Optimal Coordination Of Overcurrent Relays Research Articles

Optimal Coordination of Overcurrent and Distance Relays Using Cuckoo Optimization Algorithm

The duty of protective systems is the timely detection of fault and removing it from the power network. The accuracy of the results and reducing the execution time of the optimizing algorithm are two crucial elements in selecting optimizing algorithms in protective functions. The most important protective elements that are used in power networks are distance and overcurrent relays. In this article, a new algorithm is presented to solve the optimization problem of coordination of overcurrent and distance relays by using Cuckoo Optimization Algorithm which considers the non-linear model overcurrent relays at all stages of setting. The proposed method is tested on a standard 8-bus power system network. Also the results obtained have been compared with other evolutionary algorithms. The results show that the proposed approach can be provide more effective and practical solutions to minimize the time function of the relays and achieving optimal coordination in comparison with previous studies on optimal coordination of overcurrent and distance relays in power system networks.

Optimal Coordination of Overcurrent and Distance Relays Using Cuckoo Optimization Algorithm

The duty of protective systems is the timely detection of fault and removing it from the power network. The accuracy of the results and reducing the execution time of the optimizing algorithm are two crucial elements in selecting optimizing algorithms in protective functions. The most important protective elements that are used in power networks are distance and overcurrent relays. In this article, a new algorithm is presented to solve the optimization problem of coordination of overcurrent and distance relays by using Cuckoo Optimization Algorithm which considers the non-linear model overcurrent relays at all stages of setting. The proposed method is tested on a standard 8-bus power system network. Also the results obtained have been compared with other evolutionary algorithms. The results show that the proposed approach can be provide more effective and practical solutions to minimize the time function of the relays and achieving optimal coordination in comparison with previous studies on optimal coordination of overcurrent and distance relays in power system networks.

Optimal coordination of distance and directional overcurrent relays considering different network topologies

Most studies in relay coordination have focused solely on coordination of overcurrent relays while distance relays are used as the main protection of transmission lines. Since, simultaneous coordination of these two types of relays can provide a better protection, in this paper, a new approach is proposed for simultaneous coordination of distance and directional overcurrent relays (D&DOCRs). Also, pursued by most of the previously published studies, the settings of D&DOCRs are usually determined based on a main network topology which may result in mis-coordination of relays when changes occur in the network topology. In the proposed method, in order to have a robust coordination, network topology changes are taken into account in the coordination problem. In the new formulation, coordination constraints for different network topologies are added to those of the main topology. A complex nonlinear optimization problem is derived to find the desirable relay settings. Then, the problem is solved using hybridized Genetic Algorithm (GA) with Linear Programming (LP) method (HGA). The proposed method is evaluated using the IEEE 14-bus test system. According to the results, a feasible and robust solution is obtained for D&DOCRs coordination while all constraints, which are due to different network topologies, are satisfied.

Optimal Coordination of Directional Overcurrent Relays Using Biogeography-Based Optimization Algorithms

Optimal coordination of directional overcurrent relays (DOCRs) is a highly constrained and nonlinear optimization problem. The operating time of each relay depends on two independent variables called plug setting and time multiplier setting. As the network becomes larger and more complex, the number of relays will increase and, thus, finding the optimal solution becomes very hard. In this paper, a new population-based evolutionary algorithm called biogeography-based optimization (BBO) is proposed and the performance of ten types of constraint-handling techniques is evaluated. In addition, a new hybrid BBO with linear programming (BBO-LP) is proposed to enhance the performance of the conventional BBO algorithm. The performance of the proposed BBO-based algorithms is evaluated by using five test systems. The results show the effectiveness and superiority of the proposed algorithms compared with the performance of the other optimization methods presented in the literature.

Optimal Coordination of Directional Overcurrent Relays Using PSO-TVAC

This paper presents an efficient variant of particle swarm optimization (PSO) algorithm named Time Varying Acceleration Coefficients (PSO-TVAC) to solve the optimal coordination of directional overcurrent relays (DOCRs) in a practical power system, considering the optimum pickup current (Ip) as discrete parameter and time dial setting (TDS) as continuous parameter, in order to obtain minimum operating time for the relays, while satisfying various boundary constraints. Comparison results with the standard global optimization methods such as GA using Matlab toolbox, PSO and to other techniques showed the efficiency of the proposed variant and confirmed its potential to enhance the solution of optimal coordination of directional overcurrent replays.

