Settings Of Directional Overcurrent Relays Research Articles

Stability-Constrained Settings of Directional Overcurrent Relays With Shifted User-Defined Characteristics for Distribution Networks With DERs

Stability-Constrained Settings of Directional Overcurrent Relays With Shifted User-Defined Characteristics for Distribution Networks With DERs

Coordination of Directional Overcurrent Relays using Growth Optimizer

The protection system plays a crucial role in the generation, transmission, and distribution systems of a power network. Among various protection relay types, Directional Overcurrent Relays (DOCRs) are the most used. When abnormal conditions are detected, these relays trigger the tripping of protection devices by detecting the direction and magnitude of current flow and isolating faulty parts of the system. The present article proposes a novel approach for the coordination and settings of DOCRs using the Growth Optimizer (GO) algorithm; the main objective is to minimize the sum of operation time of the relays while ensuring the minimal time gap between primary and backup relays. This optimization problem is subject to different constraints including maximum allowable operating times, relay coordination margins, and discrete values for pickup current settings. The technique is applied to the IEEE 4-bus, 8-bus, and 15-bus test systems, and its performance is compared with that of other optimization algorithms. Results show that the proposed approach provides the proper coordination of protection systems with a high, robust, and computationally acceptable speed of convergence.

Enhanced Combined Protection Scheme Using Dual Setting Directional Overcurrent and Distance Relays Considering Severe Line Contingencies

An electrical power system must have an optimal protection system for enhanced reliability. Numerous studies have attempted to address issues with protection schemes, such as coordination constraint violations due to change in network configuration. Furthermore, in a few articles, the N-1 line contingency is considered without considering the line contingency selection criterion, resulting in a large number of constraints to deal with in the optimization problem. This paper proposes a new relay coordination scheme for dual setting directional overcurrent relay (DOCR) and distance relay based on the severity index of line outages, which is calculated by using an active and reactive performance index. The proposed protection strategy is improved with the help of an intelligent selection of the relay characteristics coefficient for dual setting DOCR along with the other relay settings. Another significant contribution is to provide a comparative analysis of standard and user-defined relay characteristics using genetic algorithm and grey wolf optimization algorithms. The modified IEEE-14 bus test system and IEEE-39 bus test system is used to validate the efficacy of the proposed protection scheme.

Optimal overcurrent relay coordination for interconnected power systems: A proper approach and improved technique

The optimum setting of directional overcurrent relays (DOCRs) is required to avoid miscoordination and avail fast response. To fulfill these requirements, it is required to prefer optimization techniques and modifications in objective functions (OF). Many researchers have adopted soft computing techniques and suggested modifications in the objective function for problem formulation of overcurrent relay coordination. Though these modifications and suggestions attain an optimum value of relay parameters, unfortunately, some of them don't follow the fundamental requirements of overcurrent relay coordination. This paper reflects on such modified objective functions and conveys a proper approach. Further, the paper proposes a new objective function as per the overcurrent relay coordination criteria. The novelty of the paper is to modify the existing objective function as per overcurrent relays coordination criteria and to add a new term in it to avoid miscoordination. The proposed objective function (POF) is applied on two power system test networks and results reveal that it is efficient and accurate.

Protection Coordination of Microgrids Using Dual Setting Directional Overcurrent Relays Based on Optimal Operating Characteristics and Curve Breakpoints

Protection Coordination of Microgrids Using Dual Setting Directional Overcurrent Relays Based on Optimal Operating Characteristics and Curve Breakpoints

Optimal coordination of directional overcurrent relay based on combination of Firefly Algorithm and Linear Programming

Optimal coordination and settings of directional overcurrent relays (DOCRs) are crucial task to ensure reliable and effective protection in power system networks. The settings of DOCRs are plug setting current (PSC) and time multiplier setting (TMS). The DOCRs coordination is well-known as a highly constrained nonlinear optimization problem. Its complexity in terms of non-linearity increases along with the network size increment. This paper proposes a hybrid optimization algorithm which consists of Firefly Algorithm and Linear Programming (FA-LP) to relax the search space by linearizing the equation of the DOCRs coordination to attain an optimal solution. Furthermore, this paper also considers a mixed type of IEC relay characteristics to attain effective relay operation. The proposed method is tested on the IEEE 8-, 15- and 30-bus test systems. The results show the reduction of total relay operating time between 15.6% and 85.5% as compared to other techniques in the literature and also being verified using the ETAP software.

