The universal overcurrent relay

A comprehensive list of nondirectional overcurrent relays would include thermal overload, inverse-time, definite time, and instantaneous relays. The list could be further classified by operating quantities including individual phase, residual, and negative-sequence current. Taken collectively and depending on the characteristic shape, pickup and time range, and dynamics, these relays span the applications for motor, feeder, and breaker failure protection. Because of the past necessity for using either discrete or specialized system relays, overcurrent characteristics for these applications may appear diverse and unrelated. However, microprocessor relay technology has advanced to where it is not only feasible, but it is of distinct economic advantage, to consider all these characteristics collectively as attributes of a universal overcurrent relay. This universal relay concept is used here to discuss the commonality, the differences, and the coordination of the elements required for feeder, motor, and breaker failure protection. The article goes on to discuss the rules for the coordination of negative-sequence overcurrent characteristics for sensitive phase-to-phase fault protection in feeders, as well as for unbalanced current protection of induction motors     

Advanced Coordination Method for Overcurrent Protection Relays Using Nonstandard Tripping Characteristics

This paper describes an advanced coordination method for an optimized protection time grading based on a new nonstandard tripping characteristic for overcurrent protection relays. The intention is the highest possible reduction of tripping times for a selective fault clearing in distribution networks protected by overcurrent relays without communication links. The new nonstandard tripping characteristic will be described from its basic idea to its constraints of the optimization problem. The optimization is solved by the method of Lagrange generalized with the Karush-Kuhn-Tucker conditions and is aimed at selective fault tripping with shorter tripping times as standard characteristics and conventional coordination methods. Overcurrent relay coordination becomes a mathematical optimization task. A comparison with the standard characteristics and conventional coordination methods shows a notable advancement regarding their average and maximum tripping times which can be achieved using this new method.     

Adaptive overcurrent protection scheme coordination in presence of distributed generation using radial basis neural network

The operational performance of conventional overcurrent protection relay coordination connected to a distribution network is adversely afected by the penetration of distributed generators (DG) at diferent buses in the network. To address this problem, this paper proposes a novel adaptive protection coordination scheme using a radial basis function neural network (RBFNN), which automatically adjusts the overcurrent relay settings, i.e., time setting multiplier (TSM) and plug setting multiplier (PSM) based on the penetration of DGs. Short circuit currents and voltages measured at diferent buses are acquired using the remote terminal units (RTU) connected to diferent buses within the terminal network. Communication between the various remotes and local end station RTUs is through hybrid communication systems of fber optic and power line communication system modules. The new adaptive overcurrent protection scheme is applied to the IEEE 33-bus distribution network with and without DGs, for single and multi-DG penetration using both the ETAP and MATLAB software. The simulation results show the proposed scheme signifcantly improves the protection coordination.     

基于改进的SOS算法的反时限过电流保护协调优化

通过优化设置继电保护定值,可以优化电力系统中继电保护装置的协调性,减小继电器动作时间,提高电力系统的可靠性。文中针对配电网中保护的协调配合问题,将反时限过电流保护的整定计算转化为一种含有多个约束条件的非线性规划问题,提出了一种基于改进的SOS算法的反时限过电流保护协调优化方案。在IEEE 3节点系统和IEEE 8节点系统中的仿真结果表明,改进的SOS算法具有更好的收敛速度和精度,能够克服解陷入局部最优,基于改进的SOS算法的保护优化协调方案能够提高保护的速动性。     

柔性直流输电系统桥臂过流保护定值配合方法

针对交流故障下柔性直流桥臂过流保护可能误动导致故障穿越失败,直流故障下桥臂过流保护拒动或慢动可能导致开关器件过流等问题,讨论了柔性直流换流阀桥臂过流保护功能在阀控和直流保护装置中的配置和定值配合关系。借鉴交流保护定值配合图的概念,提出了桥臂过流保护功能在阀控装置与直流保护装置中的优化配合方法。最后,在PSCAD/EMTDC中搭建了仿真平台,结果表明所述桥臂过流保护配合关系和定值设置方法可在交流故障下成功实现故障穿越,并可在直流极间短路等严重故障下可靠闭锁换流器并触发旁路晶闸管,降低电力电子器件的过流风险。     

基于复合故障补偿因子的微电网反时限电流保护方法

为了解决逆变型分布式能源(Distributed Generator, DG)对微电网保护速动性和协调性的影响,提出了一种基于复合故障补偿因子和天牛须搜索(Beetle Antenna Search, BAS)算法的改进反时限微电网电流保护方法。首先,通过分析故障时保护安装处的电压分布特性,并结合测量阻抗特征构建复合故障补偿因子,以解决反时限过电流保护由于短路电流变化引起的动作延时问题,提高保护速动性。同时,为了解决DG接入、微电网运行方式改变等因素引起的微电网保护协调问题,利用BAS算法对改进反时限电流保护的参数进行优化,以保证相邻保护的协调配合。最后,在DIgSILENT/PF软件中建立微电网仿真模型,以验证改进方法的有效性。仿真结果表明,与传统反时限过电流保护相比,改进保护方法在速动性方面明显提升,且在微电网不同运行模式、故障条件下均满足协调性要求。     