Fault detection and optimal coordination of overcurrent relay in offshore wind farm connected to onshore grid with VSC-HVDC

Summary A reliable protection system is needed for transmitting large amount of power over long distances. An alternating current–direct current mix network in offshore wind farm (OWF) interconnection with onshore grid offers a major challenge for faulty section identification. The transient faults in OWF system are simulated in MATLAB 7.10.0(R2010a). The fault signals, voltage and current, are retrieved at common collector platform and at voltage-source converter–high-voltage direct current sides of network in the OWF system. The detection capability of signal-processing techniques, Stockwell transform, empirical mode decomposition, and Hilbert transform, is explored for localization of different types of faults. In addition, fault events at onshore grid and those developed at the time of change in operating parameters are also simulated and analyzed. Further, the quantitative analysis for detection of fault events with the computation of maximum and mean indices and instantaneous time indices of the fault signal is presented in the study. Coordination of overcurrent relays is another challenging task in OWF interconnection with onshore grid system. The objective function of relay coordination problem is to minimize the operation time of associated relays. Time multiplier setting is used as the test variable in the objective function. An optimal coordination of overcurrent relays by using genetic algorithm, particle swarm optimization, and gravitational search algorithm is discussed in this paper. Further, these techniques are compared with hybrid meta-heuristic optimization method, a combination of particle swarm optimization and gravitational search algorithm to achieve relay coordination more efficiently. Copyright © 2015 John Wiley & Sons, Ltd.

Optimal Coordination of Directional Overcurrent Relays Using PSO-TVAC Considering Series Compensation

The integration of system compensation such as Series Compensator (SC) into the transmission line makes the coordination of directional overcurrent in a practical power system important and complex. This article presents an efficient variant of Particle Swarm Optimization (PSO) algorithm based on Time-Varying Acceleration Coefficients (PSO-TVAC) for optimal coordination of directional overcurrent relays (DOCRs) considering the integration of series compensation. Simulation results are compared to other methods to confirm the efficiency of the proposed variant PSO in solving the optimal coordination of directional overcurrent relay in the presence of series compensation.

Considering Pilot Protection in the Optimal Coordination of Distance and Directional Overcurrent Relays

The aim of the relay coordination is that protection systems detect and isolate the faulted part as fast and selective as possible. On the other hand, in order to reduce the fault clearing time, distance protection relays are usually equipped with pilot protection schemes. Such schemes can be considered in the Distance and Directional Over-Current Relays (D&DOCRs) coordination to achieve faster protection systems, while the selectivity is maintained. Therefore, in this paper, a new formulation is presented for the relay coordination problem considering pilot protection. In the proposed formulation, the selectivity constraints for the primary distance and backup overcurrent relays are defined based on the fault at the end of the transmission lines, rather than those at the end of the first zone of the primary distance relay. To solve this nonlinear optimization problem, a combination of Genetic Algorithm (GA) and Linear Programming (LP) is used as a Hybrid Genetic Algorithm (HGA). The proposed approach is tested on an 8-bus, the IEEE 14-bus and the IEEE 39-bus test systems. Simulation results indicate that considering the pilot protection in the D&DOCRS coordination, not only obtains feasible and effective solutions for the relay settings, but also reduces the overall operating time of the protection system.

Optimal co-ordination of overcurrent relays in the interconnected power systems using break points

Interconnected power systems are multi-loop structured. In such networks, the determination of settings for all overcurrent relays can be carried out in different forms and may be quite complicated.Optimal coordination of overcurrent relays is a solution to find optimal time setting of the relays in interconnected networks. However, the optimal coordination method without using correct and efficient starting points i.e. the location of initial relays in the procedure for settings may cause many miscoordinations or the solution may not converge.In this paper an innovative approach is proposed in which both optimal coordination and break points for initial relays to find the settings of overcurrent relays are utilized. The fault location is in front of main relay and network configuration is so that maximum current flows through backup relay. Therefore, network configuration is taken into consideration and the suggested approach reflects configuration changes. A comparison between optimal coordination of overcurrent relays with or without break points and the conventional procedure of overcurrent relays coordination is presented.The results show the advantages of the proposed method.

