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.     

Data-mining model based adaptive protection scheme to enhance distance relay performance during power swing

The paper presents a data-mining model based adaptive protection scheme enhancing distance relay performance during power swing for both compensated and uncompensated power transmission networks. In the power transmission network, the distance relays are sensitive to certain system event such as power swings, which drive the apparent impedance trajectories into the protection zones of the distance relay (zone-3) causing mal-operation of the distance relay, leading to subsequent blackouts. Further, three-phase balanced symmetrical fault detection during power swing is one of the serious concerns for the distance relay operation. This paper proposed a new adaptive protection scheme method based on data-mining models such as DT (decision tree) and RF (random forests) for providing supervisory control to the operation of the conventional distance relays. The proposed scheme is able to distinguish power swings and faults during power swing including fault zone identification for series compensated power transmission network during stress condition like power swing. The proposed scheme has been validated on a 39-bus New England system which is developed on Dig-Silent power factory commercial software (PF4C) platform and the performance indicate that the proposed scheme can reliably enhance the distance relay operation during power swing.     

A new approach for mitigating blackout risk by blocking minimum critical distance relays

Electric power systems are complex and commonly run near their operational limits. Power systems are basically designed based on the (N − 1) criterion. In these systems, total or partial blackouts are unavoidable. Cascading failures following an initial event is recognized as the main mechanism for power system blackouts. Undesirable activation of zone 3 of distance relays due to their local function has been identified as one of the major causes for propagation of cascading failures. In this paper, in order to mitigate the risk of power system blackouts, a novel approach is proposed for recognizing the critical line outages with the highest contribution in cascading failure and preventing their undesirable outage by blocking zone 3 of their distance relay. In this paper, based on the statistical activation of distance relays, a deterministic–probabilistic approach is developed for identifying the critical lines with the highest contribution in blackouts due to activation of zone 3 of their distance relays. In order to avoid interference of relay blocking with the main protection duty of distance relays, the proposed approach recognizes the minimum critical lines with the highest contribution in cascading failure for blocking zone 3 of their distance relays. The proposed approach is demonstrated on the New England 39-bus system and detailed simulation studies carried out to examine the validity and effectiveness of the proposed approach.     

Computer-aided protective relay setting system for large power networks

This paper introduces a protective relay setting system capable of handling a large network up to 10,000 buses. The remarkable features are such useful functions as network analysis (fault analysis, load flow calculation, zero-sequence current calculation, etc.), relay operation simulation, and automated setting coordination tasks. Fault currents in the maximum and the minimum operation networks are calculated to examine the setting values. The protection zones are searched automatically along the network connection. Protection coordination tasks among the primary and the backup relays composed of different types of relays can be performed by the relay operation simulation. The system is built on an engineering workstation, which works in cooperation with other network operation support systems. Its graphical user interface helps every engineer to examine the relay setting using a variety of databases.     

An accurate technique for locating faults by distance relays

This paper presents a new protection scheme for improving the performance of the distance protective relays in transmission systems. The determination of fault zone by the proposed scheme is based on data sheared locally with other distance relays at the same station, in addition to a command from the distance relay on the other end of the protected line. Based on analyzing this information the relay decides the correct fault zone. With the proposed scheme, the first zone in the distance relay covers the full length of the protected line while the second zone covers the full length of any line following the protected line irrespective of its length, etc. The scheme is examined against wide range of setting problems of a real part of a HV network with real relay settings. It succeeds in solving distance relay setting problems, e.g. the problem of a long line following a short line or vice versa, low in-feed, open CB at one end and high impedance faults.     

自适应碗形阻抗继电器

在详细分析了圆形和四边形阻抗继电器的基础上，提出了自适应碗形阻抗继电器新原理。它通过扩大常规姆欧继电器的动作区，极大地提高了允许过渡电阻的能力，具有动作判据简捷、速度快、技术成熟、整定方便、选相能力强、方向明确、测距精确、躲负荷阻抗能力强、便于实现自适应等突出优点，仿真计算和整机试验验证了理论分析的正确性，并已在最新研制的微机距离保护中得到应用。     

Adaptive BOWL impedance relay

An adaptive BOWL impedance relay is proposed in this paper. Compared with the circular and quadrilateral impedance relays, it has the advantages of larger coverage of fault resistance, simple criterion, fast operation, mature technique, easy setting, good phase selection, distinct directionality, accurate distance measurment, high security in heavy load and easy to realize adaption. Simulating calculation and practical tests have verified the analyses. The BOWL relay has been applied in microprocessor-based distance protection developed by our institute     

