Directional Overcurrent Relays Research Articles

Hybridization of PSO for the Optimal Coordination of Directional Overcurrent Protection Relays

In the electrical power system, the coordination of directional overcurrent protection relays (DOPR) plays a preeminent role in protecting the electrical power system with the help of primary and back up protection to keep the system vigorous and to avoid unnecessary interruption. The coordination between these relays should be pursued at optimal value to minimize the total operating time of all main relays. The coordination of directional overcurrent relay is a highly constrained optimization problem. The DOPR problem has been solved by using a hybridized version of particle swarm optimization (HPSO). The hybridization is achieved by introducing simulated annealing (SA) in original PSO to avoid being trapped in local optima and successfully searching for a global optimum solution. The HPSO has been successfully applied to five case studies. Furthermore, the obtained results outperform the other traditional and state of the art techniques in terms of minimizing the total operating of DOPR and convergence characteristics, and require less computational time to achieve the global optimum solution.

Optimal Protection Coordination of Active Distribution Networks With Synchronverters

Synchronverters are inverters imitating synchronous generators (SGs) to curb adverse impacts of traditional inverters on power networks. However, synchronverters may generate unlimited currents during faults. In addition, limiting the synchronverter’s fault currents by hard limiters could malfunction directional overcurrent relays (DOCRs). Thus, this paper employs virtual-impedance fault current limiters (VI-FCLs) that preserve the synchronverter’s voltage source model to guarantee a reliable operation of DOCRs. Also, an optimal protection coordination (OPC) scheme is developed to size the VI-FCLs and determine the DOCRs’ settings in a decoupled manner. The proposed protection scheme determines the highest values of the VI-FCLs that correspond to bolted faults at the synchronverters’ terminals. These conservative values are then relaxed by adaptively varying the VI-FCL based on the fault severity to enhance the DOCR sensitivity. Further, a short circuit calculation algorithm is formulated to incorporate the developed synchronverter with VI-FCL into an OPC program to determine the optimal settings of DOCRs that minimize the total operating time of all primary and backup relays. Case studies ensure the proposed protection scheme’s effectiveness in reliably protecting a radial 9-bus Canadian distribution system and a meshed 14-bus system powered by synchronverters.

Optimal Coordination of Protection Devices in Distribution Networks With Distributed Energy Resources and Microgrids

Microgrids are promising to enhance power distribution systems’ efficiency, quality, sustainability, and reliability. However, microgrids operation can impose several challenges to traditional protection schemes, like changes in the power flow direction and an increase in short-circuit currents. Microgrids can include several distributed generation technologies with different behaviours during short-circuit conditions, requiring additional protection schemes and devices. In this way, the optimized coordination of reclosers and fuses in distribution networks with directional overcurrent relays, which operate as interconnection devices, might overcome many imposed protection challenges. Regarding to different generation technologies, voltage-restrained overcurrent relays and frequency relays are presented as local microgrid protection for rotative and inverter-based distributed generators, respectively. The optimized coordination of these protection devices maximizes microgrid benefits and minimizes operation drawbacks by reducing interruptions impacts and energy not supplied to consumers. This work proposes, thus, a mathematical model for the optimal coordination of protection devices in distribution networks with distributed energy resources operating in grid-connected and islanded modes. The minimization technique of operating times using an elitist genetic algorithm with variable crossover and mutation processes is proposed, as well. The results show adequate coordination using passive and low-cost protection devices.

An Adaptive Overcurrent Coordination Scheme Withstanding Active Network Operations

This paper aims to present a centralized adaptive protection scheme (APS) for the directional overcurrent relays (DOCRs) considering system dynamics such as load demand variations, topology changes and DGs to mitigate the above-mentioned effects. The scheme is suitable for different types of networks whether its radial or meshed. Afterall, it can determine the actual topology with the micro-PMUs and breaker status, automatically generate relay names accordingly with the topology bus locations, establish protection coordination pairs, coordinate DOCRs for parallel lines, identify transformers to offer backup operation for differential protection, perform load flow and fault studies, execute contingency and sensitivity analysis, and lastly, coordinate the DOCRs using differential evolution algorithm so that they always have the proper settings to operate in appropriate time providing selectivity. The performance of the proposed centralized adaptive overcurrent protection scheme is tested on the highly meshed IEEE 14 bus system. The proposed scheme has shown that it can adequately consider impacts of system dynamics and DG.

