Relay Coordination Problem Research Articles

A Novel Protection Scheme for Solar Photovoltaic Generator Connected Networks Using Hybrid Harmony Search Algorithm-Bollinger Bands Approach

This paper introduces a new protection system for solar photovoltaic generator (SPVG)-connected networks. The system is a combination of voltage-restrained overcurrent relays (VROCRs) and directional overcurrent relays (DOCRs). The DOCRs are implemented to sense high fault current on the grid side, and VROCRs are deployed to sense low fault current supplied by the SPVG. Furthermore, a novel challenge for the optimal coordination of DOCRs-DOCRs and DOCRs-VROCRs is formulated. Due to the inclusion of additional constraints of VROCR, the relay coordination problem becomes more complicated. To solve this complex problem, a hybrid Harmony Search Algorithm-Bollinger Bands (HSA-BB) method is proposed. Also, the lower and upper bands in BB are dynamically adjusted with the generation number to assist the HSA in the exploration and exploitation stages. The proposed method is implemented on three different SPVG-connected networks. To exhibit the effectiveness of the proposed method, the obtained results are compared with the genetic algorithm (GA), particle swarm optimization (PSO), cuckoo search algorithm (CSA), HSA and hybrid GA-nonlinear programming (GA-NLP) method. Also, the superiority of the proposed method is evaluated using descriptive and nonparametric statistical tests.

Adaptive Protection Strategy in a Microgrid Under Disparate Operating Modes

—Microgrids usually operate in grid-connected or islanded mode. Due to substantial variation in fault current, same protection coordination scheme cannot be applied in both modes. Moreover, network topology keeps on changing due to momentary events. In this paper, an adaptive protection strategy is proposed to avoid any miscoordination between numerical directional overcurrent relays under a fault instance. Through this scheme, the relay settings can be updated online as per the operating mode and prevailing topology. The proposed tactic employs a central protection center with data storage and programming capability, smart electronic devices and communication channels to acquire and transfer real-time data. The relay coordination problem is formulated as a non-linear optimization function, with coordination time interval constraints. The optimal relay settings under both operating modes are obtained through non-linear programming and hybrid genetic algorithm non-linear programming method. To handle contingencies of communication channel failure, a novel inclusive mode settings are also introduced to protect the system in both modes even with line or DG outages. The proposed adaptive approach is tested on a nine bus radial distribution system with DGs. It has been found that the proposed scheme provides reliable system protection under different operating scenario.

The Comparison of Lately Proposed Harris Hawks Optimization and Jaya Optimization in Solving Directional Overcurrent Relays Coordination Problem

In this paper, a lately proposed Harris Hawks Optimizer (HHO) is used to solve the directional overcurrent relays (DOCRs) coordination problem. To the best of the authors’ knowledge, this is the first time HHO is being used in the DOCRs coordination problem. The main inspiration of HHO is the cooperative behavior and chasing style of Harris’ hawks from different directions, based on the dynamic nature of scenarios and escaping patterns of the prey. To test its performances in solving the DOCRs coordination problem, it is adopted in 3-bus, 4-bus, 8-bus, and 9-bus systems, which are formulated by three kinds of optimization models as linear programming (LP), nonlinear programming (NLP), and mixed integer nonlinear programming (MINLP), according to the nature of the design variables. Meanwhile, another lately proposed optimization algorithm named Jaya is also adopted to solve the same problem, and the results are compared with HHO in aspects of objective function value, convergence rate, robustness, and computation efficiency. The comparisons show that the robustness and consistency of HHO is relatively better than Jaya, while Jaya provides faster convergence rate with less CPU time and occasionally more competitive objective function value than HHO.

Smart Protection Scheme For Radial Distribution System

In this paper,the study of optimal coordination of directional overcurrent relays along with relay communication in HV substations is proposed. The relay coordination problem is non linear.It typically consist of two groups of control variables(Time Dial Settings:TDS and Plug Settings:PS). The purpose of relay coordination is to propose the suitable settings for all releases and ensure the coordination. The differential evolution is employed to solve for solutions of optimal relay coordination. The relay coordination is mainly done to improve selectivity of the relay to particular fault. ETAP is so popular for its capability for modelling of power system networks and analyzing various studies and Real Time simulations.

