An Integrated Current Differential Protection Scheme

This paper presents a new integrated protection scheme for transmission lines. The concept of the integrated protection is firstly introduced, in which a centralized protection system provides the protection of multiple power plant or a substation. A combined integrated protection relay for the protection of double circuit lines is then introduced, which combines the longitudinal current differential and the transverse current differential protection techniques. Studies show that the new relay offers more protection functions and significant economic advantages over the conventional current differential relays. A total integrated protection scheme based on current differential protection techniques is further described. In the proposed scheme, the specially designed protection relays are installed at each substation of a network and are responsible for the protection of every line sections connected to the substation busbar. The current differential algorithms with multiple settings are implemented into the relay to cover all the protected line sections. The scheme is supported by advanced communication network and standard. Studies show that the new scheme not only offer the new protection features for individual power line, but also provide the characteristics of integrated protection.