Transmission line distance protection with Dynamic Thermal Line Rating support

Worldwide analysis of recent wide area cascading failures has shown that very often they were mainly caused by the maloperation of the third zone of a distance protection relay. The load encroachment and power swing phenomena are the two dire problems to solve when dealing with the third zone of distance protection. The vast number of blackouts could have been avoided or the consequences lowered if the distance relay had not operated due to impedance encroachment while there was no such need. This paper proposes the way to improve operation of the distance protection relay by introducing a new blocking algorithm using Dynamic Thermal Line Rating (DTLR) to restrain relay from tripping when conditions in electrical power system allow for it.