反时限电流保护整定计算相关问题研究

分析比较了不同平坦度特性的反时限电流保护特点并提出其适用范围.通过建立反时限特性方程,对反时限电流保护之间的配合进行了理论分析,依据保护范围内时间差关系,得出满足选择性的2个结论:在被配合线路出口故障时上下级保护动作时间有级差;上级保护的电流倍数小于下级被配合保护的电流倍数.该结论适合于任意开环、闭环网络.在该结论基础上对反时限保护提出了切实可行的整定方案.最后,对定时限与反时限电流保护配合以及反时限与定时限电流保护 选择性配合进行了分析.     

A new approach for optimal coordination of distance and directional over-current relays using multiple embedded crossover PSO

Proper coordination between distance relays and Directional Over-Current Relays (DOCRs) in power systems is one of the important conditions for the system security. The coordination problem in interconnected systems, because of complexity of the system, is complicated and a powerful optimization program must be used in order to do the best and optimal relay coordination.In this paper at first, a new problem formulation for optimal coordination of distance relays in presence of DOCRs, as the backup relays, is proposed. Then to deal with this complex problem, as another contribution, a new Multiple Embedded Crossover PSO (MECPSO) is proposed. In the presented MECPSO by updating velocity vector, diversity of the swarm is enhanced and exploration and global search capabilities of the PSO is improved as well. In the proposed approach, with considering the effect of in-feed or out-feed currents, the optimal second zone timing of distance relays and optimal settings of DOCRs are computed. The proposed method is tested on two case studies and encouraging optimal results are obtained.     

Optimal coordination of directional overcurrent relays ininterconnected power systems

The authors present a new methodology based upon the principles of optimization theory, to treat the problem of optimal coordination of directional overcurrent relays in interconnected power systems. With the application of the proposed technique, this coordination problem is stated as a parameter optimization problem, which in general, is of a large dimension, especially when many different system configurations and perturbations are to be considered. Several optimization procedures, including direct methods and decomposition techniques, for solving this large scale coordination problem are described, and results of optimally coordinating directional overcurrent relays in power systems with up to 30 buses are presented     

Dual-setting directional over-current relays: An optimal coordination in multiple source meshed distribution networks

To guarantee a safe operating scheme against the probable faults, an accurate and fast relaying scheme is of high priority. This challenge seems to be more sophisticated in multiple source meshed distribution networks hosting distributed generations (DGs). In this case, the current experiences bidirectional flows. More recently, dual-setting over-current relays are evolved as competent countermeasures for such cases. In this way, establishing an optimal coordination strategy is recognized as the first prerequisite in assuring a safe protection scheme. To this end, the present study aims at minimizing the overall operating time of primary and backup relays. Typically, the coordination problem is carried out by adjusting two parameters namely, pick up current (Ip) and time dial setting (TDS). In contradiction, the proposed approach follows a user-defined settings supported by some operating rules. Thus, besides the aforementioned settings, the coefficients of the inverse-time characteristics are also optimized. In other words, more flexibility is attained in adjusting relay’s characteristic in regard of the network’s loading and topological changes. Furthermore, inclusion of operating rules in main objectives, not only reduces the sum of operating time of all relays, but also increases the efficiency of backup relays regarding the break points in meshed networks. In other words, the covering zone by each backup relay is increased. The proposed approach demonstrates a non-linear programming fashion which is tackled based on genetic algorithm (GA). Several numerical studies are carried out to interrogate the validity of the proposed approach encountering different fault scenarios. The obtained results are encouraging.     

Optimal coordination of directional overcurrent relays consideringdefinite time backup relaying

A methodology is presented for the consideration of definite-time backup relays in the optimal coordination of directional overcurrent relays using linear programming. It is shown that the influence of considering second-zone distance relays and breaker failure relays impose important requirements for the determination of the time dial settings of directional overcurrent relays. The paper introduces a revised formulation of the optimization problem. Results are presented for the application of the methodology on a power system with 2 generators, 9 buses, 2 transformers and 7 transmission lines     

Optimal coordination of directional overcurrent relays consideringdynamic changes in the network topology

This paper presents a method to consider the dynamic changes in the network's topology for the coordination of directional overcurrent relays using linear programming. The proper coordination constraints are included by using linear approximations for the relay dynamics. The application of the methodology as well as the importance of considering the transient configuration changes are illustrated with a practical example and a test case consisting of a real industrial power system     

Optimal coordination of overcurrent relays using a modified particle swarm optimization

In this paper, a new problem formulation is proposed to calculate the optimal relay settings of directional overcurrent relays in power systems. The proposed coordination problem is formulated as a mixed integer nonlinear problem to take into account the discrete values for the pickup current settings. A modified particle swarm optimization (PSO) algorithm is proposed to calculate the optimal relay settings. A comparison between the original particle swarm optimization based method, the proposed PSO algorithm and the GAMS solver is presented.     

