Determining optimum TMS and PS of overcurrent relays using linear programming technique

The time of operation of overcurrent relays (OCRs) can be reduced, and at the same time, coordination can be maintained, by selecting the optimum values of time multiplier setting (TMS) and plug setting (PS) of OCRs. This paper presents formulation of the problem of determining optimum values of TMS and PS of OCRs as a constrained nonlinear optimization problem. It is proposed to solve the nonlinear programming problem (NLP), using the techniques used for solving linear programming problem (LPP). Four linear programming (LP) techniques, namely, revised simplex, dual simplex, two phase simplex and Big-M methods have been used for determining optimum values of TMS and PS of OCRs, and their comparison is presented.