Getachew, Bekele (PhD)Gebrekrstos, Abraha2020-11-262023-11-282020-11-262023-11-282020-01http://etd.aau.edu.et/handle/12345678/23597Expansion planning of a distribution network answers to be mounted the services, so that the distribution network fulfills the predicted load requirement to satisfy all operational and technical constraints. Integration of distributed generations (DG) which have economical and technical benefits such as reduction in losses, improving voltage profile, reduction line loading and provides good voltage stability. This thesis mainly investigates expansion planning of Adwa distribution substation with analytical voltage sensitivity index methods to facilitate the integration of distributed generation DG into the distribution network. The results of DG are presented to determine the appropriate places and the capacity to make the distribution network highly reliable service. The feeder was selected due to its lowest voltage sensitivity index from the other feeders and due to its highest power interruption when it is compared with other outgoing feeder for the one year recorded data. In addition, the outgoing feeder KO1 at bus 50 have the least tail end nodal voltage sensitivity index of 0.002210 when it is compared with the other bus. Appropriate places are selected for the DG and their ratings are determined due to the principle of minimum system power loss. The power capacity of DG for feeder KO1 is found to be 12.70 MW and 3.30 MW as a reserve at bus 50 and the capacity of DG increases with demand growth at each year. The peak load demand forecasting for ten years for Adwa distribution substation is carried out using least squares extrapolation technique. The peak power demand reaches 75.31MW after 10 year and the load growth it increases by 7.07 present at each year. Moreover, due to presence of DG placement in the distribution network, it implements and coordinates eleven fast protection relays based on magnitude of the fault current and fault tripping time in the line. In order to reduce the impact of DG on the protection device when the capacity of DG highly increase with demand it upgrades the margin of both current and time interval of the relay. Finally, the voltage profile, voltage stability and power loss of Adwa distribution substation are compared with and without DG integration to meet the current demands as well as when the DG capacity increases to supply the increasing future demand. It is found that without DG integration, the voltage profile lies within a limit of 0.866 – 1.0 p.u while the DG integration provides an improved voltage profile within 0.974 – 1.0 p.u. It is further observed that DG integration provides an improved voltage stability and reduces the active and reactive power loss by 94.67% and 95.59%, respectively as compared to those without DG integration. Furthermore, when the DG capacity increases with increasing demand, it has positive technical benefits such as voltage profile improvement, reduction in active and reactive power losses as well as line loading. The simulation results further demonstrate successful implementation and coordination of fast protection relays. Also, the fast protection relays are successfully upgraded when the capacity of DG increases with increasing demand.en-USDistribution network expansion planningDistributed generationcoordination of relaysThesis