Directional Overcurrent Relays Research Articles

Optimal adaptive protection of smart grids using high‐set relays and smart selection of relay tripping characteristics considering different network configurations and operation modes

Much attention has been paid to optimizing smart grids (SGs) and microgrids (MGs) protection schemes. The SGs’ operation in different operating modes (especially grid-connected and islanded conditions) and various system configurations (such as the outage of each of the distribution generations) adversely influence the protection system. The adaptive protection schemes using different setting groups are suitable and reliable solutions to achieve a fast protective system. However, the literature shows a research gap in developing optimized adaptive protection schemes, focusing on constraint reduction, besides the optimal selection of time-current characteristics for direction overcurrent relays (DOCRs) and high-set relays (HSRs). This research aims to fill such a research gap. The power system analyses, such as power flow and short circuit studies, are done in DIgSILENT, and the genetic algorithm (GA) is used to find the optimum solutions. Test results of the IEEE 38-bus distribution system illustrate the advantages of this study compared to existing ones. The comparative test results emphasize that 31.78% and 21.62% decrement in time of the protective scheme in different topologies for the distribution networks of the IEEE 38-bus and IEEE 14-bus test systems could be achievable by simultaneously optimizing relay characteristics and HSRs compared to existing approaches.

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.

An adaptive bidirectional protective relay algorithm for ferroresonance in renewable energy networks

Smart grid comprises utility system and renewable resources including wind farm and solar system. It causes bidirectional flowing of power especially in distribution level, and establishing communication facility amongst utility system, distributed generations (DG), and loads. In this study, influence of occurrence of ferroresonance in the utility system is investigated on technical quantities of DFIG and operation of directional overcurrent (DOC) relay installed in wind farm is assessed by means of PSCAD/EMTDC simulation software. Smart grid stand in need of a self-healing protection; therefore, an adaptive algorithm on the basis of neural network and signal analysis tools like, wavelet transform, moreover, analysis of ferroresonance in time domain is designated for overcurrent relay. The relay with new algorithm can conform to protection strategy of smart grid. It discriminates ferroresonance from other nonlinear and transient abnormalities, which affect deviation of electrical quantities. Protection strategy established in smart grid decides on behaviour of the relay through the algorithm. It takes an appropriate decision in ferroresonant states to modify setting quantities of the relay and changes direction of operation to enhance reliability and availability of power electricity in smart grid. The relay is capable of predicting ferroresonance in the network to fulfil smart grid requirements.

A Robust Protection Scheme for Multimicrogrids Using Fault Current Limiter

The operation of multimicrogrids (MMGs) can cause significant impact on power system network, especially changes in level and direction of fault current. The fault current level may exceed rating of existing directional overcurrent relays (DOCRs) that lead to sympathetic tripping or fail to trip DOCRs in the network. It is expensive and extremely challenging to upgrade or replace the existing DOCRs in the network. If not properly addressed, this issue may hinder the deployment of MMGs in to the network. Hence, this article proposes a robust protection scheme for DOCRs coordination in MMGs without replacing existing DOCRs in network. First, the proposed scheme calculates optimal settings of DOCRs in all stand-alone microgrids of MMG during islanded mode. Then, optimal values of fault current limiters are obtained using calculated optimal settings. The main advantage of proposed scheme is that it provides one set of DOCRs settings valid for all operating modes of MMG. In this work, the DOCRs coordination problem is formulated as nonlinear problem and solved using proposed hybrid approach symbiotic organisms search (SOS) and nonlinear programming (NLP). The initial solution is determined by SOS and final solution is obtained using NLP. Further, the proposed scheme is examined during gird connected and islanded modes in two different configurations (series and parallel) of MMG, which are not stated in previous literature. Finally, simulation results are validated using numerical relay and real time digital simulator, which are interfaced through voltage and current amplifier to execute hardware-in-loop test bed.

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.

