الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 142 |  |  |
| | | from | 142 | | |
Abstract
Traditional electric distribution systems are radial in nature which
has initially been built for simple one way power delivery, an easy
protection strategy is usually, implemented using over-current relays, fuses,and reclosers that are coordinated with each other is been used. So that the device nears the fault will clear the fault first and minimize the duration
and extent of interruptions. It is so automated to safely clear faults and get
customers backing service as quickly as possible.Recent developments in energy policies and prices have directed an
increasing amount of interest at exploiting small energy resources which is commonly known as distributed generation (DG), in general, a DG provide several benefits to social and distribution network, i.e. additional
generation resources, voltage regulation, loss reduction. However, the DG does increase fault levels in the distribution system, change network radial configuration. Consequently, it has influence on existing protection
systems. It is true that protective devices may need to be changed or have
new settings. However, this requires large investment, and cannot be
established in a short period.
Normally, reclosers and fuses are coordinated based on the fuse
saving principle, where reclosers are responsible to clear temporary faults
while fuses are used to clear permanent faults. Reclosers and fuses are
initially selected to achieve the required coordination sequence, knowing
that the only current source is the substation current which makes the
current in both devices to be nearly the same at fault conditions. After
penetration of DG in distribution networks, the current flow will be due to the contribution of the substation current and the DG current, this makes
the current in reclosers and fuses to be no more the same leading to a
probable miscoordination between both devices. Finally, this might lead to
the large damage in system and the decrease in system reliability.
This study presents a methodology keeping all existing protective
devices operate normally and unchanged by determine the optimal
allocation of a DG to be connected to a medium voltage distribution feeder
such that coordination failure of the existing system protection will be
avoided. Additionally, it also takes into account other key criteria, i.e.
power loss and system voltage requirement which should be maintained
within a specific range.