地区电网继电保护整定计算智能系统的研究

提出了一种与数据库相结合的继电保护整定计算智能系统。该系统由拓扑分析、短路计算、断点搜索、整定计算四部分组成,有效地简化了继电保护整定人员的工作量,解决了保护定值相互配合的复杂问题,并开发出基于VisualBasic6.0与Ms-access相结合的继电保护整定计算软件,建立了网络参数库、继电保护参数库以及定值管理系统。该系统具有整体功能强、操作简单灵活等特点。     

An investigation into the use of adaptive setting techniques forimproved distance back-up protection

Changes in power system operating conditions adversely affect the reach point accuracy of distance relays. This paper discusses adaptation of the settings of distance relays within an integrated digital hierarchical protection system for the optimisation of relay performance. Specific reference is made to adaptation of the zone 3 setting to ensure optimal relay performance over a wide variety of operating conditions. Results illustrating the performance of adaptive methods compared to conventional fixed setting are presented for an application study of the North Wales 400 kV transmission network, UK     

基于广域网和多智能体的自适应协调保护系统的研究

介绍了一个基于广域网和多智能体的自适应协调保护系统(MAWBACPS)。系统利用IP广域网实现电网广域信息的实时交换;利用多Agent系统在解决分布式在线问题的合作求解能力,实现保护之间动作的协调。提出了尽力自适应的协调保护新思想以及线路电流后备保护的网络化自适应整定的新方法。论文还介绍了MAWBACPS的结构、通信机制、协调控制策略以及相关的智能体设计。基于上述思想和方法研制了仿真系统,仿真试验结果表明:自适应定值计算所需的时间可以被控制在允许的范围内,从而在一般情况下均可实现电网后备保护的自适应协调动作。     

基于改进遗传算法的继电保护定值优化的研究

如何获得一套满足用户期望的、保证整体性能最优的保护定值是当今继电保护整定计算中的研究热点之一。针对不同线路的定时限保护对于配合关系的重要性程度不同,以及保护延时段对于不同约束条件的侧重不同,提出了基于改进遗传算法的继电保护定值优化的算法。利用基于自适应的小生境遗传算法,采用约束区间配合点编码的方法对全电网相间距离保护的II段整定计算的优化进行了初步探索,并结合算例进行了算法的验证。     

A digital distance relay using negative sequence current

The configuration and performance of a recently developed digital distance relay using negative sequence current for remote backup protection are described. Since relays for remote backup protection are designed for remote faults, the fault current that is input to the relay is small due to the influence of current distribution factors. This in turn makes the relay sensitive to the effects of load current. In order to resolve this problem, a distance relay using negative-sequence current has been developed and put into use. The characteristics of this relay are: (1) the effects of load current are reduced, so the relay rarely maloperated due to load current during a fault; and (2) the hardware configuration of a digital relay that performs calculation on a negative component is simple and thus relatively error-free     

A New Strategy for Determining Fault Zones in Distance Relays

A new strategy (denoted P-SS) for estimating the correct fault zone in distance relays is introduced. The main difference between the P-SS and conventional setting strategies is that the P-SS does not depend on fixed boundaries for backup zones. It depends on exchanging information between local relays in the same station in addition to a command from the remote end relay. With the proposed strategy, zone-1 covers the entire length of the protected line, zone-2 covers the entire length of any next line irrespective of its length, and zone-3 covers the entire length of any line next to zone-2. The governing rules for the proposed strategy are presented. The strategy is examined against a wide range of setting problems of a real part of a high-voltage network with real relay settings. The results confirm that the P-SS achieves the required accurate, sensitive, and selective relay operation.     

