A novel approach to increase FCL application in preservation of over-current relays coordination in presence of asynchronous DGs

Introducing Distributed Generation (DG) into Power Delivery Systems (PDSs) alters protection design of these networks. Commonly approach to overcome this problem is disconnecting DG units from PDS during fault. In case of asynchronous DG type, because of installing shunt capacitive compensators, using FCL for restoration of relay coordination is not useful in some cases. In this paper, a new approach for restoration of directional over-current relay coordination using three type of Fault Current Limiter (FCL) is presented. The proposed restoration approach is carried out without altering the original relay settings or disconnecting DGs from PDSs during fault. The process of selecting FCL impedance type (inductive or resistive) and its minimum value is illustrated. Two scenarios are discussed: no compensator and whit compensator. Various simulations are carried out for both single and multi-DG existence, different DG and fault locations. The application of this approach is implemented into an IEEE typical distributed network and the obtained results are reported and discussed. (C) 2012 Published by Elsevier Ltd.