Treffer: A new iterative linear programming approach to find optimal protective relay settings.

Summary: This paper aims to present a new linearization approach to finding the optimal protective relay settings in power systems. The traditional protective relay coordination problem (CP) involving directional overcurrent relays (OcRs) is a nonconvex, nonlinear constrained optimization problem that is widely addressed in the literature. In linear programming (LP) based solution methods, the current plug settings (CPS) are fixed, and the time dial settings (TDS) are found, which though reasonably adequate but do not fetch the global solution. In nonlinear programming (NLP), both TDS and CPS are deemed to be decision variables, but NLP requires a proper initial‐point to get the best optimal solution. In this paper, the nonconvexity in CP formulation is convexified using bilinear relaxations, and global optimum is obtained. It is done by writing each bilinear term in CP formulation as a set of four linear inequalities using McCormick envelopes, and the error generated due to the linear approximations is reduced iteratively by updating the variable bounds. The proposed approach is programmed in MATLAB coding platform, and theoretical validation has been performed. The proposed approach has the advantages of being independent of initial‐point and attain the global optimum without the help of global optimization solvers. [ABSTRACT FROM AUTHOR]

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