反时限与定时限过电流保护配合的优化和改进

主要阐述了石油化工企业变电所进线的定时限过电流保护和下级变压器反时限过电流保护之间配合存在的问题,通过对定时限过电流保护整定计算优化后,使反时限与定时限过电流保护做到合理配合。     

New overcurrent RST80 relays and their time-current characteristics

The problems are considered of the operation of electromechanical overcurrent relays and construction of relay protection using their time-current characteristics. The distinctive features of new static overcurrent RST80 relays are presented. It is shown that the four types of time-current characteristics implemented in the RST80 relay provide flexible coordination with the characteristics of the protection of the adjacent equipment.     

Simulation of protective relay performance under short-circuit andtransient swing conditions

Most methods of relay coordination are based on fixed values of fault current for setting protective relays, regardless of the fact that fault currents are time-dependent. The results of alternative transient calculation procedures are presented. These take into consideration the decay of current with time and can therefore be used to identify the sensitivity of the coordination setting and potential cases of difficulty. Comparison of the static and dynamic short-circuit calculation procedures shows that the dynamic procedure, with enhanced machine modeling, produces results that agree well with national standards and minimizes the engineering design effort, with only a small increase in computational overhead. The results presented are used to compare calculated time overcurrent relay settings and tripping times, based on the dynamic short-circuit calculation, with fault clearing times obtained by modeling the relays using a traditional step-by-step dynamic analysis procedure. These two methods of calculation yield results that are in close agreement. It is also shown that inclusion of protection setting and transient modeling facilities in power system CAD packages offers the opportunity to include automatically and reliably the effect of the protection in any subsequent transient studies of the system     

小电阻接地系统接地故障反时限零序过电流保护

现有的小电阻接地系统接地保护主要采用定时限零序过电流保护,定值较高,高阻接地时容易拒动。结合反时限过电流保护的特点,在分析小电阻接地配电网单相接地故障零序电流分布特征的基础上,提出一种改进的反时限零序过电流保护方法。通过各条出线保护间的横向配合,可使保护的启动电流定值无须躲过本线路的最大对地电容电流,显著降低了其启动门槛值,提高了高阻接地故障保护能力。通过MATLAB仿真验证了提出的反时限零序过电流保护的速动性和可靠性。     

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.     

一种新型的微网自适应过流保护方法

微网灵活的运行模式给保护带来了严峻的挑战,对此提出了一种新型的微网自适应过流保护方法。以微网三处典型的故障为案例,从并网和离网角度剖析了微网自适应保护应具备的功能。以此为基础,给出了微网自适应保护方案并阐述了集中式微网保护的主从工作机制;提出了三段式自适应保护的过电流整定算法,设计了故障识别流程;基于分析传统过电流保护时限配合在微网保护中存在的弊端,提出了微网自适应保护在并网和孤岛时的动作时限优化方案,结合案例分析了其优点。理论和案例分析表明,所提自适应保护方法能够快速可靠地识别故障区域,满足微网对保护的要求。     

An interior point method based protection coordination scheme for directional overcurrent relays in meshed networks

In this work, interior point method based protection coordination schemes are presented for coordinating directional overcurrent relays. Also, for minimizing the operating times of primary and backup relays simultaneously, a new objective function (NOF) is developed. The effectiveness of the proposed solution methods and the developed objective function has been investigated on two test systems (one small and one large). The suitability of the proposed method for coordination of directional overcurrent relays in meshed networks has been established by comparing its performance with that obtained by genetic algorithm, differential evolution and two hybrid algorithms for the developed objective function. Also, the superiority of the develop objective function has also been established by comparing the protection coordination results obtained by using NOF with those obtained by the other objective functions reported in the literature.     

