A new formulation for coordination of directional overcurrent relays in interconnected networks

Abstract

Summary In large and interconnected networks, the coordination between all protective devices, without any violation, is very complicated and sometimes impossible. For obtaining reasonable and optimal coordination with suitable operating time (OT) for relays, some constraints are obliged to violation. In order to reduce the related violation and also the relays OTs, some objective functions (OFs) are proposed in literatures in which the discrimination times of the primary and backup relays is added to the OF. In this paper, for obtaining the optimal coordination of directional overcurrent relays, the OF is improved to overcome the drawbacks of the existing OF. In other words, as the main contribution, a new problem formulation is proposed so that not only the optimal settings of relays are obtained but also the OTs of the primary and specially backup relays are reduced considerably. In order to solve the proposed problem formulation, the effects of both near and far‐end faults are considered. Also, regarding the protection system flexibility, the program is capable of choosing the best characteristic for each overcurrent relay. The genetic algorithm is used as an optimization tool, and the effectiveness of the proposed method is demonstrated by comparing the coordination results for the two sample networks with those obtained by using the recent developed OFs. Copyright © 2013 John Wiley & Sons, Ltd.

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

“…The single line diagram of the 9‐bus meshed network system is revealed in Figure , and the system data are given in several studies . The system consists of 12 lines, 24 relays, and 32 experiments of primary‐backup relay pairs.…”

“…Therefore, it can be concluded that relays nos. 17, 19, 21, and 23 have no backup for such faults . In other words, one can say that relays nos.…”

“…These variables are considered to define scenario 1 (ie, number of control variables is equal to 72) and T min equals 0.10 s. On the other hand, in scenario 2, the used curve for all relays is NI while optimizing the TD, and I P for each relay (ie, number of control variables is equal to 48). Then scenario 3 is made for further verification of the proposed algorithm, where the 3‐phase short circuit faults are considered near to the relays (near‐end faults) and the fault currents are described in . The same design variables and constraints are applied similar to scenario 2 (ie, the type of time‐current characteristics of the relay is fixed at NI curve).…”

“…In other words, the primary protection schemes should perform fast and efficiently. However, when it fails, the backup relay should take the action after predefined coordination time margin (CTM) . Coordination or alternatively named selectivity is classified into (i) absolute selective and (ii) relative selective .…”

“…Promising alternative solutions to tackle the difficulties and drawbacks of the conventional methods are the applications of heuristic‐based optimization procedures, with the understanding that the relay coordination plans are formulated as an optimization problem with various complexity and nonlinearity, which can be solved using the application of heuristic‐based algorithms. Among these heuristic‐based computing algorithms are genetic algorithm (GA), ant colony algorithm, various variants of differential evolution (DE) algorithm, firefly algorithm, teaching learning optimization algorithm, artificial bees colony, flower pollination algorithm (FPA), symbiotic organism search optimization, and many more, which have been attempted to solve the relay coordination problems under various network topologies. In the study of Alam et al, 5 meta‐heuristic optimization methods are considered to solve the optimal relay coordination with comprehensive comparisons of their performances.…”