Modified Distance Relaying Blocking Scheme For Low Inertia System

The communication schemes-based distance protection is more reliable for line protection. These protection schemes are fast in fault clearance and provide a secure protection whenever the zone-based distance protection mal-operate. The available communication-based protection scheme like permissible under reach transfer trip (PUTT) and permissible overreach transfer trip (POTT) needs strong source at both ends for stable breaker operation. But for weak infeed source, these protection schemes may fail to operate. In this article a modified directional comparison blocking (DCB) scheme is presented which outperforms the permissive schemes for low inertia infeed system. Modified DCB utilizes adaptive reach setting, current reversal logic and with echo logic for protection of parallel lines with weak infeed.