一种改进的保护协调配合方法及其仿真研究

提出了一种用于继电保护协调配合计算的时间灵敏度优化配合方法,该方法以时间级差约束违背数、故障持续时间、灵敏度约束违背数和配合对动作时间差与时间级差之差的加权和作为保护系统协调配合的优化目标,并采用速度跟踪粒子群算法对其进行优化计算。以一个配电网反时限过流保护配合为算例进行了计算和分析,其结果表明TSOC方法可根据系统特点和整定需要方便、量化地对继电保护性能选择进行适当折衷,具有很好的实用性和有效性。     

Coordination of dual setting overcurrent relays in microgrid with optimally determined relay characteristics for dual operating modes

Fault current magnitude in a microgrid depends upon its mode of operation, namely, grid-connected mode or islanded mode. Depending on the type of fault in a given mode, separate protection schemes are generally employed. With the change in microgrid operating mode, the protection scheme needs to be modified which is uneconomical and time inefficient. In this paper, a novel optimal protection coordination scheme is proposed, one which enables a common optimal relay setting which is valid in both operating modes of the microgrid. In this context, a common optimal protection scheme is introduced for dual setting directional overcurrent relays (DOCRs) using a combination of various standard relay characteristics. Along with the two variables, i.e., time multiplier setting (TMS) and plug setting (PS) for conventional directional overcurrent relay, dual setting DOCRs are augmented with a third variable of relay characteristics identifier (RCI), which is responsible for selecting optimal relay characteristics from the standard relay characteristics according to the IEC-60255 standard. The relay coordination problem is formulated as a mixed-integer nonlinear programming (MINLP) problem, and the settings of relays are optimally determined using the genetic algorithm (GA) and the grey wolf optimization (GWO) algorithm. To validate the superiority of the proposed protection scheme, the distribution parts of the IEEE-14 and IEEE-30 bus benchmark systems are considered.     

Application of a proposed overcurrent relay in radial distribution networks

This paper contains the application criteria and coordination process for a proposed overcurrent relay in a radial power system with feed from one or multiple sources. This relay uses independent functions to detect faults and to calculate the operation time. Also this relay uses a time element function that allows it to reduce the time relay operation, enhancing the backup protection. Some of the proposed approaches improve the sensitivity of the relay. The selection of the best approach in the proposed relay is defined by the needs of the application. The proposed protection can be considered as an additional function protection to conventional overcurrent relays.     

基于微处理器的一种新型反时限过流保护算法

针对传统反时限过流保护算法中存在的与定时限保护配合及计算延时不准确等问题,提出了一种新型反时限特性曲线模型,然后将反时限特性曲线中的指数运算转换为微处理器能处理的运算,提出了一种利用Tailor展开和数据存储相结合的方法来拟合反时限特性曲线。该方法可以拟合任意的反时限特性曲线,且提高了时限的精度;仿真结果表明,该算法可以使反时限过流保护的动作时间误差小于0.4%,大大提高了时限精度,能够满足电力系统保护的要求。     

矿井高压电网的自适应过流保护研究

针对目前矿井高压电网过流保护经常误动或拒动的问题,提出一种基于自适应控制技术的定值整定方案。该方案通过对每条线路的电压、电流进行实时监视和分析,自动改变继电保护的整定值和特性以提高过流保护装置的灵敏性、可靠性,并通过常态闭锁、延时配合实现了保护的纵向选择性,为消除矿井高压电网长期存在的因短路故障而引起越级跳闸的安全隐患提供了技术支持。     

Overcurrent protection for distribution feeders with renewable generation

Distribution systems in Taiwan are typically radial type or normally open loop type. Distribution feeders have a simple protection system that usually employs overcurrent relays. When renewable generation (RG) is connected to the distribution feeder, the feeder changes from a single-source system to a complex multi-source system, which causes loss of the original coordination among feeder protection devices. The operation of RG units can cause protection failure. Fault current produced by RG units may reduce the current measured by the feeder relay. Therefore, this paper proposes connecting RGs to the feeder via four-way circuit switches with overcurrent relays, and dividing the feeder into several protection zones. Each protection zone is capable of isolating fault itself.The algorithm process and design procedure of overcurrent protection are also proposed for distribution feeders with RG. Results of this research provide a valuable reference for overcurrent protection that improved protection coordination and system reliability.     

基于系统电压分布曲线拟合的后备保护方案

拓扑结构的多样性和电源特性的复杂性使得基于稳态电流量的后备保护整定工作量大且失配现象时有发生,无需整定且具有自动配合功能的后备保护技术是继电保护工作人员追求的目标。在分析了传统反时限过流保护存在的问题和辐射状配电网正、负序电压故障分量分布特征的基础上,提出了基于系统电压分布曲线拟合的后备保护方案。所提方案利用综合电压序分量的系统分布与各级保护实现逐级配合的最小动作时间拟合具有反时限特性的动作曲线,得出拟合后的分段函数表达式。由其计算的保护动作时间可自动反映各保护与故障位置的拓扑关联关系,在满足选择性和快速性要求的前提下实现各级保护的自适应配合。DG接入不会改变综合电压序分量的分布特征,因而所提方法对含DG的网络具有自适应性。理论分析和仿真结果表明,所提方法可自动实现任一点故障时上下级保护的快速、逐级配合。