Optimization procedure for time setting/coordination of relays

Abstract

This paper deals with time setting/coordination for overcurrent relays in radial/weakly meshed medium voltage distribution networks. Existing procedure based on simplex method provides setting/coordination for relays with continual adjustment. In order to provide setting/coordination for relays with discrete adjustment as well, some improvements are suggested in the paper. The improvement consists of introducing mixed integer method in procedure for time setting/coordination. In such a way, relays with continual/discrete adjustment can be considered. However, application of mixed integer method is generally connected with low efficiency of calculation and its direct application in large size networks can result in convergence problems and significant time consuming. In order to overcome shortcomings of the method, in the paper is introduced a solution based on splitting of one large size problem into more smaller ones. Such solution provides high efficiency and application of setting/coordination procedure for real size networks. Consideration is supported by an appropriate example.