A protection scheme for optimum coordination of directional overcurrent relays in presence of distributed generation

The penetration of distributed generation (DG) violates the relay coordination in distribution network. The original relay settings can be restored by nullifying DG Impact. This paper presents a new protection scheme considering use of fault current limiter (FCL) and adaptive protective relaying to restore the relay coordination. The use of FCL, sometimes, increases the backup relay operating time. The adaptive protective relaying requires microprocessor based digital relays and communication system. This increases cost and complications of protective system. In context with this, a small size of FCL is used in series with DG to restore the settings of far end relays. The near end relays are replaced by digital relays to restore the original relay settings. The proposed scheme is implemented to different networks and find suitable to restore relay settings. A case study is presented to illustrate the proposed scheme.