The nature characteristic in conventional distribution networks is radial by single source supplying a downstream network. The interest about the environmental impacts and development in technologies have led to increase distributed generation (DG) interconnected in distribution networks. Protective device coordination will be affected by adding DGs to the existing network through participating to the change in direction of power flow and fault current values and direction which cause loss in settings and mis-coordination for protective devices, especially over current relays.
The effect of DG on coordination depend upon number, location and size of DG, so in this work, the Particle Swarm Optimization (PSO) technicality utilization to locate optimal location and sizeof DG to obtain minimum active power losses.The Time Current Characteristic (TCC) curves represented which depended on the over current protection relays parameters to find settings and limited any loss in it, in order to reset these relays to obtained the proper operation without intersections in time of operation and satisfy optimal coordination between primary and pack up over current protection relays.
In this work two soft wares are used, the first is Matlab R2014a for implementation of the PSO algorithm while the second software is CYMDist program for load flow analysis, short circuit current calculation and protection coordination device analysis. To verify the developed algorithm parts from Iraqi distribution network (Baghdad Al-Rusafa 33KV distribution networks). So, used two DG units with total capacity 50MW distributed in 33kV of South Al-Rusafa distribution network which represented about 9.4% from the total load of this network 533.5MW, the total active power losses reduced from 11.597MW to 6.658MW with losses reduction 6.96MW about 43% from total losses.