Optimal Coordination of Directional Overcurrent Relays Using a New Time–Current–Voltage Characteristic

With the integration of distributed generation (DG) to meshed distribution systems, the operating time of the protective system becomes a major concern in order to avoid nuisance DG tripping. This paper proposes a new time–current–voltage tripping characteristic for directional overcurrent relays (DOCRs) that can achieve a higher possible reduction of overall relays operating time in meshed distribution networks. The proposed tripping characteristic is described in detail. Moreover, the protection coordination problem is formulated as a constrained nonlinear programming problem to determine the optimal relay settings. The proposed characteristic is tested on the power distribution system of the IEEE 14 bus and IEEE 30 bus with inverter-based and synchronous-based DG units. The outcome of this study reveals that the new tripping characteristic for DOCRs achieves notable reduction in total relays' operating time over the conventional characteristic.

Optimal directional digital overcurrent relays coordination and arc-flash hazard assessments in meshed networks

Summary The article addresses the arc-flash hazard assessments combining the optimal coordination of digital overcurrent relays. A novel objective function is adopted to concurrently reduce the arc-flash hazards while adapting the optimal settings of directional overcurrent relays subjects to set of coordination constraints. The flower pollination algorithm (FPA) is applied to attain the target. The proposed FPA-based technique is employed to define three main parameters for the relay settings. The performance and value of the proposed FPA-based methodology are demonstrated on the 8-bus and 15-bus meshed networks with various fault scenarios. Comparisons with the other competitive algorithms and subsequent discussions validate its good performance. Efficacious attributes of the novel objective function are compared and highlighted over the traditional objective function commonly used by the other researchers reported in the literature. Copyright © 2015 John Wiley & Sons, Ltd.

Optimal coordination of directional overcurrent relays using NSGA-II

This paper presents a new method for coordination of directional overcurrent relays to reduce the discrimination time of the primary and backup relays, by using nondominated sorting genetic algorithm-II (NSGA-II). In order to achieve a reliable protective system, it is necessary to find a solution to avoid having large discrimination times, in addition to coordination time interval (CTI). The novelty of the paper is to reduce the discrimination time of the primary and backup relays and simultaneously reduce the operating time of primary and backup relays, by introducing a new method. In contrast to the conventional intelligent methods, the proposed method does not require weighting factors for conversion of multi-objective function into an equivalent single objective function. The effects of both near and far-end faults are considered to solve the proposed problem formulation. Also, various overcurrent relays characteristics are considered within the program to select the best of them for each relay by optimization algorithm. The proposed method is implemented in three different test cases, i.e. three, eight and IEEE 30-bus network. The results are compared with previously proposed methods.

Optimal coordination of directional overcurrent relays in distribution systems based on network splitting

SUMMARY In real case of distribution systems with several directional overcurrent relays, the designer is facing an optimization problem with an extensive search space of discrete values. Finding the optimal solution to such a problem is a time-consuming task with big chance of nonconvexity. In this paper, the optimal coordination of directional overcurrent relays in distribution systems is modeled by attempting the practical issues, that is, full discrete variables for time-current curve, time multiplier setting, and plug setting. To reduce the calculation time, the problem is solved by using a novel method based on network splitting. The problem is solved in two stages: the first one finds the optimal solution for the subnetworks individually and the second one determines the optimal setting for the relays on the tie lines connecting the subnetworks. It is shown that the proposed method improves the relays' operating times and also reduces the chance of nonconvexity of the problem. By applying the proposed method to the 30-bus Institute of Electrical and Electronics Engineers test system, the results are compared with the conventional algorithms. It is found how the practical issues related to the relay characteristics selection can affect the overall relays' time. Also, the computation time is considerably reduced with network splitting method presented in this paper. Copyright © 2014 John Wiley & Sons, Ltd.

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.

Application of Evolutionary Algorithm for Optimal Directional Overcurrent Relay Coordination

In this paper, two Evolutionary Algorithms (EAs) i.e., an improved Genetic Algorithms (GAs) and Population Based Incremental Learning (PBIL) algorithm are applied for optimal coordination of directional overcurrent relays in an interconnected power system network. The problem of coordinating directional overcurrent relays is formulated as an optimization problem that is solved via the improved GAs and PBIL. The simulation results obtained using the improved GAs are compared with those obtained using PBIL. The results show that the improved GA proposed in this paper performs better than PBIL.