Adaptive fuzzy directional bat algorithm for the optimal coordination of protection systems based on directional overcurrent relays

Despite bringing several benefits to modern power systems, distributed generation (DG) and microgrids cause a significant impact on the operation of power distribution networks, especially with regard to the protection system. The topological evolution of power distribution networks comprising DG units and the islanding capacity of microgrids have lead to significant changes in the magnitudes of short-circuit currents, consequently affecting the reliability of protection systems in terms of loss of selectivity (false tripping and/or sympathetic tripping), sensitivity (blind protection), and dynamic response (delayed trip). In this new scenario, the adoption of smart protection systems capable of incorporating advanced control and protection mechanisms is of paramount importance for ensuring the automatic reconfiguration and restoration of the power grid when undesirable phenomena like faults occur. Considering this scenario, this work proposes a novel metaheuristic called adaptive fuzzy directional bat algorithm (AFDBA), which can calculate optimal settings for directional overcurrent relays (DOCRs) in any power grid topology without the need for tuning the initial parameters. The technique is applied to three case studies, that is, the 3-bus, 9-bus, and 30-bus test systems. The algorithm performance is compared with that of genetic algorithm (GA), particle swarm optimization (PSO), differential evolution (DE), bat algorithm (BA), and directional bat algorithm (DBA). The results evidence that the proposed approach has high convergence speed, high robustness, and acceptable computational burden, while providing the proper coordination of protection systems.

Protection Coordination of Microgrids Considering Non-Standard Features of Directional Over-Current Relays

This paper presents a methodology for protection coordination in microgrids that considers account non-standard features of directional over-current relays (OCRs). In the proposed approach three decision variables are considered for each relay; namely, the standard characteristic curve (SCC), Time Multiplier Setting (TMS) and maximum limit of the plug setting multiplier (PSM). The proposed mixed integer non-linear programing model is solved by means of a specialized genetic algorithm (GA) implemented in Matlab. Several tests were performed on a modified version of the IEEE-30 bus test system considering on-grid and off-grid operational modes. The results evidenced the robustness and applicability of the proposed approach in real-size microgrids that host distributed generation and exhibit several operational modes or topologies.

An Approach to Improve Mathematical Formulation of Directional Overcurrent Relays Coordination for Interconnected Power Systems

The coordination of a large number of protective relays in an interconnected power system is a crucial task. In recent years, researchers have adopted various approaches to attain minimal discrimination time between primary and backup relay pairs for directional overcurrent relay coordination. Researchers have suggested various objective functions to overcome relay mis-coordination and to achieve optimum value of relay plug setting and time multiplier settings. This paper discusses an approach to improve the mathematical formulation for the coordination of directional overcurrent relay for an interconnected power system. Various objective functions reported in the literature are compared with the proposed objective function precisely adopting the overcurrent relay coordination philosophy. To check & analyze the robustness and suitability of the proposed objective function, a modified IEEE14-bus distribution system & IEEE 30-bus system, and IEEE8- bus system is employed. A comparative analysis of the proposed objective function and reported objective functions is presented.

Optimal Protection Coordination for Inverter Dominated Islanded Microgrids Considering N-1 Contingency

Optimal protection coordination is usually solved for the original network topology with all lines, loads, and generation intact. However, power grids may experience contingencies due to transient events, e.g., generation or line outages. Low fault currents of inverter-interfaced distributed generators (IIDGs) necessitate a sensitive and reliable protection scheme. This paper proposes a protection scheme for islanded microgrids powered by droop-based IIDGs. The protection scheme utilizes virtual impedance-fault current limiters to limit IIDGs fault currents and achieve protection coordination. A two-stage method for optimal protection coordination (OPC) of directional overcurrent relays (DOCRs) is devised. In Stage I, relays short-circuit currents are calculated. Then, constraints on the operation times of primary and backup DOCRs are formulated for the islanded topology and each possible topology following an N-1 contingency. Lastly, in Stage II, the OPC problem is formulated as a constrained nonlinear programming problem and solved to obtain the optimal DOCRs settings. A radial test microgrid that is part of a Canadian urban distribution system is used to ensure the success of the proposed OPC method.

Protection of Networked Microgrids Using Relays With Multiple Setting Groups

The protection of multiple interconnected microgrids is a challenging task because of changes in the topology of the system. A microgrid can operate in an islanded mode or get connected to another autonomous microgrid or grid-connected microgrid or directly to the utility grid. The short-circuit currents can change widely because of the connection status of a microgrid in the system of multiple or networked microgrids. In this article, a novel setting groups based scheme is presented for the protection of networked microgrids using directional overcurrent relays. The developed scheme can provide adequate protection to all microgrids under all possible interconnection among the microgrids and utility grid. A vector is generated for each possible interconnection of microgrids in the system to categorize them into four groups using <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">k</i> -means clustering. The optimum settings of relays considering all operational aspects of each group are calculated using a nonlinear programming based algorithm. Based on the topological interconnections of microgrids in the system, one of the setting groups can be enabled using a low-bandwidth communication link. The proposed protection approach has been validated on a benchmark test system for networked microgrids. The suitability and the effectiveness of the developed settings of the relays have been analyzed adequately.