Hierarchical Clustering Cuckoo Search Optimization Implemented in Optimal Setting of Directional Overcurrent Relays

This study has proposed a hierarchical clustering cuckoo search optimization (HCSO) to solve the optimal setting problems of directional overcurrent relays (DOCRs) in the power system. Different from the randomly generated stepsize θ in traditional CSO, stepsize θ in HCSO is updated by a hierarchical clustering mechanism, which can balance the searching priority of exploration and exploitation for each solution. The superiority of HCSO is evaluated by solving the DOCRs coordination problem with the 3-bus, 8-bus, and 9-bus system, presented by linear programming (LP), nonlinear programming (NLP), and mixed integer nonlinear programming (MINLP) forms. Results show that under the same parameter setting conditions, the minimum value of the objective function by HCSO has reduced by 10.93 % , 2.93 % , and 0.46 % , respectively, compared to that of CSO in the experimented cases 2, 3, and 4. It verifies that HCSO is more competitive than CSO in solving the DOCRs optimal setting problem irrespective of the DOCRs number and formulation type.

Comparative Study of Relay Coordination in a Microgrid with the Determination of Common Optimal Settings Based on Different Objective Functions

This study aims to analyze the optimal settings of directional overcurrent relays (DOCRs) for the protection of an alternating current (AC) microgrid in both islanded and grid-connected operation modes. In this context, two different types of objective functions are used for comparing the total operating time of all primary DOCRs. The optimal settings obtained in either mode of the microgrid are different due to the variable magnitude of fault currents. The proposed protection coordination scheme is formulated as a mixed-integer non-linear programming problem, and the settings are obtained using various optimization techniques such as firefly algorithm, simulated annealing algorithm, and genetic algorithm. The results show that the settings obtained in common operation modes are robust as no miscoordination of relays occurs in any of the operation modes.

Coordination of dual setting overcurrent relays in microgrid with optimally determined relay characteristics for dual operating modes

Fault current magnitude in a microgrid depends upon its mode of operation, namely, grid-connected mode or islanded mode. Depending on the type of fault in a given mode, separate protection schemes are generally employed. With the change in microgrid operating mode, the protection scheme needs to be modified which is uneconomical and time inefficient. In this paper, a novel optimal protection coordination scheme is proposed, one which enables a common optimal relay setting which is valid in both operating modes of the microgrid. In this context, a common optimal protection scheme is introduced for dual setting directional overcurrent relays (DOCRs) using a combination of various standard relay characteristics. Along with the two variables, i.e., time multiplier setting (TMS) and plug setting (PS) for conventional directional overcurrent relay, dual setting DOCRs are augmented with a third variable of relay characteristics identifier (RCI), which is responsible for selecting optimal relay characteristics from the standard relay characteristics according to the IEC-60255 standard. The relay coordination problem is formulated as a mixed-integer nonlinear programming (MINLP) problem, and the settings of relays are optimally determined using the genetic algorithm (GA) and the grey wolf optimization (GWO) algorithm. To validate the superiority of the proposed protection scheme, the distribution parts of the IEEE-14 and IEEE-30 bus benchmark systems are considered.

