Short circuit analysis and adaptive zonal protection of distribution system with distributed generators

Grid integration of Distributed Generation (DG) is considerably increasing in recent days in order to meet the ever increasing electricity demand and to reserve the fossil fuel resources. DG is expected to play an important role in modern electric power system in near future due to the support offered by current political policies and global environmental issues. Besides a lot of benefits offered by DG, it may cause negative impacts on the distribution network. The injected currents of DGs to a distribution network lead to not having a radial network anymore, and consequently network faces an inefficient protection system that was formerly designed according to the existing philosophy behind the distribution network. In the present work, an adaptive zonal protection scheme is suggested for distribution network with DG. The distribution network is divided into several zones with the help of boundary circuit breakers. The operation of these circuit breakers are monitored and controlled by the control center. The analysis is carried out in an 11 kV, 25-bus radial distribution network and the results are discussed.