Optimal Protection Coordination of Directional Overcurrent Relays in Microgrids considering Grid-Connected and Islanded Modes based on User defined Characteristics and Fault Current Limiters

Optimal Protection Coordination of Directional Overcurrent Relays in Microgrids considering Grid-Connected and Islanded Modes based on User defined Characteristics and Fault Current Limiters

Optimal restoration of directional overcurrent protection coordination for meshed distribution system integrated with DGs based on FCLs and adaptive relays

Integrating DGs in Distribution Networks (DNs) leads to miscoordination problems in Directional Overcurrent Relays (DOCRs). Optimization techniques and Fault Current Limiters (FCLs) are methods applied for restoring the coordination between protective relays. This paper proposes a new approach to solve the miscoordination problem between the DOCRs caused by the DGs into a looped DN. The Whale Optimization Algorithm (WOA) is used to obtain the optimum values of the pickup currents (Ip), and Time Dial Setting (TDS) of the DOCRs. The approach is applied to overcome the DOCRs miscoordination problem in the case of connecting FCL in series with the DG integrated with DN. The approach computes the minimum impedance value of FCL needed to be installed in series with the DGs to restore the DOCRs coordination. In the case of DN implies adaptive relays, the approach is modified to achieve the optimum combination between the FCL impedance values and the number and locations of adaptive relays to restore the coordination of the DOCRs at a minimum cost. The proposed and modified approaches are tested on 9-bus looped DN connected to DGs at different buses to prove their applicability. Moreover, several simulations are implemented to test the proposed methods for different fault locations.

An Effective Coordination Setting for Directional Overcurrent Relays Using Modified Harris Hawk Optimization

The relay optimization expresses quite a challenge for smooth and optimal operation of power system networks. The relay optimization is formulated as a mixed integer non-linear problem and is highly constrained. Furthermore, a reliable relaying system must be able to detect and isolate the faulted portion in a timely manner. Therefore, it is necessary to find optimal parameters for relay settings to be able to respond in a timely way to the encountered fault and at the same time keep in consideration the operational and coordination constraints. This paper proposes modified Harris hawk optimization (MHHO), which is based on the intelligent preying tactics of Harris hawks and the improvement of intended modifications, crowding distance and roulette wheel selection. The proposed algorithm has been tested on IEEE 8 and 15-bus systems, using MATLAB programming. The test systems are the distribution networks covering the medium level voltage for consideration. The simulation results verified the success of MHHO to find optimal settings for the relays. For IEEE 8-bus system, MHHO was able to give 35.45% improvement in the results in comparison to other algorithms. Furthermore, for the IEEE 15-bus system, MHHO showed 24.09% improvement on average. The comparison of the results obtained by MHHO with the other state-of-the-art algorithms proved that it is the strong candidate for optimization of the relay coordination problem.

A distributed adaptive protection scheme based on multi‐agent system for distribution networks in the presence of distributed generations

Distribution networks are operated in different conditions and the traditional protection systems might not be proper for all available operation conditions by using directional overcurrent relaying. Besides, the presence of distributed generations makes the protection setting and coordination more complex, and may even make it impossible to access a reliable protection system. Therefore, a fully distributed adaptive protection scheme based on the multi-agent systems is proposed to improve the reliability, selectivity and sensitivity of relays. It uses only numerical directional overcurrent relays with instantaneous characteristics as agents, so that only need to pick-up settings and react quickly. All agents dynamically update their pickup value to increase the fault detection sensitivity, and make reliable and selective on-board decisions for fault location and isolation. In addition, in order to achieve high sensitivity and mitigate miscoordination, using setting groups of relays, a novel adaptive backup protection scheme, which does not need complex computational coordination, is proposed. The proposed system is performed in the distributed manner to enhance efficiency and robustness against cyber-attacks and one-point failures. The proposed system is tested on the meshed IEEE 14-bus system and radial IEEE 13-bus system with distributed generations to evaluate its performance.

