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In this paper in order to determine the abilities and limitations of each random search algorithm for solving overcurrent (O/C) relay coordination problem, a comprehensive comparison is made. The algorithms which are chosen for the comparison are; Genetic Algorithm (GA), Particle Swarm Optimization (PSO), Immune Genetic Algorithm (IGA) and some two two step mentioned algorithms. The convergence speed and convergence reliability have been compared. Variation of convergence speed and the number of points that each algorithm explore to reach global optimum point have been also investigated. To consider equal condition, all of the algorithms programs have been run in same computer (Pentium III 3.0 GHz). Important and effective parameters of algorithms such as population size and initial populations range in the algorithms have been assumed identical. The algorithms abilities have been tested on two case studies, namely the 8 bus distribution network and 8 buss transmission systems. It will be shown that solving the coordination problem using some of the two step methods such as IGA-GA can be faster than the others. From reliability of convergence viewpoint PSO have had best performance. Success of other algorithms in this problem solving, from various aspects have been ranked. [ABSTRACT FROM AUTHOR]

In interconnected networks, it is impossible to satisfy all coordination constraints. Some methods have been proposed in the literature to determine the minimum break point set (MBPS) before the coordination procedure. In this paper, a new method is presented which coordinates overcurrent relays and simultaneously determines minimum unsatisfied constraints as broken constraints (BCs). For the implementation of this method, a new objective function (OF) is defined that also includes constraints with various weightings. These weightings determine the priority of constraints for being satisfied which are obtained by means of some expert rules. The expert rules of previous papers are modified and weighted to determine the priority of constraints. The genetic algorithm is used to optimize the OF that has an internal feedback for determining the minimum BCs considering coordination criterion. The effectiveness of the proposed technique is demonstrated by comparing the results of two sample networks with those obtained by using the recently developed techniques. [ABSTRACT FROM AUTHOR]

Abstract: Protection system failure is the main cause of cascading outages. It has been shown that the hidden failures lead to cascading outages. However, the effects of the coordination method as well as the hidden failure of the protection systems have not been investigated yet. In this paper, an algorithm based on sequential Monte Carlo simulation is proposed to find the reliability indices for different overcurrent relay coordination methods. The proposed algorithm is applied to the results of different relay coordination methods of a real network. The indices SAIFI, CAIDI, CAIFI and ENS for the results of different relay coordination methods are obtained strictly based on the contribution of the protection failure issues. Then, a comparison is made between the results of the different relay coordination methods in order to show how the coordination methods affect the reliability indices. [Copyright &y& Elsevier]

Abstract: This paper presents a method to reduce the number of constraints and detect those that make the optimization of overcurrent relay settings to be infeasible. By reducing the number of constraints, the feasibility of the optimization is increased and the run-time of the program is decreased. It should be noted that, in the optimal coordination methods, the operating times of the relays are minimized in the frame of the objective function subjects to the so-called coordination constraints. However, a new method for optimum coordination of protective relays based on only constraints has been developed by authors of the paper. The pre-processing reduction constraints method introduced in this paper can be used for any optimal coordination of overcurrent relays. The new method is supported by results obtained from a typical test network and a real power system network. [Copyright &y& Elsevier]

In this paper, a new method for optimum coordination of overcurrent relays is proposed. The proposed method is based on only constraints. Minimization is inherently included by setting the time dials to minimum and increasing their values gradually. Configuration changes of the network is taken into account. The method does not need any initial solution. It can consider both linear and nonlinear relay characteristics models. The optimal settings of overcurrent relays for 8-Bus and England Norweb networks are obtained and comparison between the new method and existing methods is made. [ABSTRACT FROM AUTHOR]