Optimal stability-oriented protection coordination of smart grid’s directional overcurrent relays based on optimized tripping characteristics in double-inverse model using high-set relay

Many studies have been devoted to developing the optimized protection schemes of smart grids. However, there is a research gap about studying the transient stability constraints in smart grids’ optimized protection schemes. Also, there is a major challenge in the transient stability-oriented protection system's speed due to increased coordination constraints and transient stability for synchronous distributed generations (DGs). This paper tries to fill such a research gap by developing a new transient stability-oriented method for optimized settings of directional overcurrent relays (DOCRs), smartly selecting relay curves in double-inverse relays equipped with high-set (HS) relays. This study's main advantage is achieving a fast and optimal protection system, while all transient stability constraints have been concerned. The proposed method has been studied in the IEEE 33-bus test system, while the GA and PSO algorithms solve the optimization problem. The comparative analysis of the test results with those of other available methods illustrates that 33.7% improvement in the sum of DOCRs’ operating time appears, while there is no stability constraint violation. The validation of speed and both coordination and stability constraints violations using the DIgSILENT simulations is another contribution of this research work.

Optimal Coordination of Directional Overcurrent Relays in Meshed Active Distribution Network Using Imperialistic Competition Algorithm

The optimal setting of directional overcurrent relays (DOCRs) ensures the fault detection and clearing in the minimum possible operation time. Directional protective relaying is carried out to coordinate relay settings in a meshed network in the presence of distributed generation. The main goal of DOCR coordination is to find the optimal time dial setting (TDS) and pickup multiplier setting (PMS) to reach the minimum total operation time of all primary relays in the presence of coordination constraints. Due to the complexity of mixed integer non-linear programming (MINLP) problem, imperialistic competition algorithm (ICA) as a powerful evolutionary algorithm is used to solve the coordination problem of DOCRs. The proposed DOCR coordination formulation is implemented in three different test cases. The results are compared with the standard branch-and-bound algorithm and other meta-heuristic optimization algorithms, which demonstrates the effectiveness of the proposed algorithm.

User-Defined Dual Setting Directional Overcurrent Relays with Hybrid Time Current-Voltage Characteristics-Based Protection Coordination for Active Distribution Network

With the penetration of renewable energy sources based distributed generation (RES-DG) in the distribution network (DN), the operating time of protection relays becomes a major concern to avoid the mis-coordination and nuisance tripping of RES-DG. It is due to the bidirectional flow of current, variance in the fault current level, i.e. high fault current in case of Squirrel cage induction generator (SCIG) based RES-DG, and low fault current for an inverter-based RES-DGs. This paper proposes a novel User-defined dual setting direction overcurrent relay with hybrid time current-voltage (UDDOR-TCV) characteristics to intensify the proposed scheme’s flexibility without any communication assistance for radial DN. The proposed model is formulated in a constrained non-linear optimization fashion and solved with the MINLP solver of general algebraic modelling system(GAMS) software to determine the optimal relay settings. The propounded protection scheme is simulated on IEEE-33 bus radial distribution system and a local 40-bus system hosting the multiple SCIG and PV based RES-DGs at optimal locations. Detailed numerical studies are carried out to show the performance of the proposed scheme. 66.848% and 68.26% reduction in relay operation time with zero mis-coordination is achieved with SCIG-WTG case and PV-units case for the IEEE-33 bus system and a similar reduction in operation time is 68.937% and 66.563% for Local-40 bus system. Moreover, the relays numbers are reduced by 32.692% and 39.7% for IEEE-33 and Local-40 bus systems, respectively, due to the forward/reverse characteristics capability of the proposed UDDOR-TCV. The performance of the proposed scheme is also evaluated on IEEE-8 bus meshed DN. The results are compared with the existing protection schemes in recent literature.