Microgrid Protection through Adaptive Overcurrent Relay Coordination

The inclusion of distributed energy resources (DER) in Microgrids (MGs) comes at the expense of increased changes in current direction and magnitude. In the autonomous mode of MG operation, the penetration of synchronous distributed generators (DGs) induces lower short circuit current than when the MG operates in the grid-connected mode. Such behavior impacts the overcurrent relays and makes the protection coordination difficult. This paper introduces a novel adaptive protection system that includes two phases to handle the influence of fault current variations and enable the MG to sustain its operation. The first phase optimizes the power flow by minimizing the generators’ active power loss while considering tolerable disturbances. For intolerable cases, the second phase opts to contain the effect of disturbance within a specific area, whose boundary is determined through correlation between primary/backup relay pairs. A directional overcurrent relay (DOCR) coordination optimization is formulated as a nonlinear program for minimizing the operating time of the relays within the contained area. Validation is carried out through the simulation of the IEEE 9, IEEE 14, and IEEE 15 bus systems as an autonomous MG. The simulation results demonstrate the effectiveness of our proposed protection system and its superiority to a competing approach in the literature.

Hybrid Protection Scheme Based Optimal Overcurrent Relay Coordination Strategy for RE Integrated Power Distribution Grid

A directional overcurrent relay is commonly used to protect the power distribution networks of a distributed system. The selection of the appropriate settings for the relays is an important component of the protection strategies used to isolate the faulty parts of the system. The rapid growth of distributed generation (DG) systems present new challenges to these protection schemes. The effect of solar photovoltaic power plants on relay coordination is studied initially in this research work. A protection strategy was formulated to guarantee that the increased penetration of solar photovoltaic (PV) plants does not affect the relay coordination time. This paper addresses these issues associated with a high penetration of DG through the use of a hybrid protection scheme. The protection strategy is divided into two parts. The first part is based on an optimal fault current limiter value estimated with respect to constraints and the optimal time multiplier setting, and then the coordination time interval is estimated with respect to constraint in Part II. The results of these analyses show that a hybrid protection scheme can effectively handle the complexity of distributed generation (DG) and dynamic relay coordination problems. In this research, three optimization algorithms have been used for calculating the estimated value of impedance fault current limiter (Zfcl) and time multiplier setting (TMS). The response time of hybrid protection schemes is very important. If the computational time of their proposed algorithms is less than their actual computational time, then their response time to address the issue is also less. The performance in all algorithms was identified to arrive at a conclusion that the grey wolf optimized algorithm (GWO) algorithm can substantially reduce the computational time needed to implement hybrid protection algorithms. The GWO algorithm takes a computational time of 0.946 s, achieving its feasible solution in less than 1 s.

Optimal coordination of directional overcurrent relays using hybrid fractional computing with gravitational search strategy

The protection system has a vital role in subsystems of the power network including the generation, transmission and distribution system. This system combines several types of protection relays including directional over current relay, differential relay, distance relay, earth faults relay, inverse definite minimum time (IDMT) relay for the protection of line, generators bus bars, transformers, line to ground faults and feeder lines of the power system. In this research paper, the overall performance of the protection system is improved by reducing the overall operational time of directional over current relays (DOCRs) through the optimal coordination between the primary and backup over current protective relays while keeping the time multiplier setting (TMS), pickup tap setting (PTS) and coordination time of interval (CTI) within the allowable limits. A new optimization strategy, namely the FPSOGSA, is developed by integrating the concept of fractional calculus inside the mathematical model of canonical particle swarm optimization and combining with traditional gravitational search algorithm to enhance the optimizer characteristics and tested on coordination problem of DOCRs in standard power systems including the IEEE 3, 8 and 15 bus networks. The results, yielded by proposed algorithm and their comparison with other well-known recently established counterparts, reveal that the synergy of FC, PSO and GSA enhance the performance of the optimizer by combining the individual strengths of these tools and finding the best global solution. The consistency, stability and reliability of FPSOGSA is endorsed by comprehensive statistical analysis based on the empirical cumulative distribution function, histograms, boxplot illustrations, quantile–quantile plots, minimum fitness evolution in each independent simulation.