Computer aided coordination of directional relays: determination ofbreak points

The directional overcurrent and distance relays of a multiloop network must be set in a sequence to ensure coordination. The starting points of the sequence are called break points. An algorithm to determine the minimum number of break points is presented. It can be readily implemented on a computer and forms a basic component of a computer-aided-design package for a protective system     

Comprehensive coordination of combined directional overcurrent and distance relays considering miscoordination reduction

This paper presents a novel approach to solve the miscoordination problem of combined directional overcurrent and distance relays in transmission and subtransmission systems. In order to reduce relays miscoordinations, a general objective function is presented to find optimum directional overcurrent relays time setting multipliers, characteristics, and pickup currents by optimization algorithms. In previous researches, different approaches have been presented but they cannot find a reliable solution to avoid from having negative discrimination times between the backup and main relay (miscoordination), which means operation of the backup relay before the main relay. Using proposed approach, not only the number of miscoordinations can be greatly decreased but also the positive discrimination times can be minimized. The proposed method is tested on 9-bus and 39-bus test system. Genetic algorithm and human behavior-based optimization are used as optimization tools to find optimum settings. The results indicate that the proposed approach is capable of solving the miscoordination problem, in addition to minimization of discrimination and relay operation times compared with previous approaches.     

Optimal computation of distance relays second zone timing in amixed protection scheme with directional overcurrent relays

This paper describes a technique to determine the optimal time setting for the second zone of distance relays when used in a mixed protection scheme with directional overcurrent relays. The technique consists of including the second zone operation time as a new variable in the original problem statement of optimal computation of directional overcurrent relays settings. It is shown that the influence of distance relays and directional overcurrent relays must be considered when the settings of these relays are computed. Numerical results obtained with the proposed method for a realistic power system are presented     

A novel approach to increase FCL application in preservation of over-current relays coordination in presence of asynchronous DGs

Introducing Distributed Generation (DG) into Power Delivery Systems (PDSs) alters protection design of these networks. Commonly approach to overcome this problem is disconnecting DG units from PDS during fault. In case of asynchronous DG type, because of installing shunt capacitive compensators, using FCL for restoration of relay coordination is not useful in some cases. In this paper, a new approach for restoration of directional over-current relay coordination using three type of Fault Current Limiter (FCL) is presented. The proposed restoration approach is carried out without altering the original relay settings or disconnecting DGs from PDSs during fault. The process of selecting FCL impedance type (inductive or resistive) and its minimum value is illustrated. Two scenarios are discussed: no compensator and whit compensator. Various simulations are carried out for both single and multi-DG existence, different DG and fault locations. The application of this approach is implemented into an IEEE typical distributed network and the obtained results are reported and discussed.     

Presolve analysis and interior point solutions of the linear programming coordination problem of directional overcurrent relays

A linear programming interior point algorithm is proposed for the solution of the problem of coordinating directional overcurrent relays in interconnected power systems considering definite time backup relaying. The proposed algorithm is a variation of the primal–dual approach that uses multiple correctors of centrality. Pre-solution problem filtering simplification techniques are used prior to the application of the linear programming algorithm. Results are presented for the application of the methodology on a realistic test case, a 115–69 kV power system with 108 buses, 86 lines, 61 transformers, and 97 directional overcurrent relays. Optimal solutions are found in an automatic fashion, using the algorithm for the settings of the ground relays as well as for the phase relays. The application of the pre-solution problem simplification techniques is highly recommended, resulting in a significant reduction of the size and complexity of the linear programming problem to be solved. The interior point approach reaches a feasible point in the close vicinity of the final optimal result in only one or two iterations. This fact represents an advantage for on-line applications. The proposed methodology and in particular the use of the presolve problem simplification techniques is shown as a new valuable tool for the setting of directional overcurrent relays in interconnected power systems.     

A novel method for optimal coordination of directional overcurrent relays considering their available discrete settings and several operation characteristics

For optimal coordination of directional overcurrent relay we propose to consider operation characteristics, pickup current and time multiplier setting of relays as optimization parameters. Each parameter is optimized independently with the aid of linear formulation of the coordination problem. First, optimal discrete values of pickup current are selected. Second, adequate operation time characteristics of relays are selected. Third, optimal discrete values of time multiplier setting are determined. The proposed method is tested on two networks: an 8-bus system and the IEEE 30-bus system. Its performances are evaluated and compared with those of the linear and nonlinear programming techniques.     

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.     

