Integration of Distributed Generation with Distribution Network Expansion Planning (Case Study: Adwa Distribution Substation)
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Date
2020-01
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Addis Ababa University
Abstract
Expansion 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.
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Keywords
Distribution network expansion planning, Distributed generation, coordination of relays