An Adaptive Protection Scheme for Coordination of Distance and Directional Overcurrent Relays in Distribution Systems Based on a Modified School-Based Optimizer

This paper presents an adaptive protection scheme (APS) for solving the coordination problem that deals with coordination directional overcurrent relays (DOCRs) and distance relays second zone time, in relation to coordination with DOCRs. The coordination problem becomes more complex with the impact of renewable energy sources (RES) when added to the distribution grid. This leads to a change in the grid topology, caused by the on/off states of the distribution generators (DG). The frequency of topological changes in distribution grids poses a challenge to the power system’s protection components. The change in the state of DGs leads to malfunction in reliability and miscoordination between protection relays, since that causes a direct effect to the short circuit currents. This paper used the school-based optimization (SBO) algorithm, which simulates the educational process, in order to deal with coordination problems. That algorithm is modified (MSBO) by modified both learning and teaching processes. The IEEE 8-bus test system and IEEE 14-bus distribution network are used to validate the proposed coordination system’s effectiveness when dealing with the coordination process between distance and DOCRs, at both the near- and far-end in the typical topological grid and with DGs in working order.

Real-time voltage stability monitoring using weighted least square support vector machine considering overcurrent protection

In this paper, a comprehensive scheme is proposed for online monitoring of voltage stability using the Weighted Least Square Support Vector Machine (WLS-SVM) that the effect of overcurrent protection for transmission lines is factored in. The operation of protection systems, due to their nonlinear effect on the system graph, changes the linear and nonlinear equations of the system which cannot be solved by conventional methods. To prevent the maloperation of the overcurrent protection system, coordination between Directional Overcurrent Relays (DOCRs) has been done by linear programming to reach the globally optimum values for DOCR settings. As a result, WLS-SVM is used by implementing collected data from Phasor Measurement Units (PMUs). In addition to solving linear equations instead of quadratic equations, WLS-SVM solves the problems of noise sensitivity and lack of sparseness of the solutions. Also, Principal Component Analysis (PCA) has been used for the dimensionality reduction of the input vector applied to WLS-SVM in this work to make it suitable for real-time applications. Moreover, the measurement errors between measurements obtained from PMUs and the reference values have been taken into account. Then, real-time power system stability monitoring is performed by predicting a voltage stability assessment index using WLS-SVM to evaluate the voltage stability status in a real-time manner. Results of the proposed method regarding efficiency demonstrate high accuracy and better performance in comparison with other approaches. The simulation of the presented approach is carried out on the IEEE 39-bus and IEEE 118-bus systems.

An Optimized Adaptive Protection Scheme for Numerical and Directional Overcurrent Relay Coordination Using Harris Hawk Optimization

The relay coordination problem is of dire importance as it is critical to isolate the faulty portion in a timely way and thus ensure electrical network security and reliability. Meanwhile a relay protection optimization problem is highly constraint and complicated problem to be addressed. To fulfill this purpose, Harris Hawk Optimization (HHO) is adapted to solve the optimization problem for Directional Over-current Relays (DOCRs) and numerical relays. As it is inspired by the intelligent and collegial chasing and preying behavior of hawks for capturing the prey, it shows quite an impressive result for finding the global optimum values. Two decision variables; Time Dial Settings (TDS) and Plug Settings (PS) are chosen as the decision variables for minimization of overall operating time of relays. The proposed algorithm is implemented on three IEEE test systems. In comparison to other state-of-the-art nature inspired and traditional algorithms, the results demonstrate the superiority of HHO.

DEVELOPMENT OF BONOBO ALGORITHM AND ITS APPLICATION FOR OPTIMAL COORDINATION OF DIRECTIONAL OVERCURRENT RELAYS IN POWER SYSTEMS

In this paper, an improved Bonobo optimization algorithm (IBO) is proposed to solve the optimal coordination of directional overcurrent relays (DOCRs) problem. This problem is important for power system protection. It is considered a nonlinear and highly constrained optimization problem. IBO aims to improve the performance of the original Bonobo optimization algorithm (BO) using Levy flight distribution and three leaders selection. Both BO and IBO are utilized to develop two solvers for optimal coordination of DOCRs. The 15-bus and 30-bus test systems are used to validate BO and IBO in minimizing the total operating time of relays with satisfying the operational constraints. The results of the proposed IBO algorithm have been compared with the original BO algorithm and other well-known algorithms. The obtained results confirmed the effectiveness and superiority of the proposed IBO algorithm compared with the other algorithms in minimizing the total operating time of relays for the optimal coordination of DOCRs. Keywords: Directional overcurrent relays; Optimal coordination; Improved Bonobo algorithm; Levy flight distribution; Three leaders selection.