Optimal coordination of directional overcurrent relays with non-standard multi-characteristics for power systems transient instability protection

Optimal coordination of directional overcurrent relays with non-standard multi-characteristics for power systems transient instability protection

Optimal coordination of DOCRs in interconnected networks using shifted user-defined two-level characteristics

This paper introduces a protection scheme for interconnected networks based on proposed Directional Overcurrent Relays (DOCRs) with user-defined two-level characteristics. By getting usage of the capabilities available in modern digital DOCRs, the proposed relay will have two user-defined characteristics; one for its primary operation and another for its backup operation (two-level characteristics) to fit a specific application or system. The coordination between the proposed relays is formulated and solved as a non-linear optimization problem to minimize their operating time and reduce the thermal impact caused by short circuit currents through electrical equipment while maintaining the technical constraints.Extensive comparative studies have been performed to ensure the effectiveness of the proposed protection scheme. Firstly, the performance of the traditional one-level characteristic relay (COLC) with two settings is compared to the conventional two-level characteristic relay (CTLC) with three settings. Then a further investigation is carried out by suggesting increasing the number of settings to seven, named as the user-defined two-level characteristic relay (UDTLC), and then to nine settings, named as the shifted-user-defined two-level characteristic relay (SUDTLC). Finally, different multi-objective functions with proper weighting factors are investigated to determine the most effective one with the best performance for the proposed idea.The distribution portion of the IEEE 30-bus system has been used to test and verify the proposed characteristics extensively. The optimal coordination problem is solved using thefminconfunction in MATLAB. Based on the achieved results, the proposed characteristics of UDTLC and SUDTLC guaranteed a considerable reduction in operating times. In addition, the achieved results deduced that using a different multi-objective formulation has little impact on reducing operating time due to using the proposed characteristics UDTLC and SUDTLC, which means solving the coordination problem is mainly dependent on the applied characteristics.

A Survey on the Development of Real-Time Overcurrent Relay Coordination Using an Optimization Algorithm

The current work is a survey on the development of real-time overcurrent relay coordination utilizing an optimization approach. Overcurrent relays are a safeguard commonly used in transmission and distribution networks owing to their low cost. Depending on the operating conditions and the location of the faults, load or fault currents in a mesh system may loop in or out of the protective zone of the overcurrent relay. As a result, directional overcurrent relays are employed to determine whether the fault is inside or outside the protective zone. The goal of overcurrent relay coordination is to find settings that minimize operating time for failures within the protective zone. In addition to this it provides scheduled backup for relays in neighbouring zones that has been pre-specified. As an outcome, the highest possible fault current observed by the relay must be greater than maximum fault currents in its protective zone detected in zones close by.

An adaptive virtual impedance fault current limiter for optimal protection coordination of islanded microgrids

Fault currents of inverter-interfaced distributed generators (IIDGs) depend on inverter controllers. Thus, IIDGs fault currents are different than those of synchronous-based DGs, both from the magnitude and waveshape perspectives. In the event of short-circuit faults, droop-based IIDGs switch between a voltage source and a current source, which increases the complexity and non-linearity of short-circuit current calculation (SCC). This paper proposes a new SCC algorithm that incorporates virtual impedance-fault current limiters (VI-FCLs) to enable modelling droop-based IIDGs as a voltage source behind an impedance. The VI-FCL was implemented as an additional control loop in the inverter control scheme to limit IIDG fault currents and achieve optimal protection coordination (OPC). Further, the VI-FCL is adaptively adjusted to enhance overcurrent protection sensitivity. A two-stage OPC algorithm for directional overcurrent relays (DOCRs) is developed. In Stage I, an optimal value for the adaptive VI-FCLs and relay currents are calculated. Stage II aims at obtaining optimal DOCRs settings. Time-domain simulations are used to demonstrate the effectiveness of the proposed adaptive VI-FCL and the accuracy of the proposed SCC algorithm. The proposed SCC algorithm and the OPC program are successfully validated using an islanded microgrid that is part of a Canadian distribution system.