Time coordination method for power system protection byevolutionary algorithm

A typical industrial power network may consist of hundreds of pieces of equipment and even more protection relays to protect the system are required. Each protection relay in the power network needs to be coordinated with the relays protecting the adjacent equipment. The overall protection coordination is, thus, very complicated. A new concept of protection coordination by time is introduced in this paper to formulate all the system relays and system equipment operation into a set of optimization equations and constraints. Its purpose is to search for an optimal protection setting to minimize the system disturbance time as well as the time of interruption of the power supply. An evolutionary algorithm is applied as a constraint satisfaction optimization tool to search for the optimal relay setting. This method can find the best protection relay coordination, which cannot be achieved by traditional methods. This is the most significant achievement of the paper     

A novel algorithm to determine minimum break point set for optimum cooperation of directional protection relays in multiloop networks

Determining minimum break point set (MBPS) is necessary before setting distance protection relays or zero-sequence protection relays in multiloop extremely high voltage power networks. Determining directional simple loops (DSLs) and relative sequence groups (RSGs) is the prerequisite of traditional algorithms which are used to determine MBPS. In order to reduce the CPU time and complexity of calculating MBPS, a new concept named as protection relay dependency dimension (PRDD) is presented for the first time in this paper. By comparison of PRDD in a multiloop network, the MBPS can be determined, and the process of comparisons will not stop until the MBPS of the multiloop networks is discovered. In the meantime, the RSG could be easily determined by means of judging whether the primary protection relay set of a protection relay is null or not. The new algorithm leaves out those laborious steps, such as determining all of the DSLs and RSGs. Some examples are given to illuminate the novel algorithm presented in the paper to be simple and effective.     

Agent-based self-healing protection system

This paper proposes an agent-based paradigm for self-healing protection systems. Numerical relays implemented with intelligent electronic devices are designed as a relay agent to perform a protective relaying function in cooperation with other relay agents. A graph-theory-based expert system, which can be integrated with supervisory control and a data acquisition system, has been developed to divide the power grid into primary and backup protection zones online and all relay agents are assigned to specific zones according to system topological configuration. In order to facilitate a more robust, less vulnerable protection system, predictive and corrective self-healing strategies are implemented as guideline regulations of the relay agent, and the relay agents within the same protection zone communicate and cooperate to detect, locate, and trip fault precisely with primary and backup protection. Performance of the proposed protection system has been simulated with cascading fault, failures in communication and protection units, and compared with a coordinated directional overcurrent protection system.     

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.     

江西电网220kV系统后备保护简化配置和整定计算

继电保护的配置、选型与整定,应遵循"强化主保护、简化后备保护"的原则。江西电网220kV系统主保护配置的加强为简化后备保护的配置和整定计算提供了物质基础;江西电网的快速发展也要求对后备保护的整定计算进行简化。本文提出了江西电网220 kV系统简化配置和整定方案,方案在保证电网安全稳定运行的前提下提高了整定计算工作效率,文中还对简化后电网的安全稳定运行提出了建议。     

A new PMU based power swing detector to prevent mal-operation of distance relay

In conventional transmission line protection, a distance relay is used to provide the primary as well as remote backup protection. The voltage and current phasors measurement needed by the distance relay for determining the impedance may be affected by the power disturbances such as power swing. Consequently, this power swing may cause mal-operation of Zone three distance relays which in turn may affect on the reliability of the whole protective scheme. To mitigate these effects and hence improve the relay reliability, this work proposes a new real-time power swing detector using phasor measurement units for blinding the distance relay only during this transient disturbance. However, this developed detector will not block relay when the power swing accompanied with faults. To validate the present work, the performance of developed enhanced distance relay is tested by signals generated by Simulink/MATLAB simulator under different conditions. The test results show that this proposed scheme provides good discrimination between the transient currents and the fault current which in turn it may contribute in enhancing the reliability of Distance relay.     

Active power based distance protection scheme in the presence of series compensators

Flexible ac transmission system (FACTS) controllers, especially the series-FACTS controllers, affect the operation of distance relays and can lead to the relays under/over-reaching. This paper aims to demonstrate the effects of static synchronous series compensator (SSSC) and series capacitive compensation (SCC), as two important series compensators, on the distance protection using theoretical and computational methods. The results of the investigation are used to develop a feasible and adequate method for eliminating the negative effects of these devices on the distance relays. The developed method measures the voltages at terminals of the SSSC and SCC by phasor measurement units (PMUs) which are then transmitted to the relay location by communication channels. The transmitted signals are used to modify the voltage measured by the relay. Different operation types and conditions of SSSC and SCC, and different faults such as phase-to-phase and phase-to-ground faults are investigated in simulations. Since the modeled distance relay can measure the fault resistance, trip boundaries are used to show the performance of the presented method. Results show that the presented method properly eliminates the negative effects on the distance relays and prevents them from mal-operation under all fault resistance conditions.