A Robust Protection Scheme Based on Hybrid Pick-Up and Optimal Hierarchy Selection of Relays in the Variable DGs-Distribution System

The increasing proliferation of distributed generators (DGs) demands a robust and comprehensive design of the communication-based adaptive protection scheme, which must be able to not only deal with the known changes in the DGs-distribution system but also handle the unknown changes due to variations in the operating mode, network configuration, and number, type, and size of DGs. On one side, with the increasing installations of DGs, the deployment of the communication system in protection is increasing to monitor the system status and select the relays’ settings accordingly. However, on the other side, if information flow does not happen due to the presence of pre-fault failure of the relay-agents and/or communication links, a protection scheme may fail to provide the suitable protection. This paper proposes a centralized adaptive protection scheme to deal with such failures and varying operating conditions. It provides optimal relays settings for varying operating conditions of the DGs-distribution system with the aim of providing fast, comprehensive, and self-adaptive protection. In order to achieve these objectives, two algorithms have been developed: the first algorithm determines optimal hybrid pick-up settings of the relays, and the second algorithm determines the adaptive hierarchies of the relays. With the inclusion of these two algorithms, the relay coordination problem has been formalized linearly. The performance of the proposed scheme has been tested and validated for various known and unknown events with different types of short circuit faults of different fault impedances on the 37-bus IEEE test distribution system in a MATLAB simulation and coding environment. The results show that the proposed method not only provides the optimal relay's coordination in varying situations but also effectively reduces the protection latency due to pre-fault failures of the relays and communication links, and low level of fault currents.

A New Mixed Integer Linear Programming Formulation for Protection Relay Coordination Using Disjunctive Inequalities

Numerical optimization-based solution to directional overcurrent relay (DOCR) coordination problem has been a widely addressed research problem in the recent past. Many linear (LP), nonlinear (NLP), mixed integer nonlinear (MINLP), mixed integer linear (MILP), and quadratically constrained quadratic programming (QCQP)-based formulations have been presented in the past literature. This paper proposes a new MILP-based formulation using disjunctive inequalities. The nonlinear DOCR protection coordination model is formulated as MILP by linearizing the bilinear terms existing in the original formulation. One of the variables in each bilinear term is discretized over its interval into a fixed number of steps. After assigning binary variables to each discrete interval, the resulting bilinear terms with binary variables are written in terms of disjunctive inequalities. The results have shown that the proposed MILP formulation fetch better optimal solutions compared with past MILP and MINLP formulations. The MILP problem is programmed in GAMS package with CPLEX solver and tested on standard 3 bus, 9 bus, 15 bus, and 30 bus systems and results are found to be satisfactory.

A Novel Convexified Linear Program for Coordination of Directional Overcurrent Relays

A novel convexified linear program for optimal directional overcurrent relay (DOCR) coordination problem (CP) is proposed in this letter. The DOCR CP is a highly constrained nonlinear nonconvex problem which was solved using various traditional and heuristic optimization techniques in the past. In this letter, the CP is formulated as a linear programming problem without fixing the current pickup settings of DOCRs. The bilinear terms in the proposed formulation are written in the form of linear inequalities using McCormick envelopes. A sequential tightening algorithm is used to update the boundary limits of each parameter based on the solution obtained in each iteration, thus tightening the convex hulls and leading to solutions near to global optimum. The performance of the proposed method is applied to various test systems among which the results of three bus test system are presented.

Application of improved invasive weed optimization technique for optimally setting directional overcurrent relays in power systems

This paper aims to study the application of a heuristic optimization technique namely, Invasive Weed Optimization (IWO) technique for optimal protection coordination in power systems. The optimal relay coordination problem is formulated as a nonlinear constrained optimization, which is solved using Improved IWO (IIWO). The proposed IIWO algorithm modifies the standard deviation expression of the weed population. The simulation results show that IIWO has faster and better convergence compared with standard IWO. To further improve the computational efficiency, a hybrid IIWO method is also proposed which is obtained by defining sequential quadratic programming (SQP) as a subroutine in IIWO for searching local solutions, thus eliminate weaker weeds in the colonization process. The proposed techniques are tested on both the 9-bus test system and IEEE- 30 bus systems and the performance is compared. Relay coordination algorithm is developed in MATLAB, and the results are found to be effective and reliable.

