Optimal Coordination Of Overcurrent Relays Research Articles

Optimal coordination of directional overcurrent relays considering two-level fault current due to the operation of remote side relay

Overcurrent relays are widely used for the protection of distribution and sub-transmission networks. The network topology change is one of the issues that affects the coordination of directional overcurrent relays (DOCR) in the meshed network. Faster operation of relay on one side of the line respect to the relay on the other side of the line, causes the network topology change during fault, and leads to a change in the short-circuit current (SCC) passing through the other side relay and it’s backup relay. In this case, the coordination between the main and the backup relays can be disturbed due to a change in the SCC passing through them. Previous studies use the highest SCC between the SCC before topology change and the SCC after topology change in coordination of relays to overcome this issue. In this paper, a new DOCR coordination method based on the dynamic model of DOCR is presented to consider the effect of network topology change during the short circuit. The new method is formulated as a linear programming (LP) problem. Efficiency of the proposed method in comparison to conventional methods is illustrated by implementing on two sample networks, 8 bus network and IEEE 30 bus network.

Nature-Inspired Whale Optimization Algorithm for Optimal Coordination of Directional Overcurrent Relays in Power Systems

In power systems protection, the optimal coordination of directional overcurrent relays (DOCRs) is of paramount importance. The coordination of DOCRs in a multi-loop power system is formulated as an optimization problem. The main objective of this paper is to develop the whale optimization algorithm (WOA) for the optimal coordination of DOCRs and minimize the sum of the operating times of all primary relays. The WOA is inspired by the bubble-net hunting strategy of humpback whales which leads toward global minima. The proposed algorithm has been applied to six IEEE test systems including the IEEE three-bus, eight-bus, nine-bus, 14-bus, 15-bus, and 30-bus test systems. Furthermore, the results obtained using the proposed WOA are compared with those obtained by other up-to-date algorithms. The obtained results show the effectiveness of the proposed WOA to minimize the relay operating time for the optimal coordination of DOCRs.

Optimum Coordination of Overcurrent Relays using Genetic Algorithm and Particle Swarm Optimization

Electrical Systems are seldom subjected to excessive currents caused due to short circuits and ground faults. Therefore, it is mandatory to protect people and primary electric power equipment from damage or disaster using suitable Protective systems. When the current exceeds the threshold level, Overcurrent (OC) Relay is operated. It is important for a protection engineer to maintain coordination time interval (CTI) among relays during overcurrent relay coordination. For quick clearance of faults, various optimization algorithms are applied to relay parameters. In this paper, Genetic algorithm and particle swarm optimization technique are used to deduce the Time Multiplier Setting (TMS) values of relays implemented on a radial network. This aids in achieving suitable OC coordination of relays.

Application of the JAYA Algorithm in Solving the Problem of the Optimal Coordination of Overcurrent Relays in Single‐ and Multi‐Loop Distribution Systems

To ensure a safe and trustworthy pattern in contradiction to the possible faults, a precise, reliable, and fast relaying strategy is of high importance in an electrical power system. These challenges give the impression of being more refined in multi‐loop distribution systems. More recently, overcurrent relays (OCRs) have evolved as proficient counteragents for such cases. In this way, inaugurating an optimal protection coordination strategy is accepted as the primary precondition in guaranteeing the safe protection of the coordination strategy. This study is aimed at lessening the overall operational time of the main relays in order to reduce the power outages. The coordination problem is conducted by adjusting only one parameter, namely the time multiplier setting (TMS). In electrical power relaying coordination, the objective function to be minimized is the sum of the overall operational time of the main relays. In the prescribed work, the coordination of the OCRs in the single‐ and multi‐loop distribution network is realized as an optimization issue. The optimization is accomplished by means of JAYA algorithm. The suggested technique depends on the idea that the result acquired for a certain issue ought to pass near the finest result and avert the worst result. This technique involves only the common control factors and does not involve specific control factors. JAYA is adopted to OCR problem and run 20 times with the same initial condition for each case study, and it has been realized that for every run, the JAYA algorithm converges to the global optimum values requiring less number of iterations and computational time. The results obtained from JAYA algorithm are compared with other evolutionary and up‐to‐date algorithms, and it was determined that JAYA outperforms the other techniques.

Optimal Coordination of Double Primary Directional Overcurrent Relays Using a New Combinational BBO/DE Algorithm

The optimal relay coordination (ORC) problem for directional overcurrent relays (DOCRs) has been solved by many conventional and modern optimization algorithms. All these studies were based on the common assumption that all DOCRs are numerical, digital “hardware-based,” static, or electromechanical. Unfortunately, the transition between these technologies does not happen instantaneously, so protection engineers could see different models of these protective relays in some real electric power systems. Moreover, when old electromechanical, static, and digital relays are replaced with the latest state-of-the-art numerical relays, the older relays are kept as backup protective devices. Some called them “primary” and “local-backup” relays, whereas others called them “main-1” and “main-2” relays. The reason behind the second terminology is the chance that the old relays could act ahead of the numerical relays. In this paper, a realistic mathematical model of the ORC problem is formulated and solved using a new hybrid evolutionary algorithm. To judge whether this realistic ORC problem is completely/partially solvable or not, the IEEE 6-bus, 15-bus, and 42-bus test systems are simulated. The results prove that the technique is an effective tool to indicate which relay sets accept/do not accept this double primary relay strategy.

Improved Firefly Algorithm for the Optimal Coordination of Directional Overcurrent Relays

In an electrical power network linear and non-linear models are used for directional overcurrent relay (DOCR) coordination issue by applying different heuristic techniques. Nature inspired algorithms (NIA) have found great interest in power system optimization issues. This paper proposes the recently developed meta-heuristic technique known as Firefly Algorithm (FA) that mimics the flashing behavior of fireflies. The implementation of the proposed algorithm has been utilized to solve the coordination of DOCR problems. The main aim of this paper is to find out the optimum values of the Time Dial Setting (TDS) to minimize the relay operating time. The modifications to original FA has been implemented in this paper to solve the DOCR coordination issues. Self-adaptive weight and experience-based learning strategy are added in the original FA, named as improved firefly algorithm (IFA). In IFA, a self-adaptive weight is presented to change the propensity of moving the best solution and ignoring the worst solution. In addition, an experience-based learning system is created and utilized arbitrarily to keep up the populace-assorted variety and improve the exploration capacity. The IFA has been tested on IEEE 6 and 30-bus systems and tested on IEEE 9-bus system for numerical DOCRs and the results had been compared with results of Whale optimization algorithm to validate the performance of IFA in case of numerical DOCR. The obtained results show that the IFA provides efficient and promising results compared to other meta-heuristic techniques mentioned in the literature. The IFA has been successfully implemented on MATLAB software programming.

Optimal Coordination of Double-Inverse Overcurrent Relays for Stable Operation of DGs

Due to the increasing penetration of distributed generations (DGs) in distribution networks, the performance of protective relays is becoming more critical to maintain the stability of the DGs especially during fault conditions. Among different types of DGs, squirrel cage induction generators (SCIGs) and synchronous DGs are sensitive to faults and might become unstable even after fault clearance. Since the fault clearing time depends on the overcurrent relays (OCRs) characteristic curves, this paper proposes a double-inverse OCR (DIOCR) characteristic to provide proper coordination while maintaining DGs stability. The proposed method defines the critical clearing time curve for each DG and combines them with DIOCRs curves and coordination time interval constraints for finding optimal DIOCRs settings. The proposed method is simulated on the IEEE 33-bus distribution network equipped with SCIG- and synchronous-based DGs. The obtained results highlight the capability of DIOCRs in protecting distribution system with DGs considering stability constraints.

A new constraint considering maximum PSM of industrial over-current relays to enhance the performance of the optimization techniques for microgrid protection schemes

The optimal coordination of primary and backup over-current relays (OCRs) scheme has become one of the main challenges in modern MV-distribution networks (DN) owing to the multi-looped structure and the increased penetration of interment nature-DGs with large-share capacities. The changeable operational topologies of microgrids in modern DN have increased the computational burden to obtain the optimal setting of OCRs. The discrimination time of OCRs scheme may be no longer sufficient or even unmanageable to provide reliable performance in the islanded and grid-connected operational modes. The numerous previously reported optimization techniques employed for OCR coordination may have some limitations/drawbacks regarding OCRs coordination and their framework. Therefore, this study provides a well-defined analytical examination of the limitations in the tripping characteristics of manufactured OCRs. A new constraint taking into consideration maximum plug setting multiplier (PSM) was purposed to improve the optimization techniques. Moreover, enhance the complementary with industrial OCRs tripping characteristics with the optimization techniques in term of coordination time interval. GA in MATLAB had been used to optimize time multiplying setting (TMS) for OCRs coordination. An IEC microgrid benchmark network implemented in ETAP to investigate the effectiveness of the proposed new constraint to enhance the constrained optimization approach in islanded and grid-connected modes.

Optimal Overcurrent Relay Coordination in Interconnected Networks by Using Fuzzy-Based GA Method

A new objective function (OF) has been proposed for mathematical formulation of directional overcurrent (OC) relay coordination in interconnected networks. The fuzzy-based genetic algorithm (GA) is applied to optimize the proposed OF for optimal coordination of OC relays. The defined fuzzy rules update the weighting factors of OF during the simulation. The miscoordination problem of OC relays is solved while decreasing the operating time of the relays. The proposed method is implemented in three different networks and the simulation results have been compared with previous studies in order to illustrate the accuracy and efficiency of the proposed method to coordinate the directional OC relays with both discrete and continuous time setting multipliers. The results have also been compared with the results of other optimization methods. Considering the coefficients of OC characteristic curves as the OF variables ensures that the proposed method has no limitation for the types of characteristic curves which will be utilized. Presenting the new term in OF, the performance of the proposed method has not been affected by the size of the networks.

Optimal overcurrent relay coordination in distribution network based on Lightning Flash Algorithm

PurposeDistribution network protection is a complicated problem and mal-operation of the protective relays due to false settings make the operation of the network unreliable. Besides, obtaining proper settings could be very complicated. This paper aims to discuss an innovative evolutionary Lightning Flash Algorithm (LFA) which is developed for solving the relay coordination problems in distribution networks. The proposed method is inspired from the movements of cloud to ground lightning strikes in a thunderstorm phenomenon. LFA is applied on three case study systems including ring, interconnected and radial distribution networks. The power flow analysis is performed in Digsilent Power Factory software; then the collected data are sent to MATLAB software for optimization process. The proposed algorithm provides optimum time multiplier setting and plug setting of all digital overcurrent relays in each system. The results are compared with other methods such as particle swarm optimization and genetic algorithm. The result comparisons demonstrate that the proposed LFA can successfully obtain proper relay settings in distribution networks with faster speed of convergence and lower total operation time of relays. Also, it shows the superiority and effectiveness of this method against other algorithms.Design/methodology/approachA novel LFA is designed based on the movements of cloud to ground lightning strikes in a thunderstorm. This method is used to optimally adjust the time multiplier setting and plug setting of the relays in distribution system to provide a proper coordination scheme.FindingsThe proposed algorithm was tested on three case study systems, and the results were compared with other methods. The results confirmed that the proposed method could optimally adjust the relay settings in the electric distribution system to provide a proper protection scheme.Practical implicationsThe practical implications can be conducted on distribution networks. The studies provided in this paper approve the practical application of the proposed method in providing proper relay protection in real power system.Originality/valueThis paper proposes a new evolutionary method derived from the movements of cloud to ground lightning strikes in thunderstorm. The proposed method can be used as an optimization toolbox to solve complex optimization problems in practical engineering systems.

On the significance of the plug setting in optimal time coordination of directional overcurrent relays

Directional overcurrent relays give primary plus backup protection to electrical distribution networks. They are coordinated and set at the optimal values to make the total operating time of all the relays in the system minimum. The Time Multiplier Setting (TMS) is used practically to provide time grading to the distribution systems. The Plug Setting (PS) provides for different pick up values for the relays to operate. However, the Inverse Definite Minimum Time relay operating time mathematical expression depends on both these settings. Here, the Firefly algorithm is used to demonstrate that, keeping the PS as a variable and the TMS at the lower bound, gives the best results and the role of TMS for time grading is relegated. This is the novelty of this paper. It is stressed that researchers are minimizing operating time at the expense of downsizing the role of TMS as a time grader.

