The time of operation of overcurrent relays (OCRs) can be reduced, and at the same time, the coordination can be maintained, by selecting the optimum values of time multiplier setting (TMS) and plug setting (PS) of OCRs This paper presents hybrid genetic algorithm (GA) - nonlinear programming (NLP) approach for determination of optimum values of TMS and PS of OCRs GA has a drawback of, sometimes, converging to the values which may not be optimum, and NLP methods have a drawback of converging to local optimum values, if the initial choice is nearer to local optimum This paper proposes a hybrid method to overcome the drawback of GA and NLP method, and determine the optimum settings of OCRs The main contributions of this paper are - 1) systematic method for formulation of problem of determining optimum values of TMS and PS of OCRs in power distribution network as a constrained nonlinear optimization problem, 2) determining initial values of TMS and PS using GA technique and finding final (global optimum) values using NLP method, thus making use of the advantages of both methods (and at the same time overcoming the drawbacks of the methods)

Optimum Coordination of Directional Overcurrent Relays Using the Hybrid GA-NLP Approach

A new comprehensive genetic algorithm method for optimal overcurrent relays coordination

Optimal coordination of directional over-current relays using Teaching Learning-Based Optimization (TLBO) algorithm

In real power systems, the network topology is subjected to uncertainty due to single-line outage contingencies, maintenance activities, and network reconfigurations. These changes in the network topology may lead to miscoordination of directional overcurrent relays (DOCRs). To overcome this drawback, corresponding to each primary/backup relay pair, a set of inequality coordination constraints which is related to different network topologies should be satisfied. In this paper, a new approach based on the interval analysis is introduced to solve the DOCRs coordination problem considering uncertainty in the network topology. The basic idea is to convert the set of inequality constraints corresponding to each relay pair to an interval constraint. In this situation, the DOCR coordination problem is formulated as an interval linear programming (ILP) problem. Using well-known mathematical theorems, the obtained ILP problem, which has no equality constraints, can be converted to standard linear programming (LP). As a result, the number of coordination constraints is significantly reduced in the proposed methods. The application of the proposed method to the IEEE 14- and 30-bus test systems proves the ability of the interval method in modeling topology uncertainty in the large-scale coordination problem.

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Optimal Coordination of Directional Overcurrent Relays Considering Different Network Topologies Using Interval Linear Programming

Considerations of weight factors and far-end faults in the directional overcurrent relay coordination problem formulation do not affect the optimal solution. This paper investigates this viewpoint and verifies that indeed by such an approach the optimality is not lost. But, this study reveals that in doing so, the coordination quality is sacrificed to some extent. It is also observed that if all remaining valid constraints (after relaxing few constraints based on the back-up coordination philosophy and strength of fault level generated) are considered and if the objective function is changed to running sum of all violating constraints, all valid considered constraints are satisfied. This study is done by simultaneously optimizing all settings in nonlinear environment by Sequential Quadratic Programming method using Matlab Toolbox. The results of the analysis on a sample 6-bus and IEEE 30-bus systems are presented in this paper.

A new nonlinear directional overcurrent relay coordination technique, and banes and boons of near-end faults based approach

When two protective apparatus installed in series have characteristics, which provide a specified operating sequence, they are said to be coordinated or selective. The coordination of directional overcurrent relays poses serious problems in the modern complex power system networks, which are interconnected. Researchers have looked upon the problem of coordination from different considerations by making use of computer aids. Many efforts have been made to the automation of the coordination process in the area of relay coordination. This paper compiles the most of the significant developments in the area of time-overcurrent relay coordination using different techniques and methodologies. It is hoped that this work will be useful for future generation researchers to find the relevant references to advance the research work in future.

Time-Overcurrent Relay Coordination: A Review

This paper proposes to introduce additional constraints in the directional overcurrent relay coordination problem to tackle the sympathy trips. This paper attempts to tackle the sympathy trips in which other relay(s) in the system operate(s) earlier in the designated primary relay. The solution to this problem requires the inclusion of some additional constraints, making the coordination problem too complex. This paper proposes to solve the problem in two phases. In the first phase, the problem is solved by a normal coordination procedure and sympathy trips are identified. In the second phase, the proposed additional constraints are imposed only for the sympathy trips identified in the first phase. For the second phase, three approaches for including additional constraints were investigated. This paper includes results of the proposed algorithm for the IEEE 30-bus system. The results amply suggest that one of the three approaches of including additional constraints successfully tackled the problem of sympathy trip

An Approach to Tackle the Threat of Sympathy Trips in Directional Overcurrent Relay Coordination

Recently, using a non-linear programming method authors have demonstrated that based on certain criteria if some non-significant selectivity constraints are relaxed, all remaining constraints happen to be feasible but the solution of coordination problem is not possible with the conventional objective function as optimization procedure leaves the solution space [20]. In coordination studies solution with the conventional objective function provides minimum relay operating times. The present paper describes an additional criterion so that the solution with the conventional objective function can be achieved. This paper also achieves the acceptable speed of the primary protection while attempting to coordinate the maximum relay pairs. Complete results are presented in this paper in this regard. This paper uses the non-linear Random Search Technique to solve the coordination problem, which has been successfully applied in many problem areas.

Application of Random Search Technique in Directional Overcurrent Relay Coordination

This paper presents a new method using GADS Toolbox in MATLAB (A Genetic Algorithm Approach) to find the optimal solution of optimal power flow based transmission losses. Optimal power flow (OPF) is a key area of concern in electric industries. The basic OPF solution is obtained with objective function as production cost minimization while satisfying a set of system operating constraints. For reactive power optimization the OPF problem is formulated as minimization of system active power losses and improvement in voltage stability of the system. In this paper GA based optimal power flow solution is presented for IEEE 30-bus test power system with objective as transmission losses minimization and optimal results by GA are also compared with solution obtained by using Particle Swarm Optimization Technique.

Dinesh Birla

Papers

A new nonlinear directional overcurrent relay coordination technique, and banes and boons of near-end faults based approach

Time-Overcurrent Relay Coordination: A Review

An Approach to Tackle the Threat of Sympathy Trips in Directional Overcurrent Relay Coordination

Application of Random Search Technique in Directional Overcurrent Relay Coordination

A New Attempt to Optimize Optimal Power Flow Based Transmission Losses Using Genetic Algorithm