Efficient coordination of ROCOF and frequency relays for distributed generation protection by using the application region

This paper proposes a method for determining the coordination of the rate of change of frequency (ROCOF) and under/overfrequency relays for distributed generation protection considering islanding detection and frequency-tripping requirements. The method is based on the concept of application region, which defines a region in the trigger time versus active power imbalance space where frequency-based relays can be adjusted to satisfy the anti-islanding and frequency-tripping requirements simultaneously. This method can be used to optimally determine the instantaneous and time-delay settings of different frequency-based relays in a unified manner. The application region can be also employed to evaluate how much an existing frequency-based protection scheme violates one of the above-mentioned requirements. In addition, it can be used to set different combinations of frequency-based relays in order to make the distributed generator frequency-based protection system as efficient as possible, since it respects the region that satisfies both requirements.     

Optimal location and sizing determination of Distributed Generation and DSTATCOM using Particle Swarm Optimization algorithm

A Particle Swarm Optimization algorithm for finding the optimal location and sizing of Distributed Generation and Distribution STATicCOMpensator (DSTATCOM) with the aim of reducing the total power loss along with voltage profile improvement of Radial Distribution System is proposed in this paper. The new-fangled formulation projected is inspired by the idea that the optimum placement of the DG and DSTATCOM can facilitate in minimization of the line loss and voltage dips in Radial Distribution Systems. A complete performance analysis is carried out on 12, 34 and 69 bus radial distribution test systems and each test system has five different cases. The results analyzed using Loss Sensitivity Factor shows the optimal placement and sizing of DG and DSTATCOM in Radial Distribution System effectively improves the voltage profile and reduces the total power losses of the system.     

基于源-荷协同的电网静态安全校正最优控制算法

为消除N-1事故情况下的线路过载和节点电压越限,提出了一种基于源-荷协同的电网静态安全校正最优控制算法。针对调整机组出力和切负荷两种静态安全校正措施,分析电网静态安全校正控制代价,在满足电网静态安全约束前提下,以系统整体控制代价最小为目标,建立电网静态安全校正控制模型。考虑可控负荷的离散特性,按切负荷代价由小到大的顺序形成切负荷控制策略表,并应用灵敏度指标从切负荷策略表中截取候选切负荷策略,分析各切负荷策略代价,协同静态安全校正控制模型,求解最小切负荷策略下发电机组出力的可行解。算例分析验证了离散的切负荷策略对应切负荷方案可行性强,避免负荷欠切和过切问题,源-荷协同静态安全校正控制能以最小控制代价有效消除N-1状态的节点过电压和线路过载。     

用遗传算法求解广义系统最优同时镇定问题

研究了用改进的遗传算法（简称GA）求解同时镇定一族线性定常广义系统的最优输出反馈控制律问题。在满足稳定性的条件,将最优同时镇定转化为一个受约束的非线性最小问题。引入了自适应机制和惩罚函数变换,对传统的GA进行改造。并用于受约束非线性问题的全局优化。计算结果和数值仿真说明GA是求解同时镇定问题的一种有效的数值方法。     

Optimal service restoration and reconfiguration of network using Genetic-Tabu algorithm

This paper represents an approach for service restoration and optimal reconfiguration of distribution network using Genetic algorithm (GA) and Tabu search (TS) method. Restoration and reconfiguration problems in distribution network are difficult to solve within feasible times, because the distribution network is so complicated with the combination of many tie-line switches and sectionalizing switches and also has to satisfy radial operation conditions and reliability indices. Therefore, this paper applied Genetic-Tabu algorithm (GTA) to find optimum value with reasonable computation time. The Genetic-Tabu algorithm is a Tabu search combined with Genetic algorithm to find a global solution. The case studies with 7-feeder model showed that not only the loss reduction but also the reliability should be considered at the same time to achieve the optimal service restoration and reconfiguration in the distribution network.     

Optimal design of symmetric fractional delay filter using firefly algorithm

A fractional delay filter is used to increase the accuracy, preciseness, time synchronization, and stability of signal processing system. However, designing a fractional delay filter for a specified delay, without affecting spectral characteristics of the signal is challenging because of nondifferentiability and multimodal nature of its objective function. In this paper, a more accurate design technique has been proposed for designing fractional delay filters, based on a recently developed firefly algorithm and its improved version. The designed filters offer variable fractional delay. A novel symmetric structure of implementation has been used to design filters. The efficacy of the proposed technique is evaluated by considering a filter design example. The performance of the proposed technique is compared with the other exiting algorithm. The comparative analysis of finite impulse response (FIR) fractional delay filter design proves that the proposed algorithm has a smaller design error and an implementation complexity than the other reported existing algorithms. In addition to this, the designed FIR fractional delay filter is implemented on Xilinx Virtex-7 for experimental validation.