Determining Optimum Time Multiplier Setting and Plug Setting of Overcurrent Relays using Continuous Genetic Algorithm

Overcurrent relays (OCRs) are the major protection devices in a power distribution system. To reduce the power outages, mal-operation of the backup relays should be avoided, and therefore, OCR coordination in power distribution network is of great importance. The time of operation of OCRs can be reduced, and at the same time the coordination can be maintained, by selecting the optimum values of Time Multiplier Setting (TMS) of OCRs. Instead of keeping the value of plug setting (PS) as fixed (while determining the optimum value of TMS), it is also possible to select the optimum values of both TMS and PS, which can further reduce the time of operation of OCRs.

The main contributions of this paper are – 1) systematic method for formulation of problem of determining optimum values of TMS and PS of OCRs in power distribution network as a constrained nonlinear optimization problem, 2) converting the problem into an unconstrained optimization problem, making use of the penalty method, and 3) applying Continuous Genetic Algorithm (CGA) technique to get the optimum solution of this problem.