Reducing the impact of DG in distribution networks protection using fault current limiters

The connecting of distributed generation (DG) to distribution network has numerous advantages. However, the presence of these sources leads distribution networks to lose their radial nature. Some problems in coordination of protection devices will occur, due to changes in short circuit levels in different points. In this paper, the effect of size and location of DGs on overcurrent relay coordination has been investigated. The use of fault current limiter (FCL) is proposed to limit fault current levels and effect of DGs on coordination of overcurrent relay during the fault. The procedure of selecting of FCL impedance type and its size is presented to restore the effective coordination of overcurrent relays. The efficiency of the proposed technique is demonstrated by comparing the results of a typical network with those obtained using the previous techniques.