的ATP仿真结果证明了该方法的有效性。     

Directional overcurrent and earth-fault protections for a biomass microgrid system in Malaysia

Over-current protection is principally intended to counteract excessive current in power systems. In distribution systems in Malaysia, non-directional over-current protection is adopted because of the radial nature of the power system used. Relay typically used in distribution network are designed to cater for current flow in one direction, i.e., from transmission network to load. However, with the forecasted increase in generation from renewable sources, it is important that adequate codes are in place with regards to their integration to sub-transmission/distribution network. Distribution network dynamically changes from “passive” to “active” network. With distributed generation connected to distribution network, power flows bi-directionally. Hence, directional over-current protection is adopted along the line between the transmission grid and the distributed generation. The bi-directional flow of power also complicates the earth fault protection. This is due to the presence of the distributed generation that will cause the line near the delta side of the transformer to be still energized after the operation of earth fault relay during single-phase-to-ground-fault. This paper investigates the directional over-current and earth fault protections used to protect the microgrid (biomass generator) in Malaysia. In this study, under-voltage relays are adopted at the delta side of the transformer to fully clear the single-line-to-ground fault, which cannot be cleared by earth fault relay. Three-phase-balanced fault and single-line-to-ground-fault at all possible locations in the network have been simulated. Simulation shows good coordination and discrimination between over-current relays.     

断线故障对零序过流保护的影响及保护新方法

在电网运行中发现,线路断线故障有可能会引起相邻线路零序过流保护的误动,特别是重负荷下的多回线路,断线故障后引起的同断面相邻线路零序过流末段保护同时误动会加剧事故扩大。通过理论和仿真分析,研究了重载线路发生断线故障的故障特性,及其对零序过流保护的影响,提出了适应线路断线故障的零序过流保护新方案,并通过实际保护装置的RTDS试验验证其有效性。     

微机变压器的相间后备保护

提出对变压器内部故障应以两套差动保护互为后备,距离继电器主要作为低压母线及馈线故障的后备保护,并建议采用负序距离继电器和椭圆形继电器为宜     

直流馈入下的输电线路距离保护动作特性分析

直流馈入使传统输电线路距离保护的运行环境发生了改变,从而对其动作特性产生影响。结合距离保护原理的特点分析了直流馈入对输电线路距离保护影响的机理,指出其影响主要在于直流系统等值电流作用于故障过渡电阻而造成测量电抗的波动变化;基于受端电网故障引发各种换相失败情况下直流系统等值工频量电流的变化特性,从理论上分析、比较了不同输电线路情况下的距离保护受直流系统影响的特点。基于PSCAD/EMTDC仿真验证了该理论分析的正确性。     

风电场接人系统继电保护的配置与整定

针对风电场接入系统联络线与风电场变压器的继电保护配置与整定,分析了风力发电机有无低电压穿越（LVRT）功能对保护配置与整定的影响,并利用MATLAB／Simulink软件仿真了具有LVRT功能风力发电机组的短路电流。仿真结果表明,低电压穿越有助于提高快速保护的灵敏度,但也增加了后备保护配置的复杂度,因此,合理的保护配置与整定值有利于保证系统的安全。     

Algorithmic-knowledge-based adaptive coordination in transmission protection

Changes in power system operating conditions can affect both the reach point of distance relays and the coordination of distance and overcurrent relays. To improve the performance of the protection system, an adaptive scheme of relay settings is proposed. That is possible since the protection relays became digital . This paper describes a system for online adaptive setting and coordination of protection relays in meshed networks where the backup protection is achieved in remote form. After changes in the state of the network, an expert system (ES) performs the detection and proposes the correction of erroneous settings of protection zones and miscoordinations between relays at different stations; through an algorithm based on a fast determination of a nonminimal set of "break-points" (BPs) relays , new time characteristics for the coordination are found. The results of the application of the developed system to a test network of 34 nodes, 55 branches, and 110 relays are shown.     

电流差动保护在逆变型新能源场站送出线路中的适应性分析

新能源电源通过电力电子装置并网,其故障特性受控制策略影响而发生根本性变化,传统继电保护原理存在适应性问题。送出线路作为新能源场站电力外送的关键通道,其主保护电流差动保护能否正确动作对于新能源高效利用和系统安全运行十分重要。针对逆变型新能源场站,推导了逆变型新能源电源短路电流表达式,分析了各相短路电流之间的相位关系及其影响因素。在此基础上,分析了送出线路发生不对称短路时电流差动保护在并网系统为强、弱两种情形下的动作性能。研究结果表明,送出线路发生两相短路时,差动保护在并网系统为弱系统时存在拒动的风险、为强系统时灵敏性下降但不会拒动;送出线路发生接地故障时,零序电流的存在使得差动保护在并网系统为强、弱系统时均能可靠灵敏动作。实时数字仿真器(RTDS)试验验证了理论分析。研究结论为逆变型新能源场站送出线路主保护配置提供了参考。     

Interactive relay coordination using microcomputer graphics

A computer procedure is presented which enables the power system designer to interactively determine tap and time dial settings of overcurrent relays for the protection of industrial power systems. The user enters data about the power system, and a fault analysis is performed. Current transformer ratios, relay types, and load currents are then input to the program and the user selects tripping times or coordinating time intervals. Computer graphics techniques are then used to display the coordination curves and settings may be changed, if necessary, until the desired protection characteristics are achieved. An example of protection design for a sample industrial power system is provided to show the procedures for program use and demonstrate its capabilities.     

双回线路跨线故障及保护动作行为分析

以山西220kV系统某线路的一次实际跨线故障录波数据为基础,分析了同杆双回线路保护安装处的电流电压特征,研究了该线路上4套不同厂家、不同型号常规微机型线路保护的动作行为,提出了同杆并架双回线保护选型应注意的问题。结果表明,异名相跨线故障期间,各端保护可以检测到零序电流,但无零序电压;变化量方向元件可以正确判断方向;采用零序电流(?)_0和负序电流(?)_(2A)构成的稳态量选相元件能正确选相;零序方向元件的动作行为不确定;相间测量阻抗增大、接地测量阻抗减小均不能正确反映故障位置。     

高压直流输电线路暂态保护分析与展望

现时高压直流输电线路保护广泛采用ABB或西门子保护方案和配置。通过对ABB和西门子行波保护动作特性仿真结果分析及运行经验表明,二者保护方案无法可靠、灵敏地切除高阻接地故障,且易受噪声等外界信号干扰。同时,对国内外直流线路暂态保护的新思想进行分析总结,提出了提高高压直流输电线路暂态保护抗过渡电阻能力及区内、区外故障暂态分析所必须解决的几个关键性问题,为日后高品质直流线路保护判据的提出提供研究方向。