Optimal Coordination of Over-Current Relays in Microgrids Using Principal Component Analysis and K-Means

Microgrids (MGs) are decentralized systems that integrate distributed energy resources and may operate in grid-connected or islanded modes. Furthermore, MGs may feature several topologies or operative scenarios. These characteristics bring about major challenges in determining a proper protection coordination scheme. A new optimal coordination approach for directional over-current relays (OCRs) in MGs is proposed. In this case, a clustering of operational models is carried out by means of a K-means algorithm hybridized with the principal component analysis (PCA) technique. The number of clusters is limited by the number of setting groups of commercially available relays. The results carried out on a benchmark IEC microgrid evidence the applicability and effectiveness of the proposed approach.

Optimal Directional Overcurrent Relay Coordination in Interconnected Networks Considering User-Defined PWL Characteristic Curve

Optimal Directional Overcurrent Relay Coordination in Interconnected Networks Considering User-Defined PWL Characteristic Curve

Fault Protection Considerations for MVDC Shipboard Power Systems Operating with Pulsed-Power Loads

Medium Voltage Direct Current (MVDC) power distribution architectures are of immense interest for various shipboard power applications due to their advantages over classical MVAC distribution systems with respect to power quality, power density, and efficiency. However, MVDC are far away from maturity when compared to MVAC with respect to fault detection and isolation. Currently, there are no standards available for applying MVDC protection systems in shipboard applications. Furthermore, due to the absence of zero crossings in DC waveforms and unique transient fault signatures, it is challenging to design effective protection system schemes to isolate faults via conventional protection systems. This paper investigates and analyses various types of shipboard MVDC dynamic fault behaviours and signatures under different DC bus disturbances such as: bus to ground, bus to bus to ground, and impact of Pulsed-Power Load (PPL) with and without faults on a shipboard MVDC distribution system. Furthermore, a communication-based fault detection and isolation system controller that improves upon a directional ac overcurrent relay protection system is proposed offering additional protection discrimination between faults and PPLs in MVDC systems. To validate the effectiveness of the proposed protection controller, different bus current disturbances are simulated within a time-domain electromagnetic transient simulation of a shipboard power system including a PPL system operating with different ramp rate profiles, pulse widths, peak powers, and fault locations

Optimal setting of DOC relay in distribution system in presence of D-FACTS

The process of selecting optimal settings for directional over-current relays (DOC relays) is a selection of time dial setting (TDS) and IP (backup current), So that changes in the system of electrical power distribution. In this work, a breeder genetic algorithm (BGA) has been applied to optimal settings of DOC relays with multisystem D-FACTS devices. The simulation consists of two network operation scenarios, scenario without D-FACTS which consisting of coordination of DOC relays against three phase faults, and the second scenarios with multi TCSC. In general, had been verified on optimal settings of relays that the impacts of TCSC insertion in 33-bus distribution system on DOC relays.

AC Microgrids Protection: A Digital Coordinated Adaptive Scheme

A significant challenge for designing a coordinated and effective protection architecture of a microgrid (MG) is the aim of an efficient, reliable, and fast protection scheme for both the grid-connected and islanded modes of operation. To this end, bidirectional power flow, varying short-circuit power, low voltage ride-through (LVRT) capability, and the plug-and-play characteristics of distributed generation units (DGUs), which are key issues in a MG system must be considered; otherwise, a mal-operation of protection devices (PDs) may occur. In this sense, a conventional protection system with a single threshold/setting may not be able to fully protect an MG system. To tackle this challenge, this work presents a comprehensive coordinated adaptive protection scheme for AC MGs that can tune their protection setting according to the system states and the operation mode, and is able to switch the PDs’ setting. In the first step of the proposed adaptive algorithm, an offline setting will be adopted for selective and sensitive fault detection, isolation, and coordination among proposed protective modules. As any change in the system is detected by the proposed algorithm in the online step, a new set of setting for proposed modules will be performed to adapt the settings accordingly. In this way, a new set of settings are adapted to maintain a fast and reliable operation, which covers selective, sensitive, and adaptive requirements. The pickup current (Ip) and time multiple settings (TMS) of directional over-current relays (DOCR), as well as coordinated time delays for the proposed protection scheme for both of the grid-connected and islanded modes of operation, are calculated offline. Then, an online adaptive protection scheme is proposed to detect different fault types in different locations. The simulation results show that the proposed method provides a coordinated reliable solution, which can detect and isolate fault conditions in a fast, selective and coordinated adaptive pattern.