Multi-objective Function Optimization for Locating and Sizing of Renewable Energy Sources and Energy Storages in Radial Distribution Networks with Digital Directional Overcurrent Relays and Digital Dual-setting Directional Overcurrent Relays

Multi-objective Function Optimization for Locating and Sizing of Renewable Energy Sources and Energy Storages in Radial Distribution Networks with Digital Directional Overcurrent Relays and Digital Dual-setting Directional Overcurrent Relays

An improved seagull optimization algorithm for optimal coordination of distance and directional over-current relays

In this paper, an improved bio-inspired optimization algorithm called Seagull Optimization Algorithm (ISOA) is proposed. ISOA is developed based on three techniques, these techniques use the collaborative optimization strategy, simulating new bird’s generation, and rearranging subgroups. The CEC2020 is utilized to obtain the role and importance of the improved algorithm. Furthermore, the ISOA is applied to find the optimal coordination of Distance and Directional Over-Current Relays (D&DOCRs). The problem of D&DOCRs coordination is more complicated and has numerous constraints. Hence, in this work, a developed object function (DOF) is proposed to set the Distance relays with minimum available settings. ISOA and DOF are tested on the IEEE 8-bus and IEEE 14-bus test systems. ISOA algorithm is used to coordinate the D&DOCRs in both the near and far ends of transmission lines. The results of test systems prove the effectiveness of ISOA to solve the coordination of D&DOCRs using the DOF.

Protection coordination of directional over current relay with distributed generation

The present &lt;span lang="EN-US"&gt;study is focussed on a comparative analysis of different meta-heuristic optimization approaches for directional overcurrent relay (DOCRs) coordination which has been discussed and presented in the literature. Further, to have a comparative analysis of the performance of the optimization methods discussed they have been tested on power system network of different sizes. To overcome such issues, this work proposed a simplex linear programming technique-based overcurrent relay method using general algebraic modelling system (GAMS). The execution of this work is done on the MATLAB 2018 a platform. Based on the obtained result the best meta-heuristic optimization method for mitigating the problem of relay coordination has been identified. Nevertheless, the operating time of the relay is high, so the fault is not corrected at a time. The developed model has been tested on test system of different sizes namely IEEE 9 bus and IEEE 14 bus system. The obtained values through series of simulation are compared with different methods for proving the proposed protection coordination scheme is more effective and efficient than others in terms of operating time and coordination time.&lt;/span&gt;

Optimal Relay Coordination for DG-Based Power System Using Standard and User-Defined Relay Characteristics

The operating time of directional overcurrent relays (DOCRs) can be reduced with user-defined relay characteristics considering plug setting (PS), time multiplier setting (TMS), and relay characteristic coefficients (λ and γ). This study presents a comparative analysis of relay coordination with standard and user-defined relay characteristics. The proposed relay coordination scheme is formulated as a non-linear constraint optimization problem. The grey wolf optimization (GWO) algorithm is used to determine the optimal relay settings and total operating time of DOCRs. The performance of the proposed scheme is tested on the standard 8-bus, 9-bus, and 15-bus systems. The results show that the total operating time of DOCRs with user-defined relay characteristics is better than that with standard relay characteristics. The results of the GWO algorithm are compared with the performance of optimization techniques used in literature to solve the relay coordination problem.

Koordinasi Adaptif DOCR Pada Sistem Transmisi Loop Multi Generator Menggunakan Modified Firefly Algorithm-Artificial Neural Network

Protection system is a very important component in the electric power distribution system. With good reliability, the distribution of electrical power will be better, one of which is by minimizing disruption to the system quickly, precisely and accurately. Components used in protection systems are directional overcurrent relays (DOCR). In this study proposed optimal and adaptive protection coordination using the Modified Firefly Algorithm-Artificial Neural Network (MFA-ANN) tested on the IEEE 9 real bus loop system with 4 generation combinations. Optimization using MFA will get the Time Delay Setting (TDS) and Ipickup (lowset) values. The ANN used is Backpropagation Lavenberg Marquardt (BPLM) After the BPLM learning process, we will get the weight and bias values of the training results and later as a reference value to get the value of TDS and Ipickup relay. The process will produce relay settings automatically based on the results of optimization and MFA-ANN training which are then simulated on the IEEE 9 bus loop system. The results achieved by MFA-ANN are suitable methods for modeling optimal and adaptive relay coordination systems. ANN training with the BPLM algorithm produces the smallest MSE value of 5.9308xE-10.

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.