An New Directional Comparison Scheme for Distribution Line Protection

This paper presents a new directional comparison protection scheme specially designed for distribution systems. A comprehensive study is performed on different directional discrimination algorithms and relaying schemes in order to assess their performances in distribution systems. An integrated solution was proposed, which combines better performed directional algorithms, such as the Negative sequence-based algorithm and superimposed component-based algorithm, etc. which together forms a new scheme to cover various system and fault conditions. Combined blocking scheme is proposed for better reliability and synchronization. Extensive EMTP simulation studies proved that the algorithm and its associated protection scheme are able to provide fast and reliable responses for all fault conditions. In particular, it is able to give correct responses adapting to the change of system operation conditions, including the changing of system configuration, power flow direction, and source and tapped-off-load conditions.