Adaptive Protection Scheme for Microgrid With Multiple Point of Common Couplings

Frequent changes in operating conditions of microgrid affect the coordination of directional overcurrent relays (DOCRs). This article proposes an adaptive protection scheme to handle DOCRs coordination problem in microgrid having multiple point of common couplings. The proposed scheme consists of two blocks: offline and online. In offline, settings of DOCRs are calculated for most important operating conditions (grid connected and islanded modes) and stored in corresponding DOCRs. The online task is performed based on local and global decision approaches. The local decision approach ensures significant less burden on microgrid central controller. Also, the proposed scheme does not cause any catastrophic conditions in microgrid when a fault occurs during critical situations. Then, coordination problem is formulated as constrained nonlinear programming problem and solved using a symbiotic organism search algorithm. The effectiveness of the proposed scheme is examined on 7-bus and IEEE 33-bus microgrids during various operating conditions. Furthermore, simulation results are validated on hardware-in-loop test bed using real-time digital simulator, numerical relays, and CMS-356 (voltage and current amplifier). From simulation and hardware results, it is noticed that proposed scheme is able to provide an adequate protection to microgrids during various operating conditions, various types of bolted faults, and high-impedance faults.

A New Approach for the Setting of Directional Overcurrent Relays by Incorporating Cascading Outages

Directional overcurrent relays (DOCRs) are the essential protective devices in distribution networks which are usually set without considering any contingencies. However, the current challenge in power systems is the existence of uncertainty and its unfavorable consequences. It sometimes appears that some elements simultaneously fail which makes other parts to be overloaded to the extent that it leads to cascading outages. Therefore, DOCRs may have mal-operation which ends in unwanted trips when there is no fault, or they may not operate in the case the fault is located within their reach point. In such cases, the coordination setting will need complex programming with many related non-linear inequality constraints. In this paper, a novel hybrid method is proposed based on multi-objective optimization including new objective functions by using the genetic algorithm (GA). Also, the cascading outages are considered in the presented method based on network data analysis. This approach is performed on distribution part of the IEEE 14-bus meshed system, and a real industrial radial feeder named TOSEE, located in Iran. The simulations have been implemented in MATLAB and PowerFactory-DIgSILENT software packages in different models, and the results are evaluated.

Non-Communication Based Time-Current-Voltage Dual Setting Directional Overcurrent Protection for Radial Distribution Systems With DG

This paper proposes a novel protection scheme equipped with time current voltage dual setting directional overcurrent relays for radial distribution systems with (distributed generation) DG without the need of communication assistance. The proposed protection scheme is formulated as a nonlinear programming problem where the main objective is to determine the optimal relay forward and reverse settings to minimize the relay overall operating times. The proposed scheme, based on the time current voltage dual settings directional overcurrent relay, is applied to the IEEE 33-bus radial distribution system with synchronous-based DG and its performance is compared against the conventional protection schemes that rely on both standard overcurrent relays and time current voltage directional overcurrent relays (proposed in the literature). The results show that, for radial distribution systems, the proposed scheme is capable of mitigating protection coordination failure due to DG reverse fault currents (a limitation in overcurrent relays), does not require communication (a limitation for meshed distribution systems) and does not require additional relays (a limitation in directional overcurrent relays) and thus making such relays more suitable for protecting radial distribution systems with DG.

Alternative Methodology to Calculate the Directional Characteristic Settings of Directional Overcurrent Relays in Transmission and Distribution Networks

When addressing the problem of calculating the settings for directional overcurrent elements, the focus is usually the determination of the pickup, time dial and operating characteristic, in order to ensure proper selectivity with adjacent protection elements, thus limiting the problem related to the settings calculation of the direction determination characteristic to the application of typical settings and general guidelines, which cannot provide a reliable measure of the suitability of such settings. The present article describes in detail an alternative methodology for determining these settings, based on a characterization of the power system where the directional protection is to be applied, through the performance of a detailed short-circuit sensitivity analysis. From this, an optimization problem is formulated and solved to obtain the main settings shaping the direction determination characteristic, and then, a series of variables are used to measure the performance of the obtained settings, and even to improve it. The obtained results show the advantages of the application of the proposed methodology over the traditional methodology, based on typical settings and general guidelines, pointing out the risks of using the later.

