Optimal Adaptive Protection Coordination with Inter-Trips and Setting Groups for Meshed Distribution Grids

Abstract

Increasing distributed generations (DGs) penetration and their plug & play operation challenge the protection coordination of distribution networks due to variable fault current levels. Adaptive protection schemes as a great solution are used to cope with DGs connection status, where the DGs statuses are transmitted to relays via communication links to activate the appropriate Setting Groups (SGs). In this paper, a new hybrid protection scheme is introduced where it is composed of relays with SGs and inter-trip links to develop more sensitive adaptive protection. In the first stage, a sensitivity index is introduced to find the critical constraints and form a set of candidate relays. Then, a new method is proposed to assign the SGs and inter-trips according to the inter-trip effect on coordination restoration. Inter-trips restore the coordination with reducing primary relay operating time reduction, whereas SGs delay the operation of the backup relays. Optimal coordination of the proposed hybrid scheme is simulated on the IEEE 30 Bus distribution grid and compared with other schemes. The results indicate that the proposed hybrid scheme is a more efficient tool to improve the performance of the protection scheme under plug & play operation of DGs achieving lower fault clearance times.