A new formulation for coordination of directional overcurrent relays in interconnected networks

In large and interconnected networks, the coordination between all protective devices, without any violation, is very complicated and sometimes impossible. For obtaining reasonable and optimal coordination with suitable operating time (OT) for relays, some constraints are obliged to violation. In order to reduce the related violation and also the relays OTs, some objective functions (OFs) are proposed in literatures in which the discrimination times of the primary and backup relays is added to the OF. In this paper, for obtaining the optimal coordination of directional overcurrent relays, the OF is improved to overcome the drawbacks of the existing OF. In other words, as the main contribution, a new problem formulation is proposed so that not only the optimal settings of relays are obtained but also the OTs of the primary and specially backup relays are reduced considerably. In order to solve the proposed problem formulation, the effects of both near and far-end faults are considered. Also, regarding the protection system flexibility, the program is capable of choosing the best characteristic for each overcurrent relay. The genetic algorithm is used as an optimization tool, and the effectiveness of the proposed method is demonstrated by comparing the coordination results for the two sample networks with those obtained by using the recent developed OFs. Copyright © 2013 John Wiley & Sons, Ltd.

An analytic approach for optimal coordination of overcurrent relays

This study presents a new analytic approach to optimal coordination of directional overcurrent relays. This approach is based on the selection of optimum pickup current and time dial setting, in order to obtain minimum operating time for the relays, while satisfying various coordination and boundary constraints. Based on the new optimal relay setting procedure, an iterative numerical solution is proposed. The proposed numerical algorithm converges to the global optimum values, which are independent of initial values and the order of relay setting. The proposed method is applied to three different test systems. The new method is compared with some previously proposed analytic and evolutionary approaches. The results demonstrate the advantages of the proposed method over the previous works.

Optimal coordination of directional over-current relays using informative differential evolution algorithm

Growing interconnection in distribution system creates new problem for protection engineers. Particularly the design of overcurrent relay coordination in such system is an independent area of research. With the availability of new artificial based optimization algorithm relay coordination research gain a new momentum. Well established artificial based optimization algorithm such as genetic and particle swam optimization are successfully applied for such applications. This paper discusses the application of informative differential evolution algorithm with self adaptive re-clustering technique for selection of TDS and PSM for optimal coordination of directional overcurrent relays. Both continuous as well as discrete version of informative differential evolution algorithm are used for optimization of relay setting. Proper combination of backup relays for each primary relay are identified by using LINKNET graph theory approach. Coordination of directional overcurrent is developed for 9 bus and IEEE 30 bus distribution systems. The aim of problem is to minimize the total operating time of primary relays and eliminate the miscoordination among the primary and backup relay pairs. Discrete types of settings for electromechanical types of relay are also discussed in this paper. Moreover, the relay coordination problem is modified for providing optimal coordination time interval between 0.2 and 0.8s among all primary and backup relays pairs. The results are compared with hybrid of genetic algorithm – nonlinear programming and sequential quadratic programming. Digsilient power factory software is used for verification of result.

Optimal coordination of directional over-current relays using Teaching Learning-Based Optimization (TLBO) algorithm

Relay Coordination in a big distribution system with multiple meshes and bidirectional power feed becomes very Complex for protection engineers. Manual and graph theory based approaches were applied successfully in small power system. In a big distribution system linear and non-linear programming based optimizing techniques are applied for relay coordination. Presently, artificial intelligence techniques are applied for optimal co-ordination of directional overcurrent relays. This paper discusses the application of Teaching Learning Based Optimization (TLBO) algorithm for optimal coordination of DOCR relays in a looped power system. Combination of primary and backup relay is chosen by using Far vector of LINKNET structure, to avoid mis-coordination of relays. Coordination of DOCR is tested for IEEE 3, 4 and 6 bus systems using the TLBO. Also, the objective function is modified to optimize the operating time between backup and primary relays. The results are compared with the optimized values of Time dial setting and Plug setting values obtained from modified differential evolution algorithm. The proposed algorithm TLBO gives optimal coordination margin between 0.3 and 0.8s and no miscoordination between primary and backup pairs. Results are also verified using Digsilient power factory simulation software.

Implementation of Full Adaptive Technique to Optimal Coordination of Overcurrent Relays

This paper proposes a full adaptive technique for setting all overcurrent (OC) relays in HV substations. This technique can be used online and there is no need to employ a telecommunication infrastructure. It is based on an appropriate equivalent circuit of the power grid in the substation, online estimation of the equivalent circuit parameters, and application of the equivalent circuit to estimate the required short-circuit currents. This full adaptive technique is used in setting the OC relays of a typical 230/20-kV substation connected to a sample 9-bus grid. Significant advantages of the proposed technique over the usual setting method are shown by comparing the corresponding results. Furthermore, the technique is improved to resolve problems due to penetration of distributed generation. Developing this adaptive setting technique is a step toward introducing self-adjustment OC relays.