Interphase Fault Relaying Scheme to Mitigate Sympathetic Tripping in Meshed Distribution System

In a distribution system when fault occurs, prior operation of any other relay which is not designated as the primary relay causes undesired shedding of a healthy line. This phenomena of unwanted relay operation is termed as sympathetic tripping. For appropriate relay operation, issue of sympathetic tripping is required to be considered while addressing relay coordination problem. This paper proposes a phase fault protection scheme, which mitigates the issue of sympathetic tripping in the meshed network. The undesired relay operation in the network is restricted by imposing some additional constraints on the conventional relay coordination problem. The proposed nonlinear optimization problem is solved by using Shannon–Wiener differential evolution algorithm. Procured optimal relay settings will provide efficient protection against each phase fault without causing sympathetic tripping. The efficacy of the proposed algorithm is examined on modified IEEE-8-bus system, IEEE-14-bus system, and IEEE-30-bus system. The obtained results are verified by using GE Mutilin, model-750/760 overcurrent relay in ETAP (industrial simulation software).

A Novel Constraints Reduction-Based Optimal Relay Coordination Method Considering Variable Operational Status of Distribution System With DGs

One of the factors that affect the level of fault currents is the number of short-circuit MVA sources present during the fault. A distribution system with distributed generators (DGs) is a multi-source system, in which DGs can be connected or disconnected to meet the high or low load requirements respectively. Also, during fault conditions, DGs can get disconnected due to their low fault ride-through capabilities. These changes in connections change the number of DGs and the operational status of the system, which in turn change the fault currents seen by relays and the ranges of maximum and minimum fault currents for which the relays settings work coordinately. This paper realizes that an increase in the proliferation of DGs makes the relay coordination problem a highly constrained optimization problem, and changes in the number of DGs make the problem more complex, which can decelerate the overall performance of relays. The aim of this paper is to reduce the complexity and design a fast, robust, and adaptive protection scheme which can efficiently work in the variable environment of the DG-distribution system. This paper proposes a novel constraints reduction-based relay coordination method which selects a small set of constraints out of large set of constraints while determining the optimal relays settings. The relay coordination problem is formulated as a linear programming problem. The performance of the proposed method is tested on the both configurations, radial and meshed, of the IEEE 38-bus distribution system. Comparative studies have been conducted to highlight the advantages of the proposed approach under changing system’s configuration with variable locations and sizes of DGs.

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.

Oppositional Jaya Algorithm With Distance-Adaptive Coefficient in Solving Directional Over Current Relays Coordination Problem

The model of directional over current relays (DOCRs) coordination is considered as an optimization problem. It is generally formulated as linear programming (LP), non-linear programming (NLP) and mixed integer non-linear programming (MINLP), according to the nature of the design variables. For each kind of formulation, the main goal is to minimize the summation of operating times of primary relays, by setting optimal values for decision variables as time dial setting (TDS) and pickup current setting (IP) or plug setting (PS). In this paper, we proposed an oppositional Jaya (OJaya) algorithm with distance-adaptive coefficient (DAC), to effectively solve the DOCRs coordination problem. Firstly, by oppositional learning (OL), the searching space of Jaya is expanded and the diversity of its population is strengthened; secondly, by DAC, the population's trends of running towards the best position and escaping from the worst position is accelerated. The performance of OJaya is evaluated by 3-bus, 8-bus, 9-bus and 15-bus testing systems, in aspects of convergence rate, objective function value, robustness and computation efficiency. The results indicate the effectiveness and superiority of OJaya in solving DOCRs coordination problems compared with standard Jaya.

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.

Optimal Overcurrent Relays Coordination using an Improved Grey Wolf Optimizer

Recently, nature inspired algorithms (NIA) have been implemented to various fields of optimization problems. In this paper, the implementation of NIA is reported to solve the overcurrent relay coordination problem. The purpose is to find the optimal value of the Time Multiplier Setting (TMS) and Plug Setting (PS) in order to minimize the primary relays’ operating time at the near end fault. The optimization is performed using the Improved Grey Wolf Optimization (IGWO) algorithm. Some modifications to the original GWO have been made to improve the candidate’s exploration ability. Comprehensive simulation studies have been performed to demonstrate the reliability and efficiency of the proposed modification technique compared to the conventional GWO and some well-known algorithms. The generated results have confirmed the proposed IGWO is able to optimize the objective function of the overcurrent relay coordination problem.

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.

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.

