Abstract
This article proposes the optimal coordination problem of protective relays within a hybrid optimisation framework which is presented based on integer coded genetic algorithm (ICGA) and non-linear programming (NLP). The optimal coordination problem of directional overcurrent relays (DOCRs) is implemented while aimed at finding the optimal plug setting multiplier (PSM) and time dial setting (TDS). In this respect, PSM is a function of the current transformer (CT) size and the tap of the relay which is discrete in nature. TDS is a function of the operating time of the relay for different short-circuit currents at different locations of the system. Here, the variables of the problem are decomposed into continuous and discrete variables. The first stage of the problem uses the ICGA to determine the size of CTs considering the permitted tap of relays while the second stage utilises the NLP method to evaluate the feasibility and optimality. The presented framework is then simulated on an 8-bus test system. The obtained results verify the effectiveness and the applicability of the optimisation technique to find the optimal settings of DOCRs.
Highlights
Using overcurrent relays are of the most primary methods to detect and isolate the faulty areas in power systems
Ref. [25] has utilized Genetic Algorithm (GA) together with linear programming (LP) known as GA-LP and Ref. [26] has adopted GA along with non-linear programming known as GA-NLP to solve the coordination problem of directional overcurrent relays (DOCRs)
An optimization framework has been developed in [27] using biogeography based optimization (BBO) together with a novel hybrid BBO combined with LP known as BBO-LP to solve the coordination problem of DOCRs
Summary
Using overcurrent relays are of the most primary methods to detect and isolate the faulty areas in power systems. PSM is obtained experimentally with respect to the load current and the fault current in linear programming techniques In such methods, TDS is the only variable which its optimal value is derived with respect to the coordination constraints of the primary and backup relays, i.e. CTI [1,2,3,4,5,6]. Some research works have utilized hybrid techniques to solve the coordination problem of DOCRs. For instance, Ref. In this respect, the ICGA is employed to determine the current setting (PSM) of the relay which is an optimization problem with discrete variables. The detailed descriptions of the ICGA method and the decomposition technique are described in the following
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