Application of a Continuous Particle Swarm Optimization (CPSO) for the Optimal Coordination of Overcurrent Relays Considering a Penalty Method

In an electrical power system, the coordination of the overcurrent relays plays an important role in protecting the electrical system by providing primary as well as backup protection. To reduce power outages, the coordination between these relays should be kept at the optimum value to minimize the total operating time and ensure that the least damage occurs under fault conditions. It is also imperative to ensure that the relay setting does not create an unintentional operation and consecutive sympathy trips. In a power system protection coordination problem, the objective function to be optimized is the sum of the total operating time of all main relays. In this paper, the coordination of overcurrent relays in a ring fed distribution system is formulated as an optimization problem. Coordination is performed using proposed continuous particle swarm optimization. In order to enhance and improve the quality of this solution a local search algorithm (LSA) is implanted into the original particle swarm algorithm (PSO) and, in addition to the constraints, these are amalgamated into the fitness function via the penalty method. The results achieved from the continuous particle swarm optimization algorithm (CPSO) are compared with other evolutionary optimization algorithms (EA) and this comparison showed that the proposed scheme is competent in dealing with the relevant problems. From further analyzing the obtained results, it was found that the continuous particle swarm approach provides the most globally optimum solution.

Optimal coordination of directional overcurrent relays using improved mathematical formulation

Achieving optimum coordination of directional overcurrent relays is a very complicated task in the large interconnected system including huge numbers of relays. In the literature, various objective functions (OFs) are reported to obtain minimum operating time of relays and minimum prescribed discrimination time between the operations of primary and backup (P/B) relays. In this paper, the performance of five well-established OFs is examined, and in addition, a new OF is proposed to improve the previously proposed OFs. The proposed OF (POF) minimises operating time of P/B relays together with discrimination time between their operations. Also, the coordination problem is formulated considering near and far-end faults and solved by using a genetic algorithm. In order to evaluate the effectiveness, the POF is implemented over the IEEE 14-bus and IEEE 30-bus distribution networks, and obtained results are compared with those obtained by using previously proposed OFs presented in the literature.

Parameter uncertainty in the optimal coordination of overcurrent relays

Parameter uncertainty in the optimal coordination of overcurrent relays

Optimal Coordination of Directional Overcurrent Relays in Microgrids by Using Cuckoo-Linear Optimization Algorithm and Fault Current Limiter

Nowadays, distributed generations (DGs) and microgrids play a significant role in development of power systems, but DGs produce several protection problems especially in optimal coordination of directional overcurrent relays (DORs). Optimal coordination of DORs is a highly constrained nonlinear programming problem, which has attracted attention of many research studies in recent years. Cuckoo optimization algorithm (COA) is introduced as an optimization tool based on behavior patterns of Cuckoos. In this paper, COA and linear programming (LP) are combined as a new hybrid COA-LP optimization algorithm in order to optimize the coordination protection of DORs in microgrids and find the optimum value of fault current limiter at the point of common coupling. The optimum settings of DORs are obtained for both modes of operation: 1) grid-connected and 2) island mode. The proposed algorithm is applied to Canadian distribution benchmark and a modified IEEE 14 bus networks and compared with particle swarm optimization (PSO) and genetic algorithm (GA). The obtained results show that the computational efficiency of the proposed COA-LP is better than PSO and GA in terms of speed and total operating time of DORs.

MILP approach for optimal coordination of directional overcurrent relays in interconnected power systems

The coordination problem of directional overcurrent relays (DOCRs) is a non-linear and non-convex optimization one. Until now, several methods based on the heuristics and non-linear programming (NLP) approaches have been proposed for solving the problem. Drawback of these methods is that they are likely to be trapped in local minima. In order to overcome the drawback, in this paper, the problem is formulated as a mixed integer linear programming (MILP) while pickup current setting (Iset) and time multiplier setting (TMS) of relays are considered as optimization variables. This formulation is easier to be solved by branch and bound (B&B) approach, because at each branch there is a linear and convex sub-problem. Furthermore, for the first time, the proposed method is guaranteed to converge to global optimal settings. The proposed method is evaluated using a 3-bus, an 8-bus, the IEEE 14-bus and the modified IEEE 30-bus test systems. The results are compared with some previous heuristics and NLP approaches. Based on the obtained results, it can be seen that, better optimal settings for DOCRs are obtained by using the proposed method in comparison with previous methods.

Gravitational Search Based Algorithm for Optimal Coordination of Directional Overcurrent Relays Using User Defined Characteristic

Due to dependency on Plug Setting (PS), Time Dial Setting (TDS), size of the network, more than one back-up relays for one primary relay and other technical constraints, coordination of Directional Overcurrent Relays (DOCRs) is an extremely constrained and nonlinear optimization problem. In this paper, a new Gravitational Search (GS) based algorithm is presented for achieving optimal coordination of directional overcurrent relays. The proposed algorithm utilizes user defined characteristic for inverse time overcurrent relays than the predefined standard curves. The user defined relay characteristic deals with constants that control the shape of the characteristics as variable adjustable values which are optimally chosen along with TDS and Plug Setting Multiplier (PSM). The performance of the proposed algorithm has been evaluated on 8-bus, 15-bus and IEEE 30-bus distribution network at different fault locations (near-end, far-end and middle point). In addition, the time of operation of some of the primary relays at different fault locations on IEEE 30-bus distribution network is also presented. At the end, comparative evaluation of the proposed algorithm with other optimization algorithms having different relay characteristics presented in the literature clearly indicates its effectiveness and superiority in terms of the sum of total primary relays operating time.

A hybrid improved harmony search algorithm-nonlinear programming approach for optimal coordination of directional overcurrent relays including characteristic selection

The objective of optimal coordination of directional overcurrent relays (DOCRs) is to search optimal relay settings. This leads to the minimum operating time of relays for faults in their primary protection zone under the coordination and boundary constraints. In this paper, relay settings are considered as pairs of - pickup current setting (Ip) and time multiplier setting (TMS), plug setting (PS) and TMS - for solving the coordination problem on 8-bus and 15-bus networks. Moreover, a new hybrid improved harmony search algorithm-nonlinear programming (IHSA-NLP) approach is proposed to solve the relay coordination problem. To demonstrate the superiority of IHSA-NLP method, obtained results are compared with the IHSA and existing methods presented in the literature. Also, the effectiveness of the proposed method is evaluated with the coordination problem considering multiple characteristics on IEEE 30-bus network.

A hybrid improved harmony search algorithm-nonlinear programming approach for optimal coordination of directional overcurrent relays including characteristic selection

The objective of optimal coordination of directional overcurrent relays (DOCRs) is to search optimal relay settings. This leads to the minimum operating time of relays for faults in their primary protection zone under the coordination and boundary constraints. In this paper, relay settings are considered as pairs of - pickup current setting (Ip) and time multiplier setting (TMS), plug setting (PS) and TMS - for solving the coordination problem on 8-bus and 15-bus networks. Moreover, a new hybrid improved harmony search algorithm-nonlinear programming (IHSA-NLP) approach is proposed to solve the relay coordination problem. To demonstrate the superiority of IHSA-NLP method, obtained results are compared with the IHSA and existing methods presented in the literature. Also, the effectiveness of the proposed method is evaluated with the coordination problem considering multiple characteristics on IEEE 30-bus network.

A fast numerical method for optimal coordination of overcurrent relays in the presence of transient fault current

In the past, many studies have been conducted on the optimal coordination of overcurrent (OC) relays. In these studies, the short-circuit current flowing through the relays is considered as fixed. In a real power network, however, for various reasons including the transient behaviour of synchronous generators, the short-circuit current that flows through the relays varies with time. Therefore, the relay settings, which are obtained with the assumption of a constant, short-circuit current, may cause miss-coordination under real conditions. In this study, a numerical method based on the dynamic model of the relay is presented using linear programming (LP) to take account of the effect of transient currents on the coordination of OC relays. The method can be used as a fast numerical algorithm in the computing software to obtain accurate settings for OC relays in the presence of various transient fault currents in the network. Furthermore, the combination of LP with a genetic algorithm is used to incorporate the current setting of the relays in the transient coordination algorithm to achieve a better operating time for the relays. The results show the effectiveness of the proposed algorithms as compared with the previously presented method.