Coordination of directional overcurrent relays in the interconnected power systems using effective tuning of harmony search algorithm

In the optimum coordination of Directional Overcurrent Relays (DOCRs), the appropriate relay settings, namely, Plug Setting (PS) and Time Multiplier Setting (TMS), are selected to minimize the operating time of relays subject to various coordination and boundary constraints. In the large interconnected power systems, the key issue with DOCRs protection is to achieve correct relay coordination with satisfying all coordination constraints. In this paper, the parameters of Harmony Search Algorithm (HSA) are tuned to effectively solve the relay coordination problem on five different test cases. Also, the relay coordination problem is formulated as Linear Programming Problem (LPP), Non-linear Programming Problem (NLPP) and Mixed-Integer non-linear programming Problem (MINLPP). In addition, the superiority of proposed method is demonstrated by comparing the obtained results with those obtained by the Genetic Algorithm (GA), hybrid GA-Nonlinear Programming (GA-NLP), Firefly Algorithm (FFA), and Cuckoo Search Algorithm (CSA).

Enhanced differential evolution algorithm for coordination of directional overcurrent relays

This paper presents an enhanced differential evolution algorithm (DE) for solving the directional overcurrent relay (DOCR) coordination problem. Comparisons among different versions of DE for coordination of DOCRs in larger and interconnected power systems are presented. The evaluation criteria consist of fitness value, number of violation and standard deviation. The outstanding DE algorithm has been enhanced in four aspects: dial reduction scheme, elitism and mediocrity scheme, mutation index renew scheme, and population reduction scheme. The enhanced-DE (eDE) shown best result in terms of execution time, result quality, robustness and convergence ability compared to the others analyzed in this research. The IEEE 14 and 57 bus systems are used to validate the proposed algorithm. A significant comparison result between eDE and DE on the IEEE 57 bus network are: execution time in seconds 364 vs. 2040, fitness value 1.933 vs. 7.91, and standard deviation of fitness value 0.018 vs. 5.52. Results are averaged values in 50 runs.

Sympathetic Trippings Blocking in Over Current Relay Coordination Algorithm during Steady State & Transient Network Topologies

Abstract In this paper an improved over current relay coordination protection technique is proposed. The proposed technique eliminates the sympathetic/nuisance tripping in an interconnected distribution system. Nuisance trippings are eliminated by incorporating the additional selectivity constraints in conventional over current relay coordination problem. Whenever the fault is cleared only from one end of the line in bidirectional fault feed lines, transient network configuration comes into existence. Transient network configuration causes the redistribution of fault in the distribution system and leads to further nuisance tripping of relays. This problem in this paper is solved by minimising the operating time gap between primary relays located at near end and far end of a faulty line to the best minimum possible value. The differential search algorithm is applied for optimization of highly non-linear over current relay coordination problem in this paper. The result presented in this paper shows that the proposed over current relay coordination technique is immune against the sympathetic/nuisance tripping and operating time difference between primary relays at near end and far end is also minimised within acceptable time margin successfully.

Optimum Coordination of Directional Overcurrent Relays Using Modified Adaptive Teaching Learning Based Optimization Algorithm

Relay coordination problem is highly constrained optimization problem. Heuristic techniques are often used to solve optimization problem. These techniques have a drawback of converging to a non-optimum solution due to the wide range of design variables. On the other hand, initial solution becomes difficult to find with shorter range of design variables. This paper presents modified adaptive teaching learning based optimization algorithm to overcome this drawback of conventional heuristic techniques. The coordination problem is formulated as a constrained non-linear optimization problem to determine the optimum solution for the time multiplier setting (TMS) and plug setting (PS) of DOCRs. Initial solution for TMS is heuristically obtained with the commonly chosen widest range for TMS values. The upper bound of TMS range then substituted by the maximum TMS value in the first initial solution. The new upper limit is obviously lower than the earlier one. Next phase of optimization is carried out with the new range of TMS for the pre-determined iterations of teacher phase. Consequent to the completion of the teacher phase, new upper bound is obtained from the available solution and optimization is carried out for the pre-determined iterations of learner phase. This process is repeated to get the optimum solution. Fixed range for PS is used to obtain the selectivity. Such a strategy of iteratively updating the upper bound of TMS range shows remarkable improvement over the techniques which employ fixed TMS range. This algorithm is tested on different networks and has been found more effective. Four case studies have been presented here to show the effectiveness of the proposed algorithm. The impact of distributed generation (DG) and application of superconducting fault current limiter to mitigate DG impact is presented in case study—III.