A dynamic objective function for communication-based relaying: Increasing the controllability of relays settings considering N-1 contingencies

Considering different configurations of a protected network in relays coordination offers higher reliability, security, and sustainability. However, overcurrent relaying in N-1 contingency states stands as a complicated problem especially in interconnected sub-transmissions systems with distance relays. To overcome this challenge, the current paper proposes a coordination scheme in which dual setting directional overcurrent relays (D-DOCRs) and low bandwidth communication links are jointly deployed instead of conventional DOCRs. By doing so, more flexibility and extensibility is provided in the coordination process. Moreover, in order to direct the relays settings toward optimal solutions, a new dynamic objective function is devised. This approach strengthens the controllability of relay settings in different conditions by pulling the variables towards the feasible region. The proposed formulation considers both standard and non-standard relay characteristics and demonstrates a nonlinear programming fashion which is solved by chaotic particle swarm optimization algorithm. Results approve that D-DOCRs in conjunction with distance relays can successfully maintain a proper coordination in N-1 contingency states, supported by the proposed dynamic approach.

Overcurrent protection of AC microgrids using mixed characteristic curves of relays

Protection of AC microgrids with islanded and grid-connected modes of operation is a major challenge as fault currents change drastically in the transition from one mode to the other. In this paper, optimum settings of directional overcurrent relays (DOCRs) considering different characteristic curves for the protection of AC microgrids with islanded and grid-connected modes of operation is presented. In this work, all the relays are considered to be associated with three variables which are time multiplier-setting (TMS), plug-setting (PS), and curve-setting (CS) to obtain their correct operating times. Here, TMS, PS, and CS are associated with time scaling, pickup current value and characteristic curve selection, respectively, of a DOCR. The proposed protection coordination problem has been formulated as a mixed-integer nonlinear programming problem and solved using the genetic algorithm in MATLAB environment. The effectiveness and suitability of the proposed approach have been demonstrated on 7 and 18 bus microgrids.

Protection Coordination for Microgrids With Grid-Connected and Islanded Capabilities Using Communication Assisted Dual Setting Directional Overcurrent Relays

This paper proposes a communication assisted dual setting relay protection scheme for micro-grids with grid connected and islanded capability. Previous work on dual setting relays has been applied to grid connected distributed generation systems only, but one major shortcoming is the failure of the backup scheme to operate in a coordinated manner. The proposed scheme relies on the use of dual setting directional overcurrent relays that are capable of operating in both forward and reverse directions, with different settings, and with a low bandwidth communication to maintain proper protection coordination. The problem is formulated as a non-linear constrained programming problem where the relay settings are optimally determined to minimize the overall relay operating time for primary and backup operation. The scheme is tested on a modified version of the IEEE 30 bus test system equipped with distributed generation and with capability of operating in an islanded mode. The proposed scheme is compared against the conventional scheme and the results show that it is capable of overcoming the problem of infeasibility, experienced by the conventional method, without the need of installing fault current limiters. Furthermore, it achieves remarkable reduction in both the primary and backup relay operating times, which was reflected in a reduction in the total relay operating time.

Optimized settings of directional overcurrent relays in meshed power networks using stochastic fractal search algorithm

Summary This paper presents a novel application of the stochastic fractal search algorithm to solve the optimal relay coordination problem of meshed power networks. The optimization problem has 3 design variables, which are the time dial, the pickup current, and the tripping characteristic of each relay and subjects to set of coordination constraints. The objective function is adapted to minimize the total operating time of the primary and backup relays while maintaining the validity of coordination within acceptable limits. Three interconnected power systems with various topologies and fault scenarios are demonstrated. Among these 3 test cases, it is worthy emphasizing that the third power system is highly penetrated with 6 distributed generators, which tangle the optimization problems with numerous relay pair scenarios. The validity and the effectiveness of the proposed method are confirmed using the simulation results, in addition to necessary subsequent comparisons to other competing approaches. The simulated numerical results and the performance measures indicate that the stochastic fractal search algorithm is viable and able to generate competitive optimal settings for overcurrent